Efficacy of high dose vitamin D supplements for elite

Owens DJ, Tang CY, Bradley
WJ, Sparks A, Fraser WD, Morton JP, and Close GL. Med Sci
Sports Exerc. 2016.
[Epub Ahead of Print].

Home Message: A Blanket high dose vitamin D supplement plan results in elevated
levels of vitamin D metabolites after the supplementation is completed. This
could result in lower than normal levels of vitamin D, which is the opposite
effect of the intended supplementation.

Vitamin D is a necessary nutrient in all individuals,
especially the physically active population, and has been shown to be
influential in muscle development and repair among other benefits. Many athletes
consume large supplemental doses of vitamin D for these reasons; however, the
long-term effects of this are not well understood. Therefore, Owens and
colleagues completed a repeated measures study with 42 elite male athletes to
identify the responses of the body to both a moderate and high dose of
supplemental vitamin D. None of the athletes reported currently taking a
vitamin D supplement, using tanning beds, or were injured. Athletes were
randomized into one of two groups. The moderate consumption group received
35,000 international units (IU) of vitamin D3 per week, and the high
consumption group received 70,000 IU per week. These doses are the most
prominently prescribed doses for elite athletes. All included athletes
continued the supplementation plan for 12 weeks during which time they had
minimal exposure to sunlight. Quantities of vitamin D
metabolites, which
break down vitamin D, were measured via blood samples taken at baseline, 6, 12,
and 18 weeks from the start of supplementation. Overall, serum levels of
vitamin D3 for both groups increased significantly during the supplementation
period. Metabolite levels were also elevated during the supplementation period;
however, upon cessation of supplementation, the levels of metabolites in the
moderate treatment group returned to baseline, while levels in the high
supplementation group had elevated levels of vitamin D3 metabolites.

The authors’ results are important for clinicians as
elevated levels of metabolites after the cessation of supplementation indicate
that metabolites continue to metabolize vitamin D3 at an elevated rate despite
intake levels returning to normal. If levels of D3 metabolites are elevated
while D3 intake levels are stable this could result in the opposite effect of
the intended supplementation such as bone pain, muscle weakness, and elevated
blood pressure. These results suggest that clinicians may not wish to suggest
blanket vitamin D3 supplementation programs, but rather, may wish to consult
with a physician for more individualize treatment. Future research should
further investigate how high-dose supplementation of vitamin D3 impacts
long-term metabolite levels for a longer follow-up period as well as how these
metabolite levels compare to more individualized treatment. Patient-reported
outcome measures may also be useful in assessing how patients subjectively feel
during the treatment period, which may also be useful to the development of
clinical best practices. Until more research can be completed, clinicians who wish
to supplement athletes with vitamin D3 should be cautious in their
recommendations, and should consult with a registered dietitian and or a
physician prior.

Questions for Discussion: Have you prescribed large-dose
vitamin D supplement programs for your athletes? If so, what other
collaboration did you have prior to and during supplementation?

Written by: Kyle Harris
Reviewed by:  Jane McDevitt

Related Posts:

Owens DJ, Tang JC, Bradley WJ, Sparks SA, Fraser WD, Morton JP, & Close GL (2016). Efficacy of High Dose Vitamin D Supplements for Elite Athletes. Medicine and science in sports and exercise PMID: 27741217