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Italian Research Links Diet With Endometriosis Risk

July 12, 2004

Women may be able to lower their risk of endometriosis by eating more fresh fruit and green vegetables. But, eating red meat and ham appears to increase their risk, according to a study published today (Thursday 15 July) in Europe's leading reproductive medicine journal Human Reproduction[1].

The researchers, from Milan in Italy, have now called for a prospective study to investigate further the possible links between diet and endometriosis.

Endometriosis is a painful and distressing condition whereby endometrial tissue, which under normal circumstances is found only in the lining of the womb, develops outside the uterus and attaches itself to ligaments and organs in the abdominal cavity. This tissue responds to the menstrual cycle as though it were still inside the uterus. The repeated growth and disintegration of endometrial tissue in the abdomen can cause bleeding, pain, inflammation, adhesions and infertility. It is estimated to affect up to five in every 100 women in Italy and probably in the rest of Europe.

The researchers used interviews and structured questionnaires to compare the medical and reproductive history, lifestyle and diet of over 500 women with clinically confirmed endometriosis with a group of over 500 matched controls with no history of the disease.

Lead researcher Dr Fabio Parazzini from the Gynaecologic Clinic of the University of Milan, explained: "We asked women about their diet in the year leading up to the interview. In particular, we asked how many times a week they ate portions of selected dietary items, including the major sources of retinoids and carotenoids in the Italian diet. We also asked about their alcohol and coffee consumption.

"We divided their intake into portions approximating to low, intermediate and high intake of the various dietary factors[2]. What we found was that there was a 40% relative reduction in risk of endometriosis in women with higher consumption of green vegetables and fresh fruit. But, for those with a high intake of beef, other red meat and ham, there was an increase of about 80-100 percent in relative risk.

"With a prevalence of 5% in endometriosis in Italy, this means that if our findings are confirmed in prospective studies, we have the potential to cut the prevalence of endometriosis to around 3-4%, which would mean about 200,000 prevalent cases (and about 10,000 new cases a year) fewer in Italy and probably 800,000 fewer prevalent cases in Europe.

There was no significant link between endometriosis and consumption of milk, liver, carrots, cheese, fish, whole-grain foods, coffee or alcohol and no association with butter, margarine or oil.

Dr Parazzini said there were some limitations in the study: the diet section was restricted to a few selected indicator foods and there was no estimate of portion size (therefore no estimate of the total intake in calories). However, since the possible relationship between diet and endometriosis was probably not known to the interviewers or the majority of women interviewed this was unlikely to have biased the results.

The association between vegetables, fruit and meat was unlikely to be due to chance because the researchers analysed several dietary items. However, it was possible there was a 'healthy woman' effect as a high intake of green vegetables, fruit and fish may be generally indicators of more health-conscious attitudes. Also, women who paid closer attention to their health may be more likely to have endometriosis diagnosed.

"However, despite these limitations, our study does suggest that there is some link between diet and risk of endometriosis and indicates that we now need a proper prospective interventional investigation to study these factors. Endometriosis is a distressing condition that affects the quality of life for many women and if there are adjustments that can be made in the diet to lower the risk it is vital that we gain really firm evidence about which foods protect and which foods increase risk."
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[1]        Selected food intake and risk of endometriosis. Human Reproduction. DO1: 10.1093/humrep/deh395. Vol.19, No. 8. Pp 1755-1759.

[2]        The analysis was based on the best possible approximations of tertiles. Milk 0,0.5-6 and around 7 portions a week; meat 0-3,4-6 and around 7 portions a week; liver 0 and around 0.5 portions a week; carrots 0, 1 and around 2 portions week; green vegetables 0-6,7-12 and around 13 portions a week; fresh fruit around 6, 7-13 and around 14 portions a week; eggs 0, 1 and around 2 a week; ham around 1, 2 and around 3 portions a week; fish 0,1 and around 2 portions as week; cheese around 2,3-5 and around 6 portions a week. Alcohol was analysed in accordance with ethanol content i.e. 125ml of wine = 333ml of beer = 40ml of spirits = 15g of pure alcohol.

MW Communications