We are now living longer than ever, and there is growing concern that
quantity of years is not nearly as important as quality of those years. As we
experience the many joys of living longer, we also must deal with myriad
consequences accompanying this aging trend. For instance, osteoporosis,
arthritis and other serious and often painful bone and joint diseases are much
more common as we get older. And, not surprisingly, seniors often struggle
daily with what was once the simple task of getting around. What choices can we
make to help ease these inconveniences of aging?
One area of particular interest is the role that diet plays in keeping
bones and muscles strong from infancy to old age. For instance, a limited
number of studies point to the possibility that optimal intake of vitamin D
might help keep our muscles strong and preserve physical function. Although
there are only few longitudinal studies investigating this relationship, their
findings have been mixed. To help understand this diet-health association,
Denise Houston, PhD from the Sticht Center on Aging at Wake Forest University
and her collaborators studied the relationship between vitamin D status and
physical function in a group of relatively healthy seniors living in Memphis,
Tenn. and Pittsburgh, Pa.
This study was part of the Health, Aging and Body Composition (Health
ABC) study initially designed to assess the associations among body
composition, long-term health conditions, and mobility in older adults. For
Houston’s segment of the investigation, she studied 2788 seniors (mean
age: 75 years) for 4 years. At the beginning of the study, they assessed
vitamin D status by analyzing each person’s blood for 25-hydroxyvitamin D,
a precursor for activated vitamin D. At baseline and then 2 and 4 years later,
the research team then determined whether circulating 25-hydroxyvitamin D was
related to the participants’ physical function. Specifically, they looked
at how quickly each participant could walk a short distance (6 m) and rise from
a chair five times as well as maintain his or her balance in progressively more
challenging positions. Each participant was also put through a battery of tests
assessing endurance and strength.
When the results were tabulated, participants with the highest levels of
25-hydroxyvitamin D had better physical function. And, although physical
function declined over the course of the study, it remained significantly
higher among those with the highest vitamin D levels at the beginning of the
study compared to those with the lowest vitamin D levels. The scientists were
not surprised to learn that, in general, vitamin D consumption was very low in
this group of otherwise healthy seniors. In fact, more than 90% of them
consumed less vitamin D than currently recommended, and many were relying on
dietary supplements.
The good news: higher circulating 25-hydroxyvitamin D is related to
better physical function in seniors. But it’s impossible to tell from this
type of research whether increasing vitamin D intake will actually lead to
stronger muscles and preserve physical function. This is partly due to the fact
that our bodies can make vitamin D if they get enough sunlight. So, it is
possible that the participants with better physical function had higher vitamin
D status simply because they were able to go outside more often.
“Current dietary recommendations are based primarily on vitamin
D’s effects on bone health. It is possible that higher amounts of vitamin
D are needed for the preservation of muscle strength and physical function as
well as other health conditions,” Houston said in a press release.
“However, clinical trials are needed to definitively determine whether
increasing 25-hydroxyvitamin D concentrations through diet or supplements has
an effect on these non-traditional outcomes.”
