Can Too Much Fat Damage Your Eggs?

IVF and fertility treatment produces fewer good eggs with high fat intake

(RxWiki News) Women undergoing in vitro fertilization (IVF) should be aware that their diet may affect their eggs. 

IVF means an egg is fertilized by sperm outside of the body, such as in a petri dish, and is sometimes called making a "test tube baby."

A recent unpublished study presented at a fertility conference found that eating too much fat is linked to producing fewer mature eggs for in vitro fertilization (IVF).

"Talk to your fertility doctor about the right diet for you."

In a study, led by Jorge Chavarro, MD, ScM, an assistant professor of nutrition and epidemiology at the Harvard School of Public Health, 147 women undergoing IVF treatment were categorized into three groups according to their fat intake. 

They calculated the total fat intake, as well as the intake of saturated, monounsaturated, polyunsaturated, omega 6, omega 3 and trans fats.

In addition to tracking fat intake, they tracked how many of the women became pregnant and how many gave birth following a fertilized embryo transfer into their womb.  The researchers also reviewed data on how their eggs developed, how the fertilization occurred, the quality of their embryos and the rate of division of the embryo.

The researchers took into account the other calories the women ate, their reasons for infertility problems, how their ovaries were stimulated to produce eggs, their weight and whether they smoked.

The calculations revealed that the women who were in the highest third of fat intake had fewer "metaphase II" eggs - the ones necessary for successful IVF procedures - compared to the women who ate the least amount of fat.

On average, the women in the group with high fat intake produced 9.3 mature eggs while the women eating the least amount of fat produced 11.6 metaphase II eggs, also called oocytes.

"Thus, having fewer mature oocytes can mean fewer embryos to choose from for fresh transfer or future transfer following cryopreservation, particularly among women who respond poorly to ovarian stimulation," said Dr. Chavarro.

They also found a link between the amount of polyunsaturated fat women ate and the quality of their embryos. Polyunsaturated fat occurs in certain types of vegetable oils like soybean and corn oil as well as fatty fish like salmon, mackerel and trout.

A higher number of poor quality embryos and more slowly dividing embryos were observed among the women who ate the most polyunsaturated fats compared to those who ate the least.

Meanwhile, a higher intake of monounsaturated fat was associated with a higher likelihood of a woman successfully giving birth. Monounsaturated fats occur in many vegetable oils - like olive oil, canola oil, peanut oil, sunflower oil and sesame oil - as well as in avocados, peanut butter and many nuts and seeds.

The women in the highest third of monounsaturated fat intake were 3.5 times more likely to become pregnant and go on to give birth after an embryo transfer compared to those who ate the least amount of monounsaturated fats.

"Different types of fat are known to have different effects on biological processes which may influence the outcome of assisted reproduction - such as underlying levels of inflammation or insulin sensitivity," Dr. Chavvaro said. "However, it is not clear at this moment which biological mechanisms underlie the associations we found."

Dr. Chavvaro cautioned that the results of the study should be replicated in other studies before recommendations are issued to IVF patients regarding their fat intake.

"While these results are interesting, this is the first time to our knowledge that dietary fats have been linked to treatment outcome in IVF," he said.

The study was presented July 3 at the 28th annual meeting of the European Society of Human Reproduction and Embryology in Istanbul.

Because the study has not yet been published in a peer-reviewed journal, its results should be regarded as preliminary and still require review by researchers in the field. The study was funded by the National Institutes of Health.

Review Date: 
July 5, 2012