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March 2018

Vitamin D and Sport Performance - More Than Just for Bones!

Written by Angela Dufour, MEd, RD, CSSD, IOC Dip Sports Nutr, CFE Performance Dietitian for the 2018 Winter Olympics

Vitamin D, otherwise known as the sunshine vitamin, is a fat-soluble vitamin that is derived from cholesterol and stored in fat. Vitamin D is well known to help us absorb calcium from the gut to promote bone development and growth. But more recent research indicates it has so many more functions for maintaining health and optimizing training and performance in athletes. It is now thought that athletes who have adequate (or higher) intakes and levels of vitamin D might increase skeletal muscle function; (mass, strength and endurance), decrease recovery time from training, increase both force and power production and improve immune function, each of which could enhance athletic performance. (1, 2). Vitamin D in its active form also acts like a steroid hormone, interacting with over 1000 genes throughout the body, serving nerve signaling and blood pressure.

Vitamin D and Athletic Performance

Bone Health

Numerous studies have proven the positive influence of vitamin D on calcium and phosphate absorption in the gut and their impact on bone density and mineralization and remodeling (4, 5, 6).

Skeletal Muscle Function and Recovery

Vitamin D can indirectly affect the recovery and construction of muscle tissue by stimulating contraction and the nervous system, thus reducing reaction time and improving balance and coordination of movement, (7, 8, 9). Vitamin D may also play a role in increasing testosterone and steroid hormones, leading to an increase in skeletal muscle hypertrophy, strength and power output (10,11).

Immune Function

High training loads of athletes make them more susceptible to bacterial infections, (upper respiratory tract, cold, flu). Some studies have shown that by taking 2000 International Units (IU) daily of Vitamin D for one year can significantly decrease the incidence of common colds and flu (12, 13, 14, 15).

Are Athletes Getting Enough

Simply put: NO! Vitamin D deficiency is on the rise throughout the world, surprisingly enough, 88.1 % of the world’ s population has inadequate vitamin D levels (16), particularly in the northern latitudes, where it can be hard to get enough sunshine, especially in the winter months. Reduced levels of vitamin D have been observed in athletes of various gender, age, and sport. Unlike other vitamins and minerals, only modest amounts of vitamin D come from food; (as seen in Table 1), instead, it is the sun’s ultraviolet B (UVB) rays that serve as our most efficient means of producing vitamin D. Therefore, athletes who train indoors or after sunset or who travel to foreign countries for training camps and competitions where dietary intakes of Vitamin D may be limited, may be at risk for Vitamin D deficiency. Severe, chronic vitamin D deficiency can lead to rickets, softened/weak-end and bowed bones that occur in children and adults, respectively.

Other factors that influence how much active vitamin D athletes can obtain from the sun include:

1. Time of year: vitamin D can only be synthesized when the sun is sufficiently high in the sky. For those living above 50° North, the sun’s zenith angle is low enough that vitamin D cannot be produced in the skin from October to early April.

2. Time of day: even during the peak summer season in Canada, UVB is only sufficient to produce vitamin D in the skin through the middle of the day, 11:00am-2:00 pm. This means that athletes training outdoors in the evening or early morning will likely produce little vitamin D, even on exposed skin.

3. Skin exposure: the most vitamin D is generated through UVB exposure on the torso, followed by the arms and legs, with the hands and face producing the least.

4. Skin pigmentation: individuals with darker skin have higher levels of melanin, which acts as a natural sunblock, slowing the production of vitamin D in theskin.

5. Altitude: UVB levels are higher at altitude than at sea level.

6. Sunscreen: blocks 95-100% of vitamin D production.

7. Cloud: complete cloud cover reduces UV levels by about half.

8. Shade & severe pollution: reduce UV by about 60%.

9. Glass: blocks UVB rays, so athletes who train indoors, even if they are exposed to daylight, will not produce vitamin D.

TABLE 1: Vitamin D Content and Some Common Foods

Vitamin D is not found naturally in many commonly consumed foods. In Canada, some foods such as milk, soy or rice beverages and margarine have vitamin D added to them. Good food sources of vitamin D include certain kinds of fish, egg yolks and milk. The following table will show you foods that are a source of vitamin D.

