The menstrual cycle decoded: Lifestyle tips to ease your symptoms, with Hazel Wallace

How much do you know about menstrual cycles? About half of us are more informed than the other half.

The menstrual cycle has great significance, affecting various aspects of health. And more than 90% of people who get their periods experience premenstrual symptoms.

However, misconceptions and limited understandings abound, leaving many people in the dark.

In today’s episode, we’re joined by Hazel Wallace. She’s a medical doctor, nutritionist, and author of The Female Factor. She’s here to give us an education about the menstrual cycle. 

Dr. Hazel Wallace describes how the cycle affects almost every aspect of the body, from heart health and sleep to metabolism. She also explains whether there’s scientific evidence behind “cycle syncing.”

Whether or not you’ve had a menstrual cycle, you’ll learn a lot from this episode. 

If you want to uncover the right foods for your body, head to, and get 10% off your personalized nutrition program.

Hazel’s book is available to buy here.

Follow Hazel on Twitter.

Follow ZOE on Instagram.

Episode transcripts are available here.

Is there a nutrition topic you’d like us to explore? Get in touch, and we’ll do our best to cover it.


[00:00:00] Jonathan Wolf: How much do you know about menstrual cycles? Half of you will be a lot more informed than the other half, but whether you've had a menstrual cycle or not, I promise you'll learn a lot during this episode. Even if you aren't having periods, I'd say it's important you listen to better understand and support the people in your life who are today.

We're joined by Hazel Wallace. She's a medical doctor, nutritionist, and author of The Female Factor here to give us an education on the menstrual cycle. In this episode, we'll learn how the cycle affects almost every aspect of the body from heart health and sleep to metabolism and even the microbiome.

How the menstrual cycle affects what you eat. We'll even find out if there's scientific evidence behind cycle syncing. I learned a lot and I believe you will too.

Hazel, thank you very much for joining me today.

[00:01:09] Hazel Wallace: Thank you for having me.

[00:01:11] Jonathan Wolf: Now I'm very excited. Now we have this tradition here on the show that we always start with a quick fire round of questions. Okay. Are you up for that?

[00:01:19] Hazel Wallace: I am.

[00:01:20] Jonathan Wolf: Brilliant, and, and we have some quiet, strict rules so you can say yes. You can say no or you're allowed a one sentence answer, but no more.

[00:01:29] Hazel Wallace: Go ahead. 

[00:01:30] Jonathan Wolf: All right. Okay. Does the stage of your menstrual cycle actually change your body's metabolism?

[00:01:36] Hazel Wallace: Yes.

[00:01:37] Jonathan Wolf: All right. Good start. I heard that many women crave chocolate just before their period. Is this true? Yes. All right. Do you think that tracking your menstrual cycle can help you to improve your health?

[00:01:51] Hazel Wallace: Yes.

[00:01:52] Jonathan Wolf: All right. All yeses so far. Can the food that women eat affect how they feel throughout their menstrual cycle?

[00:01:58] Hazel Wallace: Absolutely.

[00:02:00] Jonathan Wolf: Does intermittent fasting have any effect on how women experience their cycle?

[00:02:05] Hazel Wallace: Yes.

[00:02:06] Jonathan Wolf: Okay. And finally, you're, you're allowed to more than a yes or no. Now, what's the most unexpected thing you discovered about the menstrual cycle through your research?

[00:02:15] Hazel Wallace: I think the power that our reproductive hormones have on other aspects outside of our cycle. So our mood, our sleep, our metabolism, our gut health. I don't think that's something that many people know.

[00:02:30] Jonathan Wolf: I definitely didn't, it's definitely not what I was taught at school. And I think we can like start to unpack that and you know, maybe just as I start, I have to say as a man, I obviously dunno what it's like to have a menstrual cycle as a husband, as a father to a young daughter. It's definitely something that I would like to understand more about.

I think that we talk a lot about menopause on this show and we talk a lot about how much of a taboo it's historically been and how little it was discussed. I often talk about the fact that, you know, my mother never talked about that. She definitely never talked about her menstrual cycle either. So, you know, it's something that I learned at school in biology and otherwise.

Was almost invisible to me. And so I'm struck still actually today in 2023 by how little we discussed this. I'm really excited therefore, to sort of dive in a bit today and understand a bit more what's going on and also how it really affects people's health.

[00:03:21] Hazel Wallace: Yeah, absolutely. And I think your experience is 100% universal, even for a lot of girls and women because when you have even a conversation around puberty, you learn more about the belief. Eating phase of the menstrual cycle, but it's a typical 28 day to 35 day cycle of hormones in fluctuation. And all of those hormones change how we feel across that month, not just those five days.

And so I'm really excited that we're having more conversations about it because like I mentioned in the beginning, those hormones not, they don't just influence. Are reproductive health, they influence all aspects of health. So by looking after our menstrual health, by tapping into it, we can look after all aspects of health

[00:04:10] Jonathan Wolf: and I think a lot of people will have been surprised about that. Before we dive into that, I'd love to, just to start like right at the beginning, like what is the menstrual cycle? How does menstruation work? You know, I've heard there are these different stages, but a lot of people I think, have thought about it as like you have a period every so often, and so it's just a few days in the month and you're already saying that's not really right. Could you help to unwrap that for us?

[00:04:32] Hazel Wallace: Absolutely. I often run away in these conversations and I think it's really helpful to come back to the basics and just kind of get a basic overview. So in a textbook menstrual cycle, although I will caveat this, but not many people are textbooks, so there is a lot of variation.

We'll say that an average menstrual cycle is about 28 days, but anything between really 23 to 35 days can be considered normal. They're extremes of normal, but anything in between there tends to be normal. And so this is basically fluctuation of hormones. There's four main hormones. We mostly talk about estrogen and progesterone.

But there's also LH and F S H, and there's some higher up hormones as well from the brain. These hormones fluctuate across the month, the very start of the month, the first half of the cycle, we call the follicular phase, and the second half we call the luteal phase. And then we've got ovulation sandwiched in between.

