You may have heard people say cacao "opens the heart." For some, that's a spiritual expression. For others, it raises an interesting question: what does modern science have to say about cacao, cocoa flavanols and the circulatory system?
Over the past few decades, researchers have been exploring how the natural compounds found in cacao affect blood vessel function and circulation. These studies offer a fascinating scientific perspective on cacao and the compounds it naturally contains.
So what is it about cacao that has scientists so interested?
It comes down to a group of naturally occurring plant compounds called flavanols. Among commonly eaten foods, cacao is one of the richest natural sources of flavanols. One flavanol in particular, epicatechin, has been studied extensively for its effects on blood vessel function.
Researchers have investigated how epicatechin and its metabolites interact with the endothelium, the lining of our blood vessels, including their relationship with nitric oxide (NO), an important signalling molecule involved in vascular function.
Nitric oxide acts like a messenger. It tells the muscles in our blood vessel walls to relax.
The role of nitric oxide in vascular function is one reason researchers have been interested in studying cocoa flavanols and measures of cardiovascular function, including blood vessel function and blood pressure. (1)
What Does the Research Say?
Research on Blood Vessel Function
In the Flaviola Health Study, researchers investigated daily cocoa flavanol consumption in healthy adults over one month. The study reported changes in measures including endothelial function, blood pressure and cholesterol markers. (2)
Research on Blood Pressure
A 2017 Cochrane review examined 18 clinical trials investigating flavanol-rich cocoa and blood pressure. The review reported a small reduction in blood pressure across the short-term trials studied, while also noting differences between studies and limitations in the available evidence. (1)
Cocoa Flavanols and Acute Mental Stress
Researchers have also investigated cocoa flavanols in the context of acute mental stress. In one clinical trial involving healthy young adults, researchers reported differences in vascular responses following cocoa flavanol consumption, including measurements taken up to 90 minutes after the stress task. (3)
Long-Term Cardiovascular Research
The COSMOS trial followed more than 21,000 older adults for a median of 3.6 years to investigate cocoa flavanol supplementation and cardiovascular outcomes. The primary outcome, total cardiovascular events, was not significantly reduced. The researchers also reported findings relating to cardiovascular mortality, but noted that further research would be needed to confirm them. (4)
Cocoa Flavanols and the Brain
Researchers have also explored cocoa flavanols in relation to cerebral blood flow, including studies involving older adults. These studies contribute to ongoing research into flavanols, vascular function and healthy ageing, although further research is needed to understand their broader significance. (6,7)
Why Processing Method Actually Matters
Whether it's dark chocolate, cocoa powder or ceremonial cacao, they all begin with the same cacao bean, Theobroma cacao. The biggest difference is how that bean is processed.
Flavanol content can be affected by processing. Research has shown that processing steps, including roasting and alkalisation (Dutch processing), can influence the flavanol content of cocoa products. (8).
What Does This Research Tell Us?
Research into cocoa flavanols has explored a range of cardiovascular measures, including blood vessel function and blood pressure. While a number of clinical studies have reported interesting findings, research into longer-term cardiovascular outcomes remains ongoing and is not yet conclusive.
What we do know is that processing can influence the flavanol content of cocoa products, making the way cacao is processed an interesting part of the wider research into these naturally occurring plant compounds.
Cacao's reputation as a ‘heart opener’ has an interesting scientific parallel. Research into cocoa flavanols continues to explore their relationship with blood vessel function and circulation, adding another fascinating layer to cacao's long history of use.
References
1. Effect of cocoa on blood pressure
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD008893.pub3/full
2. Cocoa flavanol intake improves endothelial function and Framingham Risk Score in healthy men and women: a randomised, controlled, double-masked trial: the Flaviola Health Study
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594054
3. Cocoa Flavanols Improve Vascular Responses to Acute Mental Stress in Young Healthy Adults
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065749
4. Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9170467
5. COSMOS Trial Results. Brigham and Women's Hospital / Mass General Brigham. https://cosmostrial.org/results
6. Cocoa flavanols and brain perfusion
https://pubmed.ncbi.nlm.nih.gov/16794460
7. Cerebral blood flow response to flavanol-rich cocoa in healthy elderly humans
https://pubmed.ncbi.nlm.nih.gov/18728792
8. From Cocoa to Chocolate: Effect of Processing on Flavanols and Methylxanthines and Their Mechanisms of Action
https://pmc.ncbi.nlm.nih.gov/articles/PMC9698929
This article is for informational purposes only and is not medical advice. Speak with a healthcare provider before making changes related to a cardiovascular condition or medication regimen.