LONG-TERM EFFECTS OF A CHANGE FROM A MIXED DIET TO A LACTO-VEGETARIANDIET ON HUMAN URINARY AND FECAL MUTAGENIC ACTIVITY

This is an investigation of the long-term effects of a shift from a mi xed diet to a lacto-vegetarian diet and of a return to a mixed diet on the mutagenic activity in urine and faeces. The participants were 20 normal weight, nonsmoking subjects. Dietary surveys and urinary and fa ecal samples were collected before and 3, 6 and 12 months after the di etary shift as well as 3 years after termination of the lacto-vegetari an diet period. The faecal samples mere assayed for direct acting muta gens with the fluctuation test for weak mutagens and the urinary sampl es were assayed with the same assay but with a metabolic activation sy stem, the so-called S9 fraction. The dietary data showed an increase i n consumption of fruits, vegetables and dairy products and a decrease in meat, fish, eggs, sweets and biscuits during the vegetarian diet pe riod. These changes led to an increase in total carbohydrates, fibre, vitamin C and calcium and a decrease in fat and protein intake. Mutage nic activity in both urine and faeces decreased after shift to the veg etarian diet and mutagenic activity in faeces increased when the volun teers returned to a mixed diet (P = 0.025 and 0.035 respectively when comparing the diets). These data indicate that dietary factors may aff ect mutagenic activity in urine and faeces. However, it is still not c lear whether a decrease in animal products, a change in other nutritio nal factors or a decrease in frying are the main contributors to this change.