by Sara Mcgrath

Created on: September 03, 2008

Vitamin D deficiency can more accurately be called sunlight deficiency. In fact, Vitamin D is not actually a vitamin, but a steroid hormone produced in the body after direct exposure of the skin to ultraviolet B (UVB) radiation in sunlight.

"Vitamin D" occurs naturally in only a few foods, including liver, egg yolk, and fatty fish (salmon, mackerel, sardines, herring, and cod liver oil). Because only these few foods, outside of fortified foods, contain significant levels of the hormone, it is unusual for people of any age to obtain adequate levels through dietary sources alone, and it makes sense that the biologically normal means of obtaining sufficient Vitamin D hormone is through adequate sun exposure.

Risk Factors for Vitamin D Deficiency in Babies and Children

* Mother has a low level of Vitamin D during pregnancy and lactation. A baby's initial store of Vitamin D is provided by the mother's body during gestation. A Vitamin D-deficient breastfeeding mother may produce breast milk with low levels of the hormone. However, the Vitamin D in breast milk is highly bioavailable. Breast milk contains substances that facilitate and enhance the absorption of nutrients.

* Inadequate exposure to sunlight. People who spend little time outdoors, use high-SPF sunscreen, or live in northern latitudes with limited sunlight may have lower levels of Vitamin D.

* Mother and baby have darkly pigmented skin. People with darker skin have more natural protection from solar radiation and, thus, may require more exposure to sunlight for adequate Vitamin D synthesis.

* Mother and baby are exposed to lead, which inhibits Vitamin D synthesis (The FDA recently released a study that found lead in most supplements for women and children [J. Agric. Food Chem. 2008, 56, 6892-6896].)

Sun Exposure for Vitamin D Synthesis

Fear of sun exposure contributes to Vitamin D deficiency in children. In Western cultures, children spend increasingly little time outdoors. When children do go out, it is common to use sunscreen. Babies are typically covered if they go outside at all.

The amount of sun exposure required for adequate Vitamin D synthesis will depend upon how much sunlight an area receives year round and on the darkness of the child's skin.

According to information from the World Health Organization information [Butte 2002, p. 27 PDF], "Two hours is the required minimum weekly amount of sunlight for infants if only the face is exposed, or 30 minutes if the upper and lower extremities are exposed."

This guideline is from a study [Specker 1985] of exclusively breastfed Caucasian infants under six months old at latitude 39N (Cincinnati, Ohio, USA). Darker skinned infants may require three to six times the sunlight exposure to generate the same amount of vitamin D [Good Mojab 2002].

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