There is mounting evidence in the scientific literature that certain vitamins possess health benefits beyond their ability to inhibit deficiency diseases. One of the main roles proposed for some of the vitamins is that of antioxidants. Vitamin E, vitamin C, carotenoids and vitamin A are all of interest to nutritional scientists because they have antioxidant properties in vivo, and they have also been shown to be beneficial in protecting individuals from cardiovascular disease. Free radicals produced naturally in the body, as well as from chemicals or pollution in food or water can damage DNA, proteins, carbohydrates and lipids in all tissues of the body and so are thought to be important factors in the development of many disease. Antioxidants are able to quench free radical chain reactions and thus may be able to protect cells and tissue from damage.
Research show that there is an inverse relationship between antioxidant levels in the diet and the development of certain diseases such as cancer and cardiovascular disease. However, it is unclear as to the exact concentration of antioxidants in the plasma that are beneficial. Research published in the Journal of Nutrition in 19931, attempted to understand the beneficial levels of vitamin antioxidants by using data from a number of epidemiological studies that had been performed previously in European countries. The researchers found that populations with the lowest plasma concentrations of vitamin antioxidants had an increased risk of developing ischaemic heart disease (IHD). The strongest inverse association was found with vitamin E, which supports the results from other studies that have looked into the protective effect of vitamin E against heart disease.
Vitamin C was also protective of IHD, but the effect was not as great as that for vitamin E. The carotenoids β-carotene and α-carotene had a similar level of protection as seen with vitamin C, but it was unclear as to which carotenoid was providing the effect. Combining the results from many studies across Europe, the researchers suggested that the cardio-protective plasma levels of antioxidants are 27.5-30 µmol vitamin E/L, 0.4-0.5 µmol β-carotene plus α-carotene/L, 40-50 µmol vitamin C/L, and 2.2-2.8 µmol vitamin A/L. The authors also highlighted the importance of synergism between antioxidants, whereby antioxidant work together and are able to recycle one another thus potentiating their protective effects (here). A lack of one antioxidant can therefore accelerate the breakdown and destruction of others, suggesting that for optimal protection a range of different antioxidant substances is needed.
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