Labdoor analyzed 24 best-selling green tea supplements in the United States for caffeine, primary catechin and total polyphenol content, and heavy metal (arsenic, cadmium, lead, mercury) contamination.
Products ranged from having only 21.4% of its label claim to having more than 3 times its label claim for an active ingredient group - total polyphenols, primary catechins, EGCG (epigallocatechin gallate) or caffeine. Limited research suggests that benefits from green tea extracts begin at daily doses of 140 mg of catechins and accumulate with higher doses. All but 4 products measured at least 140 mg of green tea catechins per serving. Weight loss benefits of green tea have been found in research at doses of 270 mg of EGCG + 150 mg of caffeine. 8 of 25 products measured EGCG levels above 270 mg per serving. All products recorded less than 150 mg of caffeine.
Lead and arsenic levels were concerning in this batch analysis. 7 of 25 products exceeded California Proposition 65 lead limits in 1-2 servings. 5 of those products also exceeded inorganic arsenic limits in 1-2 servings. Other notable flagged ingredients include titanium dioxide, a whitening agent linked to cancer and Alzheimer’s disease, and Hoodia gordonii, a steroidal compound with dangerous potential for increasing blood pressure, heart rate, and markers of liver damage.
Analytical chemistry methods used to generate this report include High Performance Liquid Chromatography (HPLC) to quantify caffeine, total polyphenols, and individual catechins and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to screen for heavy metals. Tests for individual catechins consist of measurements for epigallocatechin (EGC), epicatechin (EC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG).
Updated 22916: Labdoor performed a category-wide update to quantify heavy metal content based on each product’s measured serving size mass.
For EGCG, the main active ingredient in green tea, product labels ranged from claiming less than a third of a product’s actual EGCG to claiming almost double a product’s actual EGCG.
Green tea supplements have no standard method for labeling active ingredients and in some cases, cited proprietary blends with unspecified quantities of secondary ingredients.
CAFFEINE: Of the 11 products that claimed caffeine content, 10 products over-reported caffeine levels. On average, products claiming specific quantities of caffeine deviated off label claims by 41.9%, ranging from having only 42.6% of the caffeine claimed on a label to having 131.5% more than a label claim.
EGCG (epigallocatechin gallate): Of the 16 products that specified EGCG content, 13 were found to have EGCG levels above their label claims. Products deviated by an average of 35.3% from their label claims for EGCG, ranging from having only 63.1% of the EGCG claimed on a label to having more than triple (306.3%) the EGCG on a label claim.
PRIMARY CATECHINS: Of the 13 products that specified primary catechin content, 10 measured primary catechin levels below their label claims. Products deviated by an average of 26.6% from their label claims for primary catechins, ranging from having only 56.4% of a label claim to having 114.0% more than a label claim.
TOTAL POLYPHENOLS: Of the 18 products that specified total polyphenol content, 15 measured polyphenol levels below their label claims. Products deviated by an average of 20.4% from their label claims for total polyphenols, ranging from having only 21.4% of a label claim to having 21.7% more than a label claim.
7 of 24 products recorded lead levels that, in 1-2 servings, exceed California’s Proposition 65 established limit for lead intake of 0.5 mcg per day.
All products in this report were screened by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for the presence of 4 key heavy metals: arsenic, cadmium, lead, and mercury. In accordance with California’s Proposition 65, the following proposed and established daily intake limits were used to assess heavy metal load and product purity: no more than 0.1 mcgday of inorganic arsenic (proposed), 4.1 mcgday of cadmium, 0.5 mcgday of lead, and 0.3 mcgday of mercury (proposed).
Lead and arsenic are both cited in California Proposition 65 as carcinogenic and reproductive toxins. 3 of 24 products exceeded the upper limit for safe daily lead intake in 1 serving. An additional 4 products exceeded lead’s safe daily upper intake limit in 2 servings. 2 products exceeded safe daily intake limits for inorganic arsenic in 1 serving. An additional 4 products exceeded inorganic arsenic’s safe daily upper intake limit in 2 servings. 5 products exceeded daily upper intake limits for both arsenic and lead in 1-2 servings.
All of the tested products passed heavy metal screens for cadmium and mercury.
NOTE: Currently, intake limits for total arsenic have only been established for drinking water. The only available guideline for arsenic in supplement products is a proposed limit from CA Proposition 65 on the inorganic component of total arsenic. Generally, inorganic arsenic species (tri- and penta-valent arsenic) are considered more toxic than their organic counterparts. Chemical analysis of this batch of products measured arsenic in total. Since research has shown that the contribution of inorganic arsenic to total arsenic is ~80% (in rice), an 80% assumption was used to project and then compare inorganic arsenic content in these products to the CA Proposition 65 proposed limit of 0.1 mcg per day.
All products performed well in terms of unnecessary fat, cholesterol, carbohydrate, and sugar content, recording an average of 100 (out of 100) in Nutritional Value scores.
