It seems that vitamin D is the “hot” vitamin to be discussing these days. There are many conflicting studies and reports out there on the effects of vitamin D. How is a parent to navigate if and when to supplement?
The American Academy of Pediatrics reports that most children in the United States do not get enough vitamin D in a day. This is what led to the recommendation to double the daily amount for babies and children to 400 IU a day (before Oct. 2008, the recommendation was 200 IU/day). It is worth noting that the Food and Nutrition Board’s vitamin D RDA is listed at 600 IU/day for children over 1 year (so even higher than the AAP). FYI, vitamin D is always measured in “IUs,” meaning international units.
How does vitamin D work?
Vitamin D is a fat soluble vitamin. It is taken into the body (either consumed or absorbed from the sun) and converted into the usable form by the liver and kidneys. Very few foods have vitamin D naturally in them (mostly fatty, oily fish). Many foods (usually dairy items) have it added to it (i.e., “fortified”). It is also available as a dietary supplement. It can also be made naturally by the body when the sun’s ultraviolet rays are absorbed by the skin and the body undergoes vitamin D synthesis.
What’s vitamin D good for?
Vitamin D is necessary for the body to absorb calcium in the gut. Vitamin D helps the body maintain the right levels of calcium and phosphate in the blood so that the bones are mineralized properly. This is why one of the complications of vitamin D deficiency is a disease called Ricketts (or soft bones). While the beneficial effects on the bones are scientifically proven, the other potential benefits are much less clear. There are some studies (the actual science is hit and miss) to support a possible link to vitamin D improving cardiovascular disease, high blood pressure, diabetes, physical performance, immune functioning, autoimmune disorders, infections, etc. Some literature also supports that vitamin D plays a role in cancer risk (decreasing risk of colon, prostate, and breast cancer, while high levels increasing pancreatic cancer risk). I don’t know that vitamin D is the miracle vitamin that popular media would like you to believe, but it certainly stands to reason that not being deficient in something will improve your overall health.
How are low vitamin D levels diagnosed?
Diagnosis is by a simple blood test (easy for me to say, drawing blood out of a kid can be terrible). While there are various tests, doctors are usually measuring the 25 (OH) D level (referred to as the 25 hydroxy level) when they do a classic vitamin D level. I’ll usually throw in a vitamin D when I am doing a routine (1 year, kindergarten, or junior high) hemoglobin test for anemia if I suspect the child may be deficient. I am all about combining pokes (getting as much out of one poke than having to poke several times for different tests) if possible in a kid.
People at high risk for low vitamin D levels:
- Breastfed babies: Women in the US are generally deficient in vitamin D, so it goes without saying that their milk is also vitamin D deficient.
- Adolescents: They have increased metabolic need and generally their consumption doesn’t keep up.
- People who live in cold places: If it’s cold outside, you never go outside, or when you do, you’re always covered (so there’s no sun exposure).
- Elderly: (I know this is a pediatrician’s blog, but I had to add it for the sake of comprehensiveness). Their thin skin doesn’t absorb sun rays as well, and kidneys don’t convert vitamin D in to the active form as well.
- People who are overweight: Vitamin D is extracted from the blood by fat cells. More fat cells, means more extraction and less in the circulation (a BMI of >30 is the magic number for problems).
- Those with GI problems: Certain medical problems (e.g. Celiac disease, Cystic Fibrosis, Crohn disease) affect the body’s ability to absorb vitamin D through the gut.
Is too much vitamin D a problem?
Keep in mind that vitamin D is fat soluble, so overdosing is possible. While toxicity is rare, it can happen. Toxicity causes anorexia, weight loss, increased peeing, kidney failure, and heart arrhythmias. These serious side effects are the reason the medical community doesn’t support supplements that “mega dose” (>2,500 IU in kids or >10,000 IU in adults).
How much vitamin D is in your food?
(Keep in mind that a kid needs 400-600 IU’s/day).
Milk (skim, low fat, and whole) in 8 oz.……….98 IU
1 Egg…………………………………………………………20 IU
Cheese (swiss, 1 oz)………………………………..…..12 IU
Salmon (3.5 oz)………………………………………….360 IU
Cod liver oil, 1 TBLSPN…………………………….1,360 IU
So unless you’re going to feed your kid a lot of cod liver oil (although I don’t know how much will be absorbed after he/she throws it up), you can see that based on actual IU values, you’ll likely need to supplement. You could also expose your skin to more sun, but I don’t feel like I should endorse skin cancer. I guess that leads us back to likely needing supplementing.
Bottom line, if you don’t farm (where you would get lots of outdoor exposure-I feel like this blog is turning into a plug for farmers), if you wear sunscreen, if you don’t drink 32 oz. of milk a day, and if you live in the northern Hemisphere, you probably don’t get enough vitamin D.