And so the first five days typically could be up to seven days, will be the bleed or menstruation or what most people know as the period. And that's when we're in a low hormone phase. So estrogen and progesterone are the lowest that they are across the cycle. And then after that, we move closer to ovulation and estrogen comes up in peaks just before ovulation and progesterone remains low.

And then after ovulation we get both hormones rising together and they peak mid luteal phase.

[00:06:06] Jonathan Wolf: it. So luteal was in the, towards the second half of this is the second half of this.

[00:06:10] Hazel Wallace: An easy way to remember it is follicular comes first, luteal comes last, and then when those hormones come back down again, we start the cycle again. So you get this really nice orchestration of hormones and as those hormones ebb and flow, that will change things like our metabolism, how we sleep, even our body temperature.

And so if we understand that we can really tap into these things and almost hack our menstrual cycle.

[00:06:35] Jonathan Wolf: It's really interesting. I was just thinking about the phases of the moon as you talk about this. Cause I know there's always been this like sort of ancient link somehow to the moon cycle and presumably our ancestors couldn't have had any. Idea about what was going on with our hormones. But it's interesting you're describing something which is really not like just switching on and off, but something which is really phasing in and out in quite a complex like interplay here.

[00:06:55] Hazel Wallace: Yeah, absolutely. And you know, these hormones also have far-reaching effects with other hormones, so there's a lot going on and there's a lot of influences within our body, but like you said, it is, it's a lot more complex than just a five day bleed.

[00:07:11] Jonathan Wolf: And so when in general today, would someone start their menstrual cycle? You know, what age and you know, I think we, we talk about perimenopause and menopause, you know, roughly when you would expect to get to menopause at the other end.

[00:07:24] Hazel Wallace: so you, in theory for a girl, she would start her first menstrual cycle when she goes through puberty, and this can vary between the ages of like nine to 12 really. And you would end it on your last menstrual cycle, which would be the menopause. And the average age in the UK here is 51, but the perimenopause, which is that transitional phase, and I'm sure that you guys have discussed this a lot in the podcast, that can be anywhere between four months for some women to 10 years.

So you could have a period of very irregular cycles whilst you're going through that transition.

[00:07:59] Jonathan Wolf: In until you get to the perimenopause. Is this menstrual cycle pretty constant for most women through their life after it starts or racially? Are there changes, you know, earlier in terms of what you experience? And the way these hormones are, are varying.

[00:08:11] Hazel Wallace: Yeah, that's a really good question. it can change threats, so it's very rare for someone to have the same. kind of pattern of a cycle from puberty all the way up to the menopause. Different things in our lifestyle can also change the length and how we experience our menstrual cycle, whether that's stress, that we're under nutrition, even sleep, and also if we go through things like pregnancy, we're in a postpartum period.

All of those things will influence how we experience our menstrual cycle.

[00:08:41] Jonathan Wolf: And why is it so complicated, Hazel? So I think I had a, like a really simplistic idea, something to do with the estrogen. It goes up and. Down because you wanna trigger like an egg. That's the start of potentially having a baby. You're describing something much more complicated, like what's going on and do we have any understanding about why it affects all aspects of a woman's body rather than you might think it's like just going to affect, you know, your womb.

Yeah. And like it would be completely cut off, but that's not at all the picture that you're painting.

[00:09:13] Hazel Wallace: Team. Yeah, absolutely. I think the more I've researched the hormone estrogen in particular, I realize how powerful it is as a hormone for all aspects of health, and not just in women and men as well, because we often talk about estrogen and progesterone as.

These female sex hormones, and while they are high in women, they're also in men, and so they have really important effects in other aspects of health. Their primary role will be in reproduction and across the menstrual cycle. The main goal is to release an egg during ovulation and also to prepare the wombs lining to support a pregnancy and.

If a woman doesn't become pregnant, then the lining falls away. That's the period and we start the process again. But estrogen, for example, I think the menopause is a great example of how important that hormone is because we go into a low hormone phase during the menopause, estrogen declines, and we see increases in cardiovascular.

Health issues and also bone health issues. And this is because estrogen affects how our arteries dilate and expand. And so we get a sharp increase in blood pressure, which increases the risk of things like heart disease

[00:10:29] Jonathan Wolf: Because the estrogen is helping your, basically, without it, these, it's worse. Is it? These arteries are no longer able to be as flexible,

[00:10:36] Hazel Wallace: So it's beneficial for a cardiovascular fitness and also in the high hormone phase in the menstrual cycle when estrogen is high, just before ovulation. We do see that as well. There may be some benefits to cardiovascular fitness, for example, for endurance sports.

[00:10:51] Jonathan Wolf: And so can you see that difference if you were a, I'm guessing probably not for the average person in the street, maybe, but if you are a, you know, sort of top end athlete, can you see differences in performance, different points in the cycle?

[00:11:04] Hazel Wallace: There was a research paper done on athletes, female athletes taking part in the last Olympics, and they were asked if they could choose any day in their cycle. To perform, to do their final event, what day would it be or where in their cycle. And majority of athletes said just after their period, and that is that high estrogen phase where we have seen from the research that there tends to be higher muscle building, potential, better mood, higher motivation levels, and a small increase in performance.

In terms of strength and endurance, and I will caveat this with the research in this space is very limited, very conflicting with all women's health research, but there is a difference there. And I think from speaking to women myself, from tracking my own cycle, you can see these patterns in strength and performance at different phases and I think it's incredibly important and really empowering to like tap into that information.

[00:12:04] Jonathan Wolf: And I'd love, actually, maybe before talking about the health, I should talk a bit more about what women experienced through this cycle. Cause I think you've already touched a couple of times. Right. On a way that you might feel differently, could you maybe talk through, and I'm guessing this is probably an average, and explain.

