A recent article in the Pediatricss journal reported data on serum levels of 25-hydroxyvitamin D, the active form of vitamin D in blood and asked this question Do Children Need More vitamin D? There is a lot of buzz in the media these days about deficiency of vitamin D, especially in kids. Beyond the screaming headlines and soundbites, it is important to look at the data an scientific way before jumping to conclusions.
In this article, I will first provide a brief background on vitamin D and explain why it is a concern these days especially for growing children. Second, I will describe the design of the Pediatric study and methods used to analyze data. Finally, I will summarize the results to support some of the key conclusions of this study.
Let me first say that there is no consensus on the threshold level of vitamin D in blood below which a child is considered deficient. Still, the authors concluded that millions of US children aged 1-11 years may have sub-optimal levels of vitamin D, especially non-Hispanic Black and Hispanic children. However, more research is needed before a decision can be made about recommending vitamin D supplementation in children.
Vitamin D – the sunshine vitamin!
Vitamin D is produced when our skin is exposed to the UV-B rays from the sun. That is why, sometimes it is also called the sunshine vitamin. It is also available from a few limited food sources such as milk, fortified orange juice and cereals, and fish such as salmon, mackerel, cod and herring. Vitamin D supplements are also available from both synthetic and natural sources. Deficiency of vitamin D is known to cause rickets, a condition which involves bone loss and deformation. Because vitamin D is also a prohormone, meaning it is involved in proper functioning of other hormones, recent research is linking vitamin D deficiency with many other diseases like diabetes, heart disease and even cancer.
Why the concern then? Well, the problem is that many parts of the world do not get enough sunlight through the year. When we do manage to get some sun, we have a tendency to overuse sunscreen because of the risk of skin cancer. Don’t stop doing that, but be aware that sunscreen blocks the UVB rays responsible for vitamin D production. As for nutrition, we know that children are picky eaters. They hardly eat fish or drink enough milk. Junk food has little vitamin D. Because of these reasons, there is a concern that kids are not getting enough vitamin D.
The Pediatrics study analyzed 2001-2006 NHANES data for kids 1-11 years old
Because of the concern over vitamin D, the Pediatrics article is very timely. Researchers from Harvard, Mass General Hospital and University of Colorado analyzed the NHANES data from 2001 – 2006, which is collected every 2 years by the National Center for Health Statistics. The NHANES uses a 4-stage sampling strategy to represent households across the country. It tends to oversample low income groups, blacks and Mexican Americans. However, statistical methods including appropriate weights are available to extrapolate the results to a nationally representative population.
In this study, the researchers obtained serum levels of 25-hydroxy-vitamin D – the “active” form of vitamin D present in the blood. They also had household interview data about the demographic, socio-economic status and vitamin use. Sample size for kids 6-11 years old from 2001-2006 was 3421 for household interview data and 2759 for serum 25(OH)D data. Sample size for kids 1-5 years old from 2003 – 2006 was 2677 for household interview data and 1799 for serum 25(OH)D data.
Serum levels were categorized as <25, <50 and <75 nmol/L. Although, there is no consensus on what constitutes as the level of deficiency in children, the Institute of Medicine has set it at less than 27.5 nmol/L while the Canadian Pediatric Society has set it at less than 25 nmol/L. Recently, a level of less than 50 nmol/L has been found to be linked to some level of bone demineralization. In adults, recent studies demonstrated that healthy levels of serum 25(OH)D may be as high as 75 nmol/L or even higher. That is why, the researchers decided to look at prevalence data for the nationally representative population of 1-11 years old children at these 3 different levels.
Average blood levels do not show deficiency, but experts believe most kids have lower than desired level of vitamin D
The mean serum level for children 1-11 was 68 nmol/L. Children aged 6-11 had a slightly lower mean level at 66 compared to those aged 1-5 at 70 nmol/L.
When taken as a whole, following prevalence levels were found:
< 25 = 1%, < 50 = 18% and < 75 = 69%
In terms of actual population numbers, this translates to 320,000 children below less than 25, 6.3 million less than 50 and 24 million less than 75. If the “average” values of the serum level gave you a sense of comfort, simply look at these prevalence numbers. Amazing!
If you consider the level of 75 nmol/L or higher as optimal, like most experts, the prevalence of serum levels below 75 was higher for non-Hispanic blacks at 92% and Hispanic at 80% compared to non-Hispanic white children at 59%. In terms of numbers, 2 out of every 3 children in the US are below this level, and nearly all of the non-Hispanic black and Hispanic children are below this threshold. If the threshold is changed to <50, then over half of non-Hispanic black children 6-11 years old fall in this category.
The current daily recommended intake from the Academy of Pediatrics is 400 IU/day. Experts believe that this is insufficient to raise the serum levels to >50 or >75 and that vitamin D supplementation may be needed in at-risk populations.
More vitamin D is good for children, but do not jump to supplements right away!
Coming back to the original question “do children need more vitamin D”, the short answer is YES. It may be tempting to simply get on a daily supplement. But I think we should try to first make small changes in our lifestyle and eating patterns. Nature did not intend us to be deficient in vitamin D, even though she gave us all a different skin color. The fact that we see low numbers in our population is a result of our lifestyle and poor diet. Get active, get outdoors – even 10-15 minutes of sun exposure on your arms and legs without sunscreen is enough. Of course, you should worry about skin cancer and use sunscreen before it is too late. Get your kids to eat healthy including a diet rich in dairy and fish unless there is an allergy problem. There are many natural ways to ensure your child gets enough vitamin D before deciding to take a supplement.
Parents – are you concerned that your child may have a vitamin D deficiency? What steps are you planning to take? Share in your comments below.