The arrival of spring and our recent interlude of unseasonably warm weather got me thinking about vitamin D, the “sunshine vitamin.”

Here in the United States conventional wisdom holds that if your child is drinking milk and spending a little time playing outside, he’s getting the vitamin D he needs. But recent research shows that this is not necessarily the case. Many children, as well as adolescents and adults, aren’t getting enough of this essential vitamin, and vitamin D deficiency continues to be a very real disease of the 21st century.

Deficiency in vitamin D can lead to rickets, a bone-softening disease most commonly seen in children in their first two years of life. Rickets can present in many ways, but common findings include decreased linear growth (height), bowing of the legs and poor weight gain.

In many cases, however, children may not manifest any physical signs during the early stages of vitamin D deficiency. In later stages of rickets they can also develop muscle weakness, respiratory infections and, because of low calcium levels, seizures. X-rays taken of children with rickets often show bony abnormalities, including osteopenia (low bone density) and fractures.

Vitamin D is essential in helping the body absorb, retain and regulate calcium and phosphorus, both of which are critical for building and maintaining strong bones and teeth. There is also mounting evidence that vitamin D may play a vital role in preventing chronic diseases of the immune and cardiovascular systems later in life.

The biochemistry of vitamin D production and use in the human body is complicated and probably of limited interest to anyone other than diehard biochemistry fans. The key point is that there are two sources of vitamin D. Production in the skin after exposure to ultraviolet radiation is one. Diet is the other.

Sunscreen interferes

When your child is exposed to sunlight it helps her body synthesize vitamin D in the skin. It doesn’t take much time in the sun to achieve this — even just a few minutes every day can suffice — but it’s easier said than done. Our greater awareness and understanding of the dangers of ultraviolet radiation and its relation to skin cancer have led to a universal push for diligent use of sunscreen by children and adults. Yet while sunscreen is certainly crucial to protecting kids from skin cancer later in life it can also interfere with sunlight’s positive role in vitamin D production.

During certain seasons, and in northern regions of the U.S., sunlight exposure can be limited. Additionally, dense cloud cover and high levels of air pollution can reduce the ultraviolet rays reaching the skin. And skin pigmentation can impede the skin’s ability to produce vitamin D. Darker-skinned people manufacture less vitamin D than those with lighter skin. Bottom line: Exposure to sunlight is neither the safest nor the most reliable way to get your vitamin D.

Dietary sources of vitamin D are quite limited. It is found naturally in only a few foods, including oily fish, beef liver, cheese, egg yolks and some mushrooms. Fatty fish — including salmon, tuna, mackerel, trout, herring, sardines and anchovies — is one of the best sources. Enriched foods are another way to increase vitamin D in our diets. Many supermarkets carry vitamin D-fortified milk, cereal, orange juice and yogurt. Vitamin D can also be taken orally as a vitamin supplement. It comes in liquid and pill forms.

Not much D in breast milk

Of most importance to newborns and infants, human milk, i.e., breast milk, contains only small amounts of vitamin D. Breast-feeding is still recommended as the best source of nutrition for infants, but even breast-feeding mothers whose diet is high in vitamin D or who are taking vitamin D supplements do not produce milk with levels of vitamin D that are sufficiently high to meet their babies’ needs.

Breast-fed infants who are darker-skinned or living in colder climates or northern regions — that includes us Wyomingites — are at even higher risk for vitamin D deficiency. Because of this the American Academy of Pediatrics recommends starting all breast-fed babies on a vitamin D supplement within the first few days of life. Preterm infants, as well as those who are on macrobiotic or strict vegan diets, are also at increased risk for vitamin D deficiency.

The long-term prognosis of children with rickets is quite good if they are adequately treated with supplemental vitamin D and calcium. But primary prevention is the best way to combat this potentially serious nutritional disorder.

The daily recommendation of vitamin D is 400 IU per day for infants younger than 1 year of age and 600 IU per day for children older than 1. If your infant is formula-fed and is consuming at least 32 ounces a day of vitamin D-fortified formula she should be receiving sufficient quantities.

For the reasons I’ve discussed here, if your baby is primarily or solely breast-fed the recommendation is to start a vitamin D supplement within the first few days of life. Vitamin D can be purchased over the counter at most pharmacies or grocery stores, and the liquid form is easily administered orally to infants and young children.

As with so many areas of health care, an ounce of prevention is worth a pound of cure. So talk with your children’s health care provider about their diet and nutritional needs and whether a vitamin D supplement is recommended.

Ed. Note: This column originally printed April 22, 2015.

Dr. Karin Klee of Cowboy Kids Pediatrics is part of a team of pediatricians who write on children’s health for the News&Guide. You can contact her via columnists@jhnewsandguide.com.

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