The South Australian study published today (Friday 4 May) in leading reproductive medicine journal Human Reproduction found that the women who ate the least fruit increased their chance of infertility by 50 per cent while those who ate fast food four or more times a week doubled their the risk of infertility – from 8 per cent to 16 cent.
The University of Adelaide study asked 5598 first-time mums across six sites in Australia, New Zealand, the United Kingdom and Ireland about what they ate prior to falling pregnant.
Among all the couples in the study, 468 (8 per cent) were classified as infertile (defined as taking longer than a year to conceive) while 2204 (39 per cent) conceived within a month.
Study leader Professor Claire Roberts from the University of Adelaide’s Robinson Research Institute said while the survey did not go into detail about what kinds of fruit or fast foods were eaten, fruit was usually considered to be rich in micronutrients that combat oxidative stress while fast foods were generally high in saturated fats.
The consumption of green leafy vegetable had no effect on conception times, which surprised the researchers.
“The best outcomes were for women who had three or more serves of fruit a day, which is quite a lot, the national recommendations in Australia for example are two serves of fruit per day,” Professor Roberts said.
“Potentially fast food is making the eggs less likely to be fertilized but also, it could be changing maternal metabolism that also has a significant affect on conception and pregnancy success in general.
“Our data was really a dose response effect so if you look at the graphs the more fruit women ate the shorter time to conception and the more fast food they ate the longer the time to conception.”
Professor Roberts said there had been a lot of research on the dietary impacts of infertile couples but very little into the diets of women generally before they tried for children.
She said while the results may not be surprising to some, it was always beneficial to have commonsense backed up by evidence.
“The difference with our study is all of our women got pregnant,” Professor Roberts said.
“It’s also an international study of over 5600 women so it means our data could be considered to be quite generalisable because we’ve looked at a lot of different women from a lot of different backgrounds.
“The Internet abounds with all sorts of advice on our health and I think it’s very important that we give women really good quality evidence that what they’re doing is the right thing to do.”
Of the 5598 women, 5258, (94 per cent) received no fertility treatments before conception and 340 did.
During the first antenatal visit at around 14-16 weeks’ gestation, midwives collected information about the time it took to become pregnant and the women’s diet. This included details of their diet in the month before conception, and how frequently they consumed fruit, green leafy vegetables, fish and fast foods. Fast foods included burgers, pizza, fried chicken and chips that were bought from take-away or fast food outlets.
Couples were excluded from the analysis if they were receiving fertility treatment due to the male partner’s infertility.
First author Dr Jessica Grieger, post-doctoral research fellow at the University of Adelaide, said adjustments were made to the relationships with pre-pregnancy diet to take account of several factors known to increase the risk of infertility such as elevated body mass index, maternal age, smoking and alcohol intake.
“As diet is a modifiable factor, our findings underscore the importance of considering preconception diet to support timely conception for women planning pregnancy,” said Dr Grieger.
“For any dietary intake assessment, one needs to use some caution regarding whether participant recall is an accurate reflection of dietary intake. However, given that many women do not change their diet from pre-pregnancy to during pregnancy, we believe that the women’s recall of their diet one month prior to pregnancy is likely to be reasonably accurate.”
Dr Grieger will continue the work and plans to identify particular dietary patterns, rather than individual food groups, that may be associated with the length of time it takes women to become pregnant.
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