5 fascinating studies: Chocolate, napping, and more

At ZOE, we love following scientific advances. And we know many of you do, too. But with hundreds of papers appearing each week, how can you keep up?

The ZOE Nutrition Research Roundup is a good place to start. Each article covers five recent studies that have caught our eye.

We’ll explain what the researchers found and what the results mean for your health. 

Today, our studies investigate whether chocolate can relieve period pain, if an afternoon nap boosts performance, and much more.

So, let’s get started.

1. Can nuts reduce frailty in older adults?

Nuts and seeds are a great source of protein, fiber, healthy fats, and other nutrients. They’re a welcome addition to anyone’s diet

Eating nuts may be linked to better heart health and metabolic health. But can adding them to your diet help reduce the risk of growing frail as you age? 

A new study asks this very question.

What did they do?

The scientists accessed data from 10,033 people in the United States aged 60 or older. This included information about what they ate and how frail they were.

What did they find?

Following the analysis, the scientists concluded that some participants who ate nuts and seeds had a lower risk of frailty than some who didn’t.

The team didn’t see this effect in Black participants or those with high levels of blood fat.

For others, the risk of frailty decreased the more nuts and seeds they ate, up to 1.02 ounces (29 grams) a day. To put that in perspective, 1 oz is around 32 peanuts or 22 cashews — about a handful.

For the participants who ate more than this every day, the risk didn’t seem to be further reduced.

What should you do?

Researchers will need to confirm these results with more studies. But if you’re not already eating nuts and seeds, they’re likely to benefit your overall health. 

Nuts and seeds can be a simple, tasty addition to:

  • salads

  • baked goods

  • pasta dishes

  • curries

  • yogurt

They also make a good snack on their own.

2. Soy may reduce signs of skin aging

Soy is a good source of protein, and it also contains isoflavones, a type of polyphenol that may support good health.

A recent study investigates whether soy protein isoflavones might also reduce the signs of skin aging.

What did they do?

The scientists recruited 44 postmenopausal women. Each received supplements containing either:

  1. soy protein with added isoflavones

  2. casein — a milk protein that doesn’t contain isoflavones

The team assessed wrinkle “severity” and skin discoloration at the start of the study, then after 8, 16, and 24 weeks.

They also measured the hydration of the participants’ skin and how much natural oil it produced.

What did they find?

At the end of the study, those taking the soy protein had significantly improved wrinkles and less skin discoloration.

However, there were no significant skin changes in the casein group.

In the soy group, participants’ skin was more hydrated at the end of the study, compared with the start. There were no differences in oil production.

These results seem pretty hopeful, but keep in mind that the study: 

  • was small

  • ran for just 6 months

  • only included people with light-colored skin 

  • only included postmenopausal women

Plus, it was funded by the United Soybean Board and the Soy Nutrition Institute Global, both of which are, unsurprisingly, pro-soy. 

This doesn’t discount the results, but it’s worth noting.

What should you do?

Soy is a healthy addition to your diet, so feel free to add it to your meals. And it might even slow signs of skin aging.

In general, ZOE recommends getting nutrients from food, not supplements. This way, get more of the benefits from the plant. 

However, this study didn’t investigate whether adding soy to your diet would benefit your skin in the same way.

If you’d like to learn more, we have a podcast episode on science-backed ways to look after your skin as you age

3. Does an afternoon nap boost performance?

After lunch, many of us feel a slump, especially if we haven’t been getting the sleep we need. In these situations, a nap can seem like a great idea.

A new study asks whether a quick afternoon snooze might improve your physical and mental performance. 

What did they do?

The researchers recruited 15 men who regularly did resistance training. On two nights, they were only allowed to sleep for 4 hours a night. 

On the third day, the participants either took a 60-minute post-lunch nap, a 30-minute nap, or no nap.

Each participant took physical and cognitive ability tests before and after the sleep-deprived nights. 

What did they find?

Napping didn’t affect physical performance, but it did improve mood and cognitive function. It also reduced tiredness. 

So, if you’ve missed some sleep, perhaps a quick nap is a good idea.

However, the study had limitations:

  • There was no control group.

  • It didn’t measure the quality of sleep during the nap.

  • It was small.

  • It only included healthy, physically active men.

What should you do?

At ZOE, we know that sleep is crucial for your overall health and well-being. For instance, a poor night’s sleep can interfere with how your body responds to sugar the next day.

So, whenever possible, try to get 7–8 hours of sleep. That way, you won’t need a nap.

In the real world, this isn’t always possible. So, perhaps a tactical nap might help.

