Trans Fat, Insulin Resistance, Threatens Female Fertility

Previously I've blogged about transfat (see this for a summary of the fat), trying to consider whether a ban on the fat in New York was a question of liberty. Also I attempted to highlight just how awful this food-additive really is for your health. Another serious health concern tied to transfat consumption had now been linked to reduced fertility in women seeking to become pregnant.

In the study, researchers from the Harvard School of Public Health in Boston looked at 18,500 women trying to conceive and found 438 cases of ovulatory problems.

The scientists found that those who took two per cent of their energy intake from trans fats, instead of carbohydrates or polyunsaturated fats such as sunflower oil, had a 70 per cent greater risk of infertility through lack of ovulation.

Those whose energy came from trans fats instead of monounsaturated fats such as olive oil were twice as likely to have problems.

He said his findings, published in the American Journal of Clinical Nutrition, suggested that women wanting to conceive should watch their trans fat consumption, as well as giving up smoking and maintaining a healthy weight.
This was particularly true for those with known problems in ovulating such as Polycystic Ovarian Syndrome.
It is not clear how the fats affect ovulation - but they may affect sensitivity to insulin, which is already known to play a role in fertility problems.

Dr Richard Fleming, from the Glasgow Centre for Reproductive Medicine called the research "very interesting".

"It sounds like a potentially devastating effect," he said.

The Food and Drink Federation declined to comment directly on the study but insisted the industry was committed to reducing trans fats levels "as low as technically possible".
A spokesman said: "We want to dispel the myth that this is a major problem. Trans fats appear in only a relatively small number of products."

Burger King said it has been using "near-zero trans fat cooking oil" since 2005 and McDonald's said its restaurants will use a new oil from April.

I decided to dig a bit deeper into this issue and get my hands on the journal article where this was published:
(Chararro et al. 2007. Dietary fatty acid intake and the risk of ovulatory infertility. Am J Clin Nutr. 85, 231-7. ) First, I noticed that the cohort was huge- 18,555 women without a history of infertility who attempted to become pregnant between 1991-1999. Diet was assessed twice during follow-up with a food questionairre.

The reasoning as to why the investigators thought fertility would be affected by transfat consumption was quite interesting. They noticed that much evidence has shown that dietary factors which affect insulin sensitivity often affect the progression of some forms of infertility. Factors which decrease insulin sensitivity, such as increased body weight and decreased exercise, have been shown to increase infertility as it creates ovulatory dysfunction. Sustained high concentrations of glycated hemoglobin (high blood sugar) are also linked to infertility.

In clinical trials of insulin sensitizers (like ones that activate the peroxisome proliferator-activated receptor gamma---PPAR-gamma), these meds have improved the metabolic profiles AND ovulatory function of women who have polycystic ovary syndrome. The reason for this is that certain food additives bind to the PPAR-gamma receptors, however this reaction is different for cis- and trans- isomers. Specifically, the trans- isomers (such as found in transfats) have been associated with greater concentrations of inflammatory markers, insulin resistance, and the risk of type 2 diabetes.

The take home message here is that transfats have a unique, and highly negative interaction with the PPAR-gamma receptor system. As drugs which enhance PPAR-gamma signaling have an effect to improve both metabolism and ovulation, and transfats do the opposite, this provides a another very strong case as to why transfats are detrimental to health.