This article was originally published in the October 2016 edition of the Tufts Health & Nutrition Letter, a publication of the Tufts Friedman School of Nutrition Science & Policy.
A study of older Dutch men provides new insight into why tea and cocoa protect against heart disease, showing for the first time that a compound called epicatechin is associated with reduced mortality from cardiovascular disease. The 25-year study followed nearly 800 men, all initially over age 65. Higher levels of epicatechin ― primarily from tea and cocoa, as well as apples ― were linked to sharply lower mortality risk from coronary heart disease and cardiovascular disease.
“While these results help to pinpoint specific ingredients that may contribute importantly to reducing the risk of a disease,” cautions Jeffrey B. Blumberg, PhD, professor at the Friedman School of Nutrition Science and Policy and senior scientist in the Antioxidants Research Laboratory at the Jean Mayer Human Nutrition Research Center on Aging, “it is critical that we keep in mind that the nutrient composition of the whole food, including the matrices in which these bioactive compounds reside, is ultimately responsible for health outcomes.”
COCOA AND TEA RESEARCH
It’s not new news that cocoa and tea seem to protect against cardiovascular disease. Large-scale observational studies, for example, have reported that participants with the highest chocolate consumption were at 37 percent lower risk of cardiovascular disease and 29 percent lower risk of stroke. A combined analysis of 14 studies of black or green tea found that consumption of three cups daily was associated with a 13 percent lower risk of stroke. Randomized clinical trials have shown that chocolate and cocoa, as well as tea, improve the function of the lining of blood vessels, help lower blood pressure and counter insulin resistance.
The Zutphen Elderly Study, source of the latest findings about epicatechin, has previously reported that cocoa intake was inversely associated with cardiovascular disease mortality, and tea intake was inversely related to coronary heart disease mortality.
“While these results help to pinpoint specific ingredients that may contribute importantly to reducing the risk of a disease, it is critical that we keep in mind that the nutrient composition of the whole food, including the matrices in which these bioactive compounds reside, is ultimately responsible for health outcomes.” — Jeffrey B. Blumberg, PhD
One possible key to these apparent benefits is epicatechin, a type of flavonoid compound. A member of a family of compounds called catechins, it’s the most abundant such flavonoid in cocoa, and is also commonly obtained from black and green teas.
HIGHEST VS. LOWEST
In the latest findings, published in the American Journal of Clinical Nutrition, epicatechin intake was estimated four times during a 15-year span based on interviews with trained dietitians. The major dietary sources were tea (51 percent), apples (28 percent) and cocoa (7 percent).
The 774 participants were all older men, initially ages 65-84. During 25 years of follow-up, 329 died from cardiovascular disease, 148 from coronary heart disease, and 72 from stroke. In men with cardiovascular disease at the study’s start, epicatechin intake was associated with a significant 46 percent lower risk of death from the disease; there was no such association, however, in those initially free of cardiovascular disease. Risk of death from coronary heart disease was 38 percent lower in participants in the top one-third of epicatechin intake compared to those in the bottom third.
“Interestingly, the actions of epicatechin and closely related flavonoids may be mediated via their metabolites generated by gut microbiota and liver enzymes, thus explaining some of the variability found in the results of studies such as this one.” — Jeffrey B. Blumberg, PhD
Epicatechin intake ranged from an average of 22 milligrams per day in the highest-intake group to 8 milligrams daily in the lowest group. Consumption in the highest-intake group would be roughly equivalent to drinking a cup of brewed green tea daily. According to research at the University of California-Davis, brewed black tea is lower in epicatechin; you’d need to drink more than four cups of black tea to get 22 milligrams.
The equation is actually a bit more complicated, however, according to Blumberg. He says, “Interestingly, the actions of epicatechin and closely related flavonoids may be mediated via their metabolites generated by gut microbiota and liver enzymes, thus explaining some of the variability found in the results of studies such as this one.”
CAUTIONS AND TAKEAWAYS
As an observational study, the findings can’t prove cause and effect. There were also potentially confounding differences between those with the highest and lowest epicatechin intake, although researchers tried to adjust for these factors. Subjects with higher epicatechin intake were generally more physically active, less likely to be smokers, and drank less coffee.
The role of catechin compounds in general also muddies the results. Says Blumberg, “Catechin intake was strongly correlated with epicatechin intake, and combined epicatechin plus catechin intake was equally associated with reduced risk of cardiovascular disease and coronary heart disease mortality.”
Researchers speculated that the inverse association between epicatechin intake and deaths from cardiovascular disease could be related to changes in the function of the cells lining blood vessels, called the endothelium. Effects of epicatechin on insulin resistance, which is a risk factor for cardiovascular disease as well as diabetes, could also be involved.
They cautioned that it’s too early to draw definitive conclusions based on this study. And, given the limited evidence, don’t consider supplements. But given the prior evidence of heart benefits from tea and cocoa products such as dark chocolate, it’s one more reason to include these foods as part of a healthy dietary pattern.
For more information, see the Tufts Health & Nutrition Letter, a publication of the Friedman School of Nutrition Science and Policy at Tufts University: Editor-in-Chief, Dariush Mozaffarian, MD, DrPH, and Executive Editor, Alice H Lichtenstein, DSc.
The Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy is the only graduate school of nutrition in the United States. The mission of the school is to generate trusted science, educate future leaders, and produce real world impact in nutrition science and policy.