All products recorded limited amounts of extraneous fats, cholesterol, carbohydrates, and added sugars. Gaia Herbs Green Tea was the only product to measure any calories, mainly from cellulose, a plant fiber, and glycerin, a sweetener often derived from animal and plant oils.
3 of 24 products were found to contain flagged ingredients including titanium dioxide, a whitener linked to cancer and Alzheimer’s, and Hoodia gordonii, a steroidal compound that can increase blood pressure, pulse rate, and markers of liver damage.
CAFFEINE: The FDA cites 400 mg (~5 cups of coffee) per day as the highest level at which caffeine is still considered safe for healthy adults. All tested products measured caffeine levels below this limit. The maximum caffeine content in this batch analysis was recorded by Applied Nutrition Green Tea Fat Burner at 145.72 mg per serving.
No limits for safety have been established for EGCG, green tea catechins, or green tea polyphenols. Currently, research suggests that EGCG is safe in bulk doses up to 1,600 mg. There is some concern that green tea products might cause liver damage in some people. The onset of related symptoms has ranged from 5 to 120 days after starting green tea supplementation. In most cases, liver function returned to normal after discontinuation.
FLAGGED INACTIVE INGREDIENTS: No synthetic sweeteners, artificial colors, or controversial preservatives were detected in this batch of products. However, titanium dioxide, a whitening agent linked to cancer and Alzheimer’s Disease, was present in 2 products, Applied Nutrition Green Tea Fat Burner and Irwin Naturals Triple-Tea Fat Burner. Hoodia gordonii, a steroidal compound that can cause concerning increases in blood pressure, pulse rate, and markers for liver damage, was noted in Spring Valley Green Tea.
All but 4 products measured at least 140 mg of green tea catechins per serving, the lowest dosage at which green tea benefits start accruing based on limited research findings.
EGCG is considered to be the most potent of the green tea catechins, but the other primary green tea catechin variants (epigallocatechin (EGC), epicatechin (EC), and epicatechin gallate (ECG)) also show some efficacy. Primary catechin content as a whole ranged from 27.9 - 484.9 mg per serving in this batch of products. The highest value was measured in MET-Rx Extra Strength Green Tea Extract (484.9 mg per serving). 4 of 24 products measured primary catechin levels below 150 mg per serving. 5 products measured more than 400 mg of primary catechins per serving.
DIABETES: In a few small clinical studies, 544 mg of polyphenols (with ~456 mg of catechins) was found to lower hemoglobin A1c levels in subjects with borderline diabetes. In people with Type I diabetes, green tea may help regulate fluctuating glucose levels. In a retrospective cohort study, men who drank 6+ cups of green tea also experienced reduced risk for Type II diabetes.
LIVER DISEASE: In population-based studies, 10+ cups of green tea protected against liver problems like alcohol-induced liver damage in men, but it should be noted that the quantity of caffeine in this dosage is extremely high and can cause other health issues like heart palpitations, muscle tremors, and gastrointestinal distress. Research suggests that green tea catechin supplements may also help with inflammatory liver diseases.
HIGH CHOLESTEROL: A meta-analysis concluded that doses of 150 - 2500 mg of catechins per day could lower total cholesterol and LDL levels and raise HDL levels, possibly by preventing dietary cholesterol from being absorbed and increasing cholesterol excretion. Notably, in May 2006, the FDA rejected a petition to allow product labels to claim that green tea reduces the risk of cardiovascular disease, one of the main concerns for high total cholesterol levels.
CANCER: Laboratory studies have found that green tea extracts have anti-inflammatory and anti-cancer properties that may prevent the growth of breast and prostate cancer cells. In humans, research evidence for reduced breast cancer risk is very limited. In a study of ~1,000 Asian American women, efficacy was demonstrated with 1 cup of green tea per day (with ~140 mg of catechins). In another study, researchers found that 3+ cups of tea per day was effective in reducing breast cancer risk, but only in women under the age of 50. Likewise, evidence for prostate cancer risk reduction was sparse. In a clinical study of about 400 Chinese men, 3+ cups of tea per day (with ~420 mg of catechins) was associated with a reduced risk of prostate cancer, but attempts to replicate these results have been inconclusive. Chemotherapy drugs may also be less effective with concurrent tea consumption.
WEIGHT LOSS: In research, 270 mg of EGCG + 150 mg of caffeine per day was shown to moderately reduce body weight, waist circumference, and body fat and increase resting metabolic rate through thermogenesis and fat oxidation in obese subjects who were not regular drinkers of caffeine. High caffeine consumers who were already adapted to regular caffeine doses experienced no weight loss effects. EGCG + caffeine should be taken intermittently in caffeine-naive individuals to maximize weight loss potential.
In this batch of products, caffeine content ranged from 0.05 mg to 145.7 mg per serving. EGCG content ranged from 25.23 mg to 373.16 mg per serving. 17 of 24 products recorded EGCG levels below 270 mg per serving, the quantity found in research to help with weight loss. Applied Nutrition Green Tea Fat Burner measured the highest levels of both caffeine and EGCG.