Raw truth about vegan diets exposed

Fontana expected the vegans to have low vitamin D levels because they avoid dairy products, which are fortified with the vitamin.

But in fact their vitamin D levels were 'markedly higher' than average.

Vitamin D is made by the skin when the body is exposed to sunlight and is the key to keeping strong bones.

'These people are clever enough to expose themselves to sunlight to increase their concentrations of vitamin D,' Fontana said.

And the vegans had low levels of C-reactive protein, an inflammatory molecule that is becoming linked with the risk of heart disease, diabetes and other chronic disease.

Furthermore, they had lower levels of IGF-1, a growth factor linked to risk of breast and prostate cancer.

Fontana does not advocate a raw food diet. But he said that to lower the risk of cancer and heart disease people should eat more fruits, vegetables and whole grains.