sunshine effect

The sunshine effect
Your Health

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DR GITA MATHAI


The sun shines almost all the year round in India. Doctors were thus surprised when studies showed that 30 per cent of urban males, 50 per cent of rural and almost 90 per cent of urban women were vitamin D deficient. This vitamin is produced naturally by the action of sunlight on skin. Only 10 minutes of exposure, particularly to ultraviolet rays that appear at sunrise, is sufficient for the daily requirement.

Vitamin D can also be obtained from cereals, almonds, spinach, soya products, eggs, meat and fish. About 5 micrograms (200 International Units) are needed daily for all individuals (men and women, including those pregnant or lactating) under the age of 50 years. Those between 50 and 70 years need 10 micrograms (400IU), while those above 70 require 15 micrograms (600IU). Excessive intake — more than 2000IU or 50 micrograms — may result in side effects and toxicity.

Vitamin D is essential for proper calcium metabolism and bone mineralisation. Deficiency occurs because of changing lifestyles. In children, inadequate intake results in rickets characterised by soft, defective bones. The rib cage may become permanently misshapen, leading to breathing difficulties, and the long bones of the legs may be bowed. Similar softening of the bones in adults is called osteomalacia. In older people, the bone structure may become damaged, resulting in osteoporosis.

Vitamin D also affects enzymes and cell division. Its deficiency may cause excessive fatigue, muscle cramps, depression, insomnia and low immunity levels. Adequate levels have a protective effect against high blood pressure, auto immune diseases and the development of certain types of cancer.

Adequate amounts of calcium are needed for the vitamin to function efficiently. Children up to one year need 200mg daily, those between one and three need 500mg, four to 10-year-olds need 800mg, 10 to 18-year-olds need 1,300mg and adults 1,000mg. Adolescents require big amounts because that’s when a “calcium bank” is being built.

Women require more calcium than men, because of the loss during pregnancy and lactation. The female hormone estrogen makes calcium metabolism efficient. However, their bones may deteriorate rapidly after menopause. The vertebrae are primarily affected, resulting in a “dowager’s hump”, and the slightest fall can result in fractures, particularly of the hip and wrist.

Men, too, may develop osteoporosis and need sunlight exposure and calcium supplementation.

Some of the predisposing factors for weak bones cannot be changed. The risk increases if you are a woman, of Asian descent, have a family history of osteoporosis and as age advances. In both the sexes, a small frame with a body mass index or BMI (weight in kilogram divided by height in metre squared) of 19 or less adds to the risk as such persons have very little bone reserve. Thyroid diseases, diabetes and malfunctions of the adrenal glands contribute to weak bones. Digestive disorders with malabsorption adversely affect calcium and vitamin D uptake as both are absorbed from the intestines.

A low calcium intake can be tackled by consuming more dairy products or taking calcium and vitamin D supplements. Weight-bearing exercises like walking, running, jumping, dancing and weightlifting are helpful for developing healthy bones.

Tobacco contains nicotine, which contributes to weak bones. Alcohol interferes with calcium and vitamin D absorption and increases the risk of osteoporosis if more than two pegs (60ml) a day are drunk .

Osteoporosis is treated with calcium supplementation. To help the mineral enter the bones, selective estrogen receptor modulators like raloxifene and other drugs like calcitonin, bisphosphonates and parathyroid hormone may be used. In women, hormone replacement therapy after menopause was initially popular, as it appeared to reverse many of the adverse health effects of menopause. However, it has side effects, and is now used only in selected women under medical supervision.

Natural supplements from evening primrose oil, ginseng, natural soy products and tropical wild yam are popular. The advantages are anecdotal and scientifically unproven.

Osteoporosis, osteomalacia and rickets are totally preventable.

• Maintain an ideal body weight (BMI 23)

• Exercise seven days a week, one hour a day

• Expose the body to the early morning sun for 10 minutes

• Take calcium supplements.



Dr Gita Mathai is a paediatrician with a family practice at Vellore. Questions on health issues may be emailed to her at yourhealthgm@yahoo.co.in