At the very first sign of cold symptoms, many people reach right for a bottle of vitamin C supplements. Vitamin C for the common cold is such a widely accepted treatment that we seek it out in lots of products, such as fortified juices, cough drops, and tea. At the very first sign of cold symptoms, many people reach right for a bottle of vitamin C supplements. Vitamin C for the common cold is such a widely accepted treatment that we seek it out in lots of products, such as fortified juices, cough drops, and tea.

Vitamin C has been studied for many years as a possible treatment for colds, or as a way to prevent colds. But findings have been inconsistent. Overall, experts have found little to no benefit for vitamin C preventing or treating the common cold.

In a July 2007 study, researchers wanted to discover whether taking 200 milligrams or more of vitamin C daily could reduce the frequency, duration, or severity of a cold. After reviewing 60 years of clinical research, they found that when taken after a cold starts, vitamin C supplements do not make a cold shorter or less severe. When taken daily, vitamin C very slightly shorted cold duration -- by 8% in adults and by 14% in children.

The average adult who suffers with a cold for 12 days a year would still suffer for 11 days a year if that person took a high dose of vitamin C every day during that year. For the average child who suffers about 28 days of cold illness a year, taking daily high-dose vitamin C would still mean 24 days of cold illness. When vitamin C was tested for treatment of colds in 7 separate studies, vitamin C was no more effective than placebo at shortening the duration of cold symptoms.

In general, vitamin C is safe to take when ingested through food sources such as fruits and vegetables. For most people, taking vitamin C supplements in the recommended amounts is also safe. The RDA or recommended daily allowance is 90 mg for men and 75 mg for women. High doses of vitamin C (greater than 2000 milligrams per day for adults) may cause kidney stones, nausea, and diarrhea.