Researchers have found that people who ate the most trans-fatty acids increased their risk of colorectal neoplasia (abnormal cell growth) and developing precancerous colorectal tumors, by 86 percent. The authors conclude:

"These results provide further support for recommendations to limit consumption of trans-fatty acids,"

Research paper details:

Vinikoor LC, et al. Consumption of trans-Fatty acid and Its Association with Colorectal Adenomas American Journal of Epidemiology 2008 168(3):289-297

Colorectal adenomas are small, benign tumors or polyps in the colon and rectum that can progress into cancer if not treated.

Trans fats are found naturally occurring in very trace amounts in meat and dairy products. But the bulk of trans fats in the modern diet are synthetically produced by the partial hydrogenation of vegetable oils, by processing vegetable oils to increase their shelf-life. They are found in many baked goods, snacks and other packaged and processed foods. Unlike other fats, trans fats have no nutritional value to the human body, but have come to be widely used in restaurants and packaged foods, because they hold flavor longer and have a greater shelf life than non-hydrogenated oils.

Although there is not much research into trans fats' contribution to cancer risk, the damaging effects of these fats on cardiovascular health are well documented. Trans fats increase the risk of factors involved in cardiovascular disease, including inflammation and irregular heartbeat.

Studies have also linked these fats to reduced fertility in women, suggesting that eating even four grams of the fats per day (an amount easily consumed in a single serving of French fries) could double the risk of infertility due to ovulation failure.

The conclusions of this study state: "Trans unsaturated fats may increase the risk of ovulatory infertility when consumed instead of carbohydrates or unsaturated fats commonly found in nonhydrogenated vegetable oils."

Research paper details:

Chavarro JE, et al. Dietary fatty acid intakes and the risk of ovulatory infertility American Journal of Clinical nutrition, Vol. 85, No. 1, 231-237, January 2007

A major factor in the prevalence of chronic diseases in industrialized nations is the unnatural diet composed of high levels of refined and processed foods (along with all the synthetic chemicals they contain). It is advisable that you eliminate harmful trans-fats from your diet.