Vitamin D is often referenced as the sunshine vitamin since the vitamin’s primary source is attained through sun exposure. Yet, many people are vitamin D deficient.
Vitamin D is a fat-soluble hormone that plays a critical role in bone health, muscle function, adaptive immunity, and many human diseases like cancer, diabetes, and musculoskeletal health.2
Vitamin D Deficiency
In fact, vitamin D deficiency is a global public health issue.
About 1 billion people worldwide have vitamin D deficiency, while over 77% of the general population is insufficient.1 So, what does that mean if you are an athlete who plays an indoor sport, trains indoors year-round, and rarely gets outside during the day?
What if you also live in the northern hemisphere? Odds are you are not getting enough vitamin D. Insufficient sun exposure can dramatically increase your risk of vitamin D deficiency. It can lead to a variety of negative health implications and hinder athletic performance.
Research has illustrated that vitamin D significantly affects muscle weakness, pain, balance, and fractures in the aging population.1
Vitamin D plays a key role in:1
Vitamin D deficiency occurs as blood levels drop to less than 20 ng/mL (< nmol/L), while vitamin D insufficiency for athletes is defined as blood levels reaching between 20-32 ng/mL (50-80 nmol/L).
Research has indicated that 40-50 ng/mL (100-125 nmol/L) seems ideal for optimizing athletic performance.1
Who’s at High Risk?
The people at high risk for vitamin D deficiency:1,5
- Decreased dietary intake: Certain malabsorption syndromes like celiac disease, short bowel syndrome, gastric bypass, inflammatory bowel diseases
- Decreased sun exposure. Roughly 50% to 90% of vitamin D is absorbed through the skin. Twenty minutes of sunshine daily, with 40% of skin exposed, is required to prevent deficiency.
- Aging adults: The ability to synthesize vitamin D decreases by as much as 75% as we age.
- Overweight and obese individuals: Those who carry excess body fat can increase their risk of up to 55% due to vitamin D being trapped in adipose tissue and being unavailable in the bloodstream.
See the previous blog on factors that influence vitamin D levels.
Athletes Who Play Indoor Sports
Athletes who play indoor sports are at a greater risk of vitamin D deficiency.
Hockey players specifically spend a great deal of their time training, conditioning, and competing indoors, making it difficult to attain vitamin D through sun exposure. To add to the statistics, another study found that as much as 88% of the population receives less than the optimal amount of vitamin D.3
Several studies link vitamin D status to bone health and the overall prevention of bone injuries in the athletic population.
Research and Vitamin D Deficiency
Studies have illustrated that inadequate vitamin D levels are linked to a greater risk of stress fractures in young men and women published in the Journal of Foot & Ankle Surgery.4
A study published in the journal, Nutrients assessed vitamin D status among college men and women basketball players in the season. The players were either allocated a high-dose, low dose, or no vitamin D depending on their circulation 25-hydroxyvitamin D levels at the beginning of the study to identify the optimal dosage of vitamin D3 supplementation optimal status.
The findings demonstrated that 13 of the 20 participants were vitamin D insufficient at baseline. Another finding was that of the athletes sampled, and the darker skin pigmentation increased the risk of vitamin D insufficiency at baseline.
Researchers found that most athletes who were vitamin D insufficient benefited from supplementation of 10,000 IU to improve their status.5
Another study concluded black professional football players have a higher vitamin D deficiency than white players.6
The study also suggests that professional football players deficient in vitamin D may also have a greater risk of bone fractures.7
Increasing power output is every athlete’s desire as it can translate into improved performance on the field. Your muscle tissues have several key receptor sites for vitamin D, and they will help support power production.1
A study in soccer players found that increasing baseline vitamin D status over an 8-week period leads to increased vertical jump and 10-meter sprint times.9
Of course, we need further research in this area to identify the relationship between vitamin D levels and power output.
Still, the current literature is promising and that, at minimum, baseline vitamin D levels should be desired.
Sources of Vitamin D
The best vitamin D sources include egg yolks, mushrooms, fortified milk, yogurt, cheese, salmon, mackerel.8
Vitamin D rich food sources:
- 6 oz. fortified yogurt = 80 IU
- 3 oz. of salmon = 794 IU
- 1 cup of fortified cereal = 40 IU
- 1 cup of fortified milk = 120 IU
- 1 egg yolk = 41 IU
- 1 cup of fortified orange juice = 137 IU
Athletes who train indoors, consume little vitamin D rich sources and live > 35 degrees north or south may benefit from a vitamin supplement of 1,500 – 2,000 IU per day to keep vitamin D concentrations within a sufficient range.
Athletes who may have a history of stress fractures, frequent illness, pain or weakness, or overtraining signs should have their vitamin D status evaluated.
Vitamin D is best absorbed when taken with a meal that contains fat.
It is important to follow up with a physician to assess vitamin D levels further and meet with a registered dietitian to discuss nutrition intervention further.
1. Ogan, D., & Pritchett, K. “Vitamin D and the athlete: risks, recommendations, and benefits.” Nutrients, 5(6), 1856–1868. 2013.
2. Umar, M., Sastry, K. S., & Chouchane, A. I., “Role of Vitamin D Beyond the Skeletal Function: A Review of the Molecular and Clinical Studies.” International Journal of Molecular Sciences, 2018,19(6),1618.
3. Bendik, I., Friedel, A., Roos, F. F., Weber, P., & Eggersdorfer, M. “Vitamin D: a critical and essential micronutrient for human health.” Frontiers in Physiology, 5, 248, 2014.
4. Elsevier Health Sciences. (2015, December 14). “Low levels of vitamin D may increase risk of stress fractures in active individuals: Experts recommend active individuals who participate in higher impact activities may need to maintain higher vitamin D levels.” ScienceDaily. Retrieved October 19, 2020.
5. Sizar O, Khare S, Goyal A, et al. “Vitamin D Deficiency.” [Updated 2020 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.
6. Sekel, N.M.; Gallo, S.; Fields, J.; Jagim, A.R.; Wagner, T.; Jones, M.T. “The Effects of Cholecalciferol Supplementation on Vitamin D Status Among a Diverse Population of Collegiate Basketball Athletes: A Quasi-Experimental Trial.” Nutrients, 2020, 12, 370.
7. National Institutes of Health – Office of Dietary Supplements – “Vitamin D – Fact Sheet for Health Professionals.” [accessed October 19, 2020].
8. Maroon JC, Mathyssek CM, Bost JW, Amos A, Winkelman R, Yates AP, Duca MA, Norwig JA. “Vitamin D profile in National Football League players.” Am J Sports Med. 2015 May;43(5):1241-5. Epub 2015 Feb 3. PMID: 25649084.
9. Close, G. L., Russell, J., Cobley, J. N., Owens, D. J., Wilson, G., Gregson, W., Fraser, W. D., & Morton, J. P., “Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function.” Journal of Sports Sciences, 31(4), 344–353. 2013.