By Rachel Johnson, Ph.D, M.P.H., R.D.
How much vitamin D should you get? That question has been a source of controversy ever since 1997 when the Institute of Medicine’s Food and Nutrition Board introduced the Dietary Reference Intakes (DRI) for the vitamin, ranging from 200 to 600 international units (IU) per day. Even then, many leading researchers believed the DRI should be set much higher—and now, their ranks are growing substantially.
In the March issue of the prestigious American Journal of Clinical Nutrition, 15 vitamin D experts from eight countries joined together to describe the “urgent need” for higher intakes of vitamin D. “Why is the science not making a difference to public health?” they implored.
Evidence is growing that vitamin D is important for much more than just bones; the vitamin seems to have a role in preventing colorectal and other cancers, diabetes, arthritis and even multiple sclerosis (MS). Interestingly though, when it comes to establishing dietary intake recommendations for vitamin D, we’re still stuck with what my friend Robert Heaney at Creighton University calls “the outdated model of simply getting enough to prevent rickets.” Heaney is frustrated that “we’re still using those recommendations even though they were made almost a decade ago, before we knew about [the vitamin’s] connections with preventing cancer, MS and diabetes.”
One of the reasons the vitamin D recommendations are so controversial is because changing them involves a paradigm shift. For the most part, nutrition experts adhere to the mantra that we can get a healthy diet through food alone. But vitamin D isn’t widely available in the food supply, and it’s almost impossible to know what people are consuming because the usual gold standard for nutrition analysis, the USDA National Nutrient Database for Standard Reference, doesn’t include vitamin D. So in order to maintain a healthy vitamin D status, “we either need to fortify the food supply more widely or encourage everyone to take supplements,” says Heaney. In Canada, where sunlight can be especially scarce during the winter months, government health officials recommend that all adults over age 50 take a supplement of 400 IU per day.
Not all experts agree, however. Steve Abrams, M.D., a pediatrician at Baylor College of Medicine and an expert on minerals in infants and children, says that while older adults may benefit, “there is no evidence that school-aged children need more vitamin D.” Although he fears that “the train has left the station” on the movement to raise vitamin D requirements, he’s not ready to recommend vitamin D supplementation for all ages—and for an entire nation. We may have more answers when the National Institutes of Health’s Office of Dietary Supplements releases a much-anticipated review of the evidence on vitamin D later this year.
Of course, official recommendations will only change if the Institute of Medicine (IOM) appoints an expert panel to re-evaluate and revise the current numbers. The IOM’s Food and Nutrition Board is beginning the process by holding a workshop in September to discuss issues surrounding the current DRIs. The informal buzz in the field is that vitamin D will be one of the first nutrients to be re-examined.
So stay tuned, because the official recommendations may be changing if the voices of dissent are heard. In the meantime, there seems to be fairly widespread agreement among experts that 1,000 IU daily of vitamin D is optimal for most people, and that the upper limit (the amount not to exceed to avoid risk of toxicity), which is currently set at 2,000 IU per day, can safely be raised to as high as 10,000 IU per day.
I’ve been around long enough to know that these policy changes may take a while. In the meantime, know that there is substantial evidence that you can safely exceed current recommendations for vitamin D intake—and likely should.