Over the past decade, mounting research has suggested that diet and body weight may have a significant impact on a couple’s ability to conceive.
Eating well and maintaining a healthy weight have been shown to increase ovulation, the release of a mature egg from the ovary. In men, the same lifestyle factors are associated with improving the quality and quantity of sperm.
Now, two large studies add to the view that nutritional factors play an important role in fertility. According to the new research, eating the right carbohydrates and avoiding being overweight can help couples become pregnant faster.
It is estimated that as many as 15 per cent of couples experience infertility, defined as unsuccessfully conceiving after 12 months of unprotected intercourse. Infertility is often associated with women, but factors that affect men are thought to be responsible for one-quarter of cases.
About the new studies
One review, published last month in the American Journal of Clinical Nutrition, pooled data from two studies that investigated the link between carbohydrate intake and fertility in couples trying to conceive without medical assistance. The analysis involved 6,977 female participants from North America and Denmark.
The researchers found that women who ate the highest glycemic load diet had a lower chance of becoming pregnant than participants whose diets had a low glycemic load. A high glycemic load diet can result in higher blood sugar and insulin levels.
Women who consumed the most added sugars also had a harder time conceiving than women whose diets contained the least.
On the other hand, consuming at least 25 g of fibre per day (versus 16 g or less) was associated with a faster time to conception. Fibre in foods can slow the absorption of sugar into the blood stream.
Eating a diet with low carbohydrate quality – e.g., high glycemic load, high added sugars, low fibre – can lead to insulin resistance, a condition when cells in the body don’t respond well to insulin and can’t easily remove sugar (glucose) from the bloodstream. It’s thought that insulin resistance can influence hormonal function and interfere with ovulation.
For the second study, published in the July issue of Obesity Reviews, researchers reviewed 60 studies that had investigated the relation between weight status and sperm quality. The combined analysis found that overweight and obesity were linked to lower sperm quality (e.g., semen volume, sperm count, sperm motility).
It’s been suggested that excess levels of leptin, a hormone that regulates fat storage, may damage sperm production. Obesity may also cause low sperm quality through increased production of harmful free radicals and inflammatory compounds.
Keep in mind, both of these evidence reviews included observational studies and therefore do not prove causality.
Diet and fertility
There’s strong evