On the ever-growing list of pros and cons of plant-based diets, the higher risk of bone fractures has been reinforced on the list of possible drawbacks. Vegans and vegetarians may be at greater risk for bone fractures than meat eaters, according to a large, longitudinal study published Sunday in the journal BMC Medicine.
Fractures in adulthood and older ages are common, but previous studies have shown that vegetarians have lower bone mineral density than non-vegetarians. Bone density is “a measure of the amount of minerals (mostly calcium and phosphorus) contained in a certain volume of bone,” according to the US National Cancer Institute. Substantially lower intakes of dietary calcium and protein have also been reported among non-meat eaters. Despite this prior research, the associations between vegetarian diets and fracture risks have been unclear until now, the study said. “This is the first comprehensive study and the largest study to date to look at the risks of both total fractures and fractures at different sites in people of different habitual dietary habits,” said the study’s lead author, Tammy Tong, a nutritional epidemiologist at the Nuffield Department of Population Health at the University of Oxford.
Because the risk differences in vegans remained after factoring in BMI and sufficient intakes of calcium and protein (by milligram), other factors that weren’t investigated may be important — such as the differences between protein and calcium from animals and from plants. “Most of these things are better absorbed from animal foods,” Tong said. “Some vegetarians say, ‘Well, if you look at the food tables, I have enough calcium.’ But calcium in whole grains is bound by phytates and in green leafy vegetables, it’s bound by oxalates.“ Phytates and oxalates are compounds that bind minerals like calcium, zinc and iron, so the minerals aren’t released and absorbed as easily in the gut. That means that although spinach and other leafy greens are high in calcium, the oxalates in them prevent the body from absorbing that calcium as much as it could from dairy.
Source: CNN