Supplement for health
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How it works
Vitamin D acts like a hormone, meaning that it is formed in one place but carries out its function in another part of the body. Most of the vitamin D used in the body is formed under the skin through exposure to the sun; ultra violet rays change it from an inactive form into an active form. Vitamin D is also crucial for encouraging the absorption of calcium from food. It directly increases the rate of mineral deposits on bones. Without enough of it, the body cannot build or maintain strong bones.
Absorption helpers The known dietary sources of vitamin D tend to contain fats or oils, which enhance its absorption.
Absorption inhibitors Cholestyramine, which is used in the treatment of high cholesterol, and mineral oil, which is used as a laxative, both reduce levels of absorption.
vitamin D supplements
The adult RDA for vitamin D (5mcg) can be obtained by eating just two canned pilchards in tomato sauce. It is recommended that those people who are over the age of 65 should consume 10mcg supplements of vitamin D per day if their diet is poor in vitamin D sources. The upper safe intake for the long term is 10mcg per day, and 50mcg per day in the short term. Optimum nutritionists recommend that adults should all consume between 10-20mcg per day, and take 10-25 mcg per day for therapeutic reasons.
PrecautionsInfants are most at risk of overdosing on vitamin D and so supplementation must only be undertaken on medical advice. Taking vitamin D-rich cod liver oil plus vitamin D supplements could result in excessive intakes.
Why take this supplement?
Anyone who has limited exposure to sunshine during the summer months, some vegetarians and vegans, older people over 55, pregnant and breastfeeding women, young children, and those concerned about developing osteoporosis may all benefit from taking vitamin D supplements daily. Asian women and children are also advised to take supplements if they are vegetarian, have low intakes of calcium, and their skin has limited exposure to sunlight. Signs of a lack of vitamin D - either through a poor diet and/or from poor exposure to sunlight - include:
RDA for adults
Top sources of vitamin D mcg/100g of food