Vitamin D deficiency: should advice on sun exposure take skin colour into account?

Evidence suggests children from South Asian ethnic groups in the UK may be at risk of poor bone health because of vitamin D deficiency.^1,2 Professor Lesley Rhodes, of the University of Manchester, is investigating the influence of lifestyle factors such as sun exposure on vitamin D levels in these children. Her work could lead to new public health messages about the benefits, and dangers, of sun exposure specifically for children with darker skin, which could ultimately prevent vitamin D deficiency.

What is the problem and who does it affect?

Reports suggest there is a resurgence of vitamin D deficiency in the UK and that children from South Asian ethnic groups are particularly vulnerable.

Vitamin D deficiency during childhood can have lifelong consequences. "Vitamin D is essential for healthy bones, especially during the growth spurt that occurs during adolescence," explains Professor Rhodes. "Prolonged vitamin D deficiency causes bones to be weak, making children prone to fractures. In severe cases it causes the bone deformity seen in rickets. There is also evidence to suggest that vitamin D might protect against some cancers, multiple sclerosis and diabetes."

Although we get some vitamin D from food, our skin produces the majority of our vitamin D when we are outside in the sunlight.

Public health campaigns encourage us to limit our summer sunlight exposure, by staying in the shade, wearing protective clothing and using sunscreen, to help protect against skin cancer. However, the darker someone’s skin is, the more sun they need to produce enough vitamin D. "There is an urgent need for more appropriate guidance on sun exposure for darker skinned children, who are less at risk of skin cancer and more at risk of vitamin D deficiency," says Professor Rhodes.

What is the project trying to achieve?

Around 125 children of South Asian descent, who are 12-15 years old and live in Greater Manchester, are taking part in this study.

‘We are monitoring the children for one to two-week periods, once during each season of the year," explains Professor Rhodes. "The children are wearing special badges that measure sun exposure. They are keeping diaries of how much time they spend indoors and outdoors, what they are doing, what they are wearing, what sunscreen they use and what food they eat. We are also assessing the children’s vitamin D levels."

The team is also measuring the strength of the sun during each one to two-week period.

"We hope to find out how lifestyle factors affect the children’s vitamin D levels," says Professor Rhodes. "Our findings are expected to lead to new national recommendations on sun exposure specifically for children from South Asian ethnic groups, which could protect them from the damaging effects of vitamin D deficiency."

What are the researchers’ credentials?

The researchers are world leaders in studying how sunlight interacts with the skin to produce vitamin D. They are experienced in sharing the findings of their work in a way that influences policy makers, professionals and the public – Professor Rhodes, for example, is an advisor to the UK’s SunSmart campaign.

References

1. Das G et al. Hypovitaminosis D among healthy adolescent girls attending an inner city school. Arch Dis Child 2006; 91: 569-72.
2. Wharton B et al. Rickets. Lancet 2003; 362: 1389-400.