| Summary: | Vitamin A is involved in metabolism of proteins, lipids and carbohydrates. It affects tissue respiration and energetic metabolism. The speed of oxidation process of citric acid cycle and process of oxidative phosphorilation are influenced by vitamin A. Anticarcinogenic effect of vitamin A is believed to exist due to β-karoten, which exerts antioxidative properties.Vitamin E proved to be effective in preventing lipid peroxidation and other radical driven oxidative events. Vitamin E acts mainly by being incorporated into cell membranes, thereby protecting them against free radical attack in the lipid phase, especially the lipoperoxyl radical, but also against O2−, singlet oxygen and OH. The antioxidant activity of vitamin E has persuaded many groups to study its ability to prevent chronic disease, especially those believed to have an oxidative stress component such as cardiovascular diseases, atherosclerosis, and cancer.
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