Junk food has never been considered healthy, but recent research paints an even gloomier picture: It could affect male fertility and fetal health.

Doctors at Harvard University and the University of Murcia found that nutrition may have a direct impact on the male reproductive system. By studying the sperm samples of 188 men between the ages of 18 and 22, the team found that those with high trans fat intakes were at higher risk of infertility.

Trans fat is an unhealthy substance, also known as trans fatty acid, made through the partial hydrogenation of oils. It is found in vegetable shortening and margarine, crackers, cookies, snack foods and other foods.

Trans fats wreak havoc with the body’s ability to regulate cholesterol and rank very high in the realm of dietary dangers. American health authorities estimate that trans fats are responsible for some 30,000 early deaths a year in the U.S. Worldwide, the toll of premature deaths is thought to be in the millions.

In the study, the researchers classified the participants into two categories: those with a “western diet” composed of high amounts of red meat, refined carbohydrates and energy drinks; and a “prudent diet” dominated by fish, fruit, vegetables and whole grains.

After assessing sperm movement, concentration and shape, the scholars found that a prudent diet was associated with higher sperm movement while the sperm of the other group was in poor condition.

Audrey Gaskins, lead author of the study, was quoted by saying to Daily Mail that the main overall finding of the work is that a healthy diet seems to be beneficial for semen quality.

“Specifically, a healthy diet composed of a higher intake of fish, fresh fruit, whole grains, legumes and vegetables seems to improve sperm motility ... which means a higher number of sperm actually move around, rather than sit still,” she said.

Dr. Jorge Chavarro at the Harvard School of Public Health revealed that a diet high in trans fat had lower sperm concentration levels.

Trans fat levels found in sperm and semen also increased.

A separate study by Harvard School of Public Health suggested that high trans fat consumption by mothers during the second trimester of pregnancy was linked to larger babies. It is not just about the adults, who may suffer from increased risk of coronary heart diseases but is about the babies, the researchers said.

The team surveyed about 1,400 women who completed questionnaires about their diets during the first and second trimesters of pregnancy. There was no correlation between trans fat consumption and fetal growth during the first trimester. But each incremental increase in trans fat consumption during the second trimester, babies grew marginally.

“We’ve been worried about the effects of trans fats for years,” said HSPH associate professor Eric B. Rimm, co-writer of the study, to the Harvard Crimson.

“It’s amazing that something we consume in such small amounts could have such large implications,” said Rimm, who emphasized that women who are pregnant should remain conscious of their trans fat consumption, especially at restaurants.

By Bae Ji-sook (baejisook@heraldcorp.com)