Sunshine, sunscreen, Vitamin D?

Considerations regarding the effects of sunshine on health seem to fall roughly along generational lines.

By the time my children were born, parents were being urged to cover childhood skin, either with clothing or sunscreen, to protect it from cancer-causing ultraviolet light.

But growing evidence regarding the importance of vitamin D and the prevalence of vitamin D deficiency among children raises questions about whether advice to avoid sunshine, 1 of the 2 sources of vitamin D, will be as unambiguous for the next generation of parents.

Using data from the National Health and Nutrition Examination Survey 2001-2004, investigators found that 9% of US children were vitamin D deficient (<15 ng/mL), and 61% had insufficient levels (15-29 ng/mL).¹ Deficiency and insufficiency appear to be even more prevalent among black children.²

This information comes at a time when the importance of vitamin D is being recognized for much more than its role in bone homeostasis. There is evidence that vitamin D is important in regulating the immune system and that it stimulates insulin secretion, regulates proliferation and differentiation of hair follicles, and may reduce the likelihood of developing certain types of malignancies.³

Kumar and colleagues also found an association between vitamin D insufficiency and deficiency and cardiovascular risk factors in children.¹ It turns out that there are receptors for vitamin D in most tissues in the body-not only in bone, kidney, and intestine-and many of those cells are capable of enzymatic metabolism of circulating vitamin D to its active form, 1,25(OH)₂ D.³

Sunshine, of course, is not the only source of vitamin D, and concern about vitamin D deficiency does not abolish equally important concern regarding risk of skin cancer from ultraviolet radiation. Growing understanding of the many roles vitamin D plays in protecting health and of the variables that contribute to insufficiency and deficiency in children may, however, lead to more nuanced and individualized recommendations regarding diet and sun exposure.

Our advice to the mothers of the future regarding sun exposure may require consideration of skin color, nutritional status, and genetic risk for a variety of conditions.

REFERENCES

1. Kumar J, Muntner P, Kaskel FJ, Hailpern SM, Melamed ML. Prevalence and associations of 25-hydroxyvitamin D deficiency in US children: NHANES 2001-2004. Pediatrics. 2009;124(3):e362-e370.

2. Gordon CM, DePeter KC, Feldman HA, Grace E, Emans SJ. Arch Pediatr Adolesc Med. 2004;158(6):531-537.

3. Bikle D. Nonclassic actions of vitamin D. J Clin Endocrinol Metab. 2009;94(1):26-34.