Explain how that varies through the phases that you've just described. How does that actually feel? what are people experiencing, and I guess not just our top class Olympic athletes. Probably not many listeners right now who are going to be competing in the next Olympics, but a lot of people who either go through this or everybody will know people who are, and I think would love to understand that better.

[00:12:41] Hazel Wallace: Yeah, absolutely. So again, like you said, this will vary from person to person, and there will be some people who almost float through their menstrual cycle and don't get much in the way of symptoms, or they're not really aware of what's happening. And then some people will be really tuned into their body and some people experience really debilitating symptoms.

[00:13:01] Jonathan Wolf: So this is basically, this is when your period would start?

[00:13:05] Hazel Wallace: Absolutely. That will be day one of your cycle, and that should last up to five days. For some women, it will continue for seven days and typical symptoms of that will be bloating, cramps, irritability. Some women feel more tearful and you also get gut related symptoms as well because you get that sharp drop in progesterone and menstruation in and of itself is an inflammatory response. So we see lots of inflammatory markers higher during this time, and so you might feel more bloated, more inflamed, and this has a knock on effect on your gut symptoms. So women tend to experience looser stools and maybe some nausea during that time as well.

So, But after that, once our hormones kind of start to settle and estrogen starts to come up again, this tends to be probably everyone's best week. If I was to pick a good week, that week after menstruation, just before ovulation and estrogen rises, now your skin looks better. We call it ovulation glow.

Your mood is better, your motivation. You're likely to feel stronger in the gym, and also at this time because of our. Metabolism. You tend to have a lower appetite during this phase, so unlike the next phase where we see a shift in the metabolism and cravings are higher, this phase tends to be a time where women don't find they've got many debilitating symptoms.

It's generally a good time, and some people refer to it as the spring of the menstrual cycle. Then after ovulation, we come into the luteal phase and progesterone, which was low, starts to come up now. And I think there's a misconception about progesterone being a bad hormone. There's nothing wrong with it, but it seems to offset some of the good things of estrogen.

And so we see an increase in temperature after ovulation by about half a degree. And this might not seem like a significant thing for many people. You know, it's just a small bump in temperature, but it has a knock on effect in our sleep. And so we see a lot of sleep disruption in this phase, which of course is going to make you feel a bit more groggy, a bit more irritable, maybe a bit off the mark when it comes to performing in work or in exercise.

And we also see more fluid retention as well, and it's a bit more difficult to hydrate. So during this time, it's really important to make sure you are consuming enough fluids. We also see. An increase in metabolic rates. So the amount of energy that we're burning at rest, and there is different numbers that are quoted in the research, but it can be on average up to 300 calories extra per day that you're burning at rest.

[00:15:52] Jonathan Wolf: That's an enormous change. 

[00:15:55] Hazel Wallace: Absolutely, And when we map the graph of progesterone rising with increase in metabolic rate and also increase in cravings, they almost all increase in tandem together.

[00:16:07] Jonathan Wolf: and then is it true that these cravings are towards particular sorts of food? I'm tending to think about things like fats and things like is that real?

[00:16:16] Hazel Wallace: Yes,

[00:16:17] Jonathan Wolf: again, is there not enough research?

[00:16:19] Hazel Wallace: It tends to be for more, high energy food, so high fat and high carbohydrate, and. That is likely because you have that increase in metabolic rate. Your body's just searching for the most energy dense type of food, and the most kind of reported craving will be chocolate.

And whether that's something that we've all thought about from a societal point of view, you know, a lot of us will relate periods PMS to chocolate. There's also a kind of a breakdown in protein, a higher breakdown in protein during that phase, and also a higher breakdown of fat. So I'm a nutritionist and a lot of the work that I do will be how to optimize your nutrition in that phase.

So making sure you're getting enough protein and healthy fats in and not just reaching for the high energy foods that aren't going to sustain you. So you wanna take a swap to instead of cutting carbohydrates completely, thinking about the quality of carbohydrates, you know, the high fiber, high fruit and veg intake.

And that will help offset to a degree those really intense cravings because that can be, also, can have a knock on effect in improving your menstrual symptoms. So they would be the main things. And then we're coming back down. The hormones are coming back down. A lot of women will experience PMS premenstrual symptoms during this time.

[00:17:40] Jonathan Wolf: And tell me a bit more about it because I think, again, that's one of those things that I'm definitely aware exists and I'm treading carefully cause my wife will definitely be listening to this. Again, I think something that's really not talked about very much. When would you expect this to start? What do most people experience?

What's the range? Cause my sense is there's a big variation because I get the sense some people, this is really quite crippling and other people, it seems like this is quite low. But again, that's very anecdotal. What's really going on? Hazel?

[00:18:07] Hazel Wallace: Yeah, so over 90% of women report. Experiencing premenstrual symptoms, and there are over 150 of them from bloating to low mood to irritability, gut symptoms, headache, breast tenderness. The list is endless, but you're right in saying there's a spectrum of how women experience this and the terminology's really important, so while over 90% of women experience premenstrual symptoms, a smaller percentage, about 20 to 40% experience, premenstrual syndrome. This is where the symptoms are so debilitating that they interfere with day-to-day quality of life, and we see this pattern emerge. One to two weeks before the next period, typically a week before, and it should end or get better when your period starts.

And that means that it's diagnostic of PMS. So we see that cyclical variation.

[00:19:08] Jonathan Wolf: And that's a lot of people you're talking about. So if you're saying 20, 40% of all women, women are slightly more than half the population and you're in this period of your life for what, like half your life or something like, that's an enormous number of people.

[00:19:23] Hazel Wallace: Absolutely.

[00:19:24] Jonathan Wolf: I'm going to guess that this is massively understudied despite this.

[00:19:28] Hazel Wallace: Yes. Yeah. There's not really much information or support out there for women. I think it's considered part and parcel of being a woman, and as someone who's gone through medical training and written a book on female health. I absolutely do not think, while it's common, I don't think we should normalize it. And I think there are lots of things we can do to support women there.

