"Should Vitamin D Supplements Be Taken to Prevent Falls in the Elderly?"
We have known for over 400 years that muscle weakness
was a common presenting symptom of vitamin D deficiency.
Bones aren't the only organs that respond to vitamin D;
muscles do too.
But, as we age, our muscles lose vitamin D receptors,
perhaps helping to explain the loss in muscle strength as we age.
And indeed, vitamin D status does appear to predict
the decline in physical performance as we age,
with lower vitamin D levels linked to poorer performance.
But maybe the vitamin D didn't lead to weakness,
maybe the weakness lead to low vitamin D.
Vitamin D is the sunshine vitamin; and so, if you're too weak
to run around outside, that could explain
the correlation with lower levels.
To see if it's cause and effect,
you have to put it to the test.
There's been about a dozen randomized controlled trials:
vitamin D supplements versus sugar pills.
Put all the studies together, and older men and women do
get significant protection from falls with vitamin D,
especially among those who start out with relatively
low levels, leading the conservative USPSTF,
the U.S. Preventive Services Task Force, the official prevention
guideline setting body, and the American Geriatric Society
to recommend vitamin D supplementation
for those at high risk for falls.
We're not quite sure of the mechanism, though.
Randomized controlled trials have found that vitamin D
boosts global muscle strength, particularly in the quads,
which are important for fall prevention, though vitamin D
supplements have also been shown to improve balance.
So, it may also be a neurological effect,
or even a cognitive effect.
We've known for about 20 years that older men and women who
stop walking when a conversation starts
are at particularly high risk of falling.
Over a 6 month timeframe, few of those who could walk and
talk at the same time would go on to fall, but 80% of those
who stopped when a conversation is initiated
ended up falling.
Other high risk groups that should supplement include
those who have already fallen once, or are unsteady or on a
variety of heart, brain, and blood pressure drugs
that can increase fall risk.
There's also a test called "Get-Up-and-Go,"
which anyone can do at home.
You time how long it takes you to get up from an armchair,
walk 10 feet, turn around, walk back, and sit down.
If it takes you longer than 10 seconds then you may be at
high risk.
So, how much vitamin D should you take?
It seems to take at least 700 to a thousand units a day.
The American Geriatric Society recommends
a total of 4,000 a day, though based on the rationale
that this should get about 90% of people up to the target
vitamin D blood level of 75 nanomoles per liter.
A thousand should do it for the majority of people, 51%,
but they recommend 4,000 to capture 92% of the population.
Then, you don't have to routinely test levels,
since it will get most people up there
and is considerably below the proposed
upper tolerable intake of 10,000 a day.
They do not recommend periodic megadoses.
Because it's hard to get patients to comply with pills,
why not just give people one megadose, like 500,000 units,
once a year, like when you come in for your flu shot or something?
And so every year, you can at least guarantee everyone gets
an annual spike in D levels that lasts a few months.
It's unnatural, but certainly convenient, (for the doctor at least).
The problem is that it actually increases fall risk,
a 30% increase in falls in those first three months of the spike.
Similar results were found in other mega-dose trials.
It may be a matter of too much of a good thing.
See, vitamin D may improve physical performance,
reduce chronic pain, and improve mood so much that you start
moving around more and, thereby, increase fall risk.
You give people a whopping dose of D, you get a burst in
physical, mental, social functioning,
and it may take time for your motor control to catch up
with your improved muscle function.
It would be like giving someone a sports car all of
a sudden when they've been used to driving some beater.
You got to take it slow.
It's possible, though, that such unnaturally high doses
may actually damage the muscles.
The evidence they cite in support is a meat industry
study showing you can improve the tenderness of steaks by
feeding steers a few million units of vitamin D;
so, the concern is that such high doses
may be over-tenderizing our own muscles as well.
So yeah, higher D levels are associated with a progressive
drop in fracture risk, but too much vitamin D may be harmful.
The bottom line is that vitamin D supplementation
appears to help, but the strongest and most consistent
evidence for prevention of serious falls is exercise.
If you compare the two, yes, taking vitamin D may lower
your fall risk compared to placebo,
but strength and balance training
with or without vitamin D may be even more powerful.