Monday, March 16, 2009

Green Tea Protects from Arthritis in Rats

Could green tea be a treatment for arthritis in humans?
Could green tea be a treatment for arthritis in humans? (Photo by nyki_m)

I wrote a while ago about a study showing that green tea protects from arthritic cartilage breakdown in vitro. As promising as in vitro studies are, they're not the same thing as testing something on whole organisms. For example, based on that study alone, it's difficult to determine how much green tea would be needed to see effects in animals or humans – or indeed, whether it even works in vivo.

But fear not: the above study is not the only piece in the puzzle. According to a paper by Kim et al., green tea extract is effective in protecting rats from arthritis. Rats with bacteria-induced autoimmune arthritis showed less signs of arthritis when they were given green tea in drinking water.

Study design

The green tea extract used by the authors contained 57.5% catechins (of total weight), of which the most abundant one was epigallocatechin gallate (EGCG). The first group of rats received 8 grams of the extract per liter of drinking water, the second group received 12 grams, and the control group received normal water.

Each group was fed for 1-3 weeks before arthritis was induced. The severity of arthritis was evaluated on the basis of erythema (redness of the skin caused by capillary congestion) and swelling in each paw.

Effect of green tea extract on arthritic symptoms

The groups receiving 8 g/L had less signs of arthritis than the control group. The rats that had received green tea in drinking water for 2 weeks showed much less symptoms compared to rats fed for only 1 week. However, 3 weeks of 8 g/L feeding wasn't more effective than 2 weeks; in fact, it was less effective, although the difference was very small.

A similar pattern was observed with the size of the dose. When the duration of the treatment was 2 weeks, the rats fed 8 grams of green tea extract per liter had less arthritis than rats fed 12 grams. In the group fed for 3 weeks, there was no clear difference.

Even though the data for lower doses of 2 and 4 g/L is not presented, the authors mention that when all the arthritis scores from different doses were compared, 8 g/L and 2 weeks of feeding was the optimal combination, with the scores following an inverted bell-shaped dose-response curve.

Effect of green tea extract on cytokines and inflammation

Green tea extract suppressed the proinflammatory cytokine IL-7. Of the anti-inflammatory cytokines IL-4 was unaffected while IL-10 was increased. Other studies have shown that the suppression of IL-7 and induction of IL-4 and IL-10 can prevent or alleviate arthritic conditions, which makes green tea look quite promising in the treatment of arthritis.

Conclusion and practical considerations

An extract of green tea added to drinking water reduced signs of bacterially induced arthritis in rats. The results are explained in part by green tea's ability to suppress the proinflammatory cytokine IL-7 while increasing the secretion of the anti-inflammatory cytokine IL-10.

The optimal dose in this study was found to be 8 grams of extract per liter of drinking water for 2 weeks before inducing arthritis. The amount of catechins per gram of extract was 57.5%, which gives 4.6 g catechins in a liter of drinking water. If we assume that the rats drank about 50 mL per day, this would amount to an intake of 0.23 g (or 230 mg) of catechins per day.

The catechin content of green tea varies, but assuming a conservative estimate of 100 mg per cup, the amount in the study would be equivalent to about 2-3 cups per day. Keep in mind, however, that this is a very rough figure – the amounts that work in rats may not work in humans.

For more information on green tea, see these posts:

Vitamin C Protects Green Tea Catechins from Degradation
Green Tea Protects Cartilage from Arthritis in Vitro
Green Tea Extract Enhances Abdominal Fat Loss from Exercise
Caffeine and Polyphenol Contents of Green Tea, Black Tea, Oolong Tea & Pu-erh Tea

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