Vitamin C

In humans, Vitamin C is a highly effective antioxidant working to lessen oxidative stress, neutralize pollutants and thus strengthen the immune system. It also acts as a substrate for ascorbate peroxidases (enzymes that detoxify peroxides such as hydrogen peroxide), an enzyme co-factor for the biosynthesis of many important biochemicals and it is an electron donor for 8 different enzymes.

In addition, C helps make collagen, a tissue needed for healthy bones, cartilage, teeth, gums, skin, and blood vessels; it also thins the blood. This vitamin is essential in sperm production and has been shown to lower intraocular pressure (IOP) in glaucoma patients when taken in massive amounts according to the September 2007 issue of GLEAMS (the newsletter of the Glaucoma Research Foundation). C cannot be advised as an alternative glaucoma treatment due to undesirable side effects of mega dose supplementation with the C vitamin (see "Toxicity" below).

The Institute of Medicine's current recommended dietary intake for vitamin C is 90 mg for men and 75 mg for women (add an extra 35 mg for smokers). The upper limit is set at 2 g per day. There is no good scientific evidence that mega doses of C improve health.

As the evidence continues to unfold, 200 to 300 mg a day appears to be a reasonable target and is easy to achieve with a good diet. Glutathione helps maintain the C vitamin and lower the required intake by recycling it. The recycling occurs after the C vitamin has neutralized a free radical by giving up an electron to the free radical. GSH in turn gives up an electron to the C, retuning the C to your system, thus vitamin C has been recycled and your immune health improved.

Food sources of vitamin C readily available to the North-American and European consumers (the C content is in given in brackets and is in mg/3.5 ounces. (3.5 oz is equivalent to 100 g): rose hip 2,000 mg/3.5 oz (100 g), black currant (200), red bell peppers (190), parsley (130), kiwi (90), broccoli (90), red currant (80), Brussels sprouts (80), wolfberry/goji (73, dried), lychee (70), persimmon (60), papaya (60), strawberry (60), orange (50), lemon (40), cantaloupe melon (40), cauliflower(40), garlic (31), grapefruit (30), raspberry (30), tangerine (30), passion fruit (30), spinach (30), raw green cabbage (30), lime (30), mango (28), cranberry (13), tomato (10), blueberry (10), pineapple (10).

For the complete list of foods and Vitamin C content in them click here.

Two extraordinary sources of vitamin C, unfortunately not available in the North America or Europe, are Kakadu plum and Camu Camu. Kakadu plum has the highest known C content, 3,100 mg/3.5 oz (100 g), that is over 5% C by weight - 60 times the concentration found in oranges. Camu Camu contains the second highest known content, 2,800 mg/3.5 oz (100 g), that is 2-3% of its fresh weight. Kakadu plums are native to Australia and Camu Camu is a native of the Amazon rainforest.

Deficiency:
The human body only can store a certain amount of C. If fresh supplies are not consumed regularly the body soon depletes itself of this necessary vitamin. The presence of large quantities of sugar either in the intestines or in the blood can slow the absorption of C. The deficiency causes scurvy and makes a person more susceptible to cold and flu viruses. Nobel prize winner Linus Pauling (1901-1994) and Dr. G. C. Willis have concluded that chronic long term low blood levels of vitamin C or chronic scurvy is a cause of atherosclerosis.

Toxicity:
C exhibits extremely low toxicity. However, very high doses (thousands of milligrams) may cause indigestion, diarrhea and skin rashes. As C enhances iron absorption, iron poisoning can become an issue to people with rare iron overload disorders.