Harvard University researchers estimate that 10% to 15% of couples trying to conceive encounter some fertility problems, and a lack of ovulation is a cause in a quarter of those cases.
The condition, known as anovulatory infertility, occurs when the ovaries don’t produce an egg. It can be caused by diet, eating disorders, excessive exercise, or cysts. Long-term use of the contraceptive pill is also a possible reason.
The study found that women who consume at least one daily serving of high-fat dairy reduce the risk of infertility caused by lack of ovulation by more than a quarter compared with those who eat only one such portion a week.
The study also found the more low-fat dairy women had, the less likely they were to ovulate.
More research is required to confirm the findings, but in the absence of further studies, the researchers advise women trying to conceive to swap low-fat dairy products like skimmed milk for whole-fat ones (but the overall calorie intake should remain within normal boundaries).