Trans fats and infertility

A very strong link between trans fats and infertility has been uncovered by researchers at the Harvard School of Public Health.

“The more trans fats a woman ate, the more likely she was to be infertile”, said Dr Jorge Chavarro of the Harvard School of Public Health.

Dr Jorge Chavarro and his team of Harvard researchers found that increasing trans fat intake by just 2 percent of total calories -- or about 4 grams of trans fats per day, an amount that is easily obtained from eating regular modern foods -- could significantly increase a woman's risks of infertility.

The Harvard team had analysed data from 18,555 healthy US women participating in the Nurses' Health Study. All were married and trying to get pregnant between 1991 and 1999.

They found that:

• For every 2 percent increase in the amount of calories a woman got from trans fats instead of carbohydrates, her risk of infertility increased by 73 per cent.
  
  
• For every 2 percent increase in calories from trans fats instead of Omega-6 poyunsaturated fats, her risk of infertility increased by 79 per cent.
  
  
• For every 2 er cent increase in the amount of calories from trans fats instead of monounsaturated fats, her risk of infertility more than doubled.

The latest research findings on trans fats and infertility were reported in the American Journal of Clinical Nutrition.

"It's not very hard to get 4 grams of trans fatty acids every day," Dr Jorge Chavarro said. "It's really a small amount of trans fatty acids that we observe having a significant effect on infertility."

Trans fats and infertility - pathways

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Trans fats and infertility / reproduction -- other issues

The latest research finding on trans fats and infertility should come as no surprise to those who have been closely following the trans fats issue.

Most news reports about trans fats mention their effects on heart disease, obesity, diabetes and cancer.

Seldom mentioned, however, is the fact that Denmark decided in 2003 to ban trans fats not just because of concerns about heart disease, but because of an issue related to trans fats and infertility -- researchers had found that trans fats could affect fetal development and lead to low birth weight of babies.

German researchers reported in 1992 that they found a correlation between the mother's trans fat intake and low birth weight in infants.

Researchers also found that trans fats find their way, unaltered, across the placenta of pregnant women and into the growing fetus. They contribute to low birth weight and mothers who consume trans fats are more likley to develop high blood pressure during pregnancy, or pre-eclampsia.

Of course, a link between trans fats and inferttility does not mean that women who take trans fats absolutely cannot conceive.

However, the baby gets harmed in other ways. Breast feeding mothers pass these harmful fats to their babies through their milk.

In a 1992 study of 198 Canadian mothers Professor Chen Zhen Yu of the Chinese University of Hong Kong found that the fat in human milk contained an average of 7.2 percent trans fat. Actual levels ranged from 0.1 to 17.2 percent.

Comparing with 51 Hong Kong Chinese women, Professor Chen Zhen Yu found an average of just 0.88 percent trans fat in their milk.

And when Professor Chen Zhen Yu analysed the milk samples of 33 mainland Chinese women, he found just 0.22 percent of trans fat in their milk.

These differences reflected the varying levels of trans fats in the mothers' diets.

Professor Chen Zhen Yu also examined the effect of feeding trans fats to lactating rats. He found that rats given a 10 percent trans fat diet produced milk with 6 percent of trans fat. Rats on a 25 percent trans fat diet produced milk with 16 percent trans fat.

Trans fats in human milk displace essential fatty acids, including highly beneficial omega-3 that are needed for the baby's brain and nervous system development.

In addition, trans fats reduce overall fat levels in milk, making them less creamy.

Trans fats have also been found to inhibit assimilation of essential fatty acids. Thus, the children of mothers who consume plenty of trans fats suffer in two ways – they do not get enough essential fatty acids, and they have difficulty assimilating whatever little they get!

Scientists estimate that people who consume trans fats need at least two years for the trans fats to leave their bodies.

Thus, women who intend to become pregnant should avoid trans fats as much as possible – long before they plan to conceive.