|
Glutathione
JoAnn Guest
Nov 08, 2003 09:48 PST
Glutathione
What does it do? Glutathione is a small protein composed of three amino acids: cysteine, glutamic acid, and glycine. Glutathione is involved in detoxification—it binds to toxins, such as heavy metals, solvents, and pesticides, and transforms them into a form that can be excreted in urine or bile.
Glutathione is also an important antioxidant.
In preliminary research, dietary glutathione intake from fruit and raw vegetables has been
associated with protection against some forms of cancer.
Glutathione has also inhibited cancer in test tube3 and animal studies.4 In preliminary research, higher glutathione levels have also been associated with good health in older adults.
Glutathione supplements appear to be efficiently absorbed in rats. However, the same may not be true for glutathione supplements in humans.
For example, when seven healthy subjects were given
a single application of up to 3,000 mg of glutathione, there was no increase in blood glutathione levels.
The authors of the study concluded "it is not feasible to increase circulating glutathione to a clinically beneficial extent by the oral administrating of a single application of 3,000 mg of
glutathione." Absorption of glutathione may be better in rats because unlike the gastrointestinal tract of rats, the human gastrointestinal tract contains significant amounts of an enzyme (gamma-
glutamyltranspeptidase) that breaks down glutathione.
Very preliminary evidence has suggested that absorption of glutathione can occur in the mouth when glutathione tablets are placed between the teeth and the inner cheek.
Some researchers believe that supplements other than oral glutathione may be more effective in raising blood levels of glutathione.
For example, in one trial, blood glutathione levels rose nearly 50% in healthy people taking 500 mg of
vitamin C per day for only two weeks.
Vitamin C raises glutathione by helping the body manufacture it. In addition to vitamin C, other nutritional compounds that may, according to preliminary research, help increase glutathione levels
include alpha lipoic acid, glutamine,12 methionine,13 S-adenosyl methionine (SAMe).
Vitamin B6, riboflavin, and selenium are required in the manufacture of glutathione. The extent to which any of these nutrients effectively increases glutathione levels in humans remains unclear.
Studies using intravenous or intramuscular glutathione have found it to be useful for preventing clot formation during operations;16 reducing the side effects and increasing the efficacy of chemotherapy drugs (particularly cisplatin in women with ovarian cancer);17 18 treating Parkinson's disease;
reducing blood pressure in people with diabetes with high blood pressure;20 and increasing sperm counts in men with low sperm counts.
A
glutathione nasal spray has also reduced symptoms in people with chronic rhinitis.
Whether oral preparations are also effective is unknown at this time. A small study in eight patients with liver cancer using oral glutathione showed modest benefits in women, but not in men, when
given in a daily amount of 5,000 mg.
An unpublished preliminary study of eight colon cancer patients also found that oral glutathione appeared to have anticancer activity.25 Nonetheless, because questions exist about the extent to which oral glutathione can be absorbed, some doctors are concerned that oral preparations may be either less effective than other forms or not effective at all.
Where is it found? Dietary glutathione is found in fresh and frozen fruits and vegetables,and fish.
Asparagus, avocado, and walnuts are particularly rich dietary sources of glutathione.
Who is likely to be deficient? A deficiency can be the result of diseases that increase the
need for glutathione, deficiencies of the amino acids needed for synthesis, or diseases that inhibit
glutathione formation.
Examples of some health conditions that are associated with glutathione deficiency include diabetes, low sperm counts, liver disease, cataracts, and HIV infection, respiratory distress syndrome,
cancer, and idiopathic pulmonary fibrosis. Cigarette smoking is also associated with low glutathione levels because it increases the rate of utilization of glutathione.
How much is usually taken? There is very little evidence that taking glutathione supplements provides any benefit, despite promising evidence about the effects of aerosol, intravenous, and intramuscular
glutathione, for people with a wide variety of conditions.
People who have a proven glutathione deficiency, which may require administration of glutathione intravenously, intramuscularly, or by aerosol, should be treated by a healthcare professional. All ovarian
cancer patients currently taking cisplatin (Platinol®) should discuss using intravenous glutathione with a healthcare professional.
Are there any side effects or interactions? No side effects or interactions are known with oral administration of glutathione.
Are there any drug interactions? Certain medications may interact with glutathione.
---------------------------------------------------------------------
-----------
References:
1. Sen CK. Nutritional biochemistry of cellular glutathione. Nutr
Biochem 1997;8:660–72.
2. Flagg EW, Coates RJ, Jones DP, et al. Dietary glutathione intake
and
the risk of oral and pharyngeal cancer. Am J Epidemiol 1994;139:453–
65.
3. Donnerstag B, Ohlenschläger, Cinatl J, et al. Reduced glutathione
and
S-acetylglutathione as selective apoptosis-inducing agents in cancer
therapy. Cancer Lett 1996;110:63–70.
4. Trickler D, Shklar G, Schwartz J. Inhibition
of oral
carcinogenesis
by glutathione. Nutr Cancer 1993;20:139–44.
5. Julius M, Lang C, Gleiberman L, et al. Glutathione and morbidity
in a
community-based sample of elderly. J Clin Epidemiol 1994;47:1021–6.
6. Hagen TM, Wierzbicka GT, Sillau AH, et al. Fate of dietary
glutathione: disposition in the gastrointestinal tract. Am J Physiol
1990;259(4Pt1):G530–5.
7. Favilli F, Marraccini P, Iantomasis T, Vincenzini MT. Effect of
orally administered glutathione on glutathione levels in some organs
of
rats: role of specific transporters. Br J Nutr 1997;78:293–300.
8. Witschi A, Reddy S, Stofer B, Lauterburg BH. The systemic
availability of oral glutathione. Eur J Clin Pharmacol 1992;43:667–9.
9. Hunjan MK, Evered DF. Absorption of glutathione from the
gastro-intestinal tract. Biochim Biophys Acta 1985;815:184–8.
10. Johnston CS, Meyer CG, Srilakshmi JC. Vitamin C elevates red
blood
cell
glutathione in healthy adults. Am J Clin Nutr 1993;58:103–5.
11. Bunin AIa, Filina AA, Erchev VP. A glutathione deficiency in
open-angle glaucoma and the approaches to its correction. Vestn
Oftalmol
1992;108:13–5 [in Russian].
12. Amores-Sanchez MI, Medina MA. Glutamine, as a precursor of
glutathione, and oxidative stress. Mol Genet Metab 1999;67:100–5.
13. Wang ST, Chen HW, Sheen LY, Lii CK. Methionine and cysteine
affect
glutathione level, glutathione-related enzyme activities and the
expression of glutathione S-transferase isozymes in rat hepatocytes.
J
Nutr 1997;127:2135–41.
14. Vendemiale G, Altomare E, Trizio T, et al. Effects of oral
S-adenosyl-L-methionine on hepatic glutathione in patients with |