Vegans Have Lower Bone Density
Nicky Phillips, ABC Science Online
Vegan Diet Affects Bones, Not Fractures | Discovery News Video July 2, 2009 -- Vegans have lower bone densities than non-vegans, researchers have concluded.
But the news isn't all bad, with the study finding an animal-free diet doesn't translate into more fractures.
The findings, published today in the American Journal of Nutrition, came out of a review of previous studies that included more than 2,500 individuals.
Research has shown that low bone density, a predictor for osteoporosis, increases the risk of bone fracture.
Epidemiologist and lead author Tuan Nguyen, of Sydney's Garvan Institute of Medical Research Garvan Institute of Medical Research , said there are four main factors that influence bone density: genetics, hormones, exercise and nutrition.
He expected vegans, those who avoid eating animal products, would have lower bone densityand therefore a higher risk of bone fracture. The study found that on average vegans had a bone mass density 5 percent lower than non-vegans.
But Nguyen said the study found vegans were no more likely to be treated for bone fractures than non-vegans.
This is probably because vegans tend to be more health conscious, he said.
"If you look at vegetarians as a whole they are certainly healthier, they tend to live longer and have lower risk of hypertension and heart disease." And there are other factors that may override the influence bone density has on fracture risk such as hormone deficiencies, smoking and lifestyle, said Nguyen.
The study also found women have lower bone densities and a higher risk of fracture.
"About 70 percent of fractures in the elderly occur in women," said Nguyen.
It's not clear why women have higher bone loss than men, but the common assumption is that the loss of oestrogen after menopause speeds up bone loss, he said. "We know oestrogen is very important in regulating bone formation and bone re-absorption."
Nguyen suspects lower levels of calcium, needed for bone formation, in the diets of vegans results in lower bone density compared with non-vegans. But he admits overall calcium is only a small contributor to bone density.
Nutritionist Rosemary Stanton agrees with Nguyen, saying that calcium is important but it is only one factor in bone density.
"The push to have everyone eat massive amounts of dairy products is invalid," she said.
Stanton said what's missing from the study is a differentiation between a good and bad vegan diet.
"Just as you can have a good omnivorous diet and bad one, so too with vegan diets," she said.
Stanton also said the study failed to consider the effects of vitamin D.
"Vitamin D is probably the most important factor in the way calcium is used and studies are showing now that a lot of people don't get enough Vitamin D."
Nguyen agress and suggests vegans monitor their calcium and vitamin D intake.