VITAMIN D

SSE #148 The Importance of Vitamin D for Athletes
Enette Larson-Meyer
KEY POINTS
(1) Vitamin D plays an important role in an athlete’s health, training and performance.
(2) Vitamin D status should be assessed as part of a routine nutritional assessment. The blood 25(OH)D concentration is the best indicator of vitamin D status. A blood vitamin D concentration of >75 nmol/L but preferably >100 nmol/L should be maintained.
(3) “Suboptimal” vitamin D status is linked to increased risk for acute illness, inflammatory injury, stress fracture, muscle pain/weakness and suboptimal muscle performance. Athletes with a history of these issues may benefit from assessment of vitamin D status.
(4) Regular consumption of vitamin D-containing foods alone is not likely to maintain sufficient vitamin D status. Sensible sun exposure (5 to 30 min of exposure to arms, legs and back at close to solar noon several times a week), regular vitamin D supplementation (1,500-2,000 IU/day), or a combination of dietary intake, sun exposure and supplementation are required to achieve sufficient status.
(5) In winter months, vitamin D supplementation is needed for athletes living at >35° north or south.
PRACTICAL APPLICATIONS
(1) Knowledge of blood vitamin D status in relation to season and the athletes’ training regimen may help athletes optimize performance and health.
(2) Vitamin D status may be achieved by sensible sun exposure (5 to 30 min of exposure depending on skin pigmentation (5 min for fair skinned and 30 min for dark skinned) to arms, legs and back at close to solar noon several times a week) and/or supplementation and dietary intake to provide at least 1,500 – 2,000 IU/day.
(3) Supplementation in winter is recommended for all athletes living/training at >35° north or south.
(4) Athletes who are unsure about status or who have a history of stress fracture, frequent illness, bone and joint injury, skeletal pain or weakness, or signs of overtraining should have their blood vitamin D status evaluated.
Vitamin D Measurement & Supplementation: What, When, Why & How? SSE #147
Graeme L. Close
KEY POINTS
(1) Vitamin D is associated with numerous important biological actions relevant to the athlete including regulating bone health, immune function, cell cycle and skeletal muscle homeostasis.
(2) Vitamin D deficiency has been linked to a number of adverse health outcomes.
(3) Athletic populations show markedly poor vitamin D concentrations, particularly during the winter months.
(4) Vitamin D deficiency is reversible through oral vitamin D supplementation and safe sun exposure.
(5) Well-designed randomized controlled trials are now required to establish the extent to which vitamin D may impact athletic performance.
SUMMARY
(1) Data suggests vitamin D deficiency is endemic and its frequency is on the rise, a consistent observation in athletic sub-groups.
(2) This may primarily be owing to a sun-shy lifestyle and poor dietary sources of vitamin D.
(3) The cost of vitamin D deficiency is sub-optimal biological function in many tissues and therefore measurement is necessary in athletes, particularly during the winter months when sun exposure is low.
(4) Appropriate biochemical methods for vitamin D assessment should be adopted and correct interpretation of results implemented.
(5) The current RDI for vitamin D (600 IU/d) is unlikely to be efficacious to prevent deficiency in the absence of sun exposure.
(6) If necessary (upon presentation of serum 25(OH)D <75 nmol/L) it is advisable to supplement with oral vitamin D3 with doses reflecting the necessity of change required in serum 25(OH)D.
Vitamin D and the athlete: Emerging insights
Owens DJ, Fraser WD, Close GL. Eur J Sport Sci. 2014 Aug 18:1-12. [Epub ahead of print]
(1) Vitamin D receptors are in many tissues suggesting a more global role for Vitamin D than previously considered.
(2) Unlike the other vitamins that are obtained through the diet, Vitamin D is unique since endogenous synthesis following ultraviolet B (UVB) exposure is the predominant route of entry into systemic circulation.
(3) Vitamin D could be better classed as a seco-steroid, given that its structure is similar to that of a steroid, and its production is derived from a cholesterol precursor (7-dehydrocholesteol) in the skin.
(4) The classification of Vitamin D status is currently subject to considerable debate with many authors opposing governing body recommendations.
(5) Regardless of the suggested optimal concentration, there is now growing evidence to suggest that many athletes are in fact Vitamin D deficient, especially in the winter months largely as a consequence of inadequate sun exposure, combined with poor dietary practices, although the consequences of such deficiencies are still unclear in athletic populations.
(6) Impaired muscle function and reduced regenerative capacity, impaired immune function, poor bone health and even impaired cardiovascular function have all been associated with low Vitamin D in athletes, however, to date, the majority of studies on Vitamin D have described associations and much more research is now needed examining causation.
Vitamin D supplementation in athletes
Larson-Meyer E. Nestle Nutr Inst Workshop Ser. 2013; Nestle Nutr Inst Workshop Ser. 2013;75:109-21. Epub 2013 Apr 16.
(1) Vitamin D deficiency can have a profound effect on immunity, inflammation and muscle function.
(2) Athletes Vit D status varies among different populations and is dependent on skin color, early- or late-day training, indoor training and geographic location
(3) Studies in athletic populations suggest that maintaining adequate vitamin D status may reduce stress fractures, total body inflammation, common infectious illnesses, and impaired muscle function, and may also aid in recovery from injury.

CANCER & STRENGTH OR RESISTANCE TRAINING

Resistance training improves fatigue and quality of life in previously sedentary breast cancer survivors: a randomised controlled trial
Eur J Cancer Care (Engl). 2015 Nov 23. doi: 10.1111/ecc.12422. [Epub ahead of print]
Hagstrom AD1,2Marshall PW2Lonsdale C3Cheema BS2,4Fiatarone Singh MA5,6Green S2,7.
AIM:
– Evaluate the benefits of resistance training (RT) on quality of life (QOL) and fatigue in breast cancer survivors as an adjunct to usual care.
DESIGN:
– 39 women who had survived breast cancer [mean age (y) 51.9 ± 8.8; time since diagnosis (m) 11.6 ± 13.2].
– The experimental group received supervised RT 3 days per week in a university clinic for 16 weeks.
RESULTS:
Perceptions of Fatigue and Quality of Life improved significantly in the RT group compared to controls

The effect of resistance training on markers of immune function and inflammation in previously sedentary women recovering from breast cancer: a randomized controlled trial
Breast Cancer Res Treat. 2016 Jan 28. [Epub ahead of print]
Hagstrom AD1,2Marshall PW3Lonsdale C4Papalia S5Cheema BS6,7Toben C8Baune BT9Fiatarone Singh MA10,11Green S12,13.
PURPOSE:
– Determine the effects of resistance training (RT) on markers of inflammation and immune function in breast cancer survivors.
METHOD:
– 39 breast cancer survivors were randomly assigned to a RT (n = 20) or control (n = 19) group.
– RT performed supervized exercise three times per week.
– Natural killer cell (NK) and natural killer T-cell (NKT) function, and markers of inflammation (serum TNF-α, IL-6, IL-10, and CRP) measured before and after training
RESULTS:
(1) Significant reduction, and large associated ESs, in RT group compared to control for change in NK cell expression of TNF-α and NKT cell expression of TNF-α
(2) No differences were observed in any serum marker.
(3) Significant improvements in all measurements of strength were found in RT compared to control
CONCLUSION:
– RT has a beneficial effect on NK and NKT cell expression of TNF-α
This indicates RT may be beneficial in improving inflammatory profile in breast cancer survivors