The Trans fat, found in processed foods, may play a role in infertility. Implicated in prostate cancer, heart disease, and diabetes, and long thought to be a significant hindrance to good health, trans fat has been associated with ovulation disorders, according to a new publication¹.

Trans fats are created in food processing. To avoid rancidity in foods, manufacturers heat oils under pressure to convert natural unsaturated fat to partially saturated fat, adding hydrogen molecules to change the bonds between carbon atoms in the long fatty molecule. Saturated and partially saturated fats are sometimes called partially hydrogenated fats. Saturated fats melt at a higher temperature, and are more stable on the grocer’s shelf. Partially saturated fat is resistant to oxidation and damage, melts at a higher temperature, and does not take on rancid odors and taste. Crisco, partially saturated cottonseed oil, was the first commercial product to be produced with the technique in the early 1900s.

Foods prepared with partially saturated fats can contain up to 45% trans fats. French fries, cheeseburgers, fried chicken, cookies, and chips are common offenders. An order of large French fries can contain 15g of trans fat. Oreo cookies contained trans fat until a lawsuit in 2003 induced Kraft Foods to alter its recipe.

Ideal for a manufacturer interested in long-term storage, saturated fats are not so well tolerated by the human body. Raising levels of LDL and lowering levels of HDL cholesterol, saturated fats have been implicated as a prime cause of the rising risk of coronary heart disease through the 20th century. According to the Nurses’ Health Study², each 2% increase in trans fat calories doubles the risk of coronary artery disease. Since trans fats carry no health benefits and are potentially risky, experts have recommended reducing trans fats to trace amounts in the diet.

Infertility has been associated with trans fat intake. A study published in the January issue of American Journal of Clinical Nutrition from a group of researchers at Harvard University found that women with ovulation-related fertility problems tended to eat more trans fats than fertile women. Obtaining just 2 percent of total calories from trans fats was associated with a doubled risk for this type of infertility. The study showed that each 2% increase in dietary trans fat calories was associated with a 73% increased risk of ovulatory infertility³.

It has been difficult to separate out the effects of total fat and trans fat, since a diet high in trans fat diet is often high in total fats. In contrast to trans, higher total fat is known to decrease the risk of ovulation problems, improving ovulation, whereas women with a diet high in trans fat have an increased risk of ovulation disorders.

Dietary fats have been linked to markers of inflammation, a possible mechanism of trans fat effects⁴. In a randomized crossover study, 50 men consumed diets for five weeks that varied in trans fat content. Inflammatory protein markers were higher in men after the trans fat diet, showing that dietary fatty acids can modulate markers of inflammation.

The data is preliminary, but concerning. Since trans fats have no benefit and carry potential risks, they are best limited in the diet. Labeling requirements now include listing of trans fat content for foods. Lawmakers in several major US locales have passed regulations banning trans fats. Tiburon, California, on a voluntary basis was the first city to have trans fat free restaurants. Restaurants in New York City and Philadelphia are barred from using trans fat containing frying oils and spreads. The ban will be expanded to all restaurant foods next year. California is considering a statewide ban on trans fats.

Reducing processed foods and avoiding trans fats in your diet is an excellent goal for all, but patients with infertility may have special concerns. While more research is required regarding infertility and diet, there is no question a healthy diet is important. A diet of diverse and balanced carbohydrates, proteins, and fats, including omega-3 fats, will provide personal and possibly reproductive benefits for years to come.

Philip Chenette, MD

References:

1. Chavarro JE et al., May 2007, A prospective study of dairy foods intake and anovulatory infertility, Human Reproduction, 22 (5): 1340-1347.

2. Hu, FB et al. 1997 “Dietary fat intake and the risk of coronary heart disease in women”. New England Journal of Medicine, 337 (21): 1491-1499.

3. Chavarro JE et al., January 2007, Dietary fatty acid intakes and the risk of ovulatory infertility. American Journal of Clinical Nutrition, 85 (1), 231-237.

4. Baer DJ et al., June 2004, Dietary fatty acids affect plasma markers of inflammation in healthy men fed controlled diets: a randomized crossover study. American Journal of Clinical Nutrition, Vol. 79, No. 6, 969-973.

Tags: Conception Health, Mind/Body, Nutrition

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