Lee Swanson Research Update

Black Tea Appears to Match Green for Weight Benefits

June 2010

Like green tea, extracts from black tea may also help reduce weight gain and cut body fat levels. The discovery was made in a new study from Japan involving rats and mice.

Supplementing the diet of lab animals fed a high-fat diet with black tea extracts suppressed body weight gain and body fat levels, with the benefits linked to reduced fat absorption. Study findings were published in Nutrition.

Interest in tea and its constituents has bloomed in recent years, with the greatest focus on the leaf’s polyphenol content. Green tea contains between 30% and 40% of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3% and 10%. Oolong tea is semi-fermented tea and is somewhere between green and black tea. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC).

Most of the studies have focused on green tea and its constituents, most notably EGCG. To date green tea has been linked to a reduced risk of Alzheimer’s, improved cardiovascular and oral health, as well as benefits in weight management and more.

"Although black tea extract contains only small amounts of these components, significant physiologic effects of administering black tea extracts were observed," wrote the researchers.

"It has been reported that the primary polyphenols in black tea are theaflavins and thearubigins. However, it has not yet been clarified whether thearubigins also have a preventive effect on obesity. Our results are consistent with the possibility that black tea-derived polyphenols are responsible for the observed physiologic effects of the black tea extracts," they added.

The Japanese scientists fed male rats a fat emulsion containing the black tea extract at a level of 500 mg or 1,000 mg per kg of body weight. Fat levels in the blood were subsequently evaluated and showed that the black tea extract "suppressed increases in rat plasma triglyceride levels in a dose-dependent manner," said the researchers.

In a separate study with female mice, the researchers supplemented their high-fat diets with either one percent or five percent of the tea extract for eight weeks.

"Administration of the five percent black tea extract suppressed increases in body weight, adipose tissue mass, and liver lipid content (reduced to 56.9% and 81.7% of control mice, respectively) in mice fed a high-fat diet," they stated.

While more research is needed, the researchers concluded that the polymerized polyphenol fraction of the black tea was responsible for the apparent weight management benefits.

Nutrition Published online ahead of print.

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