Why your daily multivitamin could be harming you with David Seres

We’re told vitamins are essential for our health; that they boost our immune systems, fight fatigue, and protect us from disease. But what if most of it isn’t true?

In the 20th century, vitamin supplements were hailed as a breakthrough, curing diseases like scurvy and rickets.

But that success story took a turn. In the US, a law passed in 1994 — helped by a Hollywood ad campaign — removed almost all oversight from the supplement industry.

Since then, a $40 billion business has grown in the shadows. One where marketing beats science, and health claims are made with barely any evidence.

For over 25 years, he’s worked as a physician nutrition specialist, caring for critically ill patients who rely on life-saving nutrition support. He received the Excellence in Nutrition Education Award from the American Society for Nutrition.

In this episode, he helps us debunk the vitamin supplement industry.

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Transcript

Jonathan Wolf: David, thank you so much for joining me today. 

David Seres: Oh, it's such a pleasure to be here. Thank you so much. I'm so honored to be asked. 

Jonathan Wolf: So we have a tradition here at ZOE. We always start with a quick-fire round of questions from our listeners. Are you up for that? 

David Seres: Sure, fire away. 

Jonathan Wolf: We have some quite strict rules, especially for professors; you can only say yes or no, or a one-sentence answer if you absolutely have to. 

David Seres: Okay. 

Jonathan Wolf: Did Mel Gibson help deregulate vitamins in the U.S.? 

David Seres: Yes. 

Jonathan Wolf: Can supplements make health claims without real proof? 

David Seres: Yes. 

Jonathan Wolf: Did scientists contribute to an obesity crisis by fearing fat? 

David Seres: Maybe. 

Jonathan Wolf: Can supplements be sold in the U.S. without approval from public health bodies?

David Seres: Yes. 

Jonathan Wolf: Pretty amazing. Final question: What's the biggest myth about vitamin supplements? 

David Seres: The biggest myth about vitamin supplements is that if some is good, more must be better, and will have health benefits, and will be safe. And it's not true. It's not true. 

Jonathan Wolf: I love it. I think those were some rather remarkable answers to the Q&A. Mel Gibson has never made it into the ZOE podcast before. Love it. 

So all quite startling. And I'd like to start maybe at the beginning of this supplement story, because I understand when they were first discovered, vitamins were a real breakthrough. They fixed deadly diseases. 

I was brought up at school in England, so they talked about scurvy and that sailors would die, and they discovered vitamins.

David Seres: I mean, the whole nickname of British sailors as Limeys was because they ate limes, and they ate limes because it cured scurvy, because there's vitamin C in limes. There wasn't vitamin C in the usual diet of a sailor.

Jonathan Wolf: So that is a brilliant example about how vitamins can save lives.

David Seres: There are many others, like the B vitamins that are added to breads and so forth, at least in the U.S.

Jonathan Wolf: So what's interesting is that today we're in a place where this supplementation is hugely widespread, in the healthy population. And the research team here at ZOE said it's now a $40 billion industry.

So I would really like to understand with you how we got here, and maybe we could just start with what these vitamins were originally designed to treat and how successful they were.

David Seres: Sure. The history of vitamins is miraculous because there were different deficiencies in different populations in the world. Iodine included, which would cause goiter and cretinism in children, vitamin D, as I mentioned, which caused rickets, vitamin C in sailors, et cetera. 

And each one of these was an enormous public health boon. I think that, ever since then, we've been waiting for the next big huge discovery around vitamins and there just, I think we, there aren't any left that we are aware of. 

Jonathan Wolf: Why do you think that the promise of vitamins has become so attractive for people who view themselves as healthy and who are not suffering from a deficiency that they're aware of, or a doctor has told them they have?

David Seres: There's a general feeling in being human that one would like to control one's destiny. And health is this mysterious black box that, if you are able to do something now that will give you extended health and longevity, that's very attractive to be able to do that. 

Vitamins have been held out as this, without good proof. But nonetheless, the ability to market them in the way that they're marketed, suggestive of health benefits, has fueled this. 

Jonathan Wolf: So when did they move from being this sort of niche thing to treat a particular disease, to sort of widespread usage here in the States?  

David Seres: I don't know that I really have an answer for you. I think it was probably a gradual sort of thing.

I know that in the nineties, a law was passed to deregulate the industry. But at the time, there was already enough money in the industry to have made large donations to political campaigns and so forth in order to promote the passage of the law. 

Jonathan Wolf: Is that where Mel Gibson comes in, who you mentioned at the beginning? Could you tell me about that? 

David Seres: There was a bipartisan effort to pass this law called the Dietary Supplement Health and Education Act of 1995, DSHEA, or d-shea as some people call it. And the primary promoters got people to believe that this was nutrition and it was nourishing. 

People also believed that the FDA was trying to regulate these substances, when in fact no such effort was ongoing. 

Mel Gibson was hired to do a commercial, in which he is in his home, in his kitchen, in his bathrobe, surprised by a SWAT team arresting him because he's got vitamins and he called for people to write to Congress. And that advertising campaign got more letters written to Congress than the entire Vietnam War.