And there's also an even smaller subset of women, about three to 8% of people who will experience PMDD, which is premenstrual dysphoric disorder, which is similar to PMS in terms of its pattern and cyclical variation, but, There's more mood disturbance and that's even more tricky to diagnose, but it is in the manual that we use in medicine for psychiatric disorders. So it is a mental health disorder

[00:20:19] Jonathan Wolf: we actually had a lot of questions around that, from our members in advance. I definitely want to dig into this during this episode.

[00:20:26] Hazel Wallace: yeah, it's something I get asked a lot and I think because there's less known about it, and I think when people from my experience, from people who have come to me, they find it very hard to get a diagnosis.

[00:20:39] Jonathan Wolf: And can you explain a bit more what that is? I think for a lot of listeners, they've never even heard of it. Yeah. What, what's going on? And for people who are worrying about this, maybe either they, they think they might be experiencing it, or maybe they've even had it diagnosed, you know, what can they do? Yeah.

[00:20:56] Hazel Wallace: So PMDD, similar to PMS, the symptoms emerge about once, two weeks before the next period, and they should improve or disappear. In the next period if it's continuing. The reason that I'm really making it clear to clarify this, if it's constant, then it's not cyclical and it's likely to be another mood disorder, but to tell that it's tied to the menstrual cycle, that will be the criteria that we'd look for.

And typically women will have some physical symptoms of PMS as well. So the things that we mentioned, like headache, mood disturbance, cramps, things like that. But they'll have significant mood disturbance and that will impact their day-to-day quality of life. So they'll find that, you know, a lot of women will even use their annual leave because they'd feel like they can't go into work, which is something that is not okay. 

And the reason I think that it's so poorly diagnosed is there's not a huge amount of information out there available. I don't think medical professionals are fully aware of the symptom spectrum and what it might look like. And like I said, I think we normalize a lot of these symptoms as a society that is just part and parcel of being a woman.

[00:22:11] Jonathan Wolf: and Hazel, when you say mood disturb buttons, that feels like it could be a lot of different things. Can it manifest in any sort of different ways in terms of your mental health, or are there, you know, more specific ways that normally you would identify as this versus something else?

[00:22:25] Hazel Wallace: Yeah, it can manifest in various ways, which is why there's certain criteria that doctors will use to diagnose it compared to other kind of symptoms like or other conditions like depression or anxiety. But typically it will be kind of low mood, tearfulness, irritability. Some women experience anger, so it can be a variation in different emotions and different moods, but it's very much tied to that, and there isn't enough research around why this happens.

There's a lot of theories why some women experience it and some women don't. When we compare, women who do and women who don't, their hormone levels actually tend to be the same. So it doesn't seem to be that, but the hypothesis is that women who experience it are more sensitive to that drop in hormones that we talked about just before the next period, that they fall off that cliff and feel a bit more sensitive to it.

[00:23:16] Jonathan Wolf: They're experiencing the same change in hormones that other women are having, which is a big change as what you're describing, but they're somehow the reaction of their body to this, which sounds pretty profound. Yeah. As somebody who's a man is having, I guess, much more stable hormones through, through my day and through my month, the impact is much higher.

[00:23:34] Hazel Wallace: Yeah, so they're more they, they feel it more, and it's the hormone sensitivity hypothesis. I think there's also some genetic variation there as well where we see it run in families. So if your sister, your mother had it, then you're more likely to experience it as well. And also there's lifestyle components.

But really from looking at the research, there's not enough to really fully understand why this is happening. And the reason that's an issue is then it makes it tricky to find. Treatment options that actually work. And I know that in the US they're a lot more advanced in terms of finding good treatment options in the form of hormonal therapy that has been shown to be effective for PMDD.

There are lots of options here in the uk. We will start with things like lifestyle advice and then we'll move towards therapy and there are medication options. In very extreme cases, some women go for surgery and have hysterectomies and their ovaries removed, but that is very rare.

[00:24:33] Jonathan Wolf: Not where anyone wants to end up.

[00:24:36] Hazel Wallace: No, but I think it highlights how severe and debilitating this condition can be for women.

[00:24:41] Jonathan Wolf: That's extraordinary. And if we step back from PMDD alone and think more broadly probably to everyone who's, who's listened to this and think about, you know, given this great description you've got of what's going on across these phases in the cycle. First thing, we had a lot of questions talking about things like living within your cycle and cycle syncing.

Yeah. And cycle syncing I had not heard of before. So could you explain what those mean and I guess what your thoughts are about them?

[00:25:08] Hazel Wallace: Yeah, absolutely. Cycle syncing has become quite, big in the last couple of years. Essentially, it's just about syncing your lifestyle to the faces of your menstrual cycle because as we mentioned, those different hormonal phases cause our body to have different needs be that sleep needs, nutritional needs.

Mood changes, that kind of thing. There's a lot of like old age wisdom around this where people will talk about the menstrual cycle in seasons, the menstruation being winter, then just before ovulation being spring, then you go into summer, then autumn and you're back again. If you enjoy thinking about it that way, that's fine.

Um, it's not necessarily science backed, but I think it's a nice way of thinking it. Better for a lot of people. I think when it comes to cycle syncing, there is a lot of validity there. We definitely need more research, but there are things we can do in terms of like our nutrition, for example, tweaking that at different phases of the cycle to optimize how we feel, how we perform, and also to reduce symptoms.

So if we think about nutrition, First and foremost, I mentioned in the beginning that menstruation is an inflammatory response, so our body is in huge inflammation because it's going through a big process. There's a lot of shedding going down, and we need to support that as best we can, which we can.

Through an anti-inflammatory diet, and what I mean by that is lots of colorful fruits and vegetables, high fiber, whole grains, legumes, omega-3 rich foods like oily fish, flax seeds, walnuts, lots of herbs and spices, and that can help dampen the immune response.

