Vitamin C is a water-soluble vitamin known to have antioxidant properties. It is also a powerful antiviral and immune system enhancer. It is important for a number of physiological processes including collagen formation, iron absorption and the synthesis of some hormones. It is also a strong scavenger of free radicals, protecting cells from oxidative damage. It is used to prevent and treat numerous conditions, from common colds to cancer, as well as many other chronic health problems. Taking large doses of vitamin C, or “megadosing,” was popularized by double Nobel laureate Linus Pauling and is still sometimes recommended to prevent colds and some chronic diseases. However, research on the efficacy of megadosing vitamin C is mixed.
One of the largest intervention studies that used vitamin C is the Women’s Antioxidant Cardiovascular Study, a randomized controlled trial that looked at the effects of ascorbic acid (vitamin C), vitamin E and beta carotene on cardiovascular events among 8171 female health professionals 40 years or older who were at increased risk for heart disease. The results showed no overall effect of the three supplements on cardiovascular events, including stroke, coronary revascularization and death. However, the placebo group had a significantly higher mortality rate than the ascorbic acid group. This was largely due to suboptimal vitamin C status at study start.
The chemistry and pharmacology of vitamin C is complex, but it has rarely been taken into account when designing clinical studies testing its effects. Its chemical lability, multiple mechanisms of uptake and absorption, rapid elimination kinetics, concentration-dependency and dose-response relationships are often overlooked. Incorporating this information into study design and analysis is essential to understanding its potential beneficial effects on human health.
In order to accurately measure plasma vitamin C concentrations, fasting is required. Since this is not a reasonable dietary restriction for the majority of the population, the use of non-fasted blood samples in many trials has led to vitamin C status measurements that are biased and inaccurate. This inevitably leads to misinterpretation of trial results.
Moreover, the high concentrations of vitamin C that are generated by megadosing can cause diarrhea and other digestive side effects in some people. High vitamin C levels can also interfere with certain medical tests and can be harmful for people with certain health conditions, such as hemochromatosis, kidney stones and those receiving chemotherapy treatment for cancer.
Because of these potential risks, it is important to choose the right supplement for you. When choosing a vitamin C supplement, make sure it is FDA-approved and follows Good Manufacturing Practices. It should also undergo third-party testing. Medical News Today has a list of the best vitamin C products that meet these requirements. You should also tell your doctor if you are taking vitamin C supplements before having any medical tests, as they may increase the amount of aluminum that is absorbed from some medications and reduce the effectiveness of some treatments. The best way to get enough vitamin C is to eat healthy, including plenty of fruits and vegetables.