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In May 2003, the Expert Group on Vitamins and Minerals (EVM), an independent expert advisory committee, reported on safe levels of intakes of vitamins and minerals in food supplements and fortified foods. As part of this the committee highlighted evidence that suggested consuming more than 1.5mg per day of vitamin A may increase the risk of osteoporosis.
Osteoporosis is caused by a loss of bone or a reduction in bone mineral density, resulting in fragile bones that break very easily. Bone loss is natural as we age but not everyone will suffer from osteoporosis. The strength of our bones and the rate at which bone is lost is affected by hormones, family history, gender, age and by a range of lifestyle factors.
The daily recommended intake for vitamin A is 0.7mg a day for men and 0.6mg for women.
Vitamin A can be obtained in two forms:
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preformed vitamin A, also called ‘retinol’, which is found only in foods of animal origin. The major dietary source of retinol is liver
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carotenoids found in plant foods act as provitamin A because they are converted to retinol in the body
Liver contains much higher amounts of vitamin A than other foods. An average portion of liver is about 100g but the amount of vitamin A in a portion is highly variable, depending, for example, on the type of liver and animal husbandry. Analysis of samples of liver shows that the typical vitamin A content of cooked liver ranges between 10 and 25 mg/100g.
A person eating more than one portion of liver a week could therefore exceed the recommended maximum of 1.5mg of vitamin A a day (equivalent to 10.5mg of vitamin A a week).
The liver content of liver pâté and therefore the vitamin A content varies between different products. Typically the vitamin A content of liver pâté is 7.3 mg/100g. This figure is based on analysis of a composite sample of a number of products.
The SACN report also noted that inadequate intakes of vitamin D might increase the adverse effects of high vitamin A levels on bone health. We get most of our vitamin D from sunlight on our skin. Therefore, people who have limited exposure to sunlight, such as older people who are housebound or people from ethnic communities who wear concealing clothing, might be more at risk from the effects of high vitamin A intakes.
Sources of vitamin D include fish, and eggs, fortified foods such as margarine, breakfast cereals, bread and powdered milk. Liver is also a source of vitamin D but high liver consumers, those at risk of osteoporosis, pregnant women or those thinking of having a baby are advised to get their dietary vitamin D from other sources.
Liver is a good source of iron in the diet, but there are other foods that also provide a good source of iron. These include red meat, pulses, bread, green vegetables and fortified breakfast cereals. |