Tannins are naturally occurring substances that fall under the category of plant polyphenols. They are believed to influence protein and lipid digestion, binding to the molecules and leading to their excretion from the body. Tannin intake, through tannin-containing food and beverage sources, may help those with high cholesterol manage their blood cholesterol levels.
Cholesterol Transport
Studies involving cholesterol and tannins also focus heavily on the lipoproteins on which cholesterol is transported within the body. High density lipoproteins, or HDLs, carry cholesterol to the liver for excretion; low-density lipoproteins, or LDLs, circulate cholesterol throughout the blood. Because HDLs help with cholesterol excretion, they are believed to be health-boosting; therefore, higher levels of HDL are preferred. Conversely, LDL levels are believed to be dangerous as blood levels climb.
Tannins, Cholesterol and Lipoproteins
Two similar studies supported the belief that tannins can help to improve blood lipid levels. The earlier study, conducted in 1992 by Yugarani and associates, examined rats fed high-fat diets in addition to various polyphenols, including tannins. The total cholesterol and LDL levels of the rats decreased over the 10-week study period. The HDL levels of the rats remained the same.
A study conducted in 1994 by Katia Tebib and associates consisted of rats divided into two groups: one group received just a high-cholesterol diet, the other group, a high-cholesterol diet in addition to grape seed tannins. The rats fed the tannins did not experience the same blood cholesterol increases as the rats who received no tannins.
Animals, Humans and Tannins
The mechanisms of cholesterol and LDL reduction in humans who eat tannin-rich diets may be the same as in rats. As of 2011, more research was needed to determine human cholesterol-lowering possibilities with increased tannin intake. If you're considering increasing your dietary tannin intake, it's always a good idea to first check with your doctor or a naturopathic physician. More animal research from Cornell University has shown that increased tannin intake can produce harmful side effects in livestock and poultry. Though no evidence currently points to toxicity in humans, it's always better to be safe before changing your diet.
Tannin-Containing Foods
Tannins are found to some degree in most foods, though some are better sources than others. To increase dietary intake of tannins, choose red grapes, red wine, coffee, oolong, black and green teas, apples, berries, chocolate, soy and soy-based foods like tofu, and legumes such as chick peas or lentils.
References
- Cornell University: Tannins: Fascinating but Sometimes Dangerous Molecules
- American Heart Association: About Cholesterol
- "Lipids"; Effects of polyphenolic natural products on the lipid profiles of rats fed high fat diets; T. Yugarani; 1992
- "Food Chemistry"; Polymeric grape seed tannins prevent plasma cholesterol changes in cholesterol-fed rats; Katia Tebib; 1994
- "Food and Nutrition Consultant"; Overview of Dietary Flavonoids : Nomenclature, Occurrence and Intake; Gary Beecher; October; 2003
