context: Vitamin C (ascorbic acid) helps tissue and bone grow and repair themselves. While vitamin C supplements are extremely popular, research has yet to establish solid health benefits. Studies have shown that vitamin C may reduce the odds of getting a cold, but only in specific groups in extreme circumstances, such as soldiers in subarctic environments, skiers, and marathon runners. Studies have not found solid evidence that vitamin C helps prevent or treat colds in average situations. Vitamin C's antioxidant benefits are also unclear. While some studies of vitamin C supplements have been promising, they have not found solid evidence that vitamin C supplements help with cancer, stroke, asthma, and many other diseases. Some evidence suggests that vitamin C may be helpful in people who have high cholesterol and in preventing cataracts, but more studies are needed to prove these effects. Data on vitamin C and heart disease are mixed. Some studies show an association between low levels of vitamin C and heart disease risk, yet many studies have linked the use of vitamin C supplements with an increased risk of heart disease. Data on taking vitamin C for hypertension are also mixed. Taking vitamin C with antihypertensive medications may slightly decrease systolic blood pressure, but not diastolic pressure. Supplemental vitamin C -- 500 mg per day taken without antihypertensives -- doesn't seem to reduce systolic or diastolic blood pressure. Type 2 diabetics who supplemented with vitamin C and remained on their antihypertensive medications seemed to have a reduction in blood pressure and arterial stiffness. Lower levels of vitamin C in the blood are associated with increased diastolic and systolic blood pressure. Studies have shown that dietary rather than supplemental sources of vitamin C are more effective in keeping blood pressure in check. A substantial number of Americans may have low intake levels of vitamin C due to the inadequate intake of fruits and vegetables. The proven and effective use of vitamin C is for treating vitamin C deficiency and conditions that result from it, like scurvy. Vitamin C also seems to help the body absorb the mineral iron. The recommended dietary allowance ( RDA) includes the vitamin C you get from both the food you eat and any supplements you take. Category Vitamin C: Recommended Dietary Allowance ( RDA) For children under 1, only an adequate intake ( AI) is available CHILDREN 0-6 months 40 mg/day Adequate Intake ( AI) 7-12 months 50 mg/day Adequate Intake ( AI) 1-3 years 15 mg/day 4-8 years 25 mg/day 9-13 years 45 mg/day FEMALES 14 to 18 years 65 mg/day 19 years and up 75 mg/day Pregnant 18 years and under: 80 mg/day19 years and over: 85 mg/day Breastfeeding 18 years and under: 115 mg/day19 years and over: 120 mg/day MALES 14 to 18 years 75 mg/day 19 years and up 90 mg/day Smokers need 35 mg/day more vitamin C than nonsmokers. Although many people take much higher doses of vitamin C, it's not clear that high doses have any benefit. Some studies have found that doses above 400 milligrams are not utilized by the body. Instead, the extra vitamin C is excreted in urine. The tolerable upper intake levels of a supplement are the highest amount that most people can take safely. Higher doses might be used to treat vitamin C deficiencies. But don't take more unless a doctor says so. Category ( Children & Adults) Tolerable Upper Intake Levels ( UL) of Vitamin C 1-3 years 400 mg/day 4-8 years 650 mg/day 9-13 years 1,200 mg/day 14-18 years 1,800 mg/day 19 years and up 2,000 mg/day Many people get enough vitamin C from their diets. All fruits and vegetables have some vitamin C. Some of the best sources are: Green peppers Citrus fruits and juices Strawberries Tomatoes Broccoli Sweet potatoes Light and heat can reduce vitamin C levels. Fresh and uncooked fruits and vegetables have the most vitamin C. Side effects. At recommended doses, vitamin C supplements are safe. However, they can cause upset stomach, heartburn, cramps, and headaches in some people. High doses of vitamin C can cause more intense symptoms, such as kidney stones and severe diarrhea. Interactions. If you take any other regular medicines or chemotherapy drugs, ask your doctor if it's safe to take vitamin C. It can interact with drugs like aspirin, acetaminophen, antacids, and blood thinners. Nicotine may reduce the effects of vitamin C. Risks. People who are pregnant or have gout, liver disease, kidney disease, and other chronic diseases should check with a doctor before using high doses of vitamin C supplements.