Lipid Disorders and Tea

Black tea and green tea are made from the same plant, but a higher level of the original substances endure in the less-processed green form. Green tea is high in catechins (especially epigallocatechin gallate, or EGCG), and black tea contains relatively high levels of theaflavins, theanine, and thearubigens. Studies have shown that special tea products that are enhanced with higher levels of of theaflavin and catechins may help reduce cholesterol.

It is not clear if regular teas have this same effect, or if tea extracts (supplements) are beneficial.

Tea, especially green tea, contains a number of active compounds that may explain its positive effect on cholesterol. May of these compounds act as antioxidants.

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One study found that green teas produced short-term improvements in cholesterol profile, with the benefits disappearing after 4 weeks.²⁶

More positive results were seen in a study that evaluated a form of green tea enriched with the substance theaflavin, found in black tea.²¹ In this fairly large (more than 200 participants), 3-month study, use of the tea product resulted in significant, ongoing reductions in LDL ("bad") cholesterol as compared to placebo.

A green tea extract enhanced with catechins has also shown promise for reducing LDL levels, according to one somewhat flawed double-blind study.⁴² However, a study involving catechin-enhanced green tea in Japanese children was less convincing.⁴⁷

There is no set recommendation for how much tea (green or black) you should drink daily to enjoy health benefits. If you enjoy tea and can tolerate the caffeine, enjoy a few cups a day.

You might also consider taking a green tea supplement. A typical dosage is 100 mg to 150 mg three times daily of a green tea extract standardized to contain 80% total polyphenols and 50% epigallocatechin gallate. However, there is no solid evidence that these supplements provide the same benefits as whole tea, especially the enriched tea involved in the studies discussed here. Also, some green tea supplements have been found to be contaminated. (See Safety Issues--Green Tea, below.)

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Safety Issues--Green Tea

As a widely consumed beverage, green tea is generally regarded as safe. It does contain caffeine, at perhaps a slightly lower level than black tea, and can therefore cause insomnia, nervousness, and the other well-known symptoms of excess caffeine intake.

Green tea extracts, however, may not be safe. There are a growing number of case reports in which use of a concentrated green tea extract was associated with liver inflammation.^35,40,50 In most cases, liver problems disappeared after the extract was discontinued. But, in two cases, permanent liver failure ensued, requiring liver transplantation.^36,40 While it is not absolutely certain that the green tea extract caused the liver problems, nor how it might do so, these reports do raise significant concerns about use of green tea extracts, especially by those with liver disease or prone to it.

Green tea should not be given to infants and young children. There are theoretical concerns that high dosages of EGCG might be unsafe for pregnant women.³⁷

Dried green tea leaf contains significant levels of vitamin K on a per-weight basis. On this basis, it has been stated that people using blood thinners in the warfarin (Coumadin) family should avoid green tea, because vitamin K antagonizes the effect of those drugs. However green tea taken as a beverage provides such small amounts of the vitamin that the risk seems minimal for normal consumption. There is one case report of problems that developed in a person on warfarin who consumed as much as a gallon of green tea daily.³⁸

Interactions You Should Know About--Green Tea

If you are taking:

• MAO inhibitors: The caffeine in green tea could cause serious problems.
• Warfarin (Coumadin): Avoid drinking large quantities of green tea.
• Folic acid: Green tea may decrease the absorption of folic acid into the blood stream.51

Safety Issues--Black Tea

As an extraordinarily widely consumed beverage, black tea is presumed to have a high safety factor. Its side effects would be expected to be similar to those of coffee—heartburn, gastritis, insomnia, anxiety, and heart arrhythmias (benign palpitations or more serious disturbances of heart rhythm). All drug interactions that can occur with caffeine would be expected to occur with black tea.

Interactions You Should Know About--Black Tea

If you are taking:

• MAO inhibitors: The caffeine in black tea could cause dangerous drug interactions.
• Stimulant drugs such as Ritalin: The stimulant effects of black tea might be amplified.
• Drugs to prevent heart arrhythmias or to treat insomnia, heartburn, ulcers, or anxiety: - Black tea might interfere with their action.
• Folic acid: Black tea may decrease the absorption of folic acid into the blood stream.

21. Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003;163:1448-53.
26. Diepvens K, Kovacs EM, Vogels N, et al. Metabolic effects of green tea and of phases of weight loss. Physiol Behav. 2005 Nov 4. [Epub ahead of print
42. Nagao T, Hase T, Tokimitsu I. A green tea extract high in catechins reduces body fat and cardiovascular risks in humans. Obesity (Silver Spring). 2007;15:1473-1483.
46. Kovacs EM, Lejeune MP, Nijs I, et al. Effects of green tea on weight maintenance after body-weight loss. Br J Nutr. 2004;91:431-437.