Too good to be true … how to read the small print of chocolate and health studies with Dr Tim Spector

By Cocoa Runners  ·  20th September 2020  ·  Tastings, The Science of Chocolate

One of our mantras at Cocoa Runners is that “Craft Chocolate tastes better, is better for farmers, better for the planet and also better for you”.

  • It is pretty easy to “show” people that Craft Chocolate tastes better.  They just need to try some
  • There are also LOTS of studies showing how direct, transparent trade leads to far higher incomes for cocoa farmers (see the Transparency Reports from Kokoa Kamili, Raaka, Omnom, etc).  Similarly Original Beans do a great job of explaining how heirloom cacao is a fantastic crop to encourage local communities to preserve the rainforest (indeed for every bar they sell they plant a tree in the rainforest)
  • However the studies around health and chocolate are far more “problematic”. It can be really hard to sort out “the wheat from the chaff” of the various claims made for chocolate.

This is one reason why we are delighted to be hosting a “Craft Chocolate Conversation” with Dr Tim Spector about his latest book, “Spoon-Fed: Why almost everything we’ve been told about food is wrong”. 

Tim is Professor of Genetic Epidemiology at King’s College, a craft chocolate aficionado, and one of the driving forces behind the crowdsourced Covid-19 app (the one that works). And his latest book is a passionate paean to the dangers and risks of “miracle cures” and hyped scientific claims for all foods.  At the same time Tim has also spent the last 30+ years researching the microbiome (our gut) and he talks a tonne of sense about how different people respond to different foods (including chocolate)

The tasting is next Thursday, 24th September, at 8-00pm.  It’s free to register on Zoom; we are also going to try to record a version of the conversation for anyone who can’t make it.  And you can buy a copy of Tim’s book, along with the ten chocolates we will be discussing and tasting, too (see here and below)

As a warm up, this week’s blog post is a light hearted, sceptical review of some of the scientific claims about chocolate.  Plus we have some advice on how to “review” these claims.  Similar to the way we encourage you to check the ingredients on a chocolate bar’s label for its ingredients, and the details of the farm where the beans are sourced, we STRONGLY suggest you review  and how many people were studied, who funded the work and your own potential “cognitive bias”.  Read on  — and then please apply Tim’s below “debunking” advise


Throughout history, chocolate has been the subject of wonderful and miraculous claims.  Both the Aztecs and Marquis de Sade were convinced of its properties as an aphrodisiac.  Earnest debates were held on its “humorous” properties by alchemists, doctors, barbers and quacks during the 17th and 18th centuries.  And two of the first three US presidents (John Adams and Thomas Jefferson) were keen that chocolate become the preferred drink in the US given it’s “nutritional benefits” (and that it didn’t come from Great Britain).

Arguably the modern fad for claiming health benefits for chocolate was a series of studies of the Kuna in the late 20th Century, which highlighted their low rate of heart attacks and coronary problems. These health benefits were attributed to their predilection for a unique drinking chocolate recipe that is very high in flavonols (as well as eating lots of fish).  There may well be something in this.  But it’s hard to translate into “normal” chocolate consumption as the Kuna were drinking gallons (over 5 large cups or almost 2 liters a day) of this beverage; and it is crafted and fermented very differently to any normal chocolate bar.

But the genie was out of the bottle. The power of associating health benefits with chocolate was immediate.  Loads more studies were launched all over the world.  And to journalists the headlines from these studies are like catnip.  Chocolate health studies make great “click bait”.


It’s fun (and also a little worrying) pulling highlights out of these studies.  For those who want to read more, “The Economics of Chocolate” (Oxford University Press published in 2016, and republished in 2019), has a whole chapter titled Nutritional and Health Effects of Chocolate of various studies. Here are a dozen (and we’ve more on the blog) claims: 

