Vitamin D has gotten a lot of attention in recent years for its potential to prevent a wide range of illnesses, including the common cold. However, a new study has found that people who took large doses of vitamin D were just as likely to catch colds as those who didn’t. Research has also shown that vitamin C won’t prevent colds either, but it has been shown to shorten the duration of colds.
Cold and flu season
Vitamin D is called the “sunshine vitamin” because the body naturally produces it when exposed to sunlight. As winter approaches, the sun falls lower in the sky, days grow shorter and most people are exposed to very little sunlight. Coincidently or not, cold and flu season kicks in at the same time.
Vitamin D and cold prevention
Research has suggested that vitamin D could be a preventive treatment for a range of diseases from cancer to multiple sclerosis because of its role in immunity, primarily by inducing the body to produce antimicrobial compounds. The potential of vitamin D as a prophylactic against the common cold has been suggested because vitamin D deficiency has been linked to higher rates of pneumonia and upper respiratory tract infections.
To investigate the cold prevention qualities of vitamin D, researchers in New Zealand gave study volunteers either high doses of vitamin D3—the form of the vitamin produced by the body—or a placebo and tracked them for 18 months over two winter cold and flu seasons.
Vitamin D, for dud
The Institute of Medicine recommends that people up to 70 years old take in 600 IU of vitamin D daily, and that people over 70 years take in 800 IU daily. Study participants on vitamin D took 200,000 IU once a month, then switched to 100,000 IU a month. The mega-dose matched those that achieved the lowest risk of disease in previous research.
When they caught colds, participants reported their symptoms. A researcher would visit them to do a swab test for the wide variety of viruses that cause colds and flu. During the study period, 593 people on vitamin D3 and 611 on the placebo caught an average of four colds, a difference the authors said was statistically insignificant in their report published in the Journal of the American Medical Association. In both groups, colds lasted an average of 12 days and those affected missed the same number of workdays.
Just another old wives tale?
In a JAMA sidebar editorial, Jeffrey A. Linder, MD, MPH, of Brigham and Women’s Hospital in Boston, said, “Results suggest that vitamin D should join the therapies listed in the Cochrane reviews as being ineffective for preventing or treating upper respiratory tract infections in healthy adults.”
The Cochrane list includes vitamin C, garlic, Echinacea, zinc, saline nasal irrigation, steam inhalation and increased fluid intake. However, once you get a cold, high doses of vitamin C could limit your suffering—to a point.
What about vitamin C?
Researchers at Australia’s National Centre for Epidemiology and Population Health analyzed more than 30 published trials involving more than 10,000 people that investigated vitamin C’s ability to prevent the common cold. The analysis showed that people taking a daily dose of vitamin C as high as 1 gram caught colds just as often as people who didn’t take extra vitamin C.
However, people on mega-doses of vitamin C were able to shake off their cold symptoms about 12 hours sooner.
The National Institutes of Health recommends 90 milligrams of vitamin C per day for men and 75 milligrams for women. If you want to boost your vitamin C intake, don’t store your pills or powders in the bathroom medicine cabinet. Vitamin C dissolves in water and steam can deplete its strength in about a week.
Natural sources of vitamin C such as citrus fruits, dark green vegetables, peppers, strawberries and cantaloupe are always best. But cooking has the same effect as shower steam. To maximize the vitamin C you get from food, eat your fruits and vegetables fresh and raw.