The evidence that chocolate and other cocoa-containing products reduce high blood pressure is not strong enough to warrant an official health claim, a team of Canadian researchers has found.
In recent years several studies have concluded that compounds found in cocoa, called flavanols, work to lower blood pressure. This has led to many popular online and print publications claiming that chocolate and similar products can be regarded as valuable therapeutics.
Typical is the website medicinehunter.com, which calls cocoa “a titan of health benefits”, stating that “even small amounts of cocoa can reduce cholesterol in the blood, and can lower blood pressure”.
Under current guidelines, about 50% of the population of the US is classified as having hypertension, so, clearly, any move to recognise cocoa and chocolate as a beneficial treatment represents a staggeringly large business opportunity.
Research has shown that flavanols – phytochemicals comprising epicatechin, catechin and procyandins – can reduce blood pressure by increasing levels of nitric oxide. However, critical issues such as dosage and long-term effects remain uncertain, matters complicated by wildly divergent experimental protocols and, in some cases, the involvement of vested interests in funding research.
In 2017 the research organisation Cochrane conducted a meta-analysis of 40 pilot treatments and found that overall they revealed “a small but statistically significant lowering of blood pressure”.
However, the researchers added that the evidence was only of “moderate quality”, and was entirely absent in some crucial aspects.
“We were unable to identify any randomised controlled trials that tested the effect of long-term daily use of cocoa products on blood pressure, and there were no trials that measured the health consequences of high blood pressure, such as heart attacks or strokes,” they wrote.
Now, writing in the journal Trends in Food Science and Technology, Canadian scientists led by Yidi Wang from the University of Manitoba, conclude the evidence is substantially weaker than previously thought.
Wang and colleagues reviewed 17 studies from the past 20 years that investigated the relationship between cocoa flavanols and blood pressure. Only nine of the papers reported that blood pressure was lowered.
“This indicated the evidence of cocoa flavanols on BP reduction was conflicting,” they write.
The researchers thus concluded that the data upon which any formal health claim must rest is “inconsistent”, and noted the “lack of high quality studies” in the field.
There is, they note, no evidence to push for regulatory bodies to pass an “authorised health claim” for cocoa or chocolate.
For the moment, thus, the best cocoa marketers and natural health gurus can legally get away with in the US is a kind of vague and fluffy suggestion that cocoa and chocolate, while undoubtedly tasting very nice indeed, might make you feel a bit better, maybe, perhaps.
“Considering the health claim systems in the US, a qualified health claim with the category ‘C’ can be attributed to cocoa flavanol intake and BP reduction, reflecting a low level of scientific evidence supporting the claim,” Wang and colleagues state.
Andrew Masterson is a former editor of Cosmos.
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