Everyone should routinely measure their 25-hydroxyvitamin D status and use sun exposure or vitamin D3 supplementation to attain a level around 40 ng/ml.
This is especially important for those whose occupations keep them out of the sun. Night workers, especially, may have difficulty manufacturing sufficient vitamin D.
In my last post on the amazing and unnatural fragility of Red Sox players’ bones, I didn’t discuss vitamin D – a crucial nutrient for bone health, and health generally – because I thought that baseball players must get a great deal of sun exposure.
But on second thought, that may not be the case.
The Red Sox Are Night Workers
Most games start in the evening, around 7:05 pm. Games typically last between three and four hours. Players often eat a post-game meal at midnight, and may not sleep until 2 or 3 am. On road stands, every third game is followed by travel, so that players arrive in the new city early in the morning. As it is often difficult to sleep on planes, it’s reasonable to guess that many players sleep during daylight hours.
Night Workers Are At High Risk for Fractures
The Nurses’ Health Study found that night workers generally had a 37% higher risk of bone fractures. But slender night workers – those with a BMI below 24 – had a 136% higher risk of fractures. 
Jacoby Ellsbury, with the most fragile bones on the Red Sox, is one of the more slender players, and might be particularly vulnerable to the night work effect. At 6’1”, 185 pounds, his BMI is 24.4.
Vitamin D Is Crucial for Bone Health
Bone mineralization is optimized at serum 25-hydroxyvitamin D levels near 40 ng/ml.  Randomized controlled trials have found substantial reductions in fracture rates with vitamin D supplementation, for instance a 58% reduction in non-vertebral fractures and a 37% reduction in hip fractures. 
Even slight deficiencies can weaken bones. In mild vitamin D deficiency, serum PTH becomes elevated in order to increase conversion of 25(OH)D to the more active form of 1,25(OH)D to compensate for the insufficiency of 25(OH)D; however, elevation in PTH increases bone resorption, leading to additional bone loss. 
Vitamin D Optimization Improves Athletic Performance
In addition to its effects on bones, Vitamin D is also critical for muscle function and coordination.  Prolonged vitamin D deficiency is associated with severe muscle weakness which improves within several weeks of vitamin D supplementation.  In another study, quickness of movement was proportional to serum 25-hydroxyvitamin D levels. As the 25(OH)D level rose from 9.0 to 37.6 ng/mL, time to perform an 8-foot mobility test decreased by 0.67 seconds.  In another study, vitamin D supplementation reduced the rate of falls by 49%. 
For elite athletes, optimizing vitamin D can make a significant difference. After noticing that athletic performance was consistently better in summer than winter, the East German and Soviet athletic machines began programs of vitamin D supplementation. These programs coincided with the rise of these nations to the top of the Olympic medal lists. 
Melatonin Is Also Important
Melatonin, the “hormone of darkness,” is released during sleep, but only under conditions of quiet and darkness. Even a small amount of light can disrupt melatonin production.
Melatonin has both direct and indirect effects on bone.  It directly affects bone mineralization and activity of osteoclasts and osteoblasts – the two cell types responsible for bone remodeling and healing – and indirectly affects bone through its effects on other hormones such as cortisol. Melatonin levels tend to decline with age, and this may be responsible in part for the higher rates of osteoporosis in the elderly. In rats, melatonin co-participates in bone loss in a model of osteoporosis. 
Melatonin may also help athletic performance. In rats, 4 weeks of melatonin supplementation just before sleep led to reduced lactate levels during exercise, delayed exhaustion, and increased glycogen reserves. [9, 10]
Everyone, but especially professional athletes who work at night, should monitor serum 25-hydroxyvitamin D levels and get sun exposure or D3 supplements at mid-day to achieve 40 ng/ml.
Everyone, but especially professional athletes who work at night, should sleep in rooms with totally opaque drapes, so that the room remains completely dark after the sun rises, until natural waking. Artificial light sources should be eliminated, for instance by turning LCD clocks face down. Melatonin supplementation may also be worth consideration, especially in the elderly or those suffering from chronic infections; time-release melatonin at bed-time is optimal.
These steps will help optimize status of two hormones crucial for bone health and, possibly, athletic performance.
Maintaining optimal vitamin D and melatonin status is tricky for night workers. It should be a priority for the Red Sox. Have they done it?
 Feskanich D et al. Nightshift work and fracture risk: the Nurses’ Health Study. Osteoporos Int. 2009 Apr;20(4):537-42. http://pmid.us/18766292.
 Bischoff-Ferrari HA et al. Positive association between 25-hydroxy vitamin D levels and bone mineral density: a population-based study of younger and older adults. Am J Med. 2004 May 1;116(9):634-9. http://pmid.us/15093761.
 Lane NE. Vitamin D and systemic lupus erythematosus: bones, muscles, and joints. Curr Rheumatol Rep. 2010 Aug;12(4):259-63. http://pmid.us/20429045.
 Prabhala A et al. Severe myopathy associated with vitamin D deficiency in western New York. Arch Intern Med. 2000 Apr 24;160(8):1199-203. http://pmid.us/10789615.
 Bischoff-Ferrari HA et al. Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged > or =60 y. Am J Clin Nutr. 2004 Sep;80(3):752-8. http://pmid.us/15321818.
 Cannell JJ et al. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009 May;41(5):1102-10. http://pmid.us/19346976.
 Cardinali DP et al. Melatonin effects on bone: experimental facts and clinical perspectives. J Pineal Res. 2003 Mar;34(2):81-7. http://pmid.us/12562498.
 Ostrowska Z et al. Assessment of the relationship between dynamic pattern of nighttime levels of melatonin and chosen biochemical markers of bone metabolism in a rat model of postmenopausal osteoporosis. Neuro Endocrinol Lett. 2001;22:129–136. http://pmid.us/11335889.
 Kaya O et al. Melatonin supplementation to rats subjected to acute swimming exercise: Its effect on plasma lactate levels and relation with zinc. Neuro Endocrinol Lett. 2006 Feb-Apr;27(1-2):263-6. http://pmid.us/16648794.
 Kaya O et al. Effect of melatonin supplementation on plasma glucose and liver glycogen levels in rats subjected to acute swimming exercise. Pak J Pharm Sci. 2010 Jul;23(3):241-4. http://pmid.us/20566433.