By Ralph D. Levinson, MD
This experimental study found that green tea extract significantly reduced inflammation in a rat model of endotoxin-induced uveitis.
The authors investigated the anti-inflammatory effects of green tea extract on endotoxin-induced uveitis in rats. Uveitis was induced via injection of 1 mg/kg lipopolysaccharide (LPS). The rats were then given 1, 2 or 4 doses of 550mg/kg green tea extract fed intragastrically. They were compared to control groups that received saline injection plus green tea extract, LPS injection plus water or green tea extract, or LPS injection plus oral dexamethasone 1mg/kg.
A second experiment compared administration of 550 mg/kg and 275 mg/kg green tea extract to control groups. There was no allocation concealment in the randomization.
Green tea extract and dexamethasone both significantly reduced inflammation compared to controls. Green tea extract and dexamethasone each reduced the number of macrophages (CD68+) and lymphocytes (CD43+) in the anterior and posterior chambers. In the aqueous humor, they decreased protein leakage, the number of infiltrated cells, and the pro-inflammatory markers TNF-α, IL-6 and MCP-1. However, while dexamethasone lowered the level of serum MCP-1, green tea extract did not, and neither had an effect on serum IL-6.
Also in all analyses, the effects of dexamethasone were significantly greater than the effects of green tea extract, with the exception of the reduction of TNF-α and IL-6 in the aqueous humor. Furthermore, multiple doses of green tea extract had no extra beneficial effect, which was hypothesized to be due to a rapid decline in its anti-oxidative properties in the aqueous humor. In the dosing experiment, 550 mg/kg green tea extract reduced the number of cells and protein in the aqueous humor but the beneficial effect with 275 mg/kg was not significant.
Since steroids have many known side effects, an alternative therapy, such as green tea extract, is intriguing. However, there have been several reports of hepatotoxicity due to green tea extract at cumulative doses as low as 5.9 grams. The dose at which green tea extract would have anti-inflammatory effects in the human eye is unknown, but the dosage used in this study would amount to 38.5 g in a typical 70 kg man. While one study did show that levels of up to 800 mg/day for four weeks (22.4 cumulative grams) are safe, the half strength dose used in another study (275 mg/kg, 19.25 g in a 70 kg man) was not effective.
There is a cautionary tale here. I would love for green tea at even close to reasonable doses to have some effect. Even a minimal effect could suggest that it may be useful to prevent recurrences of acute anterior uveitis (don’t dismiss the placebo effect if nothing else). That would empower patients, have the cachet of being natural and taste good. But even natural products, especially in doses that have pharmacologic effects, are potentially toxic. Many patients are using supplements, often without knowing what is really in them.