The Health Benefits of Green Tea Supplements

These may be recommended if you need to lower LDL cholesterol

Green tea

Verywell / Alexandra Shytsman

Green tea made from the dried leaves and leaf buds of the Camellia sinensis plant is often touted as a natural remedy with many benefits, from weight loss promotion to prevention of cardiovascular disease. Many people prefer to seek these benefits by taking green tea supplements, which are capsules that are either filled with dry green tea leaves or made with green tea extract—a substance prepared by soaking the green tea leaves in an alcohol solution to isolate active components such as epigallocatechin-3-gallate (EGCG).

Available in capsule and liquid form, green tea supplements are often marketed as a means of increasing your antioxidant intake without having to drink multiple cups of green tea daily.

Health Benefits 

Green tea supplements seem to be advertised everywhere, and media reports on their benefits (or those of supplements in general) are often less skeptical than is desired. Before taking them, it's helpful to see what the research supports—and doesn't.

Weight Loss

Many studies on the effects of supplements on weight loss measure changes in body mass index (BMI) or waist circumference before and after supplement intake without controlling for other factors. And even when a researcher does implement these controls, they are often overlooked when results are reported by others.

A letter to the editor written by two National Institutes of Health (NIH) employees and published in the journal Clinical Nutrition in 2016 offers a typifying example. In it, it's noted that the authors of a previous study in that same journal had claimed positive weight loss effects for obese women taking green tea supplements, but they decontextualized the results, neglecting to mention that the weight loss was not significant when compared with placebo. The original study was nevertheless cited 76 times.

When proponents claim a supplement helps with weight loss, they're often simplifying a variety of compounding factors, such as the effect of the supplement on energy expenditure, fat metabolism, food cravings, and nutrient absorption. A 2011 review looking at various studies of the effect of green tea supplements on these factors suggests that study results have been mixed and the impact of green tea catechins is difficult to separate from the general effect of the caffeine content of green tea.

In one study attempting to parse this out, one group consumed a drink containing 75 milligrams (mg) of caffeine with an added 583 mg of green tea catechins, and another group consumed a caffeine-matched control containing only 96 mg of green tea catechins. Body weight did not differ between the two groups after 12 weeks, however waist circumference was significantly reduced in the high green tea catechin group.

This could point to an effect of green tea catechins on fat metabolism, but does not indicate green tea supplements as an effective weight loss intervention.

Cardiovascular Disease

A study published in 2003 of 240 people does suggest that, when paired with a low saturated fat diet, the use of green tea supplements may help keep cholesterol in check.

The study involved 240 adults, all of whom had mildly to moderately elevated cholesterol levels at the study's start. Study results showed that those who took 375 mg green tea extract in capsule form for 12 weeks had a greater decrease in LDL ("bad") cholesterol than participants who took a placebo capsule for the same length of time.

LDL cholesterol is the main source of plaque that builds up in the walls of arteries, which can slow down blood flow to the heart, leading to a decrease in oxygen, chest pain, and even heart attack. When taking green tea extract leads to lower concentrations of LDL, a positive effect on heart health is expected.

The positive effect of green tea supplements on lowering cholesterol is supported by a 2011 study of 76,979 people, which found that women who drank one to six cups of green tea per day had a reduced risk of dying from cardiovascular disease compared to those who did not.

Cancer Defense

More than 50 epidemiologic studies have looked for an association between green tea consumption and cancer risk since 2006, though the results have been inconsistent. One phase II clinical trial investigating the effect of green tea extract on oral pre-malignant lesions, found an improved clinical response that increased with dose, but it was not statistically significant compared to placebo.

Biological factors associated with tumor growth were found to be downregulated in clinically responsive patients who took the extract and upregulated in nonresponsive patients at 12 weeks. In a 2009 study of 26 men diagnosed with prostate cancer, those who took four capsules of green tea extract daily had a significant decrease in certain markers that signal prostate cancer progression. This is promising, but more research is needed.

Green tea extract alone is not a successful intervention against cancer.

