In one study, researchers first measured vitamin D levels in 2,099 adults, average age 75, who then took a quarter-mile walking test as well as a stair-climbing test. Every six months for the next six years, doctors assessed mobility.
Doctors divided participants into three groups based on vitamin D levels and found that, compared to those with the highest levels of vitamin D—at least 75 nanomoles per liter of blood (nmol/L)—those with 50 to 74 nmol/L of vitamin D were 30 to 37 percent more likely to have limited or disabled mobility.
Those with less than 50 nmol/L of vitamin D were 62 percent more likely to have limited mobility, and 122 percent more likely to become disabled, doctors said.