Vitamin D and Athletic Performance

January 27, 2016 at 3:04 pm Leave a comment

Elite athletes are always searching for ways to increase performance. Vitamin D is proving to be the latest addition to up their game. Here is what the research says.

Vitamin D is necessary for bone and skeletal health. It maintains calcium balance, which is important for building bones. Current research indicates other roles for Vitamin D that affect an athlete’s health and performance, including skeletal muscle function, immunity and inflammation.

How do we get Vitamin D?

Vitamin D is obtained primarily from exposure to sunlight. UVB rays convert previtamin D3, which is found in the skin, to vitamin D3 (cholecalciferol). After further conversions in the liver and then the kidneys, it becomes the active form of the vitamin.

How much sun exposure provides an adequate amount of vitamin D?

Approximately 5-30 minutes of sun exposure between 10am and 3pm at least twice/week to the face, arms, legs, or back without sunscreen should provide sufficient vitamin D synthesis. This may be true in the summer, but northern climes (>35° N or S) do not receive sufficient UVB rays for vitamin D synthesis.

Here are other factors that inhibit vitamin D synthesis:

  • Age (decreases by 75% at age 70)
  • Skin pigmentation (darker skin does not convert vitamin D as easily)
  • Body fat (excess body fat sequesters Vitamin D)
  • Regular sunscreen use
  • Clothing
  • Atmospheric pollution and cloud cover
  • Time of day
  • Winter latitude >35° N or S
  • Sun avoidance
  • Genetics

Vitamin D is also found in the diet from a few natural foods and several fortified foods. These are oily fish (salmon, mackerel, sardines, tuna), liver, egg yolks, and irradiated mushrooms. Foods fortified with Vitamin D are margarine, breakfast cereals, bread, milk, yogurt, juice and powdered milk.Screen Shot 2016-01-28 at 10.21.17 AM

Many colleges and professional sports teams are testing serum vitamin D levels of their athletes. They are finding that a large percentage of athletes are deficient. The same can be said about the general population.

Vitamin D deficiency has been linked to a number of adverse health outcomes. There is an increased risk for many chronic and inflammatory diseases, autoimmune diseases and certain cancers.  Vitamin D deficiency also results in reduced muscle function and inflammation. Vitamin D status has been associated with stress fractures. In a study on Finnish army recruits, soldiers with insufficient serum Vitamin D levels had 3.6 times the risk of developing a stress fracture than those with sufficient levels. Similar results were found in a study of female US Navy recruits.

Fortunately, Vitamin D deficiency can be reversed by taking oral vitamin D supplements along with safe sun exposure.

Bone Health

Vitamin D signals the body to absorb calcium for bone formation. In the athletic community, Vitamin D sufficiency is related to bone health and the prevention of bone injury. An insufficient level of vitamin D is associated with an increased risk for stress fractures.

Skeletal muscle function

A symptom of Vitamin D insufficiency is musculoskeletal pain and weakness. Once the vitamin status is increased, this pain is resolved. Current research suggests that vitamin D influences the growth of muscles, especially in fast-twitch, or type II fibers. Muscle strength is also affected by vitamin D status. In those who were deficient, vitamin D repletion improved muscle performance. In athletes recovering from orthopedic surgery, Vitamin D insufficiency was found to delay rehabilitation. It has not yet been established whether vitamin D supplementation in healthy athletes will produce similar results.

Immunity

Vitamin D affects cells that defend against bacteria, fungi and viruses in the respiratory tract.   This may influence how susceptible one is to the flu and common colds. Athletes experiencing intense training, which suppresses immune function, have an increased risk of upper respiratory tract infections. In one study it was found that with increasing vitamin D levels, there was a decreased number of upper respiratory illnesses.

Inflammation

Another way Vitamin D works through the immune system is by controlling inflammation. Inflammation is associated with increased fluid and immune cells in an injured area. Vitamin D increases the number of inflammation fighting cells.b39162c9-0938-41d4-b804-d394b30cab82

While the definition of sufficiency has not been determined, a committee within the Institute of Medicine, based on its review of the most current data, arrived at these definitions:

<30nmol/L (<12ng/mL)

Associated with vitamin D deficiency, leading to                                                                                            rickets in infants and children and osteomalacia                                                                         in adults

30-50nmol/L            (12-20ng/mL)

Generally considered inadequate for bone and                                                                         overall health in healthy individuals

50nmol/L (>20ng/mL)

Generally considered adequate for bone and                                                                         overall health in healthy individuals

125mnol/L            (>50ng/mL)

Suggested optimal levels

The current DRI is 600IU for those up to age 70 and 800IU for those over 70. The Upper Limit is 4000IU. Many authorities feel these numbers are still too low, even though they were increased in 2010. Vitamin D intoxication is extremely rare.

The Endocrine Society states that at least 1,500-2,000IU/day of supplemental vitamin D is required for adults and at least 1,000IU/day for children to achieve vitamin D sufficiency. D3 is the preferred form of supplementation, as it is closest to the active form of the vitamin.

Take it from pro and collegiate athletes who think that vitamin D may be helping them to avoid injuries. According to an article in the Wall Street Journal, these players incorporate this vitamin into their daily regimen.

Taking vitamin D will not improve athletic performance; however, in those deficient in this important vitamin, replenishing their stores up to optimal levels is associated with increased performance and a decrease in injury. Insufficient serum vitamin D is associated with an increased risk of injury and reduced muscular function.

References:

Close, GL. Vitamin D Measurement and Supplementation: What, When, Why and How? Sports Science Exchange (2015) Vol. 28, No. 147, 1-4. www.gssiweb.org

Larson-Meyer, E. The Importance of Vitamin D for Athletes, Sports Science Exchange (2015) Vol. 26, No. 148, 1-6. www.gssiweb.org

Watkins, Colleen M. and Lively, Mathew W. A Review of Vitamin D and Its Effects on Athletes, The Physician and Sportsmedicine, Volume 40, September 2012.

https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

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