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.

Fontana says he is not sure if their 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. So he is proposing the hypothesis that in spite of their low bone mass, those on raw food diets actually may have a good bone quality and, therefore, healthy bones. He bases that hypothesis on the fact that their bone turnover markers are normal, vitamin D is higher than normal and inflammation is low, and they do not appear to have an increased risk of fracture, they are lighter because they take in fewer calories.

More research is needed to prove that raw food vegans have light-but-healthy bones. One study could involve following large groups of them for years to look at fracture rates. Other, more imminent studies will involve using micro MRI to get a 3-D look at bone architecture and structure. However Fontana is not recommending people follow such an extreme diet, as over the long term, a strict raw food vegan diet could pose some health problems and dictating diets is not how he perceives his role. He does conclude that improved health and a reduction in the risk of cardiovascular disease and cancer could be achieved by eating less refined and processed foods and eating instead a wide variety of nutrient-dense foods, such as vegetables, fruits, whole grains, legumes and fish.

medicine.wustl/