Do Vegans Have Lower Bone Mineral Density and Higher Risk of Osteoporosis?

How does a vegan or vegetarian
diet affect bone density, and what other factors contribute?
Watch the video to find out. "Do Vegans Have Lower Bone Mineral
Density and Higher Risk of Osteoporosis?" Osteoporosis is estimated to affect
200 million people worldwide. Literally meaning "porous bone ,"
osteoporosis is a disease characterized by reduced bone
formation, excessive bone loss, or a combination of both,
leading to bone fragility and increased risk of fractures. And bone mineral density is the
most robust and consistent predictor of osteoporotic fracture. What can
we eat to boost our bone density? Well, we know that increased
consumption of plant foods is associated with increased
bone mineral density. There's an extensive range of
micronutrients and phytochemicals packaged within plants that can be
powerful promoters of bone health, so healthcare professionals
should be encouraged to advise the increased
consumption of plant-based foods, particularly in mid-life, irrespective of the clients
underlying dietary pattern, meaning no matter how
much meat or junk they eat, adding more healthy plant
foods may help prevent the development of osteoporosis. On the other hand, a more
animal-source nutrient pattern has been associated with
a higher risk of fractures, suggesting that a more animal-based
diet is related to bone fragility.

So one would expect less osteoporosis
in those eating plant-based diets, but you don't know
until you put it to the test. "The Incidence of osteoporosis
in vegetarians and omnivores ," the first study published
nearly 50 years ago, and the density of the bones
that were measured was significantly greater in the
vegetarians than the omnivores. In fact, the average bone densities
of the vegetarians in their '70s was greater than the densities
of the meat eaters in their '50s. Bottom line, these results suggest
there's less likelihood of vegetarians developing osteoporosis in old age. Turns out, though, that
the researchers screwed up. DEXA scanning, which
is what we use now, didn't come online until the 1980s. So the researchers were
just using regular x-rays and they confused the readings,
such that darker bones on the x-ray got a higher score, but that
actually means less bone, so their conclusion should
have been the opposite of what they claimed.

So vegetarians had
worse bone mineral density. Fast-forward about 40 years,
by which time nine studies had been done on thousands
of individuals, and all in all, the results suggest that vegetarian
diets, particularly vegan diets, are associated with lower
bone mineral density, but the magnitude of the association
is clinically insignificant, meaning the difference was so small as to not
really matter out in the real world, reinforcing the fact
that vegetarian diets have no clinically detrimental
effect on bone health. And it is important to note
that the findings of lower bone mineral density didn't fully
control for key confounding factors, such as for differences
in body weight. We know that people who are
obese have stronger bones. Why? Because they're weight lifting 50 pounds
all day, every day, and maybe 100 pounds. If you walked around with a
100-pound backpack every day, your bones would grow stronger, too.

That's how you build strong
bones: weight-bearing exercise. So people who weigh
more have denser bones. And vegetarians, and especially
vegans, have such low rates of obesity that no wonder, on average they
would have lower bone density. The researchers didn't
take weight into account, but if the difference they found isn't
even clinically significant, who cares? As of 2009, the answer to the question, "Is vegetarianism a serious risk
factor for osteoporotic fracture?" the answer was no. Vegetarianism
is not a serious risk factor. By 2018, the latest meta-analysis
on veganism, vegetarianism, and bone mineral density,
was up to 20 studies, involving tens of thousands
of participants, and, again, lower bone mineral density
was found in studies of vegetarians and vegans
compared to meat eaters. The researchers conclude that
vegetarian and vegan diets need to be appropriately
planned to preserve their bones. But wait, did they account
for the obesity thing? No, they did not. They just used what are
called crude risk ratios, meaning no adjustments for
confounding factors like weight, so they didn't control for things
like age, smoking, obesity, exercise, and so their results
are really uninterpretable.

But no one had gone through
the trouble of going back through all those studies and making
the proper adjustments until now. The title gives it away: "Differences
in Bone Mineral Density between Vegetarians and Nonvegetarians
Become Marginal when Accounting for Differences
in Body Size Factors." Yes, bone mineral density values
were significantly lower among vegetarians
than among nonvegetarians, just like is the case
with nearly every study on bone mineral density
and excess body weight. But forget clinical significance;
these differences even lost statistical significance
upon adjustment for body size factors, suggesting that lower
bone mass among vegetarians is in larger parts explained by their
lower BMI and waist circumference. Thus, it's not so much the composition
of the diets of vegetarians and vegans as much as it is the fact that
they become so much slimmer.

Now a small but statistically
significant difference remained for total lower spine density,
a difference of 0.03. This was dismissed as having little
clinical relevance, but is that true? If you look at the reproducibility
of bone mineral density measurements in daily medical
practice, you can see how if you do repeat tests back-to-back,
there's some scatter in the measurements, and
so a significant difference really has to be more
than the inherent variation. And indeed, expressed as
the smallest detected difference, you really need a bone
mineral density disparity of at least 0.05 at the spine before it can be considered
a significant change, and so indeed, there does appear
to be little clinical relevance. However, even if vegetarians
and vegans basically have the same bone density
at the same weight, everyone who is skinny
is at risk. Low BMI is a risk factor for
fractures, so all persons in a low body weight category
consuming any kind of diet should be monitored
for osteoporosis.