But diets high in fat and animal protein were linked to increased risk of the disease, a cancer that attacks the lymphatic system, part of the body's immune system.
The incidence of non-Hodgkin's lymphoma has increased dramatically over the last couple of decades. Once relatively rare, it is now the fifth most common cancer in the United States and an annual increase of 4.2 per cent has been reported in Europe. The reason for these dramatic increases is unknown. It is however more common in men than in women and among people with inherited immune deficiencies, autoimmune diseases, or HIV/AIDS.
"An association between dietary intake and NHL is biologically plausible because diets high in protein and fat may lead to altered immunity, resulting in increased risk of NHL," said principal investigator Tongzhang Zheng, associate professor of epidemiology and environmental health at Yale School of Medicine.
He added that the antioxidants found in vegetables and fruits may result in reduced risk of about 40 per cent.
The study, published in the American Journal of Epidemiology (vol 159, issue 5, pp 454-466), was conducted between 1995 and 2001 on 601 women from Connecticut, aged between 21 and 84. They had been diagnosed with varying subtypes of the cancer. The study included a control group of 717 women.
Each patient was asked to fill in a food frequency questionnaire the year prior to being interviewed, giving data on consumption frequency and portion size data for approximately 120 foods and beverages. After completion, the researchers could calculate average daily nutrient intakes.
When the highest quartile of intake was compared with the lowest, the authors found an increased risk (1.7) of NHL associated with animal protein and saturated fat (1.9). Polyunsaturated fat reduced risk by 40 per cent and there was no relation for vegetable protein and monounsaturated fat.
"So far, risk of NHL associated with animal protein and fat intakes has only been investigated in American women, in three studies," said Zheng. "If the association could also be demonstrated in American men, it would provide important information towards understanding the cause of NHL."