It was very successful. 

Jonathan Wolf: So the ad was saying that I was going to have my vitamin C taken away. 

David Seres: Yes. 

Jonathan Wolf: What was this legislation going to do?

David Seres: So this legislation essentially deregulates anything brought to the market that's called a dietary supplement. And it takes away the ability for the US Food and Drug Administration to regulate these substances and left specific ways in which the supplements were allowed to advertise suggestively.

So it's actually written into this that you can say that this stuff supports heart health or supports brain health without really any direct evidence of it. 

Jonathan Wolf: So that's written into the legislation. It says, we agree that when you sell this supplement, you can say it supports heart health.  

David Seres: I think the actual wording may not be there, but these have been agreed to in subsequent rule passing.

But these are called structure and functional claims. It's complicated as to how to actually interpret that. Which actually makes it harder to regulate. 

But suffice it to say that they're still not allowed to say that they treat or cure any kind of a disease unless it's been approved by the FDA. 

 Jonathan Wolf: So they are allowed to make these health claims.

Is that different from what would happen if you were a drug or if you were something else in terms of the claims you can make? 

David Seres: Couldn't be more different. 

So a drug company has to undergo a series of randomized controlled trials, where people are randomly assigned to either the drug, or a standard treatment, or a placebo and studied over time to determine whether or not the product does what it's supposed to do.

Then that research has to pass muster with the FDA in order to be allowed to be sold as a medication or a drug. 

Dietary supplements are treated as if they were a completely different thing. Where they are nutrients, so therefore they must be safe. Thus, we don't want to deprive people of the ability to access them, and so they're available without any science necessary, without any proof of benefit necessary, and frankly, without any safety testing, although there is some accountability if that something is dangerous.

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Jonathan Wolf: I think it's a bit shocking everything that you just said, David. 

 And so basically there was this law, it was supported by this brilliant piece of advertising, which was presumably funded by the industry, 

David Seres: Presumably, and one can find that on Google. Just put Mel Gibson and dietary supplements. 

Jonathan Wolf: And so suddenly they are carved out from the way that you would treat drugs, but also sort of given permission to make claims here 

David Seres: Right. 

Jonathan Wolf: In a very different way. I'd like to get onto that in a minute, but before we do that, do you think that most Americans understand how unregulated this industry is? 

David Seres:  I don't think so, no. 

Jonathan Wolf: What do you think the impact is, therefore, on people's behavior and their health as a result of this? 

David Seres: There's a $40 billion industry. There are statistics on how many people take dietary supplements, and it's astounding. 

I'd have to look it up. I don't recall the exact amount, but more than half of Americans take some form of a dietary supplement.

Jonathan Wolf: Now, I know that there are differences between the regulations here in the States and elsewhere. So the team says that in the European Union in the U.K., which is still basically following the same rules as in the EU, apparently, the European Food Safety Authority has rejected over 90% of submitted claims since it was formed in 2008.

Is there anything equivalent in the States that is like looking at these claims and rejecting them or accepting them? 

David Seres: There's no requirement for submission of a claim to be able to sell these products. So I am not aware of any similar kind of commission. 

Jonathan Wolf: So what would prevent you from saying, take this pill, it's going to make your heart healthier.

David Seres: Well, you have to say it supports your heart health, but I could be very wealthy. I'm a well-established, credible nutrition physician, scientist, et cetera, et cetera. 

I could very easily take my credibility, put it on a label, and sell crushed-up rose hips and tell you that it supports your kidney health, and make a lot of money, and there's really nothing that precludes that.

Jonathan Wolf: Does it support your kidney health? 

David Seres:  There's not any direct evidence that taking extra vitamin C or Rose hips has any benefit for the kidneys. 

Jonathan Wolf: So you're basically saying you could make a claim that you think makes no sense in science, and that's fine.

David Seres: That's pretty close to it. Yes. 

Jonathan Wolf: Fascinating. 

David Seres: There has to be some indirect evidence that, I mean, for instance, people who have kidney stones or bladder infections, there is some evidence that increasing the acid level in your urine might help either of those.

But there is no direct evidence of doing so by taking Vitamin C has any benefit. And in fact, the studies of cranberry juice and cranberry juice concentrate supplementation for urinary tract infections have been pretty much disappointing. 

Jonathan Wolf: So we've got this huge industry which has also extraordinarily unregulated, given that it's able to make claims around health. Originally built on this very legitimate case of treating diseases.

And even now, I mean, we talked a lot about the skepticism, but I think that there are certain people and stages of life when physicians do recommend vitamins, and that's important. 

Maybe we should talk about that for a second in this context. 

David Seres: I'll be honest, I'm taking vitamin B12 because I actually developed a deficiency.

And so I'm not suggesting that in certain situations, vitamins aren't absolutely necessary, but for the general healthy population, less so. 

Jonathan Wolf:  So I'd love to discuss how we've gone from these vitamins for people who have a deficiency, to this much broader market, where they're being sold with all of these claims and what's really going on so that you can understand it.

Because I think what happens is it's very hard to differentiate between products that actually work and maybe even medicines, and those that haven't.

