Home Products Vitamins How To Order FAQ
Are Whitening Pills SAFE? Dessert Treats
Glutathione Grape Seed Extract Alpha Lipoic Acid Zinc Aspartate Glutathione Absorbants
Glutathione Absorbants
Vitamin C
Vitamin C is a water-soluble vitamin that has a number of biological functions.
Acting as an antioxidant, one of vitamin C’s important functions is to protect LDL cholesterol from oxidative damage. (Only when LDL is damaged does cholesterol appear to lead to heart disease, and vitamin C may be one of the most important antioxidant protectors of LDL.)1 Vitamin C may also protect against heart disease by reducing the stiffness of arteries and the tendency of platelets to clump together.2
The antioxidant properties of vitamin C are thought to protect smokers, as well as people exposed to secondhand smoke, from the harmful effects of free radicals. A controlled trial demonstrated the ability of 3 grams of vitamin C, taken by nonsmokers two hours prior to being exposed to cigarette smoke, to reduce the free radical damage and LDL cholesterol oxidation associated with exposure to cigarette smoke.3 The smoke-induced decline in total antioxidant defense was also diminished. These beneficial effects were not observed in nonsmokers under normal conditions (no free radical exposure).
Vitamin C is needed to make collagen, the "glue" that strengthens many parts of the body, such as muscles and blood vessels. Vitamin C also plays important roles in wound healing and as a natural antihistamine. This vitamin also aids in the formation of liver bile and helps to fight viruses and to detoxify alcohol and other substances.
Recently, researchers have shown that vitamin C improves nitric oxide activity.4 Nitric oxide is needed for the dilation of blood vessels, potentially important in lowering blood pressure and preventing spasms of arteries in the heart that might otherwise lead to heart attacks. Vitamin C has reversed dysfunction of cells lining blood vessels.5 The normalization of the functioning of these cells may be linked to prevention of heart disease.
Evidence indicates that vitamin C levels in the eye decrease with age6 and that supplementing with vitamin C prevents this decrease,7 possibly leading to a lower risk of developing cataracts.8 9 Healthy people have been reported in some, but not all, studies10 to be more likely to take vitamin C and vitamin E supplements than are people with cataracts.11
Vitamin C has been reported to reduce activity of the enzyme, aldose reductase, in people.12 Aldose reductase is the enzyme responsible for accumulation of sorbitol in eyes, nerves, and kidneys of people with diabetes. This accumulation is believed to be responsible for deterioration of these parts of the body associated with diabetes. Therefore, interference with the activity of aldose reductase theoretically helps protect people with diabetes.
Vitamin C may help protect the body against accumulation or retention of the toxic mineral, lead. In one preliminary study, people with higher blood levels of vitamin C had much lower risk of having excessive blood levels of lead.13 In a controlled trial, male smokers with moderate to high levels of lead received supplements of 1,000 mg per day of vitamin C, 200 mg per day of vitamin C, or a placebo.14 Only those people taking 1,000 mg per day of vitamin C experienced a drop in the blood lead levels, but the reduction in this group was dramatic.
People with recurrent boils (furunculosis) may have defects in white blood cell function that are correctable with vitamin C supplementation. A preliminary study of people with recurrent boils and defective white blood cell function, found that 1 gram of vitamin C taken daily for four to six weeks, resulted in normalization of white blood cell function.15 Ten of twelve people receiving vitamin C became symptom-free within one month and remained so for periods of one to three years without additional supplementation. The other two people required long-term vitamin C supplementation to prevent recurrences.
A double-blind trial found that 500 mg of vitamin C per day for one year reduced the risk of developing reflex sympathetic dystrophy (a painful nerve condition of the extremities), after a wrist fracture.16
In a small, preliminary trial, vitamin C (500 mg twice daily) combined with rutoside (500 mg twice daily), a derivative of the flavonoid, rutin, produced marked improvement in three women with progressive pigmented purpura (PPP), a mild skin condition.17 Although not a serious medical condition, cosmetic concerns lead people with PPP to seek treatment with a variety of drugs. The vitamin C/rutoside combination represents a promising, non-toxic alternative to these drug treatments, but larger, controlled trials are needed to confirm these preliminary results.
Broccoli, red peppers, currants, Brussels sprouts, parsley, potatoes, citrus fruit, and strawberries are good sources of vitamin C.
