Very high dosages of vitamin D may delay frailty in old age

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A small study in mice suggests that a dosage of vitamin D five times the current recommended amount for older adults could slow the development of frailty, however, the researchers now need to confirm this finding in humans.
Doctors currently define a person as “frail” if they display three or more of the following five characteristics: unexpected weight loss weak grip strength self-reported exhaustion low levels of physical activity slow walking speed.
Frailty tends to increase with age, affecting around half of individuals aged over 85 years. It is associated with disability, loss of independence, and increased rates of mortality.
Research suggests that people who have low levels of vitamin D in their blood are more likely to become frail. This is a particularly pressing concern, as up to 1 billion peopleglobally may have insufficient levels.
Having adequate levels of vitamin D is associated with a wide range of health benefits, including healthier bones and teeth and stronger immunity to respiratory infections. The body can synthesize its own vitamin D when the skin has exposure to the UV light in sunlight. However, during winter months in higher latitudes, and for people who spend most of their time indoors, the principal sources of vitamin D are diet and supplements.
There is some uncertainty about the amounts of vitamin D a person should consume.
The National Academy of Medicine recommend a daily intake of 600 international units (IU) for adults aged 19–70 years and 800 IU per day for individuals aged 70+ years.
According to a research group at the Veterans Affairs Western New York Healthcare System and the University at Buffalo — both in Buffalo, NY — these recommendations are largely based on optimizing bone health.
They believe that much higher levels are necessary to maintain muscle strength and prevent frailty. Their previous research in “middle-aged” mice suggests that a long-term insufficient intake of vitamin D in middle age may result in an impaired capacity for anaerobic exercise, decreased muscle mass, and increased amounts of adipose, or fat, tissue.
Their latest work in mice, indicates that not getting enough of the vitamin in older age may accelerate the development of frailty. “We found that in aged mice, low levels of vitamin D [resulted] in physical declines, such as reduced grip strength and grip endurance — the ability to sustain a grip — and that they started developing as soon as 1 month after reduction of vitamin D intake,” says first study author Kenneth L. Seldeen, Ph.D.