Listen to your body and see how you respond. Everyone’s different, after all.

4. Can probiotics ease IBS?

Symptoms of irritable bowel syndrome (IBS) include cramps, bloating, diarrhea, and constipation. 

It’s a common condition, affecting around 1 in 10 people worldwide, but because scientists still don’t fully understand IBS, current treatments don’t always work well.

Some experts think probiotics might help. But so far, studies haven’t shown a clear benefit. 

These studies have generally been small. And they’ve tended to focus on different types of probiotics, making it hard to compare results.

So, a recent study set out to take a fresh look at links between probiotics and IBS relief.

What did they do?

The scientists reanalyzed data from 82 trials, including 10,332 participants total. 

What did they find?

Overall, the scientists found “moderate evidence” that some probiotics can reduce symptoms of IBS, compared with a placebo. The symptoms included abdominal pain, bloating, and distension.

However, the analysis had limitations:

  • Only 24 of the 82 trials had a low overall risk of bias.

  • The studies had tested various strains and combinations, making it hard to compare results.

  • Many of the studies were quite short, and IBS symptoms sometimes fluctuate.

What should you do?

If you have IBS, watch this space. While the evidence is patchy, it seems that at least some people benefit from certain strains or combinations of strains.

Because everyone’s gut microbiome is different, it’s likely that different probiotics have different effects on different people. 

5. Chocolate and period pain

Primary dysmenorrhea — cramping just before a period — affects 45–95% of women of reproductive age.

Studies have shown that ibuprofen can help, but is there a more delicious way to feel better? Maybe.

A recent study asks whether dark chocolate can help reduce the pain.

What did they do?

The researchers recruited 45 participants. Each received 330 milliliters of green coconut water, 35 g of 70% dark chocolate, or 400 milligrams of ibuprofen.

What did they find?

The team found that ibuprofen was best at reducing menstrual pain. The drug and dark chocolate both relieved symptoms more than coconut water. 

And ibuprofen only performed a little better than dark chocolate. The difference was small enough that it wasn’t statistically significant.

What should you do?

This study confirms that ibuprofen can help reduce discomfort from primary dysmenorrhea. 

If you don’t have any handy, dark chocolate might do the trick, too. 

Before we get too excited, this was a small study that didn’t have a control group, so the results aren’t set in stone. Researchers need to carry out similar studies in larger groups.

However, minimally processed dark chocolate that’s at least 70% cocoa is a healthy snack in moderation. So, even if you’re just feeling the urge for something sweet, go for it.

With that, we reach the end of this edition of ZOE Nutrition Research Roundup. Join us next time, when we’ll jump into more fascinating, diet-based science.


Association between nut consumption and frailty in the elderly: A large sample cross-sectional study. JHND. (2023). https://onlinelibrary.wiley.com/doi/full/10.1111/jhn.13208 

Efficacy and safety of over-the-counter analgesics for primary dysmenorrhea. Medicine. (2020). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7220209/ 

Efficacy of probiotics in irritable bowel syndrome: Systematic review and meta-analysis. Gastroenterology. (2023). https://www.sciencedirect.com/science/article/pii/S0016508523048382 

Is implementing a post-lunch nap beneficial on evening performance, following two nights partial sleep restriction? Chronobiology International. (2023). https://www.tandfonline.com/doi/full/10.1080/07420528.2023.2253908 

Metabolic syndrome features and excess weight were inversely associated with nut consumption after 1-year follow-up in the PREDIMED-Plus study. The Journal of Nutrition. (2020). https://pubmed.ncbi.nlm.nih.gov/33300039/ 

Nut consumption in relation to cardiovascular disease incidence and mortality among patients with diabetes mellitus. Circulation Research. (2019). https://pubmed.ncbi.nlm.nih.gov/30776978/ 

Primary dysmenorrhea: Pathophysiology, diagnosis, and treatment updates. Korean Journal of Family Medicine. (2022). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8943241/ 

Single-blind randomized controlled trial: Comparative efficacy of dark chocolate, coconut water, and ibuprofen in managing primary dysmenorrhea. Environmental Research and Public Health. (2023). https://www.mdpi.com/1660-4601/20/16/6619 

Soy protein containing isoflavones improves facial signs of photoaging and skin hydration in postmenopausal women: Results of a prospective randomized double-blind controlled trial. Nutrients. (2023). https://www.mdpi.com/2072-6643/15/19/4113 

The epidemiology of irritable bowel syndrome. Clinical Epidemiology. (2014). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3921083/