The Nurses Healthy Study (III) was a prospective study. It comprised of:
* 18,555 married, premenopausal women
* Without a history of infertility
* Who tried to conceive between the study period of 1991 to 1999
Their diets were assessed twice in the follow up period by using a food frequency questionnaire.
Their diets were assessed in many different nutritional areas:
Today however, we are focusing on the effects consumption of fats had in relation to ovulatory infertility. As there is limited research in PCOS; fertility and diet; we can look at this study as this is the same type of infertility that occurs in women with PCOS.
Looking at the fat, we can learn:
* Each 2% increase in the intake of energy from trans unsaturated fats, as opposed to that from carbohydrates, was associated with a 73% greater risk of ovulatory infertility
* 2% of energy intake from trans fats rather than from n−6 polyunsaturated fats was associated with a similar increase in the risk of ovulatory infertility
* Obtaining 2% of energy from trans fats rather than from monounsaturated fats was associated with a more than doubled risk of ovulatory infertility
* Trans fatty acids increased the risk of infertility
What can we take home from this study?
There is evidence to suggest that unsaturated fats may increase the risk of ovulatory infertility when consumed instead of carbohydrates or unsaturated fats commonly found in non-hydrogenated vegetable oils.
Interestingly, the study looked at dairy foods and suggested:
* One serving a day of full fat dairy products reduced infertility risk
* One serving a day of low or fat free dairy products increased the risk
Suggested reasons for this could be by reducing the fat profile in the milk, there are now more androgen's present, and researchers have learnt that androgen's affect hormones in women.
Chavarro J and Willett W. The Fertility Diet.