Can vitamin D supplementation improve grip strength in elderly nursing home residents? A double-blinded controlled trial

BACKGROUND: Low vitamin D status is associated with reduced muscle strength, but the benefit of vitamin D supplementation is not clear. OBJECTIVE: To study whether a daily supplement of vitamin D could improve grip strength. DESIGN: A subtrial of a double-blinded, controlled trial studying the effect of vitamin D on the incidence of hip fractures and other osteoporosis fractures in a frail nursing home population. Sixty nursing home residents in 14 nursing homes in the Oslo area were given 5 ml ordinary cod liver oil daily containing 10 µg vitamin D(3) (vitamin D group) or 5 ml cod liver oil where vitamin D was removed (control group). Grip strength was measured at baseline and after 1 year with supplementation. RESULTS: Grip strength did not improve in the vitamin D group (0.4 kg increase) compared with the control group (1.6 kg increase) after 1 year vitamin D supplementation (p=0.22). Serum 25(OH)D was estimated to increase by 21.1 nmol l(−1) (p=0.002) in the intervention group compared with the control group. CONCLUSION: A group given a daily supplement of 10 µg vitamin D(3) in cod liver oil did not improve grip strength compared with a group not receiving vitamin D from cod liver oil.