According to a study by Luigi Fontana, M.D., Ph.D., research instructor in medicine in the Division of Geriatrics and Nutritional Science at Washington University in St.Louis - School of Medicine, vegetarians who don't cook their food have abnormally low bone mass, usually a sign of osteoporosis and increased fracture risk.
The study is published in the March 28 issue of the Archives of Internal Medicine.
Fontana and colleagues studied 18 strict raw food vegans aged from 33 to 85. All ate a diet that not only lacked animal products but also included only raw foods such as a wide variety of vegetables, fruits, nuts, seeds, sprouted grains and legumes, dressed with olive oil. They had been on this diet for an average of 3.6 years.
The researchers compared them to people who ate a more typical American diet, including refined carbohydrates, animal products and cooked food. The groups were matched according to age, sex and socio-economic status. In both groups, Fontana's team measured body mass index, bone mass, bone mineral density, markers of bone turnover, levels of vitamin D and inflammatory markers such as C-reactive protein and insulin-like growth factor 1 (IGF-1).
Those on the raw food diet had lower body mass indices and 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 didn't have other biological markers that typically accompany osteoporosis. They also 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, and 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.
In spite of the fact that the raw food group didn't drink milk or eat cheese, they had higher vitamin D levels than people on a typical, Western diet. Fontana attributes the vitamin D levels to sun exposure and says it is clear from research that higher rates of bone turnover equate to higher risk of fracture. But in these people, although their bone mass is low, their bone turnover rates are normal. 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 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.