Vitamin D Reduces Muscle Fatigue and Improves Efficiency
Supplementation with vitamin D could help to improve muscle functions in people with low levels of the sunshine vitamin, according to new research.
Vitamin D is an often overlooked element in athletic achievement, a "sleeper nutrient," says John Anderson, a professor emeritus of nutrition at the University of North Carolina and one of the authors of a review article published online in May about Vitamin D and athletic performance. Vitamin D once was thought to be primarily involved in bone development. But a growing body of research suggests that it's vital in multiple different bodily functions, including allowing body cells to utilize calcium (which is essential for cell metabolism), muscle fibers to develop and grow normally, and the immune system to function properly. "Almost every cell in the body has receptors" for Vitamin D, Anderson says. "It can up-regulate and down-regulate hundreds, maybe even thousands of genes," Larson-Meyer says. "We're only at the start of understanding how important it is."
New data coming from the UK is the first time a link has been found between vitamin D and muscle function, and could help to explain the physical fatigue that is commonly experienced in people with low vitamin D levels, say the British researchers behind the study.
The team, led by Dr Akash Sinha from Newcastle University, UK, report that supplementation with vitamin D for between 10 and 12 weeks significantly improved muscle phosphocreatine recovery in people with vitamin D deficiency.
Sinha and his colleagues said the findings from the study have broad implications for a large section of society:
"Patients with vitamin D deficiency often experience symptoms of muscle fatigue," explained Sinha, who presented the findings from the study at the Society for Endocrinology annual conference in the UK.
Previous research has suggested that vitamin D could help to reduce muscle and joint pain in cancer patients and could help to improve muscle power in obese people , however these are the first findings to reveal a functional benefit to skeletal muscle from supplementation with the sunshine vitamin.
"Our findings in a small group of patients with very low vitamin D levels show that muscle efficiency significantly improves when vitamin D status is improved."
More recently, when researchers tested the vertical jumping ability of a small group of adolescent athletes, Larson-Meyer says, "they found that those who had the lowest levels of Vitamin D tended not to jump as high," intimating that too little of the nutrient may impair muscle power. Low levels might also contribute to sports injuries, in part because Vitamin D is so important for bone and muscle health. In a Creighton University study of female naval recruits, stress fractures were reduced significantly after the women started taking supplements of Vitamin D and calcium.
"We'll need further research in more patients to work out how this is happening and whether non-deficient patients can benefit from this too," he said.
Sinha and his team investigated phosphocreatine recovery times in patients with vitamin D deficiency using magnetic resonance scans to measure phosphocreatine dynamics in response to exercise in the calf muscles of 12 patients with severe vitamin D deficiency - before and after supplementation with vitamin D.
The team found that phosphocreatine recovery significantly improved after the patients took a fixed dose of oral vitamin D for 10-12 weeks (average phosphocreatine recovery half time decreased from 34.4sec to 27.8sec, p<0.001).
All participants also reported an improvement in symptoms of fatigue following supplementation.
"This is the first time a link has been shown between vitamin D status and muscle aerobic function," said Sinha, who added that a parallel study performed by the group demonstrated that low vitamin D levels are associated with reduced mitochondrial function.
The group added that while their studies were small, they establish a 'clear proof of principle' and for the first time confirm a link between vitamin D and mitochondria in humans.
Sinha and his colleagues will now explore the mechanisms underpinning this effect, and also aim to establish whether vitamin D supplementation could alleviate frailty in the elderly or improve the exercise capacity of athletes.