Possible Side Effects

While tea is generally recognized as safe by the U.S. Food and Drug Administration (FDA), some tea drinkers and takers of green tea supplements do report side effects.

One study that looked at the consumption of up to 1200 mg of green tea catechins in supplement form in healthy adults reported:

  • Headache
  • Abdominal pain
  • Dizziness
  • Excess intestinal gas
  • Heartburn
  • Nausea
  • Muscle pain

In some cases, people who take a lot of green tea supplements have experienced constipation. Polyphenol toxicity has been shown to cause kidney and liver damage at doses higher than 800 mg.

Many green tea supplements contain caffeine, which itself has been associated with side effects such as anxiety, increased heart rate, and blood pressure, dizziness, ringing in the ears, and the worsening of ulcer symptoms, especially at these higher doses.


A daily dose of 700 ml of green tea extract was found to reduce blood plasma concentrations of the beta-blocker nadolol and, by extension, its effectiveness.

Current research shows that green tea supplements can potentially enhance the efficacy of certain chemotherapy drugs, while hindering others. If you are undergoing chemotherapy, ask your doctor before taking green tea supplements.

Special Concerns

According to one study referenced by the NIH, there is some concern that green tea can reduce the absorption of iron and exacerbate glaucoma when taken with a meal. This inhibition of iron bioavailability through diet is also important for those suffering from iron-deficiency anemia.

This effect was not observed when the green tea was taken between meals, and the interaction was ameliorated when foods that enhance iron absorption were taken at the same time (e.g., foods high in vitamin C, such as oranges).

If you are breastfeeding, experts recommend limiting your caffeine consumption to 300 mg per day, and green tea supplements should be factored into that daily intake. The same goes for pregnant women, who are encouraged not to exceed 200 mg of caffeine per day due to an increase risk for miscarriage.

Dosage and Preparation

The leaf buds, leaves, and stems of the Camellia sinensis plant are steamed at high temperatures, producing the substance known as green tea. This process maintains the polyphenol content, which is decreased in black tea; though it comes from the same plant, a fermentation process is used instead.

Green tea supplements are prepared by extracting the beneficial substances from green tea and enclosing them in capsules to be taken orally. Useful substances found in green tea supplements include: catechins, caffeine, l-theanine, vitamin A, vitamin B2, folic acid, b-carotene, vitamin E, saponins, fluorine, y-aminobutyric acid (GABA), chlorophyll, and minerals such as potassium, phosphorus, magnesium, and calcium.

These amounts differ between supplements, so it is important to check the label. A moderate dose of caffeine is considered to be around 400 mg. Dosages of green tea catechins in supplements can range from 5 to 1200 mg. In terms of a moderate dose, 90 to 300 mg is common; 800 mg or higher is considered a high dose and is associated with a greater risk of harmful side effects.

What to Look For

Make sure you read the Supplement Facts labels on each product as you assess which brand of green tea supplements is right for you. The Supplement Facts label lists the active ingredients per serving as well as any fillers, binders, or flavorings.

According to one U.S. study, 19 green tea supplements were evaluated for tea catechin and caffeine content, and the analyzed values were found to be inconsistent with what was listed on the product labels. If possible, look for a seal of approval from a third party quality testing organization such as ConsumerLab. These seals of approval establish that the product contains the ingredients as listed, a number of contaminants below the threshold for harm, and was manufactured properly.

According to one epidemiological study, ready-to-drink tea products have lower polyphenol contents than loose-leaf teas, and it is unclear how this translates to supplement products.

Other Questions

Should I be concerned about aluminum toxicity?

According to one study referenced by the NIH, aluminum is found in tea plants in varying quantities and can accumulate in tea products to an unknown degree. There is no evidence of aluminum toxicity associated with taking tea products. To be safe, those with renal failure may want to be more careful of this and speak to their doctors.

Are there decaffeinated green tea supplements?
Yes, but the results from studies with caffeinated green tea supplements cannot be assumed to apply.

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