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

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 chocolate-related health claims and how many people were studied, who funded the work and your own potential “cognitive bias”. 

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 can be far more problematic. It is often really hard to separate “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).


Throughout history, chocolate has been the subject of truly 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 that chocolate is somehow healthy can be sourced from 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 their habits into “normal” chocolate consumption as the Kuna were drinking gallons (over 5 large cups or almost 2 liters a day) of this beverage – which 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. To journalists the headlines from these studies are like catnip; after all, chocolate health studies make for great “click bait”.


It’s fun (and also a little worrying) pulling highlights from the chocolate-as-cure-all discourse. For those who want to read more, The Economics of Chocolate (ed. Mara P. Squicciarini and Johan Swinnen 2019), has a whole chapter entitled ‘Nutritional and Health Effects of Chocolate’ which collates various studies. Here are a dozen (the book has even more … but these provide a reasonable overview of the breadth of topics covered): 

  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 (at 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…)

It looks like 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, cure your depression, think better or want to fall in love someone has done a study where the solution is “EAT MORE CHOCOLATE”.

Some scientific studies really are too good to be true.

So, to help you separate fact from (fantasy) fiction, here are some of Tim’s tips on seeing through the jargon:

  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, I could rarely 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.   

As ever, thanks for your support

Spencer, Simon, Lizzie and Harmony

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

  1. Would like to hear a clear description of the line between Raw Cacao/Cacao vs processed Cocoa or chocolate. The Cadmium levels advertised on brands which can be reviewed online through independent labs. Cacao powder vs Cocoa powder, Cacao Nibs vs Cocoa chocolate chips.

    The actual Cacao drink of the indigenous peoples of SA and it’s history to compliment your articles
    would be nice.

    Good articles but would like to see more technical descriptions.

    1. Thanks for your thoughtful comments. Please see below for some suggestions on further reading and some first pass answers

      i) For more on raw chocolate, please see some of our blog posts —
      ii) Cadmium is an important topic, and look for a blog post soon. But please note that ALL the chocolate bars we import are tested for their cadmium levels, generally at country of origin (and note: Cadmium is primarily an issue in South America, not e.g., Madagascar, West Africa, Asia etc.) One quick aside: cocoapowder, because if contains (roughly) half the cocoa butter of “chocolate”, has higher cadmium levels.
      iii) We’ll also look at writing an article on how the Aztecs, Olmecs etc. drank chocolate — we’ve a little information here
      iv) if you want some “technical” debunking, again we’ve more in chocopedia — e.g., look at
      Thanks again

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