In the body, dangerous naturally occurring substances called free radicals pose a risk of harm to many tissues. The body deploys an “antioxidant defense system” to hold them in check. Glutathione, a protein made from the amino acids cysteine, glutamic acid, and glycine, is one of the most important elements of this defense system.

Glutathione does much of its work in the liver, although it is also found elsewhere in the body. Besides fighting free radicals, it helps keep various essential biological molecules in a chemical state called “reduced” (as opposed to “oxidized”). In addition, glutathione can act on toxins such as pesticides, lead, and dry cleaning solvents, transforming them in such a way that the body can excrete them more easily.

Nutrients such as vitamin C and vitamin E also help neutralize free radicals. In the 1990s, such antioxidant supplements were widely promoted for preventing a variety of diseases, including cancer and heart disease. Unfortunately, this hope has largely floundered as the results of large, reliable studies have come in. During this period, oral glutathione became popular as an additional antioxidant supplement but glutathione is not absorbed when taken by mouth, so such supplements are almost certainly useless. It may be possible, however, to raise glutathione levels in the body by taking other supplements, such as vitamin C, cysteine, lipoic acid, and N-acetylcysteine. Whether doing so would offer any health benefits remains unclear.

Requirements/Sources

There is no dietary requirement for glutathione. The body makes it from scratch, utilizing vitamins and common amino acids found in food.

Glutathione levels in the body are reduced by cigarette smoking. Various diseases are also associated with reduced levels of glutathione, including cancer, cataracts, diabetes, and HIV infection.1

Therapeutic Dosages

A typical recommended dose of oral glutathione is ranges from 50 mg (and higher) per day. As a general rule, glutathione taken by mouth is destroyed.2 Therefore, no matter what the dose, it won’t make any difference.

It is possible that some glutathione may be absorbed if it is held in the mouth and allowed to dissolve, but this has not been well studied.3

A more promising method for raising glutathione levels in the body involves taking supplemental cysteine or antioxidant supplements. Evidence suggests that cysteine (often supplied in the form of whey protein, which is high in cysteine) can raise glutathione levels in people with cancer, hepatitis, or HIV.4-7

In addition, because vitamin C has overlapping functions with glutathione, vitamin C supplements may spare some of the body’s glutathione from being used up, thereby increasing its levels in the body.8,9 The antioxidant supplement lipoic acid appears to raise glutathione levels as well.10-15

Other supplements that might raise glutathione levels include N-acetylcysteine,16-19 glutamine,20 methionine,21 and S-adenosyl methionine (SAMe).22

Therapeutic Uses

Various websites promote glutathione for a wide variety of health problems, from preventing aging to enhancing sports performance. However, oral glutathione supplements may be useless for any condition since they do not appear to be absorbed or stay in the body for any length of time.

There is a bit of evidence that injected glutathione might offer a few heath benefits, such as preventing blood clots during surgery,23 reducing the side effects and increasing the effectiveness of cancer chemotherapy drugs such as cisplatin,24-26 treating male infertility,27-31 and alleviating symptoms of early Parkinson’s disease.32,33 Although oral glutathione is not likely to provide the same benefits, it is at least theoretically possible that taking the nutrients described in the previous section (and thereby raising glutathione levels indirectly) could offer similar benefits. However, there is no direct evidence to indicate that this hypothesis is true.

A small randomized trial showed some promise that glutathione may remain in the body with regular use. Fifty-four adults were given a glutathione supplement (250 mg per day or 1000 mg per day) or placebo for 6 months. Glutathione levels in blood increased in those taking the supplement, with a greater response seen in those taking the higher dose. The supplement group also demonstrated a reduction in oxidative stress. However, blood levels of glutathione returned to their original baseline level within 1 month of stopping the supplement.34

Safety Issues

Firm glutathione dosages have not been established, though most supplements range up to 1,000 mg per day. There are no known side effects or toxicities, but some people may be more sensitive to it than others. Talk to a healthcare professional before taking any glutathione supplements.