Plant diet may not be bad for bones
may have healthier bones than previously thought, shows US
research.
Researchers at Washington University School of Medicine in St. Louis studied 18 strict raw food vegans, aged from 33 to 85, and found that although their bones were light in weight, they may be healthy.
The vegans, who had been on the diet for an average of 3.6 years, had lower body mass indices than a comparable group following a more typical western diet, including refined carbohydrates, animal products and cooked food.
They also had significantly lower bone mass in important skeletal regions such as the hip and lumbar spine, sites where low bone mass often means osteoporosis and fracture risk. But they did not have other biological markers that typically accompany osteoporosis, shows the study, published in the 28 March issue of the Archives of Internal Medicine (vol 165, pp 1-6).
"For example, it is clear from research that higher rates of bone turnover equate to higher risk of fracture," said lead author Dr Luigi Fontana. "But in these people, although their bone mass is low, their bone turnover rates are normal."
In other areas too, the raw food group appeared to be healthier than the conventional diet group. They had less inflammation, indicated by low levels of C-reactive protein, which is made by the liver as a response to inflammation in the body. They also had lower levels of IGF-1, one of the most important growth factors regulated by calorie and protein intake. High levels of IGF-1 have been linked to risk of breast cancer and prostate cancer.
And in spite of the fact that the raw food group did not drink milk or eat cheese, they had higher vitamin D levels than people on a typical, Western diet. Fontana attributed the vitamin D levels to sun exposure.
"These people are clever enough to expose themselves to sunlight to increase their concentrations of vitamin D," he said. "I thought vitamin D might be a problem for them, but it was not."
Fontana also measured levels of the hormone leptin, which seems to play an important role in the regulation of bone metabolism. In some transgenic mice, low leptin levels are related to high bone mass. But interestingly, the raw food dieters had both low levels of leptin and low bone mass.
In short, the people on the raw food diet are lighter with lower body fat. They have less bone, but they have normal markers of bone turnover, higher-than-normal vitamin D and very low levels of leptin and inflammatory markers.
Fontana added however that the team is not yet sure whether the vegans' bones are healthy or not. Current clinical measurements would indicate that many in this group have osteoporosis or less severe bone loss called osteopenia. But with low levels of inflammation, normal bone turnover and high vitamin D, Fontana says the usual clinical parameters may not apply.
"For example, post-menopausal, frail women with osetoporosis have low bone mass and an increased risk of fracture," he said. "But they also have increased circulating levels of inflammatory molecules called cyotkines. That's a different biologic condition from what we are seeing in the raw food vegans."
"We think it's possible these people don't have increased risk of fracture but that their low bone mass is related to the fact that they are lighter because they take in fewer calories."
Further study is needed to prove that raw food vegans have light-but-healthy bones.
