Green tea extract

What is green tea extract?

Green, black and oolong teas all come from the same plant, Camellia sinensis. As the National Center for Complementary and Integrative Health explains, green tea is made by steaming, pan frying and drying the leaves without fermenting them, which preserves high levels of catechins, a group of polyphenols. The most abundant catechin is epigallocatechin gallate (EGCG). Green tea also naturally contains caffeine and the amino acid L-theanine.

Green tea extract concentrates these compounds into capsules or powders, often standardized to a percentage of total catechins or EGCG. Extracts can deliver far more catechins than you would get from drinking tea.

What the research says

Green tea is one of the most studied weight-management ingredients, and the results are consistently modest. A Cochrane systematic review of randomized trials lasting at least 12 weeks in overweight or obese adults concluded that green tea preparations appear to produce a small, statistically non-significant weight loss that is not likely to be clinically important. Green tea had no significant effect on keeping weight off.

NCCIH summarizes the evidence similarly: the catechins and caffeine in green tea may have a modest effect on body weight, and results depend on the product’s composition and a person’s physical activity. Green tea extracts have also been found to lower total and LDL cholesterol slightly. Large studies on cancer and heart disease prevention have been inconsistent.

We rate the evidence as limited for weight management. Drinking green tea is a healthy habit, but concentrated extracts should not be expected to produce meaningful weight loss on their own.

How it’s used in supplements

Green tea extract appears in countless fat burners, energy products and antioxidant formulas. Safety is the key issue. NCCIH reports no safety concerns for green tea as a beverage in adults, but side effects of extract supplements include nausea, constipation, abdominal discomfort and increased blood pressure. Liver injury, though uncommon, has been reported, mostly with extracts in tablet or capsule form, and people with a specific immune-related gene variant appear to be more susceptible.

Green tea can also interact with medications. NCCIH notes that high doses reduce blood levels of the beta-blocker nadolol, that green tea extract can lower levels of the cholesterol drug atorvastatin, and that an interaction with raloxifene has been shown. Because green tea contains caffeine, pregnant women should keep total caffeine moderate.

In Java Burn, Camellia sinensis is listed without an amount, so its caffeine and catechin content are unknown. Keep in mind that it is added to coffee, which means your total caffeine intake will be higher than from coffee alone. In Claritox Pro, green tea is likewise listed without an amount.