Vitamin C (ascorbic acid) was popularized by two-time Nobel Laureate Linus Pauling due to its many functons in the body. One of the least stable vitamins, vitamin C cannot be manufactured in the body, and among food sources is only found in fruits and vegetables. In addition to acting as a potent anti-oxidant and immune system enhancer, vitamin C is essential for the formation of collagen, which acts as the basis for the body's connective tissue. As a result, vitamin C contributes to the overall health of blood vessels, capillary walls, cartilage, joint linings, ligaments, vertebrae, bones, teeth, and skin, and plays a vital role in wound healing. It also aids in the metabolism of amino acids and cholesterol, and in the synthesis of hormones, and helps the body cope with the effects of stress. In addition, vitamin C's detoxification properties make it useful for protecting the body against heavy metal toxicity, environmental pollutants, and nicotine poisoning. It also effective in fighting bacterial and viral infections, and acts as a natural histamine, making it useful for dealing with allergies.

The best food sources of vitamin C include citrus fruits, rosehips, cherries, cantaloupe, papaya, strawberries, red and green peppers, parsley, and dark green and leafy vegetables.

Because vitamin C is not reasdily stored in the body, it must be daily supplied through the diet or supplementation. The most famous sign of vitamin C deficiency is scurvy, a disease that today is extremely rare. Other deficiency symptoms include anemia, reduced resistance to infections, increased tendency towards bruising, slow wound healing, bleeding gums, and mouth ulcers.