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the fitness skeptic is a blog that takes a critical look at the health and fitness industry.

in it I'll examine the claims, products, practises and commonly held beliefs and SCRUTINISE the evidence.

My aim is to separate what is true from what is not and encourage fitness consumers and fitness professionals to become skeptics. 

I’ll take no prisoners when it comes to criticising the scam artist or highlightling the bogus but I’ll also give credit where credit is due.

Welcome to the fitness skeptic

Could Dark Chocolate Improve Performance?

The idea that chocolate could be an ergogenic aid is like music to my ears. Not because I'm interested in the science, which I am, but because I love chocolate, particularly the dark variety and an excuse to eat more would be awesome.

But before we get too exited about the idea of stuffing our faces with chocolate to improve our performance, we better check what the evidence is for the claim. 

Why on earth would chocolate be an ergogenic aid?

Dark chocolate is abundant in substances called flavanols which are phytochemical (plant based) compounds also found in tea, apples, grapes, cherries, broad beans, broccoli to name but a few.  One such flavanol, epicatechin, has been shown to increase the amount and availability of nitric oxide (not to be confused with the anaesthetic and sometimes recreational drug nitrous oxide) in the body. Other foods specifically rich in nitrates have previously been studied and shown to have ergogenic effects. So the question is can dark chocolate elicit the same responses.

Previous studies have shown that dark chocolate has beneficial cardiovascular effects when taken by hypertensive patients. The mechanisms for this are related to the influence nitric oxide has on vasodilation (dilation of blood vessels) and the positive effects this has on blood pressure.

However not much research had been done on the benefits of dark chocolate during exercise and none had been done specifically looking at the potential ergogenic effects.

Enter Rishikesh Kankesh Patel from Kingston University London.

Using 9 moderately trained men, (not the largest of test groups) Mr Patel (soon to be Dr Patel I should think) examined the effects of dark chocolate on a number of important indices for exercise performance, namely; VO2 max (the maximum rate of oxygen usage during exercise), Gas Exchange Threshold (a little complicated to explain this one but take it from me it's important during exercise!), blood pressure, oxygen cost (how much oxygen was used) and blood lactate (a measure of lactic acid production in the muscles).

The subjects diets were controlled over the period of the experiment to ensure no other nitrate rich foods were consumed and the participants were blinded with regards the aims of the study. (All good in the experimental design stakes). Following the measurement of base levels, the subjects were randomly assigned either dark chocolate or a white chocolate control at a given amount (40g a day) for 14 days. Measurements were then taken again after which the subjects switched to the other type of chocolate. Following this a further set of measurements were taken.


Let's break them down.:

VO2 Max - (Measured using an incremental cycle ergometer test)

Dark Chocolate -VO2 was 6% higher compared with base line after dark chocolate consumption. Unfortunately this wasn't statistically significant essentially meaning the differences could have been down to chance :-( 

White chocolate control- No difference compared with base line

Oxygen cost - (Measured during a 20 minute steady state cycle ergometer test)

No differences between dark and white chocolate results as compared to the base line measures.

Blood Pressure -

No statistically significant differences shown in exercising BP between dark and white chocolate as compared to base line.

Blood Lactate -

No statistically significant differences shown between dark and white chocolate as compared to base line.

Gas Exchange Threshold- (Taken from the VO2 data)

A 21% increase from the base line was shown after dark chocolate consumption whereas there was no increase after the white chocolate consumption.  

So as you can see the results are a little mixed but the VO2 and gas exchange measurements are interesting. The increases shown here after dark chocolate consumption could really be beneficial to performance and this was supported during a distance time trial test the subjects under took.

Distance Time Trial Results - (2 minute all out effort)

After dark chocolate consumption, the participants showed an 17% increase in distance covered compared to base line and a 13% increase as compared to white chocolate consumption. Both of which were statistically significant.

So what does all this mean?

Well if you've made it this far and you were hoping I'd say that you should immediately go out and buy a lifetimes supply of dark chocolate you're going to be disappointed.

The fact that the study only had a small number of participants and the equivocal results mean we cant be sure about the potential ergogenic effects of dark chocolate. The bottom line is that although there could possibly be an ergogenic effect, we'll need to wait until further studies are done before us chocolate lovers have a valid excuse to eat more. Furthermore there a number of other questions that need answering. For example, what type of dark chocolate is best?  I am assuming different brands made from different cocoa beans have differing flavanol levels? Also, how much would be the optimum dose? And if I already have a diet high in nitrate rich foods would dark chocolate still be beneficial?

Finally, remember we're looking at dark chocolate here. Milk chocolate simply doesn't contain enough flavanols so eating a shed load of dairy milk is never going to be beneficial!  

Fitness Skeptic Score

Dark chocolate as an ergogenic aid gets an FSS of:

Hoping one day for a 10!!


Dark chocolate supplementation reduces the oxygen cost of moderate intensity cycling. THE JOURNAL OF THE INTERNATIONAL SOCIETY OF SPORTS NUTRITION. Dec 2015.

Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. JOURNAL OF APPLIED PHYSIOLOGY, 1 March 2011 Vol. 110 no. 3, 591-600

Improvement of Endothelial Function With Dietary Flavanols Is Associated With Mobilization of Circulating Angiogenic Cells in Patients With Coronary Artery Disease. JOURNAL OF THE AMERICAN COLLEGE OF CARIOLOGY, 13 July 2010.



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