Procysteine
Cysteine is a non-essential amino acid used for protein synthesis. Although we make some cysteine in our cells, it is also the rate-limiting amino acid for the synthesis of glutathione, a small molecule that plays many essential roles in cells. Cysteine is unstable, somewhat toxic, and weakly mutagenic when taken orally or by injection. But procysteine, a modified form of cysteine, is somewhat less toxic, and much more stable "on the shelf" than cysteine (White et al., 1993). It is rapidly converted into cysteine and carbon dioxide inside cells. This conversion makes it good for raising intracellular concentrations of cysteine, which, in turn, raises intracellular levels of glutathione.
Glutathione is made up of three amino acids, linked together like the amino acids in normal proteins. But, glutathione is a small molecule. It is important in many cellular functions including the folding of proteins into their correct structures. It also is an antioxidant (Kehrer and Lund, 1994) that detoxifies free radicals directly by interacting with them. And, it also is an important contributor to the detoxification of many free radicals and foreign chemicals by enzymes (Hayes and Pulford, 1995; Talalay et al., 1995). For example, it aids in the enzymatic detoxification of lipid peroxides and hydrogen peroxide.
The synthesis of glutathione is often limited by the supply of free cysteine. The concentration of free cysteine is very low in plasma. Low levels of glutathione lead to a decrease in intracellular antioxidant activities, and a decrease in the activities of the enzymes which depend on correct intracellular oxidation-reduction potential for their structure and activity.
There are no large clinical trials that demonstrate health benefits from glutathione or NADH supplementation. But a decrease in glutathione levels has been found in aging animals and humans, and in various disease states (Meydani et al., 1995). Glutathione levels decrease in the lens of the eye as we age. Lower glutathione levels have been found in the lens, spleen, liver, kidney and heart of old mice compared to young mice. In one study, half of elderly subjects had lower blood glutathione concentrations than younger subjects. There is a positive correlation between tissue glutathione levels and lifespan in mice. Glutathione inhibits liver cancer growth in humans and oral cancer in hamsters. Thus, the decline in glutathione levels with age may be related to the increase in cancer.
The decrease in glutathione levels with age also may partly explain the age-related decrease in immunity. And, decreased glutathione may partly be responsible for the liver's loss of detoxification ability. This loss is found in most mammals, including humans. Low glutathione levels are associated with arthritis, diabetes, heart disease and cataracts.
In clinical studies in the elderly, higher glutathione levels are associated with fewer illnesses and the perception of improved health. Finally, dietary supplementation with glutathione, or with supplements that raise glutathione levels, appears to improve the immune response in humans and experimental animals.
NADH
NADH (a form of nicotinamide adenine dinucleotide) is a coenzyme that assists enzymes involved in energy production within mitochondria. NADH plays an important role in the generation of ATP, the body's energy currency, and has been found to be deficient in several age-related degenerative diseases. Uncontrolled studies in Europe have found NADH beneficial for patients suffering from Parkinson's disease, Alzheimer's disease, and depression (Birkmayer, et al, 1990).
NADH also is needed for the regeneration of glutathione after it becomes oxidized (Sies and Stahl, 1995; Kehrer and Lund, 1994). If NADH levels are depleted, glutathione levels also may fall. Thus, supplementation with NADH also may help restore glutathione to its active form.
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