[00:26:52] Jonathan Wolf: This is sort of particularly in the first week from the point when you have your period that's when this inflammation level is highest.

[00:26:59] Hazel Wallace: Yeah, absolutely. It'll begin just before the period begins because the hormones have already dropped and you know, an anti-inflammatory Mediterranean style diet is good all cycle round, but maybe at that time you wanna load up on the leafy greens. You wanna get in more berries. You want to really make sure that you're supporting your health during that time.

[00:27:20] Jonathan Wolf: I think no one here is ever gonna say you shouldn't eat like that. But you're saying we all know the reality of how we're balance life and balancing this, that actually. If there's a period when you would want to be closest to what many people listen to this, we'll think about as sort of probably their ZOE diet, like that week in particular can have the biggest impact and can it really affect how you feel?

[00:27:39] Hazel Wallace: Yeah, it can help with your menstrual symptoms in terms of menstrual cramps and have a knock on effect to your overall health during that time. I mentioned earlier that also some people have gut issues where they find they've got looser stools, they've got some nausea, so you may want to think about how you can support yourself nutritionally there. Staying hydrated, avoiding things like caffeine and other stimulants, fried or fatty foods can also make it worse. So thinking about how nutrition can really optimize that phase. I'm also a huge advocate of movement during menstruation. I know that when I was going through puberty during school, a lot of girls would skip PE during their periods and I think a lot of people have the notion that it's unsafe or we should not exercise during our period. It could make it worse, and actually the evidence suggests otherwise the opposite.

[00:28:34] Jonathan Wolf: So tell, tell us a bit more about that

[00:28:36] Hazel Wallace: That regular activity can actually reduce menstrual symptoms and also how heavier period is amazing. Yeah, and you know, this was, this is evidence from the Cochrane review where we pool lots of research together and we look at.

The pool of it and see how good quality it is. And this is based on women regularly exercising, so that will be three times per week. We don't know whether the same effect applies if you stop exercising, so it's unlikely to do you any good if you just do one exercise session?

[00:29:10] Jonathan Wolf: And then stop for 26 days. That's not a pattern. There's never any like good cheats. I have to say it's very disappointing things about this podcast, and no one comes to and says, oh, well you can just exercise once a month and you'll be fine. so you're saying here like, just make sure that like regular exercise has been shown to be helpful, but you are saying don't stop through this period.

[00:29:29] Hazel Wallace: Don’t stop during this period.

[00:29:30] Jonathan Wolf: actually continuing might well be helpful and reduce some of these symptoms.

[00:29:35] Hazel Wallace: Yes. And whenever I talk about this, you know, as we mentioned, women experience this. Menstruation on a very huge spectrum, so some people find it very hard to even get outta bed, and the thoughts of exercising is the last thing they wanna do. First of all, if you are bedbound, that is not a normal symptom and you should be speaking to your GP or your doctor about that.

But if you find that exercise is the last thing that you wanna do, or that doing something high in intensity is something that would make you feel worse. Low intensity exercise in particular. Yoga, there's a lot of trials around yoga and the benefit in menstrual symptoms and also PMS, and that's likely because.

Of the mind body connection. So you're moving your body, but you're also doing a lot of breath work during the practice and you're tuning into how you feel in your

[00:30:25] Jonathan Wolf: And there are real studies showing that?

[00:30:27] Hazel Wallace: Real studies, showing the benefits of this.

[00:30:29] Jonathan Wolf: that's really interesting and showing it tied to, not just generically that this is good for you. Cause it seems like the evidence for exercise in general is really compelling, but particularly towards these symptoms you might have in this first week.

[00:30:41] Hazel Wallace: Absolutely. It's interesting because yoga seems to be the one practice that has been really well researched when it comes to p m s and menstrual symptoms.

[00:30:49] Jonathan Wolf: Are there any other things that you, maybe there's not quite as much evidence, but you would guess you might be able to, to swap in instead?

[00:30:55] Hazel Wallace: Well, the research kind of points to all forms of moderate intensity exercise, and so that's really anything where you can kind of hold conversation, but maybe you can't sing. So brisk walking. It could be riding a bike, it could be going to an exercise class, it could be going for a run. I think it's very individual and you know, While I can sit here and say, you should be doing three times a week exercise and it should be of this intensity.

Do whatever feels good for you and all movement counts.

[00:31:29] Jonathan Wolf: Amazing. Now, you mentioned a number of other things I do, I don't wanna miss out on, about the way that the menstrual cycle is affecting your, your health, and I think you talked about sleep, you talked about stress. Could you just tell us what else is actually changing through this cycle?

[00:31:44] Hazel Wallace: Sleep is really interesting and I would definitely love more research in this, especially when it comes to sleep architecture. So when we're talking about the different stages of sleep, but as a brief overview, we do see a lot of sleep disturbance just after ovulation and in that premenstrual period. So just before the next period.

I mentioned earlier that there's an increase in body temperature, which happens after ovulation, and it remains elevated until the next period. And this can affect our sleep because we are so sensitive to temperature shifts when we're sleeping. It can have a knock on effect on not just our quantity, but.

The quality of our sleep. It's also quite interesting in that some studies have even looked at how our sleep architecture changes in that second phase.

[00:32:35] Jonathan Wolf: when you say sleep architecture. I love the idea that I have sleep architecture. Can you explain a little bit more what that means?

[00:32:42] Hazel Wallace: So when we talk about sleep architecture, we're talking about the different stages of sleep.

So people might have heard about, you know, REM sleep and non REM sleep, and we'll go through cycles of this threat. The night and old stages of sleep are important, whether it's light sleep or deep sleep or REM sleep, but they all offer different. Benefits to us and when we go into that luteal phase, there's some evidence to say there's less REM sleep, which is that dream sleep.

