Vitamin C: Cure for the Common Cold?
For years vitamin C has been revered for its supposed effects on preventing and curing the common cold. Despite what supplement producers try to suggest however, little evidence actually exists to prove this theory. In fact, recent findings suggest that, if anything, vitamin D may be the most helpful in preventing colds and flues.
It isn’t that vitamin C has no role in cold prevention/healing. Vitamin C is essential to enhancing immune function. It’s mostly the amount of vitamin C needed that is often mistaken. The RDA for most adult women is 75 mg/day and for adult men is 90 mg/day. Once the RDA is reached, there aren’t significant benefits shown to taking a higher dose. Meeting the RDA for vitamin C daily may actually help reduce your risk of catching a cold and may reduce the duration (by about 1 day). Once you have the cold, however, taking a super dose of vitamin C has not been shown to provide any significant benefit.
Best Food Sources: The best food sources of vitamin C are generally peppers, citrus fruits, and green vegetables. When you think of vitamin C, what’s the first food that comes to mind? For most people, it’s an orange. An orange is an excellent source of vitamin C, 1/2 cup of orange juice provides about 45 mg, nearly 75% of the RDA for women (about 50% the RDA for men). Here are a few examples of vitamin C-rich foods you might not have guessed:
- Guava: 1/2 cup of guava provides over 225 mg, more than 300% of daily vitamin C RDA
- Red Bell Pepper: 1/2 cup provides over 100 mg, 160% daily vitamin C RDA for women (over 100% for men)
- Kiwi: 1/2 cup provides about 80 mg, over 100% RDA for women and about 90% RDA for men
- Broccoli: 1/2 cup provides about 40 mg, more than 50% RDA for women and about 45% RDA for men
Vitamin C Functions:
- Important antioxidant
- Aids in collagen synthesis (needed for healthy bones, blood vessels and wound healing)
- Enhances iron absorption (It’s especially important for vegetarians to get adequate vitamin C to help enhance iron absorption from non-animal sources)
- Healthy immune system (white blood cells contain high concentrations of vitamin C)
Between 70-90% of vitamin C is absorbed in the small intestine from daily intakes of between 30 and 200 mg. Excess vitamin C is not well absorbed and will mostly pass through the body unused through the kidneys and out in urine.
Luckily, if you have been taking a vitamin C super-dose of 1,000mg you are not likely to experience severe toxicity symptoms. There are some risks, however, when taking vitamin C above the Upper Limit of 2,000 mg/day. Vitamin C toxicity causes GI distress including nausea, abdominal cramps, and diarrhea. Continued use levels above the UL may also increase risk for kidney stone formation. Like most vitamins, toxicity symptoms are not reached from food consumption but may be reached when an individual is taking a high dose supplement.
Who Needs More? Certain populations may benefit from taking additional vitamin C beyond the RDA for the average person. People who are exposed to more oxidative stress, for example, need an additional amount because vitamin C is needed to act as an antioxidant. Smokers, because they are exposed to high levels of damaging free radicals, (as well as individuals who are regularly exposed to second-hand smoke) consume an additional 35 mg/day. Additional vitamin C intake does not protect smokers from damage but the extra intake is needed to maintain adequate vitamin C levels in the body because their supply is depleted faster. Burn and surgery patients, women taking oral contraceptives, and athletes may also need to take more vitamin C than the standard RDA.