• Vitamin D Prevents rickets in infants
• It  treats psoriasis
• It may treat senile osteoporosis
• It prevents bone loss in periodontal disease

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.

Taking 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:

• Poor growth
• Bone deformities
• Rickets
• Osteomalacia
• Bone pain
• Muscle weakness
• Constipation

Therapeutic uses

• Breastfeeding Young babies could be at risk of developing soft, rickety bones, which bend and bow if there are low levels of vitamin D in their mother's breast milk. This is usually due to the mother eating a poor diet and having little exposure to sunlight. Breastfeeding mothers who take 10mcg per day of vitamin D supplements can avoid this problem.
• Osteoporosis By taking vitamin D supplements daily, elderly people and those at risk of developing osteoporosis may help to increase the beneficial effects of calcium absorption by the body to help strengthen bones and prevent any brittleness developing.
• Periodontal disease People with weak gum tissue may benefit from taking vitamin D supplements daily in order to help reduce any further loss of their jawbone from periodontal disease.
• Psoriasis Those people who suffer from psoriasis may find that they also have low levels of vitamin D. The symptoms of this skin condition may improve if psoriasis sufferers increase their daily dietary intakes of vitamin D.

Chemical names

• Cholecalciferol
• Calciferol
• Ergosterol

Preparations
 

• Cod liver oil
• Capsules
• Tablets
• Liquid

RDA for adults

5mcg

Top sources of vitamin D mcg/100g of food

• Cod liver oil Source210mcg/100g
• Herring19mcg/100g
• Mackerel18mcg/100g
• Sardines11mcg/100g
• Rainbow trout10.6mcg/100g
• Salmon8.0mcg/100g
• Margarine7.9mcg/100g
• Fresh tuna7.2mcg/100g
• Eggs1.75mcg/100g
• Cheddar cheese0.26mcg/100g