Food	Serving Size	Vitamin D (IU)
Vegetables and Fruit	This food group contains very little of this nutrient
Orange juice, fortified with vitamin D	125 mL (½ cup)	50
Grain Products	This food group contains very little of this nutrient.
Milk and Alternatives
Soy beverage, fortified with vitamin D	250 mL (1 cup)	86
Milk (3.3 % homo, 2%, 1%, skim, chocolate milk)	250 mL (1 cup)	103-105
Skim milk powdered	24 g (will make 250 mL of milk)	103
Yogurt (plain, fruit bottom), fortified with vitamin D	175 g (3/4 cup)	58-71
Meat and Alternatives
Egg, yolk, cooked	2 large	57-88
Pork, various cuts, cooked	75 g (2 ½ oz)	6-60
Deli meat (pork, beef, salami, bologna)	75 g (2 ½ oz)/ 3 slices	30-54
Beef liver, cooked	75 g (2 ½ oz)	36
Fish and Seafood

Salmon, sockeye/red, canned, cooked or raw	75 g (2 ½ oz)	394-636
Salmon, humpback/pink, canned, cooked or raw	75 g (2 ½ oz)	392-447
Salmon, coho, raw or cooked	75 g (2 ½ oz)	338-422
Snapper, cooked	75 g (2 ½ oz)	392
Salmon, chinook, raw or cooked	75 g (2 ½ oz)	383-387
Whitefish, lake, cooked	75 g (2 ½ oz)	135
Mackerel, Pacific, cooked	75 g (2 ½ oz)	343
Salmon, Atlantic, raw or cooked	75 g (2 ½ oz)	206-245
Salmon, chum/keta, raw or cooked	75 g (2 ½ oz)	203-221
Mackerel, canned	75 g (2 ½ oz)	219
Herring, Atlantic, pickled	75 g (2 ½ oz)	202
Trout, cooked	75 g (2 ½ oz)	148-208
Herring, Atlantic, cooked	75 g (2 ½ oz)	161
Roe, raw	30 g (1 oz)	145
Sardines, Pacific, canned	75 g (2 ½ oz)	144
Halibut, cooked	75 g (2 ½ oz)	144
Tuna, albacore, raw or cooked	75 g (2 ½ oz)	99-106
Mackerel, Atlantic, cooked	75 g (2 ½ oz)	78
Tuna, white, canned with water	75 g (2 ½ oz)	60
Fats and Oils
Cod liver oil	5 mL (1 tsp)	427
Margarine	5 mL (1 tsp)	25-36
Other

Goat’s milk, fortified with Vitamin D	250 mL (1 cup)	100
Rice, oat, almond beverage, fortified with Vitamin D	250 mL (1 cup)	85-90

Source: "Canadian Nutrient File 2015"

www.hc-sc.gc.ca/fn-an/nutrition/fiche-nutri-data/index-eng.php [Accessed From www.dietitians.ca, January 2018].

How Much is Enough?

The optimal dosage varies depending on the individual and the institution providing the guidelines in order to recap the above-mentioned performance benefits. Table 2 represents the recommendations of the Institute of Medicine (IOM), while the Endocrine Society (ES) recommends a slightly higher intake. Various organizations differ in what they determine is the lowest desirable serum level of Vitamin D in order to achieve full health benefits (17, 18, 19).

How Much Vitamin D Should Athletes Aim For?

Table 2: Recommended Dietary Allowances for Vitamin D (Institute of Medicine, 2010)*

Age in Years	Aim for an intake of international units (IU/day)*	*Stay below IU/day**
Children <1 yr	400	1000-1500
Children 1-8	400	2500-3000
Children and Adults 9-70	600	4000
Men and Women 51-70	600	4000
Men and Women 71 and older	800	4000
Pregnant and Breastfeeding Women 19 and older	600	4000

*based on evidence to maintain blood levels of >50 nmol/L [11, 80, 81].

Are Vitamin D Supplements Needed for Athletes

Vitamin D supplementation can be considered safe and appropriate for athletes who have low blood levels of vitamin D. Although exact levels are currently undetermined, it is suggested to be higher than general standards. In the absence of available screening and monitoring (e.g. blood work), a routine vitamin D supplement of 1000 IU of vitamin D per day may be considered safe and reasonable for all athletes. However, performance studies done on athletes were supplemented with 5000 IUs/day which is far greater than the recommended dosages of 600– 2000 IU/day. Thus, it remains unclear, but athletes may benefit from higher levels of Vitamin D than current recommended daily intakes in order to increase skeletal muscle function and reduce the risk of stress fractures. (2,20, 21, 22)
Vitamin D Types

There are two major forms of Vitamin D; D3 (cholecalciferol) and D2 (ergocalciferol). Vitamin D2 is mainly used in the fortification of foods, and is absorbed lower than vitamin D3. Vitamin D3 is made in the skin and found naturally in foods.