The recommended dietary allowance (RDA) for vitamin C in nonsmoking adults is 75 mg per day for women and 90 mg per day for men. For smokers, the RDAs are 110 mg per day for women and 125 mg per day for men. Most clinical vitamin C studies have investigated the effects of a broad range of higher vitamin C intakes (100–1,000 mg per day or more), often not looking for (or finding) the “optimal” intake within that range. In terms of heart disease prevention, as little as 100–200 mg of vitamin C appears to be adequate.21 Although some doctors recommend 500–1,000 mg per day or more, additional research is needed to determine whether these larger amounts are necessary. Some vitamin C experts propose that adequate intake be considered 200 mg per day because of evidence that the cells of the human body do not take up any more vitamin C when larger daily amounts are used.22
Some scientists have recommended that healthy people take multi-gram amounts of vitamin C for the prevention of illness. However, little or no research supports this point of view and it remains controversial. Supplementing more results in an excretion level virtually identical to intake, meaning that consuming more vitamin C does not increase the amount that remains in the body.23 On the basis of extensive analysis of published vitamin C studies, researchers at the Linus Pauling Institute at Oregon State University have called for the RDA to be increased, but only to 120 mg.24 This same report reveals that “. . . 90–100 mg vitamin C per day is required for optimum reduction of chronic disease risk in nonsmoking men and women.” Thus, the multiple gram amounts of vitamin C taken by many healthy people may be superfluous.
The studies that ascertained approximately 120–200 mg daily of vitamin C is correct for prevention purposes in healthy people have typically not investigated whether people suffering from various diseases can benefit from larger amounts. In the case of the common cold, a review of published trials found that amounts of 2 grams per day in children appear to be more effective than 1 gram per day in adults, suggesting that large intakes of vitamin C may be more effective than smaller amounts, at least for this condition.25
Some people develop diarrhea after as little as a few grams of vitamin C per day, while others are not bothered by ten times this amount. Strong scientific evidence to define and defend an upper tolerable limit for vitamin C is not available. A review of the available research concluded that high intakes (2–4 grams per day) are well-tolerated by healthy people.26 However, intake of large amounts of vitamin C can deplete the body of copper27 28 —an essential nutrient. People should be sure to maintain adequate copper intake at higher intakes of vitamin C. Copper is found in many multivitamin-mineral supplements. Vitamin C increases the absorption of iron and should be avoided by people with iron overload diseases (e.g., hemochromatosis, hemosiderosis). Vitamin C helps recycle the antioxidant, vitamin E.
Glutamine
In animal research, glutamine has anti-inflammatory effects. Glutamine in combination with N-acetyl cysteine promotes the synthesis of glutathione, a naturally occurring antioxidant that is believed to be protective in people with HIV infection.1 Evidence indicates that intravenous glutamine supplementation increases the survival rate of critically ill people.2
Glutamine is found in many foods high in protein, such as fish, meat, beans, and dairy products.
Few healthy people are glutamine deficient, in part because the body makes its own. During fasting, starvation, cirrhosis, critical illnesses in general, and weight loss associated with AIDS and cancer, however, deficiencies often develop.
Healthy people do not need to supplement with glutamine. A physician should be consulted for the supplemental use of glutamine for the support of serious health conditions.
No significant side effects have been reported in glutamine studies.
Methionine
People with AIDS have low levels of methionine. Some researchers suggest this may explain some aspects of the disease process,1 2 3 especially the deterioration that occurs in the nervous system that can cause symptoms, including dementia.4 5 A preliminary study has suggested that methionine (6 grams per day) may improve memory recall in people with AIDS-related nervous system degeneration.6
Other preliminary studies have suggested that methionine (5 grams per day) may help treat some symptoms of Parkinson’s disease.7 However, another form of methionine, S-adenosylmethionine (SAMe) may worsen the symptoms of Parkinson’s disease and should be avoided until more is known.8 9 10 11 12
Methionine (2 grams per day) in combination with several antioxidants, reduced pain and recurrences of attacks of pancreatitis in a small but well-controlled trial.13
Meat, fish, and dairy are all good sources of methionine. Vegetarians can obtain methionine from whole grains, but beans are a relatively poor source of this amino acid.
Most people consume plenty of methionine through a typical diet. Lower intakes during pregnancy have been associated with neural tube defects in newborns, but the significance of this is not yet clear.14
Amino acid requirements vary according to body weight. However, average-size adults require approximately 800–1,000 mg of methionine per day—an amount easily obtained or even exceeded by most Western diets.
Animal studies suggest that diets high in methionine, in the presence of B-vitamin deficiencies, may increase the risk for atherosclerosis (hardening of the arteries) by increasing blood levels of cholesterol and a compound called homocysteine.15 This idea has not yet been tested in humans. Excessive methionine intake, together with inadequate intake of folic acid, vitamin B6, and vitamin B12, can increase the conversion of methionine to homocysteine—a substance linked to heart disease and stroke. Even in the absence of a deficiency of folic acid, B6, or B12, megadoses of methionine (7 grams per day) have been found to cause elevations in blood levels of homocysteine.16 Whether such an increase would create a significant hazard for humans taking supplemental methionine has not been established. Supplementation of up to 2 grams of methionine daily for long periods of time has not been reported to cause any serious side effects.17
At the time of writing, there were no well-known drug interactions with methionine.