The more trans fats a woman eats, the more susceptible she becomes to ovulation-related infertility, a recent study conducted at the Harvard School of Public Health in Boston concluded. Yet another reason to avoid processed fatty foods was established by Dr Jorge Chavarro and colleagues, who published their findings in the American Journal of Clinical Nutrition.

For every two percent increase in the amount of calories a woman consumes from trans fats rather than carbohydrates, she increases her risk of infertility by 73 per cent, the study found. If a woman replaces healthier omega-6 polyunsaturated fats with trans fats, then her risk increases further by 79 per cent. Similarly, for every two percent of calories a woman consumes from trans fats rather than monounsaturated fats, her risk of infertility more than doubles.

The study included 18,555 healthy women who attempted to become pregnant from 1991 until 1999. A total of 438 women were diagnosed with ovulation-related infertility.

These figures indicate the link to be significant and increased by relatively low levels of trans fat in a woman's diet. On average, a woman whose total number of calories is 1,800 only needs to eat a mere four grams of trans fat to amount to two percent of her total intake. This threshold is particularly low when considering that an average single portion of fried chicken contains seven grammes of fat. 'It's not very hard to get four grammes of trans fatty acids every day', commented Dr Chavarro.

It is believed that the trans fats interfere with the function of a cell receptor known to be involved with inflammation, glucose metabolism and insulin sensitivity, and now thought to be important in the ovulation process. Drugs that stimulate this receptor's activity have been shown to increase the fertility success rate of patients who have polycystic ovary syndrome.

Trans fats have already been associated with several other health related problems such as elevated cholesterol levels, coronary heart disease, obesity and diabetes. 'Even for somebody who's not trying to get pregnant, it is a very good idea to stay away from them', warned Dr. Chavarro. He recommends that people avoid foods with 'hydrogenated' or 'partially hydrogenated' oil contents.

Trans fats are found in processed vegetable oils commonly used in margarine, pizza, biscuits, cakes and most commercially processed baked goods and pastries. The oil is partially hydrogenated, a chemical process which solidifies it in order to lengthen food's shelf life. These fats do not have any nutritional benefit and can be replaced. As a spokesman for the UK Food and Drink Federation observed at the end of July 2006, 'There is no need to have trans fats in our diet at all'.

The US Food and Drug Administration (FDA) now require that labels state when packaged food contains more than half a gramme of trans fat. In the past year the UK's Food Standard Agency has undergone pressure to adopt similar US FDA guidelines. This January the FSA and Department of Health announced that they will discuss banning the use of trans fats.