Transcript: Tea and Artery Function
Our endothelium, the inner lining of our blood vessels that controls the function of every artery in our body, appears to play a critical role in a variety of human disorders, including peripheral vascular disease, stroke, heart disease, diabetes, kidney failure, cancer, and blood clots.
Unfortunately, endothelial cells only live about 30 years, and their replacements don’t seem to function as well. So, as men and women approach the ages of 40 and 50, there is a progressive decline in endothelial function. At age 50 or 60, we can no longer tolerate the risk-factor burden that we were once able to tolerate as teenagers, thanks to the progressive decline in endothelial function. But that’s what we used to think. There are increasing data to suggest that age is not an immutable risk factor; it’s not just an inevitable consequence of aging. In the Chinese population studied, they did not see the same progressive decline.
The older Chinese in their 60’s had the arterial function of young folks in their 20’s. These data suggest that progressive endothelial dysfunction is not an inevitable consequence of aging but might be related to prolonged exposure to environmental factors more prevalent in Westernized countries than in China. What could the cause have been? Well, traditional Chinese diets include green tea, which has been shown to have a beneficial effect on endothelial function within 30 minutes of consumption, and lasting at least two hours. It wasn’t the caffeine, which alone had no effect. They suspect it was the flavonoid phytonutrients in the leaves.
Black tea appears to work about just as well as green tea, but then, why is green tea associated with lower heart disease risk, but black tea not? In fact, in two British studies, tea consumption was associated with an increased risk of coronary artery disease. Maybe it’s because the Brits drink their tea with milk, whereas green tea is typically drunk straight. If only there was a country that drank black tea, but without milk. There is, the Netherlands, and in those studies, black tea was associated with the same drop in risk as the green tea studies; so, maybe it is the milk. But you can’t really know until you put it to the test.
They found the addition of milk to black tea completely prevents the biological activity of tea in terms of improvement of endothelial function. And so, that could explain it. It appears casein is the culprit, though soy protein was recently found to have the same nutrient binding effect.
The European Society of Cardiology issued a press release about the study showing the protective effect of tea was totally wiped out by adding milk, and suggested consumers should consider cutting down. Milk-drinkers were not amused, “as long as the reported results are not confirmed in a fair number of humans who drink their tea outside the lab setting, we will continue to add milk to ours.” The researchers responded, challenging the notion that their study wasn’t big enough. They had 16 people, and the results were highly significant. Across those 16 people, the addition of milk to tea not only reduced, but completely blunted the effects of the tea. And, uh, the rationale for drinking tea in a lab setting was because they were doing an experiment. Were they supposed to drag the equipment to a Starbucks or something? The milky tea drinkers asserted that, as doctors, just as we would not prescribe a new drug to patients if it was studied only in one small study, milk abstinence should not be recommended to tea drinkers, apparently forgetting that the reason we don’t prescribe drugs without overwhelming evidence is because drugs can kill; so, the benefits better outweigh the risks, but what’s the downside of a little milk abstinence?
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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