Could you just help me to understand how the science is being used to trick someone and contrast that with what you would view as the right way to do the science?

David Seres: Sure. A couple of things. First of all, some of the evidence might come out of a Petri dish where a cell might react to a substance, and then that cell being part of an organ system. You can sort of take very indirect evidence like that to, to say, well, it is involved in the normal biology of this tissue, so therefore it supports that tissue.

Jonathan Wolf: I mean, that sounds good. What's wrong with that? 

David Seres: Well, the problem with that is that it's indirect evidence and biology's very complicated.

It's incredibly, wonderfully complicated in that if there's one reaction to a certain perturbation, there's bound to be other counter reactions in order to keep things smooth.

And so I like to say that if you do A and get B and do B and get C and do C and get D, the likelihood of doing A and getting D is close to zero because of all the intervening processes that can happen. It's never a straight line in biology. 

Jonathan Wolf: You could see something in a sort of Petri dish, you know, like when I was at school doing right, you know, biology, and I can show that I add this one chemical and something happens to one cell.

But that isn't the same as saying that if I take this ingredient, like as a human being every day, that suddenly I'm less likely to get dementia. 

David Seres: Right. So the other problem beyond that, the biology is complicated, is that there's a lot of good evidence that anything that's an association that's found in nutrition between a level and some sort of health outcome, that those associations are actually more likely due to the underlying condition than they are due to the level of the nutrient.

So let me give you an example. Men with prostate cancer were seen to have low levels of Vitamin E and Selenium. And so a study was done, a proper study over 10 years where people were given Vitamin E, selenium, both, or a placebo, and anyone who received either vitamin E or Selenium had about 18% increased rate of prostate cancer.

So the decreased levels that we're seeing were due to the cancer itself, not a cause of the cancer. And subsequent studies have shown not only that there's a causal relationship between vitamin E, selenium, and prostate cancer, but also cancer recurrence. 

Jonathan Wolf: So you are saying they measured people who had prostate cancer and they discovered that they were low in, you said selenium and vitamin E. 

And they're like, Oh, that looks bad. So what about if we supplement people who don't yet have prostate cancer, and hopefully that will mean they don't get prostate cancer. 

They did a big study where they also compared it with people who didn't get any of these interventions and they got the exact opposite of what they expected, which is, if you took the selenium and the vitamin E, you actually increased your chance of getting prostate cancer.

David Seres: That's precisely correct. And this was a very large study. 

It was, I think, 30,000 men over 10 years. It's called the Ohio Men Study, and up until recently, at least, it was posted on the National Cancer Institute website as a precautionary tale. And there are many more. 

Jonathan Wolf: Help us to understand that because I think a lot of people listening to that will be like, Well, that doesn't sound right, you were low on this thing, and now we're giving people higher amounts. So surely that must stop you getting prostate… 

David Seres: Well, it doesn't work that way because you have to at least conceive of the notion that you got those low levels because of the prostate cancer, not that the low levels caused it. So it could work both ways.

And in this case, it absolutely showed that the low levels did not cause the prostate cancer. 

Jonathan Wolf: So this example might be, we were discussing before that we were both a bit grayer than we were maybe when we were younger. So you might say, Ah, people who are getting grayer hair are getting older. So if we just stop you getting gray hair, you won't age.

But we're both laughing because it's obvious that even if you stopped us getting gray hair, we are going to keep aging. 

David Seres: Well, take it to the extreme. The more times you breathe, the closer you are to dying. Thus, please stop breathing because I'd like you to live for a long time.

And there's so many different examples of this happening in biology and in nutrition specifically.

Jonathan Wolf: And so how does this link back to the claims around vitamins? 

So you're explaining how these vitamin companies take something in a Petri dish and then they make a claim about how it's great to take this vitamin. And I think you were then using, you know, this example with prostate cancer to show how that doesn't work. 

How does that turn out for real, in a claim that I might see in a supplement, you know, at the drug store? 

David Seres: Well, you'll never see that kind of science reflected in those claims because there's no requirement that those claims are any more than suggestive. 

Jonathan Wolf: Are there other ways that the supplement industry might use science in a way that sort of deceives you, versus the reality of what's going on?

David Seres: The advertising often says, ‘supported by dozens of studies’ or ‘has been studied by…’

Unfortunately, one of the only ways to regulate any of this is through legal action in the U.S. and the only way to bring legal action is if there's fraudulent advertising or they break the rules and make claims directly about a disease.

One such example was a memory supplement that was litigated for seven years and finally the company lost their appeal and lost in court, and has changed their advertising.

But they, for the longest time, claimed that the reason that they could say that they helped memory was based on a study that was done.

They did something that was completely improper from a statistical perspective, if you take a large enough data set and analyze it enough times, you'll find something. It's a statistical certainty that you'll find something that is statistically significant but not relevant and not properly statistically significant.

So they took a subgroup of findings in this study that they had done. It was a randomized trial, but the overall outcome, which was based on validated scoring, which only included the whole thing, that it showed nothing. 

