DESCRIPTION

Vitamin D is called the "sunshine vitamin."

There are two types of vitamin D:

1. Cholecalciferol (vitamin D3), found in animal liver oils, and the effect of sunlight on cholesterol deposits in the skin.

2. Ergocalciferol (vitamin D2), which is produced when ultraviolet light affects the precursor ergosterol (the "vegetarian" form of vitamin D).

In the 17th century, the smog and naturally dull English weather caused many children to have rickets (twisted, malformed limbs). Rickets became known as "the English disease."

Vitamin D is stored in the liver and is fat soluble. Children need more vitamin D than adults.

BENEFITS

The most important role played by vitamin D is in bone development. It works by being converted to a hormone which itself controls calcium absorption which again in turn affects bone development. This is why children have a higher requirement of vitamin D than adults.

Vitamin D is essential for the development of strong, healthy teeth.

DEFICIENCY SYMPTOMS

The adult version of rickets is osteomalacia, for which symptoms include brittle bones, bone pain and muscular spasms.

In children, knock-knees are the most evident sign of vitamin D deficiency. Children may be late in growing teeth. Children grow with an unnatural posture.

REQUIREMENTS (RNI)

THE RNI VALUES (COMA 1991) FOR VITAMIN D

It was decided by the COMA panel that in the three to 65 year age group, vitamin D formed from skin exposure to the sun was usually sufficient to satisfy needs, and that an extra dietary supply was therefore generally unnecessary.

WHO MAY NEED TO SUPPLEMENT

Vegetarians and vegans, because vitamin D is mostly in animal products

Elderly or housebound people, who are also unlikely to have sufficient exposure to the sun

Women who have had a series of pregnancies and as a result become short of calcium

Breast-feeding women whose milk may be short of vitamin D, especially during winter

BEST FOOD SOURCES

THERAPEUTIC USES

Strengthens bones and teeth

Treats rickets (A deficiency of vitamin D leads to development of rickets.)

SAFETY

Vitamin D can be the most toxic of all the vitamins, so care must be taken not to exceed the recommended guidelines. However, vitamin D is safe up to five times the recommended amount. Too much vitamin D will affect the kidneys, heart and lungs.

INTERACTIONS AND CONTRAINDICATIONS

Vitamin D is important for the absorption of calcium and phosphate. Although vitamins A and D are often found together, they are not, in fact, co-dependent.

Some cardiac drugs when taken with vitamin D may cause irregular heart rhythm, so consult your doctor if this is likely to affect you.