Limit exposure to air and sunlight. Avoid soaking the food in water for long periods. Cook food in minimal amounts of water. Microwave cooking preserves the vitamin C because water is not added. Cook food in largest pieces possible.
Heat reduces some of the content of vitamin C in food.
Freeze-drying of fruit cues minimal loss of Vitamin C. Frozen and canned foods, picked at the prime and optimally processed, may have more vitamin C than fresh produce that has been stored for a long time with poor temperature and humidity conditions. Many people believe in the benefits of supplementation of vitamin C, sometimes as high as 3000 mg a day. Large amounts of vitamin C can cause nausea, abdominal cramps, diarrhea and nose bleeds. Researchers disagree as to whether large doses of vitamin C cause kidney stones. Vitamin C supplementation is recommended for groups with special considerations because the vitamin C is depleted in fighting the free radicals.