Commercial supplements can be in either form, however, Vitamin D3 may be the more effective.
Bottom Line

Given the outlined numerous benefits of adequate Vitamin D to an athletes’ health, training and performance, it is important for athletes to get their Vitamin D status checked regularly during training. Parents and coaches can encourage more Vitamin D foods consumption to reap the sport performance benefits. However, in order to achieve optimal levels of Vitamin D, athletes who are at risk or who have below desirable levels (actual amounts are under review) (3, 18) may still need additional Vitamin D supplementation especially during winter months. More research is needed in athlete specific situations to determine optimal amounts of supplementation for its potential ergogenic benefits, but growing evidence has supported that 600– 800 IU/day may not be sufficient for optimal levels of vitamin D, in athletic population.
References

1. Int Soc Sports Nutr. 2015; 12: 33. Published online 2015 Aug 19. doi: 10.1186/s12970-015-0093-8

2. Dylan T. Dahlquist, Brad P. Dieter, and Michael S. Koehle. Plausible ergogenic effects of vitamin D on athletic performance and recovery,

3. Bendik I, Friedel A, Roos FF, Weber P, Eggersdorfer M. Vitamin D: a critical and essential micronutrient for human health. Front Physiol. 2014;5:248.

3. Holick M.F.: Vitamin D deficiency. N. Engl. J. Med., 2007; 357: 266-281

4. Peckenpaugh N.J.: Mikroskładniki w zbilansowanych posiłkach: witaminy, minerały i fitozwiązki. In: Podstawy żywienia i dietoterapia, ed. Peckenpaugh N.J., Elsevier Urban & Partner, Wrocław, 2010, 93-95

5. D’Antona G, Lanfranconi F, Pellegrino MA, Brocca L, Adami R, Rossi R, et al. Skeletal muscle hypertrophy and structure and function of skeletal muscle fibres in male body builders. J Physiol. 2006;570(Pt 3):611–27.

6. Pfeifer M., Begerow B., Minne H.W., Schlotthauer T., Pospeschill M., Scholz M., Lazarescu A.D., Pollähne W.: Vitamin D status, trunk muscle strength, body sway, falls, and fractures among 237 postmenopausal women with osteoporosis. Exp. Clin. Endocrinol. Diabetes, 2001; 109: 87-92

7. Stein M.S., Wark J.D., Scherer S.C., Walton S.L., Chick P., Di Carlantonio M., Zajac J.D., Flicker L.: Falls relate to vitamin D and parathyroid hormone in an Australian nursing home and hostel. J. Am. Geriatr. Soc., 1999; 47: 1195- 1201

8. Close GL, Russell J, Cobley JN, Owens DJ, Wilson G, Fraser WD, et al. 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. J Sports Sci. 2013;31:344–53.

9. Herbst KL, Bhasin S. Testosterone action on skeletal muscle. Curr Opin Clin Nutr Metab Care. 2004;7:271–7.

10. Urban RJ. Growth hormone and testosterone: Anabolic effects on muscle. Horm Res Pædiatrics. 2011;76:81–3.

11. Close GL, Leckey J, Patterson M, Bradley W, Owens DJ, Fraser WD, et al. The effects of vitamin D(3) supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study. Br J Sports Med. 2013;47:692–6.

12. Welch TR, Bergstrom WH, Tsang RC. Vitamin D-deficient rickets: the reemergence of a once-conquered disease. J Pediatr. 2000;137:143–5.

13. Simpson R, Thomas G, Arnold A. Identification of 1,25-dihydroxyvitamin D3 receptors and activities in muscle*. J Biol Chem. 1985;260:8882–891.

14. Gregory SM, Parker BA, Capizzi JA, Grimaldi AS, Clarkson PM, Moeckel-Cole S, et al. Changes in vitamin D are not associated with changes in cardiorespiratory fitness. Clin Med Res. 2013;2:68.

15. Bendik I, Friedel A, Roos FF, Weber P, Eggersdorfer M. Vitamin D: a critical and essential micronutrient for human health. Front Physiol. 2014;5:248.

16. Endocrine S. Evalutation, treatment, and prevention of vitamin D deficiency: An endocrine society clinical practice guideline. 2011.

17. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999;69:842–56.

18. 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. Am J Clin Nutr. 2006;84:18–28.

19. Vieth R. Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. J Steroid Biochem Mol Biol. 2004;89–90:575–9.

20. Cannell J, Hollis B. Use of vitamin D in clinical practice. Altern Med Rev. 2008;13:6–20.

21. Heaney RP. Assessing vitamin D status. Curr Opin Clin Nutr Metab Care. 2011;14:440–44.

22. Stacgowicz, M Lebiedzinska, A. The role of vitamin D in health preservation and exertional capacity of athletes, Postepy Hig Med Dosw (online), 2016; tom 70: 637-643