We all could use more Vitamin D.
We need more Vitamin D.

When patients have asked me whether to give their kids vitamin supplements, my opinion has been lukewarm.  Most foods are supplemented with vitamins, even junk food!  There's no harm in a daily supplement, but I have not felt strongly about it.

Until now.  I have seen a steady stream of recent research suggesting that vitamin supplements, especially with Vitamin D, might be useful.

People with low blood levels of Vitamin D have reported 40% more frequent respiratory infections.  The association is even stronger for those with asthma or other lung diseases. (Arch Intern Med. 2009; 169:384-390.)

Teenagers with low Vitamin D levels are twice as likely likely to have high blood pressure, obesity, and high blood sugar.  They were also more likely to have cholesterol problems.  The same finding has been previously reported in adults.  Low Vitamin D levels have direct effects on blood pressure metabolism and insulin levels, and might also be a marker for poor diet.  Vitamin D tends to be drawn into fat tissue, so people with obesity probably need higher Vitamin D intake.  (doi:10.1542/peds.2009-0213)

And, of course, Vitamin D's relationship to bone health is well known.  This has led to universal supplementation of milk with Vitamin D, to complement milk's calcium supply.  Kids should be happy about this; they don't need to swallow cod liver oil any more!

Vitamin D deficiency turns out to be surprisingly common.  61% of American children have low serum Vitamin D levels, and almost 10% are frankly deficient.  Only 4% of kids take regular children's vitamin supplements.  (doi:10.1542/peds.2009-0051)

As a result, the AAP now recommends Vitamin D supplements for all children, 400 IU ("International Units") per day.  (Most children's vitamin supplements provide this amount, but check the label to be certain.)  But even this may turn out to be insufficient for some kids.  Obese children, and kids taking seizure medications, might need more.

What do I recommend?

Infants fed with breastmilk should be given a daily vitamin supplement, starting at 1 month of age (such as Tri-Vi-Sol).  (Formula already contains vitamin supplements, so infants taking more than 16 ounces of formula per day don't need Tri-Vi-Sol.)
For kids over 1 year, and actually into adulthood, a regular vitamin supplement (any brand) should be given daily.  Any brand should be fine; I suggest you find a brand that also provides mineral supplementation, such as iron, zinc, and even selenium.
Unfortunately, blood testing for Vitamin D is problematic.  Some doctors recommend keeping levels above 20 ng/ml; but others recommend levels above 20 ng/ml.  Lab testing and reporting of Vitamin D levels are not yet standardized.  And Vitamin D levels vary normally with the seasons.  So I don't recommend blood tests except under specific circumstances.

And don't forget to check my handout on Calcium supplements (click here).

     --  David Epstein, MD