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I run an exercise class for people with chronic respiratory diseases. I have been asked what would be the safe amount of vitamin A they can eat a day or week? Vitamin A is a fat-soluble vitamin, which means it can be stored in the body. It’s needed for growth, reproduction and development and helps to keep our skin, hair and eyes healthy. It also helps to strengthen our immune system so we’re less likely to pick up infections. Plus, vitamin A is important for healthy mucus membranes, found in the respiratory tract, for example. And if that’s not enough, beta-carotene (which the body uses to make vitamin A) is a powerful antioxidant and so may help to protect against cell damage by mopping up an excess of potentially harmful molecules called free radicals.
Vitamin A is available to the body in two forms: retinol and beta-carotene. Retinol is found in liver, liver products such as pate, whole milk, cheese, butter, egg yolk, oily fish and margarine. Beta-carotene is found in dark green vegetables like spinach and watercress, and yellow, orange and red fruits like carrots, tomatoes, dried apricots, sweet potatoes, red peppers and mangoes. The Department of Health recommends that adult women should have 0.6mg of vitamin A daily, and men 0.7mg a day. As a general guideline, most people should be able to get all the vitamin A they need by eating a balanced diet. There’s currently insufficient evidence to suggest that increasing intakes of vitamin A by taking supplements will improve lung function, although sufferers should always follow the advice of their GP, doctor or dietitian. In contrast, some evidence suggests that supplements may actually do more harm than good. In a well-known American study – the Carotene and Retinol Efficacy Trial (CARET) – supplements of beta-carotene were actually found to increase the risk of lung cancer, particularly amongst smokers and those who had been exposed to asbestos. However, there’s no evidence to suggest that the beta-carotene we get from fruit and vegetables causes any harm and so most people should aim to have five servings of fruit and veg every day. Meanwhile, research has shown that having an average of 1.5mg of vitamin A each day over many years – more than twice the recommended amount for adults – may affect the bones, increasing the risk of fractures. As a result, the Food Standards Agency recommends that postmenopausal women and older men – both of whom are at a greater risk of the bone-thinning disease, osteoporosis – should avoid having more than 1.5mg of vitamin A each day as it’s such a rich source of this nutrient. This means not eating liver or liver products more than once a week and making sure any supplements taken contain less than 1.5mg of vitamin A daily (or avoiding them completely if you eat liver each week). The Food Standards Agency also recommends that pregnant women or women planning a pregnancy should avoid liver, liver products and supplements containing vitamin A as large doses of this nutrient have been linked to birth defects. However, it’s important to follow the advice of your GP, doctor or dietitian.
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