And I think it was Matthew Walker who said that this is like emotional first aid. So it's really important for how we feel in our emotional wellbeing. And if we get less of it, So if we've had a bad night's sleep, we tend to feel a bit more groggy, a bit more irritable, maybe a bit more emotional the next day, and we see that drop in that REM sleep in that lal phase.

[00:33:35] Jonathan Wolf: which is the second half of the…

[00:33:37] Hazel Wallace: The second half of the cycle, and that's something that I'm really trying to understand is how does it affect women? How does our sleep change across the cycle, but also across the menopause, during the perimenopause when we're pregnant, postpartum, because our hormones have massive influences on our sleep.

As a kind of a general statistic as well, women typically sleep more than men, but have. Worst quality sleep, and that's for multiple reasons.

[00:34:07] Jonathan Wolf: So that's not just this sort of menstrual cycle that you're talking about.

[00:34:10] Hazel Wallace: Yeah, hormones play a role, but they're not the only thing. Women tend to ruminate a bit more at night, so they'll stay awake thinking about things they have to do.

We also tend to suffer with conditions that will keep you awake, so, Women are twice as likely to experience anxiety and depression in their lifetime experience. Things like overactive bladder, so having to wake up in the night to go for a whee and heartburn or reflux is also more common as a general rule, although it varies from household to household.

Women tend to be primary caregivers, so they're waking up to look after kids or elderly parents.

[00:34:44] Jonathan Wolf: I was gonna say, nevermind, they're the only ones who get pregnant, which having been through this period, time definitely messes with your sleep. So,

[00:34:49] Hazel Wallace: Absolutely. Pregnancy insomnia is a thing.

[00:34:52] Jonathan Wolf: I think having a child inside you kicking is not ideal for sleeping. Do we understand anything about what's going on in things like our immune system through this period?

Because you talked about this very inflammatory phase at the beginning. I think I know where you're gonna tell me, which is this is really under researched. But do we, do we understand how that might be changing through the cycle?

[00:35:10] Hazel Wallace: It is very under-researched. but there are a few papers who have looked at changes in the immune system across the menstrual cycle, so that high inflammatory phase during menstruation, there's also a lower white cell count. So white cells are really important for fighting off pathogens or viruses and things like that that come into our body.

So, There is a suggestion that you might be more susceptible to getting colds and flus during that time as well, which is even more reason to get in more leafy greens and healthy fruits and veggie

[00:35:43] Jonathan Wolf: It's amazing and, and I did wanna pick up on this thing about sort of the lack of scientific studies cuz it's something that Sarah Barry, our chief scientist talks about a lot and she's done an enormous number of these randomized clinical trials in her career. And one of the things she and other guests have talked about is just sort of how few studies there have been, not just specifically on women's health, but actually on women.

And particularly on women premenopause, exactly because of what we've been discussing today, which is this sort of complexity of, the change in women's responses during the cycle means that historically, particularly for things like nutrition research, they would've had to have two or three times as many women in a study to try and sort of average out the changes that you're seeing.

And because they have small funds, they'd be like, well, we just can't even do that. And so there's this sort of, ridiculous situation where so many of these studies have only been carried out on men and equally well, no one's really looked at what seems like, you know, obviously incredibly important, which is if you're seeing this big change during the cycle, presumably the sorts of, you know, the way you might think about medical treatment or even drugs would presumably want to change during this period.

[00:36:56] Hazel Wallace: Absolutely. And most of the medical research we have is based on a male body, and it's only been the last decade or maybe the last two decades that there's been a huge drive to. Include females in medical studies because we've previously just assumed that women are just smaller men and therefore we can just extrapolate all this data onto women.

But as we've just said, and you know, in this entire podcast episode, we're very different from a kind of a hormone profile point of view, but this also changes our physiology, our metabolism. Even our anatomy. And so it's really important that we take that into consideration. And this is why we know so little about the menstrual cycle and even when we do research on it, just taking calendar methods.

So assuming that every woman is 28 day cycle with ovulation in between, most researchers will just assume that and we'll just use calendar methods, but that's not accurate because. Even if someone menstruates, we can't assume that they will ovulate in that month. Some women will have a month where they don't ovulate.

So really to be doing the best research, we should be taking urine tests, blood tests as well, to find out where women are at the cycle. And for researchers, that's a huge inconvenience, a huge expense, and it's just easier not to do the research. So there needs to be a bigger drive there and. Like you, you mentioned it may change how we, how women respond to treatments, how women present to hospital with different conditions.

I think one of the biggest examples that I discussed in the book and is incredibly important is the difference in heart disease between men and women. And there's this old age assumption that. Heart disease or heart attacks as a man's disease where women are just as likely to die from it, and actually in the UK are more likely to die from it than men are because of how they are, because of the delays and diagnoses, and also how they respond to treatment.

And if we look at heart attacks, for example, women may present slightly differently. They may not present with the typical central crushing chest pain. They may present with nausea, a feeling of palpitations or anxiety, and they may not assume that they're having heart attacks. And because they don't fit the perfect profile of what we deem to be a heart attack patient doctors may not assume that they're having it either, and these delays are incredibly important when it comes to heart attacks. 

In medicine we say time is muscle because we wanna reperfuse your heart as quickly as possible if you're having a heart attack. And so if we have a delay getting to hospital, then we have a delay getting your diagnosis. Even the tests that we use, the blood tests, which check the enzyme levels of your heart muscle, they have found to be too high for women.

So the cutoff is too high. And only recently I actually had a friend send it to me now in hospitals, they've got now sex specific cutoffs. Now it's not across the board, not all hospitals, they're trialing it in certain hospitals, but it just goes to show how for very long, We've been having cutoffs, which are too high for women, and the amount of women who would've been turned away, sent home.

You're not having a heart attack when you were,

[00:40:25] Jonathan Wolf: It’s a really terrible story.

[00:40:27] Hazel Wallace: It’s terrible, and that's why over the last 10 years in England and Wales, women are more likely to die from a heart attack than a man is because of these delays. And it is harrowing and it's horrible to think it in this day and age that happens, but it's because.

