Wednesday, August 18, 2010

Sunlight, Milk, Vitamin D

Vitamins! What a boring topic. I used to think so--in fact, a year or two ago I rarely recommended vitamin supplementation for my patients. My previous mantra was "Eat a healthy diet and you won't need vitamins." Then the new vitamin D supplementation guidelines were published in 2008. Study after study confirmed that children (and adults, actually) do not get enough vitamin D on a regular basis to reliably prevent problems with bone health. Some studies show that adequate vitamin D consumption is linked to lower levels of autoimmune diseases and helps fight infections.

In fact, I have been so convinced by this information that I actually take a vitamin D supplement myself! If you knew me well you would understand how amazing this is. I have always had trouble swallowing big pills, such as vitamins. Prenatal vitamins were impossible for me, and I actually took children's chewable vitamins during my pregnancies. However, I have gotten used to the vitamin D and I take it each night.

I have brought my kids along on this vitamin ride, too. They prefer gummy vitamins, and are supposed to take two each day. Sorry, Dr. VanEs--I know you don't like the sugar in these sticky vitamins--but I promise that they brush their teeth! My children will be the first to tell you that sometimes I forget to get a new bottle of vitamins for them when they run out. I resolve to do better, but I am a busy mom, and not perfect even in regards to my own medical advice.

The vitamin D recommended daily allowance for children from birth to age 18 is 400 IU (or international units) per day. Supplementation starts at birth. If a baby is formula fed, then after they reach one liter of formula per day they are getting enough vitamin D. Infant vitamins are usually given in drops, while children's vitamins are chewable or gummy. You should read the labels, especially in the infant drops. Normally 1 ml would give 400 IU, however some drops are super concentrated and provide 400 IU in a single DROP. It is possible to overdose on vitamin D and cause vitamin D toxicity, but there is a fairly wide margin of error. Most vitamin D supplements are in the form of vitamin D-3 (not 2).

It is possible to get vitamin D from sun exposure, and the lighter your skin the less sun exposure you need. The sun activates vitamin D that is inactively resting in your skin, making it possible for your body to use what is already there. In the United States, on average, it has been shown that we spend more than 90% of our time indoors! Top that with using recommended sunscreen during sun exposure and it doesn't add up to enough sun exposure to be sure you have enough vitamin D.

I have seen attempts to calculate how much sun exposure is needed per day on skin that is not treated with sunscreen, taking into account the degree of pigmentation in the skin. This seems too complicated and unreliable to me, plus I doubt most people will be pushing their kids out the door in just a bathing suit in the dead of winter. What about a break from vitamin D supplements in the summer? Are you organized enough to get your children to sunbathe without sunscreen for a set period of time each day in the summer, and then remember to apply the sunscreen right away when the timer goes off? How will you handle cloudy days? Will you remember to restart their vitamin D during the colder months of the year? I think you should just have them take the vitamin and use sunscreen liberally to prevent sunburn and skin cancer.

It is possible to get vitamin D through breast milk. However, mothers must take very high doses of vitamin D (much more than is in a prenatal vitamin) to achieve adequate levels for their babies. Even then the levels in the milk may not be consistent and the mother may be at risk for vitamin D toxicity. Not enough is known about this to recommend it.

It is possible to get vitamin D from formula and from vitamin D fortified milk. You must consume a liter (about a quart, or 32 ounces) per day to get enough vitamin D. So if kids are big milk drinkers (4 8oz cups per day) they probably don't need extra vitamin D. Newborns don't drink that much formula right away, so technically they should receive a supplement until they do. However, they will come pretty close to the recommended daily allowance in just a few weeks, and almost certainly by 4-6 months of age, so I don't usually recommend the supplement for a formula fed baby.

What about measuring levels of vitamin D? This is tricky, because the level in the blood at any particular point in time does not always reflect overall body stores of vitamin D. Except in cases of chronic disease with malabsorption of nutrients (such as children who have had large sections of their bowel removed) checking vitamin D levels is not very helpful in determining vitamin D status. Most insurance companies won't pay for this test anyway, and if I would order it for a patient I would have no idea what it really means. Please don't ask me to order a vitamin D level for your child. Why poke your child (causing pain and stress) and run a test that is imperfect, difficult to interpret, will cost you money, and won't change my advice to you? There are limits to technology, and this is one of them. Take the vitamin, life goes on.

Vitamin D supplementation is one of those recommendations where the intervention (taking the vitamin) doesn't have very many down sides, and the benefit is potentially pretty big. So I am recommending that all my pediatric patients take 400 IU of vitamin D3 per day, with less or no supplementation needed for formula fed babies and big milk drinkers (4 cups milk per day).

My primary source of scientific information for this blog was the following publication:

Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents--Wagner et al.122(5):1142--AAP Policy

The publication is available online at the American Academy of Pediatrics web site (, and it has a large list of references/scientific studies on which the recommendations are based. As a member of the AAP I have no trouble accessing this study online, I don't know if it is accessible to a non-member.

Please remember that the purpose of this blog is to provide you with more information and insight into how I personally think about health and illness. I am not trying to personally diagnose or treat your child. For that you need to discuss the problem with your medical professional. Other sources of information on the web could include, or