According to an epidemiological study published in the Journal of Nutrition, vitamin D deficiency increases the likelihood that healthy, older adults will have an incidence of disability.
 
In a 4-year follow up to a study called ELSA (English Longitudinal Study of Aging) involving individuals ages 50 years and older, vitamin D deficiency significantly increased the risk of incidence of “disability in basic activities of daily living,” and that this risk was independent of sex.
 
The participants of the study had their vitamin D concentrations assessed by serum measurements, and were classified as either sufficient or deficient according to a threshold of 30 nmol/L. The report of any difficulty to perform one or more activities within the Basic Activities of Daily Living index was considered to be a disability.
 
 While previous cross-sectional studies have demonstrated this association, none of these studies had been longitudinal study which made comparisons over an extended period of time.
 
The authors said that the role of vitamin D in the musculoskeletal system is one of the main mechanisms by which they believe this risk occurs.
 
“Low serum 25(OH)D concentrations decrease the expression of genes responsible for myogenesis and reduce the synthesis of muscle contractile proteins and the influx of [calcium] into the sarcoplasmic reticulum of muscle cells,” the authors said. “These biological mechanisms compromise the muscle repair mechanism, alter the kinetics of muscle contraction, and compromise musculoskeletal function. They also lead to decreases in muscle strength and mass and cause atrophy, especially for type II muscle fibers. Damage to the musculoskeletal system can compromise BADL [basic activities of daily living] performance and represents a risk factor for disability.”
 
In addition, because vitamin D is necessary to healthy immune function, the authors theorized that deficiency could result in a chronic, low-grade systemic inflammation which could contribute to conditions such as hypertension, diabetes, obesity, and cancer, and these multiple mechanisms might represent additional risk factors for the development of disability.
 
Regardless of limitations present in this study, such as all of the disability symptoms being self-reported, a drop-out rate which could have induced a small source of bias, and lack of data on issues which could reduce concentrations of vitamin D, the authors concluded that maintaining sufficient concentrations of this vitamin could help prevent the development of disability in individuals 50 years and older.