Sarcopenia, which is the loss of muscle mass, is a major issue for people as they get older but not as much attention is given to a similar issue called dynapenia. That’s the loss of muscle strength. Both can lead to similar outcomes and both can be addressed through nutrition. New research shows vitamin D is critical to muscle strength as a deficiency in that vitamin increases the risk of dynapenia by as much as 78 percent.
Scientists at the Federal University of São Carlos (UFSCar) in Brazil and University College London (UCL) in the United Kingdom studied the effects of vitamin D deficiency on muscle strength and published their findings in the journal Calcified Tissue International.
Dynapenia is a major risk factor for the elderly as it can lead to incapacity later in life. Lack of muscle strength is a contributing factor in falls which can lead to hospitalization and even death. That’s a reason why researchers focused their efforts in understanding some of the causes.
"Vitamin D is known to participate in various functions of the organism," said researcher Tiago da Silva Alexandre from UFSCar. "Actually, it's a hormone and its many roles include helping to repair muscles and releasing calcium for muscle contraction kinetics. It was therefore expected to cause muscle alterations of some kind. That's exactly what our study proved.
"Endocrine disorders such as vitamin D deficiency or insufficiency can lead to loss of bone mineral density as well as a reduction in muscle mass, strength and function," he said.
Researchers looked at a pool of more than 3,200 study participants over the age of 50 who did not have dynapenia. They were tested for grip strength, which is considered a general measure of overall muscle strength, and their progress was tracked for a period of four years.
The study data revealed those who were deficient in vitamin D had a greater than 70 percent chance of developing dynapenia by the end of the four-year period. Researchers used the figure of 30 nanomoles per liter of blood or less as the measure of deficiency. Study participants with a measure of 50 nmol/L were considered to be in the normal range.
"This is itself an important finding as it shows that vitamin D deficiency heightens the risk of muscle weakness by 70%," said study author Maicon Luís Bicigo Delinocente. "However, because we knew there are many worldwide cases of people with osteoporosis who take vitamin supplements, we needed to try to measure the effectiveness of vitamin D supplementation."
A careful analysis showed when researchers removed the study participants who were taking vitamin D supplements from the survey they found even an even greater danger.
"We found that the risk of developing muscle weakness by the end of the four-year period was 78% higher for subjects with vitamin D deficiency at the start of the study than for subjects with normal vitamin D levels, and 77% higher for those with vitamin D insufficiency [30-50 nmol/L]," Delinocente said.
Alexandre added, "It's necessary to explain to people that they risk losing muscle strength if they don't get enough vitamin D. They need to expose themselves to the sun, eat food rich in vitamin D or take a supplement, and do resistance training exercises to maintain muscle strength."