In 1747, a British Royal Navy surgeon conducted the first recorded controlled experiment. He proved that vitamin C prevented scurvy. Scurvy is now rare, but it was once common among sailors, pirates, and others who spent long periods of time onboard ships. When a voyage outlasted the fruit and vegetable supplies, the lack of vitamin C led to scurvy.

Vitamin C, also known as ascorbic acid, is water-soluble, which means that leftover amounts exit the body through the urine. Therefore, we need an ongoing supply in our diet for normal growth and development. Signs of vitamin C deficiency include fatigue, muscle weakness, joint and muscle aches, bleeding gums, leg rashes, and eventually scurvy.

Most experts recommend getting vitamin C from a diet that is high in fruits and vegetables, rather than from taking supplements. Good sources include citrus fruit (lemon, lime, orange, grapefruit), apple, melon, mango, berries, papaya, kiwi, watermelon, tomato, asparagus, broccoli, cabbage, cauliflower, dark leafy greens (kale, spinach), peppers (especially red), potato, and fortified food (bread, grain, cereal).

Why do people take vitamin C supplements? There is quite an unbelievable list of reasons. It has been used to prevent and treat the common cold. It is also used to treat gum disease, skin infections, HIV, stomach ulcers, tuberculosis, dysentery, bladder and prostate infections. It is also used to treat depression, Alzheimer and other dementias, stress, fatigue, ADD and ADHD, heart and arterial diseases, hypertension and high cholesterol, glaucoma, prevention of cataracts and gallstones, treatment of constipation, Lyme disease, heat stroke, hay fever, asthma, cystic fibrosis, infertility, diabetes, chronic fatigue, arthritis, cancer and osteoporosis. Finally, it has been touted to improve physical endurance, slow the process of aging, and help with the symptoms of withdrawal.

But what has Vitamin C actually been scientifically proven effective for? It’s truly amazing how much research has gone into this question. We can certainly agree that it does prevent scurvy. However, further studies of potential health benefits have provided conflicting results:

■ It does not appear to have any effect in the treatment of rheumatoid arthritis.

■ There is no clear evidence that vitamin C supplements help to prevent cardiovascular disease.

■ There is no evidence that supplements reduce the risk of myocardial infarction, stroke, or cardiovascular mortality. (One analysis found that it might reduce the risk of stroke.)

■ The use of high-dose IV vitamin C is not recommended as an anticancer agent.

■ Studies failed to find support for the prevention of breast cancer, but it might be associated with increased survival in those already diagnosed.

■ There is weak evidence that vitamin C might protect against lung cancer.

■ Taking vitamin C has no effect on the risk of prostate cancer.

■ There are mixed or weak results regarding a link between vitamin C supplements on the risk of colorectal cancer.

■ Studies examining the effects of vitamin C on the risk of Alzheimer’s disease have been conflicting. Maintaining a healthy dietary intake is probably more important than taking supplements.

■ No significant effects were found on preventing or slowing age-related cataracts.

■ Some research has shown that vitamin C may improve the absorption of dietary iron, and therefore help in treating anemia. Research is ongoing.

■ Vitamin C supplements appear to have no effect on overall mortality.

Finally, the effect of vitamin C on the common cold has been extensively researched. Surprisingly, it has not been shown effective in the prevention of the common cold (with one exception: when exercising vigorously in cold environments). Taking vitamin C supplements does not reduce the incidence or severity of the common cold in the general population, though it may reduce the cold’s duration.

Are there any risks associated with too much vitamin C? When obtained from food sources and supplements in the recommended dosages, vitamin C is regarded as safe. For most healthy individuals, the body can only hold and use about 250mg of vitamin C each day. At times of illness, during recovery from injury, or under conditions of increased oxidative stress (including smoking), the body can use greater amounts. Very high doses of vitamin C (greater than 2,000 mg/day) may contribute to kidney stones, as well as cause severe diarrhea, nausea, and gastritis.

The vast majority of uses for vitamin C are based on tradition and hearsay, or on marketing, rather than on hard scientific data. Many studies have been poorly conducted, and more and better research would be needed before I would recommend supplements for my patients.

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.