Vitamin C

Vitamin C (ascorbic acid) is an antioxidant and reducing agent found in certain foods. Humans cannot synthesize vitamin C, and it can be obtained only through selective dietary intake or with OTC supplements. This vitamin might help prevent some cancers, cardiovascular disease, and even the common cold. Although a wide range of health benefits have been ascribed to vitamin C, these claims are supported by evidence that varies in its depth, character, and veracity.

Almost all fruits and vegetables contain some vitamin C. Citrus fruits are commonly known sources, but other foods with high vitamin C content include:

• Bell peppers (especially red)

• Broccoli

• Brussels sprouts

• Cantaloupe

• Strawberries

• Potatoes

• Chili peppers

• Cabbage

A link is well established between vitamin C levels and thyroid function, making hyperthyroidism and thyrotoxicosis significant risk factors.

People at risk for vitamin C deficiency include babies who are fed only cow's milk or plant-based beverages (almond milk) during the first year of life, and pregnant and lactating women. Individuals with disease of the small intestine such as Crohn's, Whipple, and celiac, as well as those who undergo gastric bypass surgery, also are at risk.

Other contributors to vitamin C deficiency include:

• Alcoholism

• Certain restrictive diets

• Smoking cigarettes

• Anorexia nervosa or anorexia due to other diseases, such as AIDS or cancer

• Type 1 diabetes

According to NIH, the USRDAs for vitamin C are as follows:

• Adult men (age 19 years or older) – 90 mg

• Adult women (age 19 or older) – 75 mg

• Pregnancy (age 19 or older) – 85 mg

• Lactation (age 19 or older) – 120 mg

People who smoke may need an additional 35 mg/day.

Although high vitamin C intake does not appear to cause excess iron absorption in healthy individuals, chronic consumption of high doses of vitamin C might result in tissue damage due to iron overload in those with hereditary hemochromatosis.

Although no acute toxic dose for vitamin C has been determined, the chronic toxic dose is more than 2 g/day.

Drug Interractions:

Vitamin C may decrease the efficacy or levels of omadacycline by inhibiting gastrointestinal absorption. This applies only to the oral form. Optimally, dosing of tetracyclines and vitamin C should be separated and closely monitored if they must be used together.

Other medications, including aluminum, chemotherapy drugs, estrogen, protease inhibitors, statins, niacin, and warfarin, may also interact with vitamin C.

Author

Paddy Kalish OD, JD and B.Arch