For years and years, we've excluded women and assume that we are exactly the same in terms of physiology, how we present with conditions, how we respond to treatments, and it's very much a different story.

[00:41:00] Jonathan Wolf: Well, that is a rather depressing story, so I suspect everybody here is going to be reading up on what a heart attack does look like from man versus women. When we'll try and get a link from Hazel that we can put in the show notes. Now, I think. In general, we're probably not gonna solve that for people on this show, but I would love to switch to like what people can do.

And I know that one of the things you'd like to talk about is actually tracking your cycles. I'd love for you to explain what that means and why it might matter, and then maybe talk about some of the other things that you can do. And, and we had a teaser question about intermittent fasting at the beginning that you answered today.

Would definitely like to make sure that we captured alongside just sort of both nutrition and lifestyle changes that you, you might be able to make. You know, across this, this cycle.

[00:41:44] Hazel Wallace: Yeah. For sure. I think menstrual cycle tracking is probably the most important first step for all people who are menstruating. And the reason for this is not only is it really practical from a, you know, whether you're trying to get pregnant or avoid pregnancy. Or just understand when your next period's coming.

It's really helpful for you to be informed as to what's your normal, because we've discussed multiple times on this episode that there is variation in terms of what is the normal. So you know, you might be someone who's not a 28 day cycle. You actually are. 30 days or 31 days. But that's your normal and it happens every month and that is healthy for you and that's fine, but it's also really helpful to inform conversations with health practitioners Should something go wrong. So you miss a period, three cycles in a row, at least you can have all that data to go, this is my usual, this is what usually happens for me. This is not normal. I need support. 

And I go beyond, or I'm a huge advocate of going beyond just tracking things like when you're ovulating or menstruation, but tracking your cravings, how you're sleeping, your strength and energy levels, your mood, track everything.

And you can go as old school and just be pen and paper and track them. But now there are so many apps out there that make it so simple where you just have to click a button and. Move a toggle and that can help you do it without having to like faff around by getting your diary together…

[00:43:20] Jonathan Wolf: and what you get out from doing this? You start to understand, I guess, what your normal is. What can you do as a result?

[00:43:27] Hazel Wallace: Well, it can help you tailor your nutrition. It can help you tailor your training. If you know that certain points of your cycle, you have four nights of bad sleep, maybe on those nights you make your room a little bit cooler, you change your pajamas, you get into bed a little bit earlier to offset those things.

It's how we can essentially cycle sync. But, Keeping the individual and personalized to us, and I'm a huge fan of that instead of, we can use the research as a guide, but not the rule. The most important research that you can get is from yourself.

[00:44:00] Jonathan Wolf: That certainly sounds like it makes a lot of sense. And in terms of other things that you can do during this period, you mentioned a little bit already on what you should eat. Is there anything else that people should be thinking about throughout the period? I know that you haven't, for example, mentioned anything about iron, which I know is something people talk about.

Like is there anything else that you should think about in terms of nutrition?

[00:44:22] Hazel Wallace: Yeah, absolutely. So if we kind of look at menstruation, that days of bleeding, as we mentioned, an anti-inflammatory diet's, really important from reducing that inflammation, which will help reduce symptoms, but also support your immune system during that time because your bleeding and because iron deficiency anemia is so prevalent in premenopausal women.

Upping up your iron intake is really important. And you know, we can get this from animal-based sources like meat and fish, but also you can find it in lots of plant-based sources, whole grains, legumes, leafy greens, nuts and seeds.

[00:44:59] Jonathan Wolf: So you don't need to be eating meat in order to get the iron that you need.

[00:45:02] Hazel Wallace: No, absolutely not. And I think, you know, if we're focusing on getting a good variety of foods, you should be getting all the nutrients that you need.

There's some evidence that if you add some vitamin C to plant-based iron, you can actually increase the absorption. So for example, if you're having hummus, which is made of chickpeas, and that's an iron source, Squeezing some lemon juice on top may help increase the absorption of iron during that time.

And also, we mentioned things like gut health. So during menstruation I would avoid things like caffeine, fizzy drinks, spicy and fatty foods, things that you know are gonna stimulate your gut. So you might just wanna be a bit more cautious about it. During that time. People will. Vary in terms of their sensitivity to fiber if they're experiencing looser stools.

So you might have to moderate it during that particular time, but you might be fine. Again, monitoring your symptoms. If you find no changes to your gut issues or gut symptoms, then you can have as much fiber as you can tolerate.

[00:46:05] Jonathan Wolf: and this being the ZOE podcast, I have to ask you about the microbiome, but I think I know what you're gonna say. Do we have any understanding about whether the microbiome is actually fluctuating during this cycle as a result of all of these massive changes?

[00:46:17] Hazel Wallace: there's actually very little to no research done around the changes to the microbiome during menstruation, there's some emerging and when it comes to advising women about gut symptoms around menstruation, for example. I often say, you know, you could try a probiotic, but there's absolutely no trials looking at how probiotics could improve gut related menstrual symptoms, which blows my mind.

So if there are any researchers listening to this podcast, please do a trial on that because I think it would be absolutely fantastic to help support women during that phase and, and kind of find out how we can offset some of those gut symptoms.

[00:47:04] Jonathan Wolf: We're now running the world's largest nutrition science study, and this is an area that Sarah and others are really interested in because actually the scale of the data that we're now starting to to get allows us to start to piece together some of these changes. Although you obviously.

Need sometimes to think really carefully about how you can do these measurements. Because you know, often people are doing, you're doing an at-home test, you're doing that at a point of time. Or even if you're doing something measuring blood sugar over a week or two, that's not the whole cycle. Yeah. So it's clear a lot to do and I think we're, we are really interested so we should follow up after this and see whether we can do something that could shed I think some light, cuz I think we generally see these things are very interlinked.