But these subgroups that they found, they found after 30 or 40 subgroup analyses, they found two that went in the right direction, which made no sense if you looked at which ones were and were not statistically significant.

But they thought they could then claim that they had good evidence that they improved memory. It was a biological impossibility that this product would work. It was a protein, and proteins don't get out of the intestine intact, and they most certainly don't get into the brain intact.

There are barriers that biology has provided to prevent that from happening. So it really had no chance of working. 

Jonathan Wolf: And David, because that's a really strong story, are we sure that they don't work? You're saying that they said, Hey, we've done this study, we've got these results. We've claimed that this memory pill is going to make your memory pill better.

David Seres: Yes, we're sure. Their study, which was done properly in a large group, and in a validated memory score, failed. And it's only through manipulation of the statistics that they were able to claim any benefit. 

What we really want is a study that gives us information that's actionable, gives us information that talks to us about cause and effect.

So the majority of research that people hear about on the evening news and so forth, is what we call observational. And observational research takes two things to see if they both occur at the same frequency, or a similar frequency in a certain situation. 

So thus, do men with prostate cancer have lower vitamin E levels? Yes, they do. But the problem is, as I've discussed, the cause and effect. In this situation, it's been shown that the low levels are the effect of the underlying condition, not the cause. 

In order to be able to speak to cause and effect, you need to do what's called a randomized trial. A randomized trial, takes a population and randomly assigns them to a treatment or a standard of care or a placebo, which is like a sugar pill. 

If that's the only thing that's different between the two groups to see whether or not that thing works. Now, biology is complicated, I've said this before. 

People are very heterogeneous in their makeup and their genetics and their underlying conditions and their, you know, all of the different things that their environment and their socioeconomic status.

And so in order to sort of smooth that out, instead of having white rats that are all of the same genetic makeup. What we have to do is do large studies in order to drown out the potential confounding variables, such as I've mentioned. 

Jonathan Wolf: And so I'm guessing you're going to tell me that most people selling supplements do not do randomized trials of their supplement before they sell it?

David Seres: That's correct. 

Jonathan Wolf: Is it quite common, nonetheless, to do randomized trials for your supplement? 

David Seres: It’s actually fairly common to find randomized trials done, but usually it's by scientists. It may sometimes be, you know, supported by the industry. 

But the results of most of those studies have failed to show benefit in the general healthy population for any of these supplements.

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Jonathan Wolf: Many supplements now have many different things in them, don't they? They're not just a vitamin, there's lots of different things. 

What's the difference between the randomized trial you're describing and saying, this is based on science and I've got papers against these ingredients? 

Because that sounds good.

David Seres: Well, it does, and that's how it's easily used to sell. But you are corrupting the science to say that.

Because let me explain it a little bit differently. There's a lot of data, and a lot of data is observational and showing these correlations, versus doing good randomized trials which lead to better conclusions around cause and effect.

What's also confusing is that, yes, okay, maybe it is based on science, but at what level is it? Is it science in a Petri dish, or is it real actual science in real people or even in animals, to show the health benefit from giving more of a substance?

Jonathan Wolf: So we talked a lot, I guess, about there being issues around claims, around supplements.

I guess it's also true that one of the reasons that there's mistrust around science is that scientists can also make mistakes, right? And they can change their mind and say that we said something in the past and now we said something now. 

I think that that can cause a lot of loss of trust amongst the public.

David Seres: I'm glad you raised this because it's one of the things that I think we're suffering from as a society to a great extent, to the point where being an expert immediately makes you suspect. 

That people think that you're just in it for the money or you're in cahoots with the drug companies or whatever.

I think we got there by not caring enough about how we messaged our recommendations and the strength of the evidence on which the recommendations are based. 

When I say evidence and when somebody says evidence-based medicine, what they're really saying is that the quality of the data comes from a variety of levels of evidence. 

Where the highest level of evidence is randomized controlled trials, but the lowest evidence of just a case report or two, could influence guidelines on which we base our medical practice or our dietary practices, et cetera.

So, people need to understand these nuances, and we've done a terrible job as science of explaining them, changing major dietary recommendations when we discovered that perhaps they were incorrect and basing them on observational studies, initially, that perhaps didn't really rise to the level of making public health recommendations.

Like, for instance, I think you mentioned earlier the idea that we should completely do away with all the fat in our diet. And while it's not proven, there was certainly a rapid rise in obesity when people started to adopt that kind of a diet. 

I think scientists need to look inward at their responsibility for this. But from the science information consumer's perspective, I could fully understand how somebody would look at us changing our mind about something, or eggs in or out this time.

I mean, if you know anything about the U.S. dietary guidelines, this was a joke for years, that when we change our minds, it suggests we don't know what we're doing. Or because, why I follow guidelines is to live longer, happier, and healthier. And the stakes couldn't be any greater than that. 

You've just told me that what you told me before might have shortened my life or ruined my health. I don't want to listen to you anymore. 

For whatever reason, it's been hard to get the scientific community at large to recognize this and to take part in how we communicate this to the public, so that people understand these nuances.

When we make recommendations, they're the best we've got at the time, and this happened with COVID. People were very angry that the recommendations seemed to be moving.

