Vitamin D: A generation at risk

vit_dA study in the November Pediatrics adds to mounting evidence that the U.S. population is starved of an important nutrient—vitamin D. Based on the latest analysis of national data, roughly 20 percent of all children in this country fall below the blood level of vitamin D recommended by the American Academy of Pediatrics (50 nmol/L).

And far more—two thirds—fall below 75 nmol/L, the level many people now believe should be the standard. A shocking 80 percent of Hispanic children and 92 percent of Black children fall short.

If not corrected, this deficiency will put an entire generation of children at greater risk. Vitamin D is now recognized to have hormone-like functions that are important to health, helping regulate the immune system and curbing cancerous tendencies in cells. Recent studies have linked vitamin D deficiency to a host of illnesses including osteoporosis, heart disease, diabetes, cancer, autoimmune disease, respiratory infections, childhood wheezing and winter-related eczema.

Why have our levels dipped? A variety of factors are conspiring:

  • Children aren’t getting enough vitamin D from food. Generations ago, kids were given daily doses of cod liver oil. Then vitamin-D fortified milk came along – but kids simply aren’t drinking enough of it – four solid cups a day are needed – opting instead for juices and soft drinks. Today, almost 90 percent of 1 year olds drink juice, most of which isn’t fortified, and more children are drinking soy milk, rice milk and other substitutes that often lack vitamin D. Liver or fatty fish (salmon, tuna, mackerel, sardines) are also good D sources, but few children consume them in significant amounts.
  • Summer sunlight is our primary means of acquiring vitamin D, but children are spending less time in it—lured indoors by TV, movies and computer games, or because of a lack of safe places to play outside. They’re also using sunblock, which is good in protecting against skin cancer, but also decreases vitamin D production in the skin.
  • Darker-skinned children are at particular risk – their skin pigmentation reduces absorption of the UVB rays that promote vitamin D production.

“We actually think that 100 nmol/L may eventually prove to be the healthy level for vitamin D,” says Jonathan Mansbach, MD, of Children’s Hospital Boston, who led the study. “And very few U.S. children are at that level.”

Mansbach acknowledges that we need randomized, controlled trials to show definitively that vitamin D improves these health problems. But in the meantime, given the preponderance of data, he thinks parents should ask their pediatrician about vitamin D supplements. A good multivitamin may contain enough, but children with darker skin or at northern latitudes may also need vitamin D drops.

“Because the safety profile of vitamin D is so high,” says Mansbach, “we’re finding more and more evidence than getting enough may be important to long-term health.”

Read some of the the news coverage of this study in Time, U.S. News and World Report, the Associated Press and the LA Times. Also read an interesting Q&A from the Boston Globe on whether vitamin D can prevent the swine (H1N1) and seasonal flu, or the common cold.