Vitamin D is one of your body’s most critical nutrients. It regulates calcium homeostasis, thereby supporting everything related to bone health, from bone resorption to bone remodeling. But beyond this, many consider vitamin D’s biologically active form (i.e. the metabolite produced by the kidney) 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] to be a steroid hormone. (If you want to geek out on the science, take a look at this article.) Functioning as a hormone, vitamin D plays a role in everything from immune function, to healthy brain development, to muscle, to optimally functioning cardiovascular and respiratory systems.
This is all to say that vitamin D is an essential nutrient. Our body’s manufacture vitamin D from sun light exposure, which is one reason I go on regular walks outside when the sun’s shining.
Many people are deficient though. In the United States, more than 40 percent are, and the prevalence of deficiency is about two-fold higher among African Americans.
But these figures are likely on the low end. The prevalence of vitamin D deficiency is determined based on Recommended Dietary Allowances, or RDA, set by the Institute of Medicine. More and more researchers, however, are questioning the accuracy of current guidelines, and believe they significantly underestimate the amount of vitamin D needed for optimal human health.
Current guidelines recommend 600 IU per day for people up to age 70 and 800 IU per day for older ages. On the high end, there is a risk of toxicity if you consume too much vitamin D (such as in supplement form). The recommended upper limit is 10,000 IU per day.
When re-examining data used to determine both the upper and lower recommended limits of vitamin d, researchers found a statistical error and that current guidelines could be off by several orders of magnitude. In fact, based on the new analysis, it’s in a totally different ballpark. Instead of 600 IU per day, the researchers found “8895 IU of vitamin D per day may be needed.” That’s more than a ten-fold difference! A separate analysis found that an intake of 3875 IU per day might be needed.
The two estimates differ quite a bit. They also use two different sets of data. Either way, both come to the same basis conclusion: current guidelines likely underestimate daily vitamin D intake significantly.
So as the days become longer heading into spring and summer, spend a few extra minutes outside soaking up the sun.