Can Chocolate Improve Endurance Sports Performance?

It's the Easter long weekend and what better time to talk about chocolate and sports performance.

But before we dive into the topic, let me introduce myself. My name is Taryn, and I am an Advanced Sports Dietitian with a passion for endurance sports. I have been helping athletes of all levels achieve their nutrition goals for over a decade now. If you're interested in improving your triathlon nutrition, I invite you to grab my Triathlon Nutrition Checklist, which is available for free at dietitianapproved.com/checklist. It's a 50-step checklist that covers everything from pre-workout meals to post-race recovery.

Now, let's talk about chocolate. I know it's not something you would typically associate with triathlon nutrition, but hear me out. In 2015, a paper was published exploring the idea of chocolate and performance, and I think it's worth discussing again. While chocolate is high in calories and sugar, dark chocolate, in particular, contains a number of beneficial compounds that may have a positive effect on exercise performance.

One of the primary compounds found in chocolate is cocoa. And cocoa is rich in a group of compounds called flavanols, which have been shown to have a number of potential health benefits. Flavanols can improve blood flow, which in turn improves cardiovascular function. They are rich in antioxidants, which help to reduce inflammation after exercise. They can also help improve insulin sensitivity and cognitive function.

Now, it's worth noting that while cocoa is rich in flavanols, fruits and vegetables also contain them. So, I'm not suggesting you eat chocolate to get flavanols. But there have been several studies investigating the effects of chocolate consumption on performance.

The study that I want to discuss today was published in the Journal of the International Society of Sports Nutrition in 2015. The researchers found that consuming dark chocolate for 14 days improved cyclists' performance time trial. The study involved nine moderately trained cyclists who were put through their paces in the lab. Their baseline VO2 max was measured before completing a 20-minute ride at 80% of their gas exchange threshold followed by a two-minute all-out time trial.

In a crossover design, they then consumed 40 grams of either flavanol-rich dark chocolate or flavanol-deficient white chocolate for two weeks before repeating the exercise testing again. After a seven-day washout period, they crossed over to the other arm and repeated 14 days of the chocolate supplementation.

The researchers found that dark chocolate consumption resulted in a 17% increase in the distance covered in that two-minute time trial compared to the baseline, which was about 300 metres. There was also a 13% increase compared to the white chocolate trial of about 200 metres difference. The dark chocolate supplementation also increased their gas exchange threshold by 21% from baseline and was 11% higher compared to white chocolate. There was no difference between the groups in the 20-minute moderate-intensity cycle.

So, it seems that the flavanols found in dark chocolate act in a similar way to beetroot juice but through different mechanisms. Beetroot juice is high in nitrates, which convert to nitric oxide in the body and help to reduce the oxygen cost of exercise when it's submaximal. The flavanols found in dark chocolate appear to increase nitric oxide bioavailability.

Now, let's put our critical thinking hats on for a minute. When reading a study like this, there are a few things to consider. 

• Firstly, you can't effectively blind the cyclists to what arm of the research they're in. Obviously, they're going to be able to tell if they're being supplemented with white chocolate versus dark chocolate. So, there may be a placebo effect if they believed dark chocolate would be of benefit.
• The cyclists were regular punters, within a healthy weight range (just) BMI 23.75-24.55kg/m2, but were far from elite athletes with VO2 max values of 41.90 +/- 5.4ml/kg/min. (A typical cyclist's VO2 max would roughly sit around 80-90ml/kg/min; so double this).
• The study had a very small sample size of only 9 cyclists. So it’s hard to draw firm conclusions.
• The Participants' diet was only controlled in the 24hrs preceding exercise testing. There are many confounding food choices that could have affected the results such as nitrate concentration or carbohydrate quality of the diet.
• Dark chocolate contains a small amount of caffeine – caffeine is well established as a performance-enhancing supplement and may in part be responsible for the observed performances.
• The flavanol concentration of the chocolates was never specifically tested so conclusions cannot be based on the flavanol explicitly.

So where to from here?

The study, while only small, certainly shows some merit and warrants further research in the area. At the end of the day, what harm can come from consuming 40g of dark chocolate each day right?

It is worth noting that chocolate is high in calories and sugar. Minimal nutritional value – so I'm not suggesting you start adding it to your triathlon performance meal plan.

To prevent unwanted weight gain, stick to no more than 40g/day (2-3 squares). Not all chocolate is created equal – have a look at the packet next time you buy and choose chocolate with at least 70% cocoa solids to ensure you’re getting the highest concentration of flavanols.

Move over coconut oil, beetroot dark chocolate will be the next big thing – you heard it here first 🙂 If anyone creates such a product, I claim royalties!

Reference:

Patel, R. K., Brouner, J. & Spendiff, O. 2015. Dark chocolate supplementation reduces the oxygen cost of moderate-intensity cycling. Journal of the International Society of Sports Nutrition, 12, 1-8.

To dive deeper, listen to the Triathlon Nutrition Academy Podcast, EP 88 - Can Chocolate Improve Endurance Sports Performance?  

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