Until recently, the relationship between vitamin D and athletic performance received minimal attention. My colleagues and I began to evaluate this relationship in 2009, when we wrote the first paper about vitamin D and athletes in 50 years.
In 2010, I wrote a book on the subject. For some reason, if you search for the book on Amazon, some of the resellers on Amazon are asking $1,700.00 for a single copy. Does anyone know how that ruse works? I believe you can still purchase the book on the publisher’s website for $15.95:
Since our 2009 paper alerting team physicians and athletic trainers to the importance of vitamin D in athletic performance, there have been 24 studies examining the prevalence of vitamin D insufficiency [25(OH)D
Farrokhyar F, Tabasinejad R, Dao D, Peterson D, Ayeni OR, Hadioonzadeh R, Bhandari M. Prevalence of vitamin D inadequacy in athletes: a systematic-review and meta-analysis. Sports Med. 2015 Mar;45(3):365-78. doi: 10.1007/s40279-014-0267-6. Review.
Now a Canadian group has reviewed selected papers on the recent evidence that supports vitamin D has an effect on athletic performance.
Dahlquist DT, Dieter BP, Koehle MS. Plausible ergogenic effects of vitamin D on athletic performance and recovery. J Int Soc Sports Nutr. 2015 Aug 19;12:33. doi: 10.1186/s12970-015-0093-8. eCollection 2015. Review.
They reviewed five areas in some depth.
1) Oxygen consumption
Cross-sectional studies on oxygen consumption are mixed. However, Jastrzebski et al performed a single-blinded trial of supplementation with 6000 IU/day of vitamin D3 versus a placebo during an 8-week training cycle in 14 elite lightweight rowers with sufficient 25(OH)D concentrations (>30 ng/mL).
The research team wanted to determine the effects of vitamin D supplementation on VO2 max. VO2 max is a measurement used to determine the maximum amount of oxygen an athlete can utilize. They demonstrated a significant increase in VO2 max of 12.1 % and 10.3 % in the vitamin D group and placebo group, respectively.
2) Muscle inflammation
In a randomized, double-blind, placebo-controlled study, Barker et al. reported that 4000 IU/day for 35 days attenuated the inflammatory biomarkers alanine (ALT) and aspartate (AST) immediately following 10 sets of 10 repetitions of peak isometric force eccentric-concentric jumps. Furthermore, although peak power output decreased throughout the sets and repetitions in both of the groups, the supplementation group only decreased by 6%, while the placebo group’s power decreased by a significant 32%. This significant discrepancy persisted at 48 hours.
3) Force and Power production
Cross-sectional studies of force and power are certainly mixed. Close et al. conducted an 8 week randomized controlled trial in 30 athletes using 5000 IU/day of vitamin D or a placebo; the vitamin D group had a significant improvement in 10-m sprint times (P = 0.008) and vertical jump (P = 0.008) when compared to the placebo group. When Close et al. attempted a RCT using weekly doses of vitamin D, they found no effect on performance, showing – perhaps – vitamin D must be given daily.
4) Testosterone production
Testosterone is known to affect athletic performance; that’s why it’s banned. Pilz et al. conducted a 12-month, double-blind, randomized control trial in 54 non-diabetic obese males and demonstrated that the group receiving 3300 IU/day of vitamin D had a significant 30% increase in circulating total testosterone (P=0.001), bioactive testosterone (P=0.001) and free testosterone levels (P=0.001).
5) Vitamin K
For the first time, the authors raised the question, “is vitamin K important for athletic performance?” To the best of my knowledge, no studies exist on the subject.
The authors concluded:
“Based on the research presented on recovery, force and power production, 4000-5000 IU/day of vitamin D3 in conjunction with a mixture of 50 mcg/day to 1000 mcg/day of vitamin K1 and K2 seems to be a safe dose and has the potential to aid athletic performance.”
“Lastly, no study in the athletic population has increased serum 25(OH)D levels past 40 ng/ml (100 nmol/L), (the optimal range for skeletal muscle function) using doses of 1000 to 5000 IU/day. Thus, future studies should test the physiological effects of higher dosages (5000 IU to 10,000 IU/day or more) of vitamin D3 in combination with varying dosages of vitamin K1 and vitamin K2 in the athletic population to determine optimal dosages needed to maximize performance.”
I advise team physicians and athletic trainers to make sure their athletes have, at least, “natural” blood levels of vitamin D. Free-living hunter-gatherers in modern day equatorial Tanzania have mean levels of 46 ng/ml. Nature may know what it is doing.
As far as vitamin K is concerned, we agree that it is a “co-factor” of vitamin D. That’s why I advised Bio Tech to put vitamin K in the only vitamin D formula the Vitamin D Council endorses, D3Plus, which, by the way, contains 800 mcg of vitamin K as well as the co-factors, magnesium, zinc and boron.