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Vitamin C
What is it? Overview Usage Side Effects and Warnings

What is Vitamin C?

Although most animals can make vitamin C from scratch, humans have lost the ability over the course of evolution. We must get it from food, chiefly fresh fruits and vegetables. One of this vitamin's main functions is helping the body manufacture collagen, a key protein in our connective tissues, cartilage, and tendons.

From ancient times through the early nineteenth century, sailors and others deprived of fresh fruits and vegetables developed a disease called scurvy. Scurvy involves so-called scorbutic symptoms, which include nonhealing wounds, bleeding gums, bruising, and overall weakness. Now we know that scurvy is nothing more than vitamin C deficiency.

Scurvy was successfully treated with citrus fruit during the mid-1700s. In 1928, when Albert Szent-Gyorgyi isolated the...

According to numerous double-blind, placebo-controlled studies, regular use of vitamin C supplements can slightly reduce symptoms of colds and modestly shorten the length of the illness. 1 However, taking vitamin C at the onset of a cold probably will not work. 2 Regular use of vitamin C does not seem to help preventcolds. 3 One exception is the “post-marathon sniffle”—colds that develop after heavy exercise. 4 Vitamin C may be helpful for preventing this condition, although not all studies agree. 5 Two double-blind studies suggest that the use of vitamin C combined with vitamin E might slightly reduce the risk of developing preeclampsia , a complication of pregnancy. 6 However, a much larger follow-up study failed to find benefits. 7 Two studies...

Safety Issues

The US government has issued recommendations regarding tolerable upper intake levels (ULs) for vitamin C. The UL can be thought of as the highest daily intake over a prolonged time known to pose no risks to most members of a healthy population. The ULs for vitamin C are as follows:

  • Children
    • 1-3 years: 400 mg
    • 4-8 years: 650 mg
    • 9-13 years: 1,200 mg
  • Males and Females
    • 14-18 years: 1,800 mg
    • 19 years and older: 2,000 mg
  • Pregnant Women
    • 18 years old or younger: 1,800 mg
    • 19 years and older: 2,000 mg
  • Nursing Women
    • 18 years old or younger: 1,800 mg
    • 19 years and older: 2,000 mg

However, even within the safe intake range for vitamin C, some individuals may develop diarrhea....