Vitamin D, infants and teenagers: Your basic rock and hard place

Lately there have been a bunch of good news / bad news studies about vitamin D.

The good news: its benefits and preventive properties. The bad news: low levels of vitamin D in teenage girls and breast fed infants.

What should a pediatrician or a parent make of this new information? That's a tough question because it's not yet clear what it all means nor what (if anything) we should do about it.

Even tougher (at least for me): one of the conclusions I've come to from the new information contradicts some of my previous advice! That doesn't bother me: the beauty of science is that you must always be open to being wrong; you always need to re-evaluate in the face of new evidence.

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Advice-giving and sausage
Some advice-givers feel their advice should be like sausage: better to just consume the final product, but never see how it is made.

But I want you guys to be informed consumers of medical and parenting advice. Whenever possible, I'd like you to understand the science (or lack) that goes into the latest recommendations. And I'd like you to keep an open, questioning mind about about what people like me advise you to do.

Anyway, I've done my homework about vitamin D. Here is what I've found and here is my opinion.

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First, a crash course on vitamin D

• Vitamin D is more like a hormone than a vitamin. It plays a vital role in regulating the calcium in our bodies and making our bones strong.
• Vitamin D is usually made by converting a natural form of cholesterol - via exposure to ultraviolet (UV) light while in the blood vessels of our skin - to a non-active vitamin D, which is then further transformed in the kidneys and in the liver into its active form.
• Sun exposure is the most important source of vitamin D.
• As teenagers, we add on about 1/3 of our adult bone mass. It is widely accepted that if weaker bones are made during adolescence, there is a greater risk for softer bones ("osteoporosis") in later life.
• Breast milk contains inadequate vitamin D.
• Before cow's milk was supplemented with vitamin D, a nasty bone disease called rickets was quite common in children.
• The Institute of Medicine estimates that 2000 International Units (IUs)/day (e.g., found in 16 ounces of milk or formula) is needed to maintain good levels (some believe it should be even higher in older children and adolescents).
• The darker the skin, the less efficient the sun's rays are in activating vitamin D.

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The benefits of vitamin D
There is good scientific data to suggest that adequate vitamin D levels in children and adolescents has major benefits, including:

• Stronger bones as adults (especially in post-menopausal women).
• Better lung function in teens.***
• A protective effect against contracting some cancers (e.g., colon, breast****, prostate, ovarian).
  

Low vitamin D levels
Two very recent studies suggest that low vitamin D levels may be a lot more common than we thought:

• In a study of 51 (14 white/37 non-white) teenagers in England, 73% had low vitamin D levels. Dark-skinned girls were especially likely to have much lower levels. The low levels were felt to be due to reduced sunshine exposure, not to reduced vitamin D intake*.
• 78% of breast fed infants in Iowa who did not receive supplemental vitamin D were deficient (especially in the winter). **

Now, it's not clear how low is "too low" and what the consequences of low levels might be (if any). I'm going to make the leap - given what has been learned of its potential benefits - that low levels are not a good thing (especially in adolescence) and that children should maintain good levels of vitamin D.

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The rock and the hard place
Not so long ago I railed against direct sun exposure and urged you to obsessively apply sunscreen to your kids. That's my story and I'm sticking to it (pretty much).

But now I'm thinking I may have gone a little overboard in saying the only good sun exposure is no sun exposure, since it looks like too little direct sun exposure may lead to low vitamin D levels. (Alas, sunscreen probably blocks vitamin D production in the body. For more details, see this story)

So, what to do? Sun or no sun? Vitamin supplements or no? The rock or the hard place?

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There is no clear-cut answer. In trying to look at all the data and listening to the experts, I've come up with the following three recommendations:

1. All exclusively breast fed infants should receive vitamin D supplementation until they are taking in sufficient vitamin D from other sources, e.g., fortified cereal, milk, oily fish (unlike the next two recommendations, this is not controversial).


2. All kids should get about 10-15 minutes of direct sun exposure (i.e., no sunscreen and not through a window) on his/her neck, arms and legs a few times a week -- perhaps a little more in winter, a little less in summer; a little more if your child is dark-skinned, a little less if s/he is very fair.


3. Teenagers should take a vitamin D supplement (preferably the active vitamin D3 form), perhaps 500 Units or so.

-- Beware: With regard to vitamin D supplements, more is not better. Vitamin D is "fat soluble," meaning that, unlike "water soluble" vitamins (in which any excess is just peed out of the body), vitamin D is stored in fatty tissues and can be toxic after a certain high level is reached. The safe upper limit taken per day for adults is felt to be 2,000 IUs / day (although some argue that is too low).

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What about for your own self? Hey, it's tough enough for me to figure out what to advise for kids, so I'm not going there! For a sensible way to deal with this as an adult, see this article ). Personally, I'm taking 1,000 IU of vitamin D3/day.

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Having watched the sausage being made, you no doubt realize this is hardly the last word on this important topic. Yes it's confusing and, yes, there are no clear answers and, yes, it's kind of arbitrary. But, based on what we know now, it's my best judgment.

Stay tuned and watch medical science in action. As we learn more, we'll be able to refine (or change) these recommendations. That's how "evidence-based" medicine works. That's the kind of advice you should be looking for from your doctor.

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Articles cited:
* Hypovitaminosis D among healthy adolescent girls attending an inner city school.
Das G, et al. Archives Diseases of Childhood, July 2006

** Vitamin D deficiency in breastfed infants in Iowa
Ziegler E, et al. Pediatrics, August 2006.

*** http://www.webmd.com/content/article/122/114787.html

**** Boston Globe: Does Vitamin D Reduce The Risk of Cancer?

Related Topics: Pregnant? Vitamin D Aids Baby's Bones, Vitamin D. May Lower Some Cancer Risk

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