  1. “..  an average consumption of 10g/ day of chocolate induced positive effects on cognitive performance, with maximum benefit depending on the variety of chocolate consumed (flavonoids-rich type) (Nurk et al 2009)”
  2. “… a habitual chocolate consumption of 10g of dark chocolate per day (corresponding to 4.2g of cocoa) was associated with lower systolic blood pressure compared to no, or very low, cocoa intake” (Buijsse et al 2006)
  3.  “… Almoosawi and colleagues (2012) found that 20g per day of dark chocolate improved cardiovascular risk factors in health, overweight and obese subjects”
  4. “Research conducted in the Netherlands on young healthy women explored the relationship between appetites and levels of gastrointestinal hormones … results showed that smelling and eating 30g chocolate induced appetite suppression and were inversely correlated with levels of ghrelin, a hormone which stimulates appetite (Massolt, 2010)”
  5. 21 healthy men aged 25-30, were given dark or white chocolate for 28 days.  They were given 25g three times a day ((4,6 and 8pm).  And those who were given dark chocolate saw a “decrease in blood sugar” (Rusconi, 2012)
  6. 15 women, aged 20-40 years, were given 100g of 70% dark chocolate (Di Renzo) in two 50g portions in morning and evening. “After chocolate consumption, a significant increase in HDL cholesterol level and a significant decrease of total cholesterol/ HDL cholesterol ratio were observed and.  In addition “a reduction in abdomen circumference” was noted.
  7. Hermann and colleagues (2006) suggest that “70% dark chocolate improves vasodilation by 80% in young healthy smokers starting from two hours after chocolate ingestion and lasting for up to 8 hours”
  8. “… people with an average age of 57 years who’d been eating chocolate five times a week for the last few years, and run 3-4 times a week, have a lower BMI that those who eat chocolate less often” (Golomb and colleagues)
  9. In a study by Parker and Crawford in 2007 3000 people who described themselves as being depressed, 45% craved chocolate. “Chocolate is high in branch-train amino acids, and especially in tryptophan, which increases the blood level of serotonin, the neurotransmitter producing calming and pleasurable feelings”.
  10. “Chocolate was found to coat the teeth, thereby preventing tooth decay… Tannins in cocoa were found to promote healthy teeth as they inhibited the formation of dental plaque (Matsumoto, 2004)
  11.  “A double blind study of 30 healthy subjects divided into two groups one consuming a 20g per day of high flavonol level chocolate and one consuming a conventional dark chocolate …. confirmed that a regular consumption of rich-in-polyphenols chocolate confers significant photoprotection and can be effective at protecting human skin from harmful UV effects (Williams et al 2009)
  12. “Chocolate is rich in theobromine (an alkaloid stimulant that acts on the body in ways similar to caffeine) and other compounds similar to caffeine) and other compounds similar to the cannabinoids, that act on the central nervous system, producing euphoric, aphrodisiac and stimulating effect (Di Tomaso et al 1996).  It also contains phenylethylamine, a molecule  released during intimacy, when people are infatuated or fall in love, and it further promotes the release of serotonin … producing some aphrodisiac and mood lifting effects (no study quoted for this one, and to be fair the authors say more work is needed on this one …)

So if you smoke or are healthy, if you are male or female, looking to lower blood sugar, reduce the size of your “abdomen circumference”, end your cravings, stop being depressed, think better or want to fall in love more someone has done a study where the solution is “EAT MORE CHOCOLATE”.  If you are starting to scratch your head, we do too.  

Some scientific studies really are too good to be true.

And this is one of the areas that we will discuss with Tim.  He can explain far more what is going on here.  But in advance a couple of points on the importance of “reading the small print”

  1. Just as we encourage you to check the ingredients in your bar of chocolate, check how many people the study has involved.  In the above, only in a few cases could I find the number of people “studied”.  
  2. Similarly, just as you want to know the farm/estate/co-operative where the beans in your bar are from, when checking a study it’s worth trying to find out who has paid for the research.  Vox did some research in 2017 of 100+ studies carried out on chocolate by Mars and found “they overwhelmingly drew glowing conclusions about cocoa and chocolate — promoting everything from chocolate’s heart health benefits to cocoa’s ability to fight disease”.  Similarly when we dug into the health benefit claims for Coconut Sugar we discovered that the “proof” that Coconut sugar generates lower GI spikes was based on a study of 11 people financed by the Philippine Coconut Marketing Agency.  Hmmm
  3. Beware of what is variously described as “cognitive bias”, “motivated reasoning” or “wishful thinking”. Psychologists warn us to beware that we all are more likely to notice what we want to notice. And this is very true when we see “justifications” for savouring our favourite craft chocolate bars.   

For more debunking, please do join our Craft Chocolate Conversation with Tim Spector.  We’ll also discuss his work on the microbiome and discuss the ten different craft chocolates he has selected.  Register (for free) for the zoom call here, and you can purchase his book and tasting kit here (more details are below) 

As ever, thanks for your support

Spencer, Simon, Lizzie and Harmony

P.S. If you missed last Sunday Brunch, tune in again here and see below for the bars that were savoured by Tim, Simon and their guests Elizabeth Tan and Jeremy Vine