Antioxidant Activity of Tea Unaffected by Milk

The antioxidant activity of green and black tea (Camellia sinensis (L.) Kuntze, Theaceae) in the body (in vivo) is well established, but an important question remains: Does the addition of milk to tea inhibit the bioavailability of antioxidant tea polyphenols? Not according to the results of this Dutch study, which showed that a single dose of either black or green tea with or without milk caused a significant rise in plasma antioxidant activity.

The crossover study compared the antioxidant effects of green tea, black tea, and non-carbonated mineral water with or without milk in 21 healthy volunteers. Each participant received a dose of one of the six test substances on six different days. A single dose of tea was defined as 2 g of tea solids in 300 ml of water (Lipton Research Blend, Lipton, Englewood Cliffs, NJ). The researchers utilized the ferric reducing ability of plasma (FRAP) assay to measure both plasma antioxidant and catechin levels. Blood samples were taken before consumption of the test substances and again 30, 60, 90, and 120 minutes after consumption. According to the results, both green and black tea caused a significant rise in plasma antioxidant and catechin levels, but the effect of green tea was significantly greater at all time points. The addition of milk to either type of tea did not significantly alter responses.

While a limited number of studies support these results, others have shown that milk had a negative impact on the antioxidant capacity of tea. An earlier study published in the European Journal of Clinical Nutrition concluded that while the addition of milk to tea had no effect on antioxidant activity in vitro, it did appear to interfere with absorption of tea polyphenols in vivo. The authors of the older study offered two possible explanations for this effect. First, because milk proteins can cause complexation (binding) of tea polyphenols, the researchers proposed that milk/polyphenol complexes resist gastric breakdown, rendering the polyphenols unavailable for absorption. They also theorized that milk might hinder polyphenol absorption by increasing gastric pH

On the other hand, the authors of the more recent study suggested that the antioxidant assay utilized by Serafini and colleagues (called the Total Radical trapping Ability of Plasma, or TRAP assay) might be less reliable than the FRAP method, as TRAP may be associated with a higher degree of variability. - Evelyn Leigh, HRF

Oolong tea helps in the treatment of stubborn atopic dermatitis

An open Japanese study suggests that consumption of oolong tea (Camellia sinensis) helps speed clearance of recalcitrant atopic dermatitis lesions.

The 118 study participants continued their usual dermatologic treatments but also drank oolong tea (10 g steeped in 1000 mL water a day, divided into three doses).

Beneficial results were noted after one to two weeks, and 74 (63%) of the participants showed marked to moderate improvement of lesions after one month.

After 6 months, 64 patients (54%) still demonstrated a good response to treatment.

The study builds on animal research showing that oral administration of green, black, or oolong tea suppressed allergic skin reactions. Uehara M, Sugiura J, Sakurai K.

No colchicine in ginkgo: Independent testing refutes results of flawed research

Independent analyses of raw powdered Ginkgo biloba and ginkgo extract have discredited a recent study suggesting that ginkgo supplements contain the toxic alkaloid colchicine. The flawed study, "Identification of Colchicine in Placental Blood from Patients Using Herbal Medicines," by Petty et al., was released on the American Chemical Society's website on August 4, 2001, but apparently has not yet been formally published. The authors of the study warn that consumption of ginkgo supplements by pregnant women may pose dangers to developing fetuses, based on an analysis that they believe revealed the presence of colchicine in ginkgo.

Major media sources have publicized the study's conclusions, but herb experts and other scientists have strongly criticized the validity of the conclusions and the research methods used by the researchers. Some have suggested that the investigators misidentified a non-toxic ginkgo compound as colchicine. This ginkgo compound reportedly has a structure similar to that of colchicine, and the researchers failed to perform a test necessary to differentiate between the two. "Ginkgo simply does not contain colchicine," said HRF President Rob McCaleb. "These scientists should have done their homework before submitting their erroneous conclusions for publication."

Ginkgo has been the subject of hundreds of clinical, pharmacological, chemical, and toxicological studies, not a single one of which has identified colchicine as a gingko constituent. "For the authors to say 'such supplements should be avoided by pregnant women or those trying to conceive because the colchicine in them could affect the viability of a fetus,' as quoted in Chemical and Engineering News, is an unacceptable leap, give the questions raised about this report, and its conflict with the existing scientific literature with colchicine," said John Cordaro, president and chief executive officer of Council for Responsible Nutrition (CRN). Both CRN and the American Herbal Products Association (AHPA) commissioned third party analyses of finished ginkgo products sold in the US. Colchicine has not been detected in any of the products.

In addition, a comprehensive search of the scientific literature on ginkgo conducted by Dr. Norman Farnsworth, Distinguished Research Professor of Pharmacognosy at the University of Illinois at Chicago, further confirmed that colchicine has never been detected in ginkgo or ginkgo products. "Anyone who thinks that colchicine can be found naturally in ginkgo is not qualified to be a peer reviewer of this paper," Farnsworth said. -Evelyn Leigh