Tea is an ancient drink that dates back over 5,000 years. People have not only enjoyed its distinct taste but have also used it for medicinal purposes as well. Today, tea is the most commonly consumed beverage on the planet, second only to water. Tea drinking is on the rise at a rate of 2% per year. Among the many purported benefits of drinking tea such as reduced cancer rates and promoting overall longevity, tea has traditionally been believed to be effective at lowering cholesterol. Now, science has found hard evidence to support this claim.
Tea is derived from the leaves of the plant Camellia Sinensis. There are three major types of tea: green, oolong, and black. The difference between these teas is based upon the amount of fermentation that is involved in their processing. Tea leaves are harvested soon after their buds have sprouted. Once harvested, the leaves are allowed to dry to remove moisture and wither. The withered leaves are then either rolled or crushed exposing certain chemicals in the plant to air. Once these chemicals are released, a process called oxidation occurs in which chemicals in the tea leaves are allowed to change naturally. Although this procedure involves an oxidative chemical process, it's generally referred to as fermentation. This fermentation process is stopped by drying the tea leaves in hot air. The amount of time of fermentation determines which type of tea will be produced. Green tea has no significant fermentation, as its leaves are immediately steamed or heated thereby inhibiting any type of oxidation. Oolong tea is produced after 30 minutes of fermentation, and black tea after 60 to 90 minutes.
The chemical in tea that appears to have a cholesterol benefit is called catechin. Catechins are a class of chemical compounds called polyphenols. Four distinct types of catechins are found in tea. Interestingly, the more fermented the tea leaves, the less catechin is present. Therefore, green tea has the highest concentration of catechin, while black tea has the least. Catechin is a chemical that also is found in other foods reported to have cholesterol benefits such as grapes and red wine. Catechins reduce cholesterol levels by two main effects. First, they promote the removal of plasma LDL in the liver by increasing the number of binding sites on the liver for LDL. Secondly, they inhibit the absorption and re-absorption of cholesterol in our intestines. Bile, which is rich in cholesterol and is made by the liver, is secreted into the gut in order to aid in the absorption of fat. Catechins appear to block the re-absorption of bile back into our bodies. Therefore, cholesterol excretion is increased through the gut.
The evidence for the benefit of drinking tea comes from a variety of observational studies as well as basic animal research. Asian countries are known to have a high rate of smoking, yet paradoxically have low rates of heart disease and lung cancer. Several population studies have shown that those people who drink a significant amount of tea on a daily basis (i.e., more than three cups per day) seem to have lower rates of heart disease. Animal studies in rats specifically looking at commonly consumed teas such as green, oolong, and Pu erh showed a reduction in total cholesterol and LDL levels. The cholesterol lowering effect was greater with the least fermented teas such as green and jasmine. And finally, a Chinese prospective study demonstrated that theaflavin - enriched green tea extract - was able to lower total cholesterol by ~10% and LDL by ~15% in a 3 month period. HDL was only minimally increased. No significant side effects were reported.