This study looked at 2 age groups; 55 to 65 (725 people) and 65 to 88 (1237 people). The idea was that since vitamin D is directly connected to muscle health, would the resulting decrease in muscle affect people’s ability to do normal things like; dressing, walking up or down stairs, cutting their toenails, standing from a sitting position, driving their car, or walking for 5 minutes.
After factoring for things like age, physical activity, and chronic disease, they looked at two vitamin D subgroups… those with vitamin D blood serum levels <20 ng/ml (deficient) and >30 ng/ml. The vitamin D deficient folks from both age groups had significantly greater number of physical limitations after the follow-up period (3 years for the older group and 6 years for the younger group).
It’s very common for people, especially the further north you live, to be under 20 ng/ml. Even if you are taking a vitamin D supplement, you should be tested.