Infertility is estimated to affect up to 15 per cent of couples. And while the underlying issue here can be with either the woman or the man (or both), one relatively common cause of infertility relates to a problem with ovulation (the normal release of an egg from the ovary about every month). Sometimes, problems with ovulation can relate to a condition known as polycystic ovarian syndrome or ‘PCOS’. Individuals with this condition often have problems with sugar and insulin regulation in the body. A mainstay of medical treatment for PCOS are drugs designed primarily for diabetes. Treating women with PCOS with these drugs has been found to improve ovulatory function.
Other evidence has linked higher levels of HbA1c (a measure of blood sugar control over the last 2-3 months) and reduced fertility.
These lines of evidence suggest that, generally speaking, high levels of blood sugar-disruptive carbohydrates in the diet might be bad news for female fertility.
The extent to which a food raises blood sugar can be measured and is expressed as its glycaemic index or ‘GI’. However, the extent to which a food disrupts blood sugar and insulin will depend not just on its GI, but how much we eat of it. One way to get an idea of the overall effect of a food is to take its GI and multiply it by the amount of carbohydrate found in a standard portion of food. Divide this by 100 and we have a measurement known as the ‘glycaemic load’.
In a recent study published in the European Journal of Clinical Nutrition, researchers at Harvard Medical School and the Harvard School of Public Health in the USA assessed the relationship between intake of dietary carbohydrate in women’s diets and their risk of fertility related to problems with ovulation (ovulatory infertility) .
Two measures of carbohydrate used by the researchers were the glycaemic index (GI) and glycaemic load (GL) of the diets. The GI measures the extent to which a food raises blood sugar. However, the extent to which a food really disrupts blood sugar and insulin will depend not just on its GI, but how much we eat of it. One way to get an idea of the overall effect of a food is to take its GI and multiply it by the amount of carbohydrate found in a portion of that food. Dividing this by 100 gives us the glycaemic load.
The results of this study found that compared to women eating diets of lower GL values, those eating diets with the highest GL were 92 per cent more likely to suffer from ovulatory infertility. Total carbohydrate intake was also associated with risk of ovulatory fertility, with highest intakes associated with a 91 per cent increased risk compared to the lowest intakes. GI was also associated with enhanced risk, but only in women who had not had children.
One explanation put forward by the authors for their results is that a high carb diet might displace certain fats in the diet that might have positive benefits for fertility (including saturated and mono-unsaturated fats).
But of course another explanation is that carbohydrates can induce biochemical and physiological effects that may directly hamper fertility.
This study, I think, adds yet another potential reason to be wary about over-consuming carbs, particularly those that tend to disrupt blood sugar and insulin levels.
Chavarro JE, et al. A prospective study of dietary carbohydrate quantity and quality in relation to risk of ovulatory infertility. European Journal of Clinical Nutrition 2009;63:78-86