I think Dr. Fauci did the best he could communicating during COVID as to why the recommendations were changing. 

But that's kind of a new thing, that science has really stood back and said, but we're science, we are credible and you should listen to us. As opposed to explaining, you know, why the recommendations might change.

Jonathan Wolf: And I guess I can see how this is hard to then know how to navigate because you are putting this really important thing about your health and you're asking experts to help to advise you. And then they change their mind. 

And then you see all these supplements which tend today to be promoted by influencers and people that you feel you have this real relationship with great confidence. And I guess you're looking for that reliability. 

Before I switch on to what we should do, I would love to talk about maybe nutrition in this context for a minute. 

You've mentioned before about low-fat. Where were you on low-fat in the past and where are you today? 

David Seres: Well, I was with all of my colleagues and that was the recommendation, when I, early in my career, trying to counsel people on weight loss and so forth. 

That's what we told people to do because that's what we were all led to believe was the evidence. 

Jonathan Wolf: And what is your view on that advice that you gave? 

David Seres: It was bad advice. It was bad advice. In fact, a low fat diet may in some people at least be predisposed to weight gain, so it probably made it harder.

In order to eat a low-fat diet, you've got to eat a relatively high-carb diet. And carbohydrates have an effect on appetite hormones and so forth that we're discovering now. 

Jonathan Wolf: My sort of simple rule after eight years at ZOE is that you recognize a good scientist because they say, Oh, I've changed my mind on things. And they also say, I don't know. 

So, I really like the fact that you're talking about the things you've changed your mind about. 

David Seres: You and I agree on that. 

Jonathan Wolf: Because I think it gives you a lot more confidence about the things that someone says with confidence because they are open to changing their mind.

Now I think we've sort of unpacked both the regulatory environment, which is a sort of free for all. We talked about the science that you'd like to see about, like randomized control trials for that exact product to prove that it works.

But also how the science can get distorted and misled either intentionally, where you're sort of cherry picking this particular paper or something that you did in a Petri dish or even unintentionally.

We've also said like, scientists can also just make mistakes. I'd love to bring this back round to the beginning about pills and supplements. And now say, okay, given all of this, what really should be the advice? 

And I'd love to start with the vitamins and talk about what should we all be taking. 

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David Seres: So what we should be taking is the time to make sure we have a relatively balanced diet. If we have the luxury and the ability to afford it. 

And really, in my not very humble opinion, that is reliably eating food that looks more like it looked when it either was harvested or alive, swimming in the ocean, et cetera. 

So less processed, more sort of healthy and fresh. But that's easier said than done. For people who are unable to access that, to do the best they can with that. 

As far as taking supplements is concerned, unless you have an identified risk or a deficiency that your doctor has recommended that you take a supplement, there is really no benefit to any of these with a couple of minor exceptions.

So, for the general healthy population, the recommendation is don't waste your money, and that what you're doing may in fact have risk that has not been identified, because these have not been studied properly in long-term studies, such as I've mentioned with the vitamin E and selenium. 

Jonathan Wolf: It's a very powerful statement.

I'd love to run through a few specific vitamins so that people I think will say, yeah, but I know I need to take vitamin C, because everyone knows that that's really good for you. 

Come on, David. Surely that's an exception, isn't it? 

David Seres: No. The studies in vitamin C have shown really no salutatory benefit for, again, for healthy people who don't have a deficiency. 

With one minor exception, and that is in performance athletes. A couple of studies have shown that intense skiers and marathon runners had fewer colds if they took vitamin C, which is a thorn in my side. 

But the data is the data, and those were randomized trials. So if you are in one of those groups and want to decrease your frequency of common cold, then perhaps vitamin C is something that you should consider, but at much lower doses than what are usually prescribed. 

Jonathan Wolf: If I'm going to the gym a few times a week, don't I get to count…

David Seres: Nah. 

Jonathan Wolf: No? Okay. So you think really of no benefit. What about Vitamin D? 

David Seres: Oh boy. So vitamin D is a real headache for those of us who want to adhere to science on this. 

The story of vitamin D is actually kind of interesting in that some years ago, a laboratory arbitrarily decided to label a certain range of vitamin D level as insufficient, based on very weak evidence.

But they labeled it insufficient, so now all of a sudden, 50% of the population has vitamin D insufficiency and it created a billions of dollar industry in vitamin D testing.

So that's piece number one.

In the randomized controlled trials of the general population, vitamin D has not shown to have much benefit. There have been some studies in older folks that showed maybe a slight decrease in the incidence of falls, but really not anything that's enough of a bang for your buck that I would recommend taking it.

And of course all of these have the potential for side effects and deleterious effects. 

Jonathan Wolf: So just to confirm, David, you are not taking vitamin D. 

David Seres: I am not taking vitamin D. 

Jonathan Wolf: And you think that at least for the healthy population, again, even if the lab test says that they're insufficient in vitamin D, that you don't need to go and take this?

David Seres: Right, now, this is debated hotly in the very lowest of those levels, as to whether or not this really constitutes a deficiency or not. 

