Last week, the Institute of Medicine (IOM) issued its long awaited report on vitamin D and calcium recommendations. Why is this report so important? Well, in addition to shedding light on all the reports of vitamin D deficiency, the report’s recommendations influence dietary requirements for school foods, the Nutrition Facts panels on packaged foods, and pretty much all nutrition-related initiatives sponsored by the federal government.
The vitamin D and calcium dietary reference intakes (DRIs) were last updated in 1997, which is not that long ago in science time. Since there has been significant and well-publicized research on vitamin D, the IOM prioritized a review of the existing recommendations. Several news organizations, including the New York Times and the Wall Street Journal were quick to put out summaries of the IOM’s final report. The IOM report and the articles cited are difficult to interpret because unlike most other nutrients, vitamin D can be naturally produced by our bodies. This mechanism makes it very challenging to issue broad public health recommendations. Suffice to say that if you weren’t confused before, you probably are now. Here’s what to keep in mind:
- The IOM increased vitamin D recommendations for all individuals (from 200IU to 600IU for those aged 9-50, from 400IU to 600IU for those aged 51-70, and from 600IU to 800 for those over age 70). Also increased are the upper limits for intake, which have gone from 2000IU to 4000IU for those aged 9-70. The recommendations assume limited exposure to sunlight, and therefore count diet as the primary source of vitamin D.
- There is limited variety among foods rich in vitamin D. We can thank the USDA for analyzing the nutrient content of thousands of foods and compiling this list of foods, sorted by vitamin D content per serving. It is overwhelmingly clear that fish is the best source of vitamin D (sockeye salmon provides over 800IU), with fortified milk coming in a close second (lowfat milk has 117IU). It isn’t impossible to meet the new recommendations through diet, but it’s not easy if you don’t eat seafood or dairy.
- Exposure to direct sunlight is, and always will be, the best way to increase your vitamin D levels. The only exception to this rule is if you are genetically unable to metabolize vitamin D (a blood test can help confirm this condition). If there is little sunlight where you live, if you have dark skin, or if you are over 50 years old, you are less efficient at converting sunlight into vitamin D (note: less efficient does not mean unable). Note also that we are blessed with the ability to store vitamin D, which means that we can make extra in the summer and use it in the winter. Taking advantage of this inborn ability requires that we be out in sunlight without sunscreen for about 10-20 minutes – this window varies by skin tone and by sun intensity – per sunny day.
The take home is that you should do what you can to make vitamin D through sunlight exposure. Given the assumptions made by the IOM, we can infer that getting more vitamin D from sunlight means you can rely less on diet for vitamin D. If there are major hurdles to spending some time in the sun, try to increase the amount of seafood and milk in your diet. If your physician has told you you are unable to produce vitamin D because of a genetic condition (or if you’re a vegan that hates being out in the sun), supplements are probably warranted.