What's the problem?

Vitamin D deficiency, particularly in children, is a growing problem worldwide.

The most serious consequence of this deficiency in children is rickets, a nutritional disorder that leads to bone deformities such as bowed legs.

In New Zealand, the 2002 National Children's Nutrition Survey of 5-to-14-year-olds found that:

• 4 percent of children surveyed were vitamin D-deficient
• nearly 33 percent of them had vitamin D levels low enough to affect bone density.

As well, two surveys have found that almost half the population is likely to have insufficient vitamin D.

Who's missing out?

People with dark or olive skin are at greater risk of vitamin D deficiency than those with light skin. Melanin, the pigment in skin, acts as a natural sunscreen - so people with darker skin need greater exposure to sunlight, to synthesise similar amounts of vitamin D. The National Children's Nutrition Survey found that 60 percent of Pacific children were vitamin D-deficient, compared with 32 percent of all children in the survey.

Others at risk are people in communities where the skin must be covered up for cultural or religious reasons, the elderly (if they are house-bound), and breast-fed babies of vitamin D-deficient mothers.

As well, our lifestyle and work environment could be contributing to vitamin D deficiency. In summer, a few minutes' sun exposure most days in mid morning or early afternoon to the face, arms and hands or legs is enough to maintain vitamin D levels.

But in winter, when UV levels are low and days are shorter, it's tempting to stay inside in front of the TV or computer. Many people leave for work early in the morning, drive to work, eat lunch inside, and drive home - for 5 days a week. Some wear sun-protective skin creams all year round to protect against UV-ageing of their skin.