Women who eat more fast food spend longer trying to get pregnant, while those who eat more fruit conceive more quickly, researchers in Australia reported Thursday.
It’s one more finding adding to evidence that a healthy diet can help make people more fertile.
Women who ate fruit less than one time a month took about two weeks longer, on average, to get pregnant than women who ate fruit three times a day or more, the team at the University of Adelaide in Australia found.
"It shows that healthier foods support conception, while unhealthier foods do not so much," Jessica Grieger of the university's Robinson Research Institute, who led the study team, said in an interview.
And yes, there were women who only ate fruit once a month. "I cannot comment on that," Grieger said, laughing.
U.S. guidelines recommend eating two to three servings of fruit a day, so the optimal fertility diet falls within normal dietary recommendations.
The team studied more than 5,500 women in Australia, New Zealand, Ireland and Britain who, at the start of the study, had never had a baby.
When the women were 15 weeks pregnant, they were asked about specific foods they ate and how often. The list was detailed and included fresh fruit, leafy green vegetables, specific types of fish, burgers, fried chicken, tacos, pizza and fries.
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Their records also included details on when they began trying to become pregnant.
Those who reported eating the most fast food and the lowest amount of fruit took two to three weeks longer to get pregnant than those who ate the most fruit and the least fast food, the team reported in the journal Human Reproduction.
“This supports our findings of a protective effect of fruit, but we did not find an association with green leafy vegetable or fish,” the team wrote.
“Fruits and vegetables contain a range of antioxidants and phytochemicals, and these may beneficially impact fertility,” they added.
“As we only asked about green leafy vegetables and did not ask about orange or other types of vegetables, we did not capture total vegetable intake, potentially limiting the impact they may have on fertility.”
Almost all the women conceived without fertility assistance. Most were of average weight and were 28 years old on average.
"We had quite a fertile population," Grieger said. "Only 8 percent of the women were actually infertile, which is defined as taking 12 months to conceive."
Fast food may affect fertility because of its high saturated fat content, the team speculated.
“The specific dietary components of fast food and their relationship to fertility have not been studied in human pregnancies. Fast foods are energy dense with high amounts of saturated fat, sodium and sugar,” they wrote.
It could be some of the fatty acids that are found at particularly high levels in fast food affect the egg cells, they wrote. Egg cells are high in saturated fatty acids and it's possible a woman's diet affects the balance of these fat components, Grieger said.
The team also did not question the male partners of the women but noted that other studies show a healthy diet higher in fruits and vegetables is linked with healthier sperm.
Other research has found that smoking and obesity can interfere with fertility for both men and women.
“Healthier foods or dietary patterns have been associated with improved fertility, however, these studies focused on women already diagnosed with or receiving treatments for infertility, rather than in the general population,” the researchers wrote.
According to the Centers for Disease Control and prevention, age is a major factor in how long it takes a woman to conceive.” About one-third of couples in which the woman is older than 35 years have fertility problems,” the CDC says.
Smoking, excessive drinking, extreme eight gain or loss and extreme physical or emotional stress can also hurt fertility, the CDC says.
Doctors generally tell couples to try to conceive for a year before they’re defined as having fertility problems.