Vitamin D: Finally Something Experts can Agree Upon
When did choosing something to eat becomes as confusing as understanding climate change? While experts may argue about the impact of greenhouse gas accumulation on the environment, lives are much shorter. If nutrition is important, our health is the result of daily decisions. In this world of information overload, what should one do about nutrition? Case in point – vitamin D.
In 2010, after a thorough review of the literature, the Institute of Medicine(IOM) issued new vitamin D recommendation. The Recommended Dietary Allowance (RDA) was increased from 400 IU daily to 600-800 IU daily (depending upon age and sex). Since then, experts have challenged the report (Veugelers & Ekwaru, 2014; Heaney et al, 2015), arguing that the IOM committee underestimated the requirement statistically. In both papers, the authors argue for an RDA > 4,000IU daily. The IOM responded ( http://www.iom.edu/Global/News%20Announcements/How-the-RDA-for-Vitamin-D-Was-Determined.aspx ), validating their calculations. What should I think?
It is time to shift the argument from setting dietary vitamin D recommendations to nutrition assessment, i.e. serum 25(OH)D3 concentrations. The only way to give responsible vitamin D guidance to someone is by measuring their status. Consider your car. The number of miles it can be drive depends upon the amount of gasoline in the tank not the amount of gas that was purchased last time, or even the date you last purchased gasoline. Future mileage depends upon the total amount of gas in the car when you leave the pumps, not the amount that was added to the car or the rate at which it was added.
A new study reports exercise training increases strength and balance training in elderly home-dwelling women. Vitamin D supplementation maintained femoral bone mineral density and increased tibial trabecular bone density. This is great news. However, expect to read stories that vitamin D did not reduce risk of falls. The headlines will probably fail to mention baseline serum 25(OH)D3 concentrations averaged ~70 nmol/L and increased to 90 nmol/L in the supplemented group. Previous research found increasing serum 25(OH)D3 above 60 nmol/L has little impact on lower-extremity function while it does benefit bone mineralization up to 60 nmol/L. Uusi-Rasi and colleagues confirm these findings. When serum 25(OH)D3 concentrations are almost 70 nmol/L, vitamin D supplementation primarily affects bone health and not muscle function.
Experts agree that serum 25(OH)D3 concentrations should be above 50 nmol/L and below 100 nmol/L - 2011 IOM Committee; Veugelers & Ekwaru, 2014; Heaney et al, 2015. All of those who vigorously debated the vitamin D RDA agree on this point – optimal serum 25(OH)D3 concentrations. Let’s focus on measuring things we agree upon rather than those we don’t.
Is your vitamin D tank full, half-full or closer to empty? Ask your doctor to check your progress on maintaining vitamin D levels between 50-100 nmol/L.
Uusi-Rasi K, Patil R, Karinkanta S, Kannus P, Tokola K, Lamberg-Allardt C, Sievanen H. Exercise and vitamin D in fall prevention among older women: A randomized clinical trial. 2015 JAMA Intern Med doi: 10.1001/jamainternmed.2015.0225
Heaney R, Garland C, Baggerly C, French C, Gorham E. Letter to Veugelers PJ and Ekwaru JP. A statistical error in the estimation of the Recommended Dietary Allowance for Vitamin D. 2015 Nutrients doi: 10.3390/nu7031688
Veugelers PJ, Ekwaru JP. A statistical error in the estimation of the Recommended Dietary Allowance for vitamin D. 2014 Nutrients doi: 10.3390/nu6104472
Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes, B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. 2006 Am J Clin Nutr 84(1):18-28