We hear a lot about the sunshine vitamin. When it’s a health-related topic, it seems to be popping up everywhere – Athletics, Wellness, Science, Medicine, etc.
There are few arguments against vitamins, and vitamin D is a hotly debated topic.
Not whether we need it or not but how much we need is nowhere near agreed upon by different agencies. Here’s what you need to know!
How Much Vitamin D?
The discussion surrounding vitamin D isn’t actually new. There are published research papers dating all the way back to 1942 about how much we actually need. Back then, it was 400-500 IU, at least according to the Technical Commission of the League of Nations. The same article suggests giving babies (with even lower needs at ~250 IU) up to 1,200 IU (1).
Nowadays, babies are recommended 400 IU, children and adults 600 IU, and seniors (71 years or older) 800 IU by the Institute of Medicine.
The Vitamin D Council recommends, however, adults get 2,000 IU daily.
That’s over triple the IOM recommendation, and it is halfway to the tolerable upper limit of 4,000 IU.
The idea behind daily dosing is what will maintain blood levels at healthy concentrations. Even this is debated. The number you want to be above is 20 ng/mL of 25-hydroxyvitamin D for “optimal skeletal health” … or above 30 ng/mL, depending on who you talk to.
The numbers might seem close, but as a percentage, they’re very different when usually this sort of topic reaches consensus among experts.
20 ng/mL comes from the IOM. 30 ng/mL is the minimum suggested by the Endocrine Society, which says 40-60 ng/mL may be optimal. So, now we’re only off by as much as 300%?
Research On Vitamin D
Analytics is becoming increasingly popular. We hear it constantly in sports now. This is great for scientists like us. Here are some “analytics” on vitamin D.
From Osteoporosis International 2017 a study looked at vitamin D and risk of falls and function in elderly women over 2 years (2). They were initially evaluate for vitamin D at baseline, and 20 ng/mL was considered adequate.
If they were below, they supplemented 800 IU daily to maintain levels above 20 ng/mL and compared with those that were above without supplementation.
Even though everyone had “sufficient” levels, they all had reductions in function and more falls over time.
The few differences between groups seems to be isolated to the first 12 months, and the authors concluded, “a level of 30-40 ng/mL may be most beneficial,” and, “IOM guidelines may not be adequate.”
In science, we have to say “may” because we always leave the door open for alternative hypotheses based on other investigations, but the study suggests that 20 ng/mL IS inadequate. Here’s another study.
The title really says it all, “Vitamin D Concentrations > 40 ng/mL are Associated with 65% Lower Cancer Risk” (3). It was actually 67% versus 20 ng/mL or less.
One more good title, “Maternal Vitamin D concentrations ≥ 40 ng/mL Associated with 60% Lower Preterm Birth Risk” (4). It was actually 62% versus 20 ng/mL or less, and as much as 78% when stratifying based on race.
Unfortunately, it’s not always unanimous. Another study examining participants over 3 years found that 100,000 IU of vitamin D monthly had 0.3% greater incidence of cardiovascular disease than controls, or, statistically, no difference (5).
It’s a little weird that they did 100,000 IU per month instead of daily dosing of smaller quantities, but as a fat-soluble vitamin, it tends to stick around a while, so the study is not terribly designed.
But it does create indecision and highlights the state of the conversation – a mix between strongly positive observations and null results.
Vitamin D Benefits
So far we’ve mentioned cancer, cardiovascular disease, bone health, and premature birth risk.
Many other topics have been investigated, and it would seem that vitamin D can help some conditions but not others. (as an aside, at least some studies do support vitamin D for reducing CVD risk).
Therefore, it would seem logical to increase the recommendations. Benefits for some, no difference for others. Not to mention, quite a few other benefits, for athletes and non-athletes alike!
Here’s a quick list of the pros column:
- Reduces Blood Pressure
- Reduces Fat Mass
- Decreases All-Cause Mortality
- Reduces Frequency of Asthma Attacks
- Improves Insulin Sensitivity
- Decrease Inflammation
- Increases Testosterone in Men
- Lessens Risk for Multiple Sclerosis
Now if you’re outside all the time – soaking up the rays and trigger vitamin D production.
You probably eat a pretty healthy diet (eggs, yogurt, fish, orange juice, milk, cereal, and more all contain good quantities of vitamin D). Do you need to supplement vitamin D?
Probably not to get to 20 ng/mL. There’s a pretty good chance you’re getting “enough” already and keeping levels above suboptimal.
Getting some extra vitamin D sure does seem to be more optimal, though, doesn’t it? There’s no controversy in our mind – a little more is a lot better.
- Mackay, H. M. M. (1942). How Much Vitamin D?. British Medical Journal, 1(4238), 421.
- Kotlarczyk, M. P., Perera, S., Ferchak, M. A., Nace, D. A., Resnick, N. M., & Greenspan, S. L. (2017). Vitamin D deficiency is associated with functional decline and falls in frail elderly women despite supplementation. Osteoporosis International, 28(4), 1347-1353.
- McDonnell, S. L., Baggerly, C., French, C. B., Baggerly, L. L., Garland, C. F., Gorham, E. D., ... & Heaney, R. P. (2016). Serum 25-hydroxyvitamin D concentrations≥ 40 ng/ml are associated with> 65% lower cancer risk: pooled analysis of randomized trial and prospective cohort study. PloS one, 11(4), e0152441.
- McDonnell, S. L., Baggerly, K. A., Baggerly, C. A., Aliano, J. L., French, C. B., Baggerly, L. L., ... & Wineland, R. J. (2017). Maternal 25 (OH) D concentrations≥ 40 ng/mL associated with 60% lower preterm birth risk among general obstetrical patients at an urban medical center. PloS one, 12(7), e0180483.
- Scragg, R., Stewart, A. W., Waayer, D., Lawes, C. M., Toop, L., Sluyter, J., ... & Camargo, C. A. (2017). Effect of monthly high-dose vitamin D supplementation on cardiovascular disease in the vitamin D assessment study: a randomized clinical trial. JAMA cardiology, 2(6), 608-616.