A new study suggests that vitamin D supplementation may not reduce the risk or severity of the common cold.
The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It is used, alone or in combination with calcium, to increase bone mineral density and decrease fractures. Recently, research also suggests that vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), cancer and several autoimmune diseases.
In a new study, researchers randomly assigned 322 healthy adults to one of two groups. The first group received one dose of 200,000 IU vitamin D3 by mouth, a second dose of 200,000 IU one month later, and then 100,000 IU once monthly for 18 months. The second group received a placebo in the same frequency as the vitamin D group. The development of the common cold was the main outcome measure. Severity and duration of cold symptoms were also evaluated.
The researchers found that a significant difference between the number of colds in the vitamin D and placebo groups was lacking, with 593 and 611 colds in the vitamin D and placebo groups, respectively. Furthermore, the severity and duration of cold symptoms was similar between groups.
The authors concluded that vitamin D supplementation may not reduce the risk or severity of the common cold. Additional research is necessary.
In addition to vitamin D, many other integrative therapies have been studied for their potential to reduce the risk, severity and duration of the common cold. There are conflicting results regarding the effect of zinc formulations in treating the duration and severity of common cold symptoms. Although zinc may be beneficial in the treatment of cold symptoms if taken at the onset of symptoms, more studies are needed to clarify which zinc formulations may be most effective, which rhinoviruses are affected by zinc and if nasal sprays provide a useful alternative application route for zinc treatment.
Scientific studies generally suggest that vitamin C does not prevent the onset of cold symptoms. However, in a subset of studies of people living in extreme climates or under extraordinary conditions, including soldiers in subarctic exercises, skiers and marathon runners, vitamin C significantly reduced the risk of developing colds, by approximately 50 percent.
For more information about integrative therapies for common cold treatment and prevention, please visit Natural Standard's Comparative Effectiveness Database.
For more information about vitamin D, please visit Natural Standard's Foods, Herbs & Supplements Database.