Despite its claim to fame, don't count on mega-doses of vitamin C to prevent a cold. A major review of 30 studies with more than 11,000 subjects found that vitamin C failed to reduce the incidence of colds. However, when duration and severity of colds was examined, a slight benefit was found among those who took daily supplements containing 200 mg or more of vitamin C. Cold duration was shortened by 8 percent in adults and 14 percent in children, and people missed fewer days of work and school.
The recommended daily intake for vitamin C is 75 mg for women and 90 mg for men, with smokers requiring an additional 35 mg. Depending on age and gender, children need 25 to 75 mg each day. Get your daily C from foods such as citrus fruits and juices, papaya, strawberries, tomatoes, bell peppers, cantaloupe and broccoli—all excellent sources and packed with other nutrients as well. If you choose to take vitamin C supplements, don't exceed 2,000 mg per day.