But without really good study, I really can't support that. When it's just a matter of opinion, people like to butt heads; when there's good, strong evidence, there's no fight. 

Jonathan Wolf: Is there any harm from taking mega doses of vitamin D? 

David Seres: Yes. Vitamin D at high doses can be very toxic. There are real, potentially even deadly consequences, 

Jonathan Wolf: So I think, again, particularly for people who might not have heard anyone talking about vitamins on previous podcasts, I think will be really shocked. 

Because I think they're generally presented as something with no downside. Like, Why not take it? It's sort of like insurance. You can't harm yourself after all, they sell it, and it looks just like the things you get as medicines and that's all supposed to be safe. 

So when could it be dangerous?

David Seres: Vitamin D helps regulate your calcium uptake from the intestine and if you save too much calcium, you can put deposits down in different tissues, the kidneys, the coronary arteries, and so forth.

And I should be very careful to say that there are some studies that associate the use of calcium supplementation with an increased incidence of coronary disease. But that's not a randomized trial and it's not a cause-and-effect relationship proven. 

But it worries me enough that without any good proof of benefit and with the potential for harm, this is just one example of how it might be harmful, that I would shy away from taking it. 

Jonathan Wolf: So David, I think you are caring for critically ill patients who are relying on lifesaving nutrition support when you're with patients. Is that right? 

David Seres: That's correct. 

Jonathan Wolf: So in those cases, are there a lot of sort of exceptions to the skepticism that you're talking about? In those cases suddenly, are you giving them all of these different vitamins? 

David Seres: No, no, no. And in that situation, there are many examples of how we've been misled. 

Vitamin D being a big one. Vitamin D is a fat, so it doesn't just float around in the bloodstream. It has to be adhered to a protein. And that protein level drops during illness. 

So the vitamin D level drops during illness. And so of course, because there's an association between vitamin D levels and survival, everybody promoted vitamin D supplementation in the ICU. And when the randomized trials were done, they showed no benefit.

Now, if you go to the search engine that we use to find articles, it's called PubMed, you will find about 400 such studies in critically ill patients, looking at the correlation between vitamin D levels and survival, and then analyses, and summaries and so forth of that phenomenon. There are four or five randomized controlled trials, but those all showed no benefit.

I received a call in April of 2000 when COVID was just starting to take off. I got a call from a journalist and said, Did you see this article? 

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Now, at the time, the big journals had made it possible for you to submit an article and have it be viewed publicly, clearly labeled as not reviewed, but before peer review so that people could get a sense of what was going on,  scientists could get a sense of what was going on and do something about it.

Somebody had done this with an article that correlated historic blood levels of vitamin D with some COVID outcome. I don't remember what it was, whether it was survival or incidents, it doesn't matter. And the authors had concluded that vitamin D might improve COVID.

Well, I explained to the journalist that this was very derivative. It wasn't direct evidence. It was very poor quality evidence, so it really didn't amount to something that was actionable except perhaps to design a study, a proper study. 

He said thank you and wrote a responsible piece on this, but it appeared on the national news two nights later.

I've been tracking this and now we're over 2000 papers discussing the relationship between vitamin D and COVID, and the four or five randomized controlled trials that were done showed no benefit whatsoever. 

So this is the kind of thing that happens even in medicine when we mislead ourselves about vitamins and so forth.

We would love for vitamins to be something that would have a benefit to our patients. Something magical that we hadn't discovered, but that mostly we've failed in that. 

Another example in the critically ill patients was vitamin C. There was a lot of interest in using vitamin C in large doses in very, very critically ill patients based on some observations.

That's how it always starts though. 

I got to stop and say, it always starts with good observations, but the observations are what we call hypothesis-generating. They give us a question that we want to study.

So anyway, vitamin C is associated with outcomes in the seriously critically ill patients, a lot of interest in that. Randomized trials failed to show enough of a benefit and potential harm so that we don't do that.

Jonathan Wolf: I'm a little shocked by all of that, to be honest, because I would've expected that healthy people, able to eat a healthy diet, vitamins don't help. 

But I would've thought people who are really, really sick in intensive care would've been the sorts of group who would benefit from something like this.

Because you know, they're not going to be eating a nice plant-heavy diet and all the rest, mean we all know what hospital food is like. 

So I'm actually really shocked that you're saying even in that extreme a situation where it sounds like there've been a lot of randomized control trials.

There's no benefit?

David Seres: That's correct. 

Jonathan Wolf: So where does that leave us as we go into old age? Because I have also heard people say, Well, you know, the evidence against vitamins is not so strong as we're healthy. 

But you know, in the same way that we believe in certain vitamins when you're pregnant and there's strong evidence, it seems like it makes sense to move to a multivitamin once you're 65 plus or something like that.

And I'm looking at you now thinking that you are going to tell me something really unexpected about this? 

David Seres: Yeah, I, you know, again, there is some suggestive evidence that people who take multivitamins may have a decreased incidence of dementia and some other things, but it's still very weak. 

Given the frequency over my career with which I have been surprised by the harmful effect of something, I really just can't get behind the idea of wholesale supplementation simply because you're over a certain age. 

