Vitamin D is a nutrient (well, technically a hormone) that has had a substantial amount of research devoted to it over recent years. As someone who enjoys keeping up with the latest findings, I am often dismayed at the outdated — and often inaccurate– information shared with the public.
Below, three crucial, but little-known, vitamin D facts everyone must know for the sake of their health.
1. Current Vitamin D Recommendations Are Too Low
When I suggest to a client that they supplement 4,000 to 6,000 International Units (IUs) of vitamin D a day, their first reaction is usually one of two: “But I already take a multivitamin” or “Wow! That sounds like a lot”.
It does sound extreme when you consider that the current recommended daily intake is set at 600 IUs for anyone between the ages of 14 and 70 (this was increased a little over a year ago from the former recommendation of 400 IUs). Your average multivitamin provides anywhere from 400 to 600 IUs.
The problem is that the 600 IUs recommendation is based on research that solely examined vitamin D’s role in bone health. While that is certainly one function of vitamin D, there are many more (almost every cell in the human body has vitamin D receptors). Newer research has implicated D in blood glucose control, mood disorders, and heart health.
Besides, when we make vitamin D from the sun, we can make up to 10,000 International Units a day under optimal conditions (certainly calls into question some recommendations which set an Upper Tolerable Limit of 2,000 IUs). And, while anecdotal, the only way I have seen deficiencies corrected — in both clinical and outpatient settings — was with supplementation of anywhere from 4,000 to 10,000 International Units a day (depending on the severity of the deficiency).
2) You Don’t Make Vitamin D From the Sun Year-Round
Many individuals who learn they are vitamin D deficient are often surprised since “they are always out in the sun”. Depending where you live, though, your ability to make vitamin D is inhibited for many months.
There isn’t full agreement in the health field, but the most common belief is that if you live north of the 35th parallel (see map here), your body is unable to make vitamin D from the sun for several months (roughly from November to April). For what it’s worth, some people abide by the “33rd parallel” theory, while others think “the 37th parallel” is more accurate.
The point is — if you’re north of Los Angeles, you are not making vitamin D for many months, even if you are out in the sun, at noon, wearing next to nothing. The reason? The sun’s UVB rays — the ones responsible for vitamin D production — don’t reach you.
3) There Are A Lot of Barriers to Vitamin D Production
Let’s say you live in an area where you can make vitamin D year-round. Or that you’re all the way up in Boston, but it’s the middle of July, so the UVB rays are on and poppin’. You are getting all your vitamin D from the sun, right? Not quite. There are many barriers that can inhibit vitamin D production:
- Air pollution.
- Sunscreen. “Sunscreens with SPF ≥ 15 almost completely inhibit vitamin D3 production”. Keep in mind that most commercial moisturizers contain SPFs in the 20s, 30s, and 40s.
- Time of day. The general rule is that if your shadow is longer than your body, the sun’s rays are not high enough to produce vitamin D.
In summary: 600 IUs of vitamin D a day won’t cut it. You owe it to yourself to have proper levels, and, to do so, you can’t depend on sunlight or the paltry amounts fortified in food.