Vitamin D and the athlete, by Carmen Bosmans

Midday sitting outside the gym for my daily tanning session and thinking about a subject to write about this week. Not really getting anywhere so I decided to take a Snapchat of myself in the sun and hashtagged it as "vitDgains". I normally sit under the glare of the sun before, after and even in between my training to soak up the natural vitamin D. I also take extra supplements of it in the morning.  But what is 'Vit D' all about? How does it affect my athletic performance? I found an interesting study online from the National Center of Biotechnology Information called  'Plausible ergogenic effects of vitamin D on athletic performance and recovery'. The main purpose of the review was to 'examine vitamin D in the context of sport nutrition and its potential role in optimizing athletic performance'. Here's a snippet of the report: Introduction Vitamin D, a fat-soluble and a essential vitamin, which can be produced in your skin in response to sunlight. Vitamin D travels in the bloodstream and undergoes a thee-stage process. It travels to the liver and kidneys where its hydroxylated by enzymes to become its biological active form 25(OH)D that will interact with vitamins D receptors, which are located in almo st every tissue in the body. Sources
  • Sunlight: about 20 min a day is recommended
  • Diet: vitamin D can be found in various food products
  • Milk
  • Salmon
  • Sardines
  • Egg yolk
  • Vitamin D supplements
Five key areas of study:
  1.  Oxygen consumption The study determines the effects of vit D supplementation on VO2 max. VO2 max is a measurement used to determine the maximum amount of oxygen an athlete can utilize. They give elite rowers a supplement of 6000IU/day during a 8 week training cycle. They demonstrated a significant increase in VO2 max of 12.1% compared to the placebo group that is only 10.3%.
  2.  Muscle inflammation According to Barker T, Schneider ED, Dixon BM, Henriksen VT, Weaver LK. Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise. He demonstrated that 4000IU/day for 35 days for 35 days of vitamin D in healthy and moderately active adults   The inflammatory biomarkers alanine (ALT) and aspartate (AST) decreased. When performing 10 sets of 10 repetitions of peak isometric force eccentric-concentric jumps. Although peak power output decreased throughout the sets and repetitions in both groups, the supplementation group only decreased by 6% compared to 32% decrease in the placebo group
  3.  Force and power production An 8 week randomized control trail in 30 athletes using 5000IU/day of VIT D or a placebo. The VIT D group had a significant increase in 10 m sprint times and vertical jump when compared to the placebo group.
  4.  Testosterone production Testosterone is an endogenous hormone important for muscular adaptations to training. In a 12 month double blind, randomized control trail with 54 males demonstrated that the group receiving 3300IU/day of VIT D had a significant 30% increase in total circulating testosterone.
  5. Vitamin K Does Vit D improve physical performance in athletes? Based on the research presented on recovery, force and power production, 4000-5000IU/day of vitamin D with a mixture of 50mcg/day to 1000mcg/day of VIT K seems to be a safe doses and has the potential to aid athletic performance.
Dosage for optimal performance
  •  The IOM defines inadequate stores of 25(OH)D as 30-50 nmol/L and deficiency <30 nmol/L and sets the upper limit of dietary intake of VIT D to 4000IU/day
  • The ES Defines VIT D deficiency at levels of 25(OH)D <50 nmol/L , insufficiency as 25(OH)D between 51-75 nmol/L and upper limit of dietary intake of VIT D to 10000IU/ day The optimal dosage of vitamin D is clearly controversial. Although It's had been shown that it takes roughly 2000-5000IU/day of vitamin D of all sources in order to optimize bone health by maintaining 25(OH)D levels of 75 to 80 nmol/L Lastly, athletes may benefit form 25(OH)D levels >100 nmol/L in order to increase skeletal muscle function and reduce the risk of stress fractures.
I suggest that you let your  doctor measure your plasma 25(OH)D in order to determine if supplementation is needed. Ideal should be between 75-100 nmol/L.


  By: Carmen Bosmans, InnerFight Performance Coach