Scientists in the US have dismissed the theory that people who eat meat absorb more calcium than vegetarians.
Researchers at the ARS Western Human Nutrition Research Center in California, investigating bone health to uncover nutritional approaches to reducing the risk for osteoporosis, report unexpected results when comparing the effects of different diets on bone formation.
Physiologist Marta D. Van Loan and colleagues recruited 48 healthy, non-smoking women, aged 18 to 40, as volunteers for the 10-month study. Of these, 22 were vegans, who do not eat meat, poultry or dairy products, and 26 were omnivores.
Osteoporosis causes dense, healthy bones to become weak, thin, porous and more likely to fracture. An estimated 10 million Americans have osteoporosis and it is rapidly being recognised as a major threat to public health in developed countries.
Van Loan and colleagues found that the rate at which calcium was removed from bones was the same for omnivore women as for the vegan women. The finding runs counter to a well-known theory that individuals who eat animal-derived foods will likely lose more calcium from their bones.
Some researchers have developed a hypothesis that sulphur-containing animal proteins are the culprit behind the bone disease as they lead to a build-up of acid. Alkali calcium is used up faster to balance the acidity.
The second unexpected finding indicated that the vegan volunteers formed new bone at a significantly faster rate than the omnivore volunteers. That happened even though the omnivore volunteers were taking in more calcium than the vegans. Both the omnivores and the vegans took in about the same amount of other bone-building nutrients, such as magnesium.
"One would not have predicted a significantly greater amount of bone formation for vegan volunteers than for omnivore volunteers," Van Loan said.
The implication for people who eat high amounts of animal protein may be important, according to the researchers, as over time, the net effect of a lower amount of bone formation would likely be a decrease in bone density.
Van Loan explained: "If you have less bone formation, the result is the same as if you had an increase in bone resorption. So, even though bone resorption was the same in both groups of volunteers, the lower amount of bone formation in the omnivore women could lead to a decrease in their bone density."
Full findings are reported in the ARS magazine.
