Vitamins A and E: Why are these antioxidants good for you?
Gerontologist Denham Harman, also known as the ‘father of the free radical theory of ageing’, was the first to discover the concept of free radicals in 1954. Free radicals are now suggested as one of the major contributors to ageing.
Free radicals are reactive molecules and are involved in disease development. Sources of free radicals include stress, pollution as well as smoking and high alcohol consumption. The need for antioxidants in our daily life is thus crucial due to increased exposure to such free radicals.
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What are antioxidants?
Antioxidants are thought to be able to slow down ageing and thus improve skin health through preventing reactive oxygen species from causing damage to our biological system. This is done by detoxifying these reactive oxygen species and thus be able to repair the resulting damage on proteins, fats, and DNA.
Antioxidants are also capable of repairing damaged molecules like your DNA, can promote the destruction of cancer cells, and thus stop cancer growth.
With healthy DNA, immune systems are strengthened. By preventing brain ageing, better memory performance and prevention of progressive cognitive impairments can be expected, suggesting antioxidants’ role in preventing diseases like Alzheimer’s.
Beta-carotene (a substance from which vitamin A is formed from) and vitamin E are believed to be weapons against heart disease and cancer. Both these vitamins are fat-soluble antioxidants, which can protect your cell membranes.
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Vitamin A: What is it and why we need it
Vitamin A is derived from beta-carotene (plant sources) – which is responsible for the red-orange colour of some vegetables and fruits, especially carrots and sweet potatoes – and from retinoid (animal sources).
Vitamin A is needed for healthy skin and mucus membranes, for good eye health and vision and aids in building our immune system. Some studies have suggested that at least four daily servings of beta-carotene rich fruits and vegetables are required to lower cancer and heart disease risk.
According to Singapore Health Promotion Board, about 750mcg of vitamin A in terms of retinol activity equivalents (2,500IU/day) is required every day in normal adults. However, the US RDA suggests not taking more than 3,000mcg per day (10,000IU/day).
Vitamin E: What is it and why we need it
Vitamin E comes in eight different subtypes with different antioxidant activity. Out of these subtypes, alpha-tocopherol has the greatest antioxidant activity, and it is the only form that is recognised to meet human requirements. Common dietary sources of vitamin E include raw vegetable oils, eggs, and nuts.
In the human body, vitamin E protects cell membranes and circulating serum lipoproteins from oxidation, thereby possibly delaying chronic diseases, inhibiting the ‘wear-and-tear’ pigments (also known as lipofuscins) accumulation, which is a sign of ageing.
One study conducted found out that people who take at least 200IU vitamin E per day have 37 per cent lower risk of developing cardiovascular diseases.
There is no dose range of vitamin E recommended by the Singapore Health Promotion Board but generally, World Health Organization considers doses between 150-720mg (225IU to 1,080IU) a day to be a range without side effects.
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This article was written by Ng Jia Min and Ng Jiaying, Pharmacists, Pharmacy Department, Singapore General Hospital (SGH), a member of the SingHealth group, for HealthXchange.
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