Flashback Friday: Do Vitamin D Supplements Help with Diabetes, Weight Loss, and Blood Pressure?
“Do Vitamin D Supplements Help with Diabetes,
Weight Loss, and Blood Pressure?” My last in-depth video series on vitamin D
was done more than 4 years ago, as in 15,950 papers ago.
I had a lot of catching up to do. Review articles like this
continue to be published, touting vitamin D as
a veritable cure-all. The vitamin D receptor is found in most
tissues of the body, including the brain. Upwards of 2,000 genes may
be regulated by vitamin D. Within 24 hours of vitamin D exposure,
you can change the expression of hundreds of genes.
The term vitamin,
though, is a misnomer. Vitamins by definition cannot
be synthesized within our body, but we can make all the D we need
with sufficient sun exposure. D is not a vitamin, but a hormone
produced by our skin in response to sunlight exposure. It’s not just a hormone of calcium
regulation and bone health, but a hormone of fertility
immunity, and brain function. But is it a panacea
or a false prophet? Remember when vitamin E
was the vitamin du jour, touted as curative for
many clinical disorders? Vitamin E: the radical protector, with
supplement sales in general forming a billion-dollar business
to capitalize on the public’s fears. After all, those with low levels
of vitamin E in their blood had a 50% higher cancer risk. Hey, and
what about vitamin A or beta-carotene? After all, people who eat lots
of greens sweet potatoes, and other beta-carotene-rich
foods have a lower risk of cancer. So, hey, let’s give people
some beta-carotene pills.
But when they were put to the test,
beta-carotene pills increased cancer rates. Beta-carotene, vitamin A, and vitamin E
supplements may increase mortality. In effect, we’d be potentially paying
to shorten our lifespan. So you can understand the skepticism in
the medical community regarding claims about vitamin D, which is now
enjoying its . . . “moment in the sun”. Having a half-billion dollar vitamin D
supplement industry doesn’t help matters in terms of
getting at the truth, not to mention the highly lucrative vitamin D testing
industry that loves to talk about the studies suggesting having higher
vitamin D levels may reduce the risk of heart disease, and cancer, and diabetes,
autoimmune diseases, and infections.
However, most of this research stems
from observational studies, meaning studies that correlate higher D levels
in the blood with lower disease risk. But that doesn’t mean vitamin D
is the cause. It’s like the early
beta-carotene data. Higher levels in the blood may have
just been a marker of healthy eating. Who has high beta-carotene levels? Those who eat lots of greens
and sweet potatoes. Just like vitamin D levels may also just
be a marker for healthy behaviors. Who has high vitamin D levels?
Those that run around outside. And those who run around outside,
RUN around outside. Higher vitamin D levels may just be a sign
of higher physical activity, for example. So when you see studies like this, showing
significantly lower diabetes rates among those with higher vitamin D levels,
it doesn’t mean giving people vitamin D will necessarily help.
You have to put it to the test. And when you do, vitamin D
supplements fall flat on their face. No benefit for preventing
or treating type 2 diabetes. So when supplement companies
wave around studies like this, suggesting vitamin D deficiency plays a role
in obesity because most population studies show lower vitamin D levels
in the blood of those who are obese, is that just because they’re exercising less,
or simply because it’s a fat-soluble vitamin? And so it’s just lodged in all that fat.
One might expect obese sunbathers
would make more vitamin D since they have more skin surface
area, but the same exposure leads to less than half the D because
it gets socked away in their fat. That’s why obese persons may require
2 to 3 times the dose of vitamin D, though they may get it back
when they lose weight and release it back
into their circulation. So that would explain
this population data. And indeed when you put
vitamin D to the test, try vitamin D as a treatment for
obesity, it doesn’t work at all. Similar story with artery health. Those with low vitamin D levels
have worse coronary blood flow, more atherosclerosis, and
worse artery function.
But if you put it to the test
in randomized controlled trials, the results are disappointing. Also ineffective in bringing
down blood pressure. So this all adds to this
growing body of science, casting doubt on the ability of vitamin D
supplementation to improve anything beyond just falls, fractures, the common
cold, and all-cause mortality — Wait! What? Vitamin D supplements
can make you live longer. That’s kind of important.
I’ll explore that next.
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