Jonathan Wolf: And is that because you're cautious that potentially we're taking in these individual chemicals more than we would do through our natural food, and therefore it potentially has a harmful effect, rather than it just being a waste of money?

David Seres: Well, both, and that would be one of many different possible reasons. But as I said, biology's complicated and we don't know until we have really good studies done.

It's never quite made sense to me that people don't think of vitamins taken for health benefit in the same way they would think about medications.

If you're taking them for salutary health benefits, why would you not want to make sure that they'd been properly tested? 

The answer, I think, goes back to people wanting control of their health outcomes, not trusting the experts and so forth. 

And I understand that, but I wish we could get people to think about this in a different way.

Jonathan Wolf: I think also a lot of people listening to this are going to be really surprised that it isn't more tested, that there aren't more like proper randomized controlled trials for each of these things, proving that it works. 

Because they are sold to look like medicines, the marketing around them, let's say, you know, even maybe the influencers behind them. This all feels like they've done some real tests.

I think you're saying there's a mix between they haven't or even where they've been doing these, like some of these vitamins you're talking about, the results have been much less compelling than I would've expected. 

David Seres: Right. I also just want to point out that these studies are expensive to do. To do a 30,000 person, 10-year study cost millions of dollars and you know, the vitamin supplement industry doesn't have, I don't think, the kinds of money that… I don't know, maybe they do, that the drug industry has to support these kinds of studies.

The government has not been forthcoming, the U.S. government in, in supporting these kinds of studies to a large extent. And I think that it's likely that these studies would fail to show benefit enough, that the industry is not that interested in doing them.

I don't know that for sure, but it's just money. It is my supposition. 

Jonathan Wolf: So David, what about probiotics? 

David Seres: Probiotics are bacteria that are given for health benefit. It's a very funny term because most of the probiotics are not normal inhabitants of the intestine, and there've been decades and decades of looking at supplementing these bacteria to look for a health benefit. 

There have been some small ones. There were some studies that said that it might decrease the incidence of ear infections in kids, you know, some such.

But these are essentially yogurt bugs for the most part. There's some yeasts and some others that are not, but they're not normal inhabitants of the intestine, therefore they don't survive much past the stomach.

So to expect a salutatory benefit from any of them seems to me far-fetched. That's changing. There are some bugs that normally inhabit the intestine that people are experimenting with, but that's still in experimental stages. These have been around for 30, 40, 50 years on the market. 

I think your listeners would also be interested in hearing about some of the other terminology around this.

You're hearing a lot these days about prebiotics. A prebiotic is simply something that the bacteria eats, and in most cases it's a fiber that's fermented by the bacteria. 

Now, there are a lot of reasons why that might have a salutary health benefit in that the breakdown products of fiber fermentation, include substances that are food for the colon.

But the idea that giving more of this has a positive benefit has not been proven. And in fact, some of the studies that have been done have been really disappointing.

And they're hard to do because the main thing that we're looking at are things like developing colon cancer.

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But a prebiotic is just a fiber. I will also say that there are many fibers on the market that are fermentation resistant, and that's because they're used for constipation, because they pull water into the intestine. 

You don't want a lot of fermentation if you're giving a lot of fiber because the other byproduct is gas. So, you know, one of the side effects of taking these is a lot of bloating and gas. So with the good comes the bad.

Then the newest and latest, which the term has been around forever. But there are some products that are being sold as synbiotics, SYN-biotics, and syn-, meaning together, just means a prebiotic and a probiotic, putting it together in a pill and given to you.

Jonathan Wolf: So you are, I think it's fair to say, you know, one of the world's top physician nutrition practitioners, right? 

You're combining this together with people who are really sick. So this really matters.

Having sort of laid waste to the supplement landscape, what is the best way to eat for our health?

David Seres: Well, as I said, I think first of all, we're really unsure of our recommendations. 

It's important to understand that because our recommendations are not based on long-term randomized trials, and I don't know that we'll ever get those in actual diet because they're very difficult to do. Imagine being told you have to eat a certain way for a decade. 

It's less impossible than we had thought previously. People are getting much better at behavior change interventions. But suffice it to say that those kinds of studies are extremely difficult to do at best, and so we don't have good randomized trials over long periods of time, yet.

Now, there are some shorter-term randomized trials where, for instance, the experimenter provides the diet. But those are again, expensive and take a long time to really figure it out. 

Then we have to look at the heterogeneity, the differences between people. It may be that you and I would have better health benefits from different diets. That I might be healthier in the long run with a high-fat diet where you might be healthier in the long run with a low fiber diet.

It's the ability to pull apart the biology and understand this in its infancy, the being able to personalize nutrition, which is really being promoted. I don't think it's ready for prime time. 

Jonathan Wolf: And if you were going to give the core tenets, it's only what we have, right? We have to give advice based upon the data that we have.

What would be the key things that you would be advising someone for eating for their health? 

David Seres: So for people who can afford it, a diet that's got a lot of things that look more like what it looked like when it was harvested or when it was on the hoof, the wing, or in the water. 