[00:47:45] Hazel Wallace: Yeah, absolutely. And I think we know, obviously how powerful the link is between our gut and our brain and our gut and our immune system and all these other systems. So it makes sense that there's a link between our menstrual health and our gut. And you know, even when it comes to estrogen, we know that there's an.

Like a lot of estrogens metabolized as well in the gut. So it's really important that we're optimizing our gut health across our menstrual cycle. And also, you know, with menstrual cycle related conditions like PCOS and endometriosis, I suspect there's a really strong link there as well. And we do see some gut dysbiosis in conditions like PCOS.

[00:48:27] Jonathan Wolf: Oh, it sounds fascinating to try and understand more. Now, before I let you disappear, I have to follow up on the intermittent fasting. What can it do?

[00:48:35] Hazel Wallace: So, I am slightly skeptical in advising, intermittent fasting for women who have menstrual cycles because women are very sensitive to the amount of energy available. So if they go for long periods without food, we can see menstrual cycle abnormalities. So longer cycles, bigger gaps between cycles.

Not everyone, but. Women tend to be more sensitive compared to men when it comes to intermittent fasting. So I'm slightly cautious to advise it. I know that some women do it and it doesn't affect their cycle, and I think the reason this is, is because in the feeding window they're ensuring that they're getting in enough calories and enough nutrients.

So for women who do wanna try it, I would say you have to be really, really clear on getting enough nutrients and. Most importantly enough calories in that feeding window. And it might be that you don't go for huge windows where you're fasting, so you're slightly more, cautious and going for maybe a 14 hour window of fasting as opposed to anything bigger than that.

That would be my biggest piece of advice. Again, most of the research on fasting is on mice and men, so more research on women, please, and then we can better advise moving forward.

[00:49:54] Jonathan Wolf: We've actually just done a massive study with participates on the ZOE Health study around intermittent fasting. As far as I know, we haven't looked at the data specifically for, women who are still going through their menstrual cycles. I think that's something really interesting, that we will definitely follow up on in general.

Seems to be something that works really well for most people. So it's interesting to hear the caution. By the way, it's miserable for me. I'm one of these people who's tried intermittent fasting and did it in this study and I hated it. It was bad for my mood, but interesting. It's the reverse of the average, which again is down to, I think one of the things we believe a lot here about this personalization, that's not one answer for, for everybody. Our bodies are so complicated.

[00:50:35] Hazel Wallace: Yeah, absolutely. It's something that I've discussed at length with Tim Spector about when it comes to fasting and women, and we've both agreed that we definitely need more research there to really understand how it affects the menstrual cycle and how we can optimize. Both that protocol to suit women who are menstruating because it might be, we have to tweak it at certain phases of the cycle.

[00:50:58] Jonathan Wolf: Correct. And I think one size fits all is definitely not something we believe there or anything else. Hey, I have lots of questions, but we definitely hit time. I'm gonna try and do a summing up and please correct me if I got any of this wrong, if that's okay. so. I think the, you know, my first takeaway is it's a very complex cycle.

A lot more complicated than I think many people Imagine as like you have your period, that's a few days of the cycle and everything else is like sort of stable actually. You're describing this very complex thing with not even just two hormones, but even more of these going up and down. There's quite a lot of individual variation, but if we take that sort of average is around 28 days then you've also got this big difference between the period sort of in the first week, which is associated with this period, and then what you're seeing in sort of the second half of this environment that a lot of people actually feel really quite good after their period has come.

They can be very positive tha. during the time when you're having your period, the enormous number of women are having symptoms and I think a rather extraordinary sort, I think you said 20 to 40% are people are having really severe symptoms such that it's really impacting their quality of life. That all of this is incredibly understudied.

So our understanding about exactly how this impacts your health is it's sort of shockingly under understood. There are people who have sort of this extreme PMDD, which is really affecting your, your mood, significant mood disturbance. There are, however, some things that you can do. I think nutrition is a thing you've really led with and that interestingly, particularly in that period after your, just having your period, you're in this very inflammatory state.

It's not a great place to be. And actually eating this sort of really gut healthy diet that, you talked about, can potentially really reduce that level of inflammation and therefore reduce your symptoms, make you feel better, presumably be good for your long-term health. And this is all the classic sort of high fiber plant led diet.

Interesting you said exercise actually is not only good full stop, so exercising regularly three times a week and it's not crazy exercise. It's like enough that you can't sing, but actually you could still talk, can really reduce your symptoms throughout the cycle and that you don't need to stop during your period.

In fact, probably you should keep doing it and. What else can you do? Well, sleep may be worse through periods of this. You gotta, if you understand your cycle and you're tracking it, so you start to understand what your normal is and you therefore understand this is the living with your cycle, how can you adjust what you're doing in order to be better?

Gut issues are quite common, so thinking about potentially how you might need to adjust what you eat. And then I think at the end, we talked about intermittent fasting where you're quite cautious and it sounds like you're mainly cautious about people eating enough calories, enough food, so it can potentially work, but don't just assume that this is this wonder solution actually, it sounds like you, you're concerned there might even be some issues here.

[00:53:46] Hazel Wallace: Yeah. Yeah, that would be a perfect summary, I think, of what we discussed.

[00:53:51] Jonathan Wolf: I think I missed quite a few things, but I love it. Thank you so much for coming in and hopefully we'll figure out how to follow up with some studies to push forward the science here.

[00:54:00] Hazel Wallace: Absolutely. Thank you for having me.

[00:54:01] Jonathan Wolf: It's a pleasure. Bye-bye. 

Thank you, Hazel, for joining me on ZOE Science & Nutrition today. We've heard a lot today about how each of us has this unique body, whether a man or a woman. If you want to understand how to support your body with the best foods for you, then you may want to try ZOE's personalized nutrition program. You can get 10% off by going to

As always, I'm your host, Jonathan Wolf. ZOE Science & Nutrition is produced by Yella Hewings-Martin, Richard Willin, and Alex Jones here at ZOE. See you next time.