By Jeffrey B. Blumberg, Ph.D., F.A.S.N., F.A.C.N., CNS-S, Member of the Editorial Board, Herbalife Nutrition Institute
February 7, 2017
Over the last few decades, a large body of scientific knowledge has accrued to reveal important contributions to health from phytonutrients, bioactive compounds found in plant foods (other than essential micronutrients like amino acids, minerals and vitamins). The largest group of phytonutrients is polyphenols, about two-thirds of which are flavonoids. A great deal of research has been focused on the flavonoid class of flavanols, which are found at their highest concentrations in cocoa and tea.
Basic research experiments as well as observational studies of large populations and randomized clinical trials strongly indicate that flavanols may affect multiple risk factors for cardiovascular disease, including elevated blood pressure, inflammation, insulin resistance and more. Our knowledge of the mechanisms underlying these actions is limited but is steadily emerging around the health and function of the blood vessels and other target tissues.
Several systematic reviews and meta-analyses (statistical analyses that combine the results of multiple scientific studies) have been published showing a positive relationship between the consumption of cocoa flavanols and cardiovascular health. For example, an international team of researchers examined 42 acute and short-term randomized clinical trials of chocolate or cocoa found modest reductions in blood pressure and insulin resistance, increases in flow-mediated vasodilation (blood vessel expansion), and improvements in HDL- and LDL-cholesterol.1 Importantly, these findings are consistent with results from a group of Swedish researchers of six long-term population studies involving over 144,000 people showing chocolate consumption is associated with a lower risk of heart attack and heart disease.2
Clinical trials on chocolate and cocoa have convinced the European Food Safety Authority to conclude that cocoa flavanols help maintain blood vessel elasticity and normal blood flow in healthy adults. To receive this benefit, it recommends that cocoa flavanols be consumed daily from high-flavanol sources of cocoa powder (2.5 g), dark chocolate (10 g), and/or cocoa extract (200 mg).3 Of course, when choosing ways to consume cocoa flavanols to promote heart health, it is important to maximize this benefit while avoiding excessive fat and sugar found in chocolate products.
Like chocolate, tea (whether green, oolong or black) is rich in flavanols though, of course, the phytonutrient profile of each is different. As with chocolate, there are many systematic reviews and meta-analyses of tea and its benefits on heart health. Investigators in the UK analyzed 10 short-term clinical trials of green or black tea and found significant reductions in blood pressure in people with pre- and hypertensive ranges.4 A systematic review and meta-analysis by scientists in China of 22 long-term population studies involving over 856,000 individuals found that increased tea consumption was associated with a reduced risk of coronary heart disease, cerebrovascular disease and cardiac death.5 This and other tea studies suggest these benefits follow a dose-response relationship with consumption between 1 and 5 cups per day providing about 100 and 500 mg of tea flavanols, respectively, per 200 mL. However, it is important to note that determining the amount of flavanols in a cup of tea is challenging because their concentration is dependent on a number of factors, including the type, form and preparation of the tea.
Both cocoa and tea have rich and complex histories of traditional use. Dating from 2000 B.C., the ancient Olmec of Mesoamerica considered cocoa as a divine gift; indeed, cocoa is from the genus Theobroma, a term derived from the Greek for “food of the gods.” In 1528, when the Spanish Conquistador Hernán Cortez returned to Spain from the New World, he became cocoa’s first trans-continental advocate for the food made from the fruit seeds of a tree. Tea originated in southwest China about 1500 B.C. and was considered to have important medicinal properties. Portuguese priests and merchants were introduced to tea in the 16th century, and then the drink eventually found its way to great popularity in Britain during the 17th century.
New Uses for Flavanols
Today, we are looking at new ways to use the flavanols from cocoa and tea to promote heart health by formulating effective and safe amounts from extracts into functional foods, beverages, and supplements. It is also worth noting that emerging research suggests that these flavanols may also have benefits on outcomes beyond heart health, including cognition, diabetes, gut microbiota, and metabolic syndrome.5,6
And while the handful of studies referenced here look promising, there is a long way to go before the effect of consumption of flavanols can be predicted in individuals, and products that contain them are not drug products and should not be consumed to avoid or treat heart problems. No one should substitute consumption of tea or cocoa for well-understood heart-health habits of diet and exercise. Someday, though, we will better understand how these substances can be used to maintain good heart health.
- Hooper L, et al. Am J Clin Nutr. 2012;95:740-51.
- Larsson SC, et al. Heart. 2016:102;1017-22.
- EFSA NDA Panel. EFSA J. 2014;12:3654.
- Yarmolinsky J, et al. Nutr Rev. 2015;73:236-46.
- Zhang C, et al. Eur J Epidemiol. 2015;30:103-13.
- Blumberg JB, et al. Eur J Nutr Food Safety. 2015;5:1-31
- Blumberg JB, et al. Adv Nutr. 2014;5:547-9