To avoid the heavily processed foods and really to shift away from meat, and animal products. But I'm not sure that completely doing away with them in the diet is necessarily the right thing to do. 

For instance, speaking of B12, there is no such thing as a vegan B12. It's all from animal sources. 

And the way that they sell vegan B12 is by taking B12 that's from an animal and growing it in a yeast that takes it up, and then now it's yeast B12, but the yeast didn't make it. 

Jonathan Wolf: One thing that comes up a lot on this podcast from other scientists that I haven't heard you mention, is this idea that for most of us in the West, we're actually living with a deficiency of fiber and a deficiency of sort of a diversity of plants.

David Seres: Yes. 

Jonathan Wolf: What's your view on that? 

David Seres: I am of the opinion that it's probably real, based on the evidence that's available. 

I want to make sure that I say this in that way, because it could turn out to be that eating nothing but Fritos is the healthiest diet in the world. But I doubt it.

I'm saying that it is my current opinion that that seems to be the way we're headed. If we were able to, to ever do the kind of study that we'd have to do, there's enough suggestive evidence. 

Again, it's suggestive and smaller studies that have been done that use things that are sort of way points, things that identify risk. 

Those studies are suggestive enough for me to get behind this enough to say that if you want recommendations from me, I don't know what I'm talking about. Science doesn't really know what it's talking about, but as best we can tell, this is probably the way to go. 

Jonathan Wolf: And you say that with that note of caution because you feel that unless you've been able to do this randomized control trial, so you've randomly associated people between eating beef burgers and bacon on one side and plants and olive oil on the other hand. 

You haven't got this highest level of test, and so you feel that you can't have that level of conviction you'd like to have about this choice.

David Seres: That's well said. Yeah. I don't have the conviction because of the lack of good evidence. 

Jonathan Wolf: So, final question, David. 

If you were going to say one thing to people listening to say, this is what I would suggest you do tomorrow, what would it be? 

David Seres: It would be look at your diet and don't go to the vitamin store.

Jonathan Wolf: Brilliant. Thank you very much.

I'd like to do a quick summary of what we've covered and I mean, the thing that really sticks in my mind is that there is no benefit from vitamins, even from people who are so sick they're in intensive care and they're hooked up to things and they're definitely not able to eat a healthy diet.

I'm shocked by that because I’m sort of like, well, surely they would be benefiting from vitamins. 

David Seres: Well, in truth, most of them, at least, there's an attempt to feed them with food, you know, with a tube with a product that has vitamins and minerals in it, but to varying success depending on how sick they are.

Jonathan Wolf: It's quite striking to me. 

And then you said more broadly that we've ended up in a situation particularly bad here in the U.S. But you know, it's replicated, I think, around the world where the level of regulation around supplements is very low. 

They're able to make a lot of scientific claims, but ones that you wouldn't be able to make with medicines. Most of the time they haven't run some sort of randomized control trial on their product, which you've said over and over again is the high bar of whether or not to really believe in a result. 

David Seres: Correct. 

Jonathan Wolf: Instead, they've done some amazing jobs about running advertising campaigns, either to allow regulation in the first place in the U.S. or just to support their products, and to convince us based upon often much looser claims that this works.

Then I think we talked about some specific vitamins. Because I was like, sure, sure, sure, but come on, vitamin C. And you were like, No, unless you're a downhill skier or run marathons. 

And for vitamin D, much to my surprise, you said again, there's a story about a lab creating a range that says half of the population in the U.S. was deficient and that wasn't based on any real science and that they've now done all of these follow-up studies.

Again, you can have much lower levels of vitamin D and it didn't matter. And they looked at this vitamin D supplementation. And again, you've said in the vast majority of cases, it doesn't seem to have had an impact. 

So for you, don't take vitamin D. And actually, if you take super doses of it, you said you could actually be risky. 

David Seres: Well, don't take it unless you've discussed that with a doctor. There are guidelines as to the levels and the risk factors associated with low vitamin D levels so that population has been sort of addressed in medical guidelines.

Jonathan Wolf: So make sure that you follow what your doctor says. 

As I went through, you know, asking you about this, you're like, Well, what about when you're older? And you're like, No. 

Also, you don't really see the evidence. So I think what's amazing is with all of this research you've done, you sort of come out very skeptical about these traditional vitamins.

I think what you've also said is, the current generation of probiotics that are out there are really based upon things that you could happen to grow easily rather than anything that lives inside your gut. 

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So fundamentally, you need to think about the food that you're eating and how do you get, you know, the right sort of food which you describe as, you know, avoiding processed food, getting things much closer to to whole food and plants, the sort of things that come up everywhere.

But finished, I think with a really interesting challenge, which is, you know, you've changed your mind repeatedly you feel like you've made advice like low fat in the past that now you know is wrong. 

And it makes you personally feel much more cautious about giving really strong advice because you recognize that you can't do those sorts of randomized controlled trials on an entire diet. 

So ultimately, it's always going to be this sort of blend of data.

David, it was such a pleasure. 

David Seres: A pleasure for me too. I really enjoyed it.