Tonight, is the third part to our look into the largest Nurses Study and its dietary intake links to fertility, and the third macro nutrient we are exploring is Carbohydrates.
To recap - the Nurses Healthy Study (III) was a prospective study. It comprised of:
18,555 married, pre-menopausal women
Without a history of infertility
Who tried to conceive between the study period of 1991 to 1999; 8 years
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:
Interesting this study found there was not any significant difference for rates of ovulatory infertility dependent on the amount of carbohydrates the women consumed. But what they did find was the quality of carbohydrates eaten mattered. Foods with the high Glycaemic Index (GI) values correlated more with infertility. Women who consumed carbohydrates with the highest GI rating had 92% more ovulatory infertility.
What is Glycaemic Index? This refers to the rate the carbohydrate is digested and glucose is released into the blood stream. The lower the GI rating, the slower the carbohydrate is digested and glucose (sugars) are being released.
In PCOS, this is not the first study which has shown benefits to women eating more low GI carbohydrate food sources over high GI foods.
The Australian literature review published in 2013, was completed by Lisa Moran, Kate Marsh and 10 more authors; reviewed 4 154 articles and found overall there were improvements in menstrual regularity for women who followed a low GI diet, whereas when a high GI carbohydrate diet was followed there was increased free androgen index in the women.
Kate Marsh, Australian Dietitian, has also published a study in 2010 looking specifically at how following a low GI is important for PCOS. This study found that:
in the overweight and obese population (study group of 96), by following a low GI diet, menstrual cycles improved and
with the modest weight loss (4 to 5% of body weight), the low GI diet provided a 3-fold improvement in insulin sensitivity
To follow a low GI carbohydrate diet, you switch your carbohydrate food sources over to the low GI version. Examples of some low GI carbohydrate foods are:
Hi-fibre bran cereals ie Allbran, Kelloggs Guardian
Low-GI or seed bread ie Burgen Breads; Helga’s Wholemeal and Wholegrains; Tip Top 9 Grain.
Wild, long-grain and brown rice
Whole corn (tinned, frozen or on the cob)
From now understanding the Nurse’s Study (plus a few more supporting articles) on the role diet can have on ovulatory infertility, how can you pull all this information together to form an optimal diet? My encouragement is to form a food plan using the following food groups:
Whole fresh foods
Plenty of vegetables and fruits
Good quality protein especially fish, eggs, and legumes
Healthy oils and fats especially extra virgin olive oil and avocados
Nuts and seeds
Low GI carbohydrates
Then meal plan a week. Your meal times come around every week, so plan for them. This is a discipline but it’s incredibly valuable. It will create your direction.
Chavarro J and Willett W. The Fertility Diet.
Marsh et al, 2010, “Effect of a low glycemic index compared with a conventional healthy diet on polycystic ovary syndrome”. The American Journal of Clinical Nutrition, Volume 92, Issue 1, July 2010, Pages 83–92,
Morean et al, 2013, Dietary Composition in the Treatment of Polycystic Ovary Syndrome: A Systematic Review to Inform Evidence-Based Guidelines. Journal of the American Academy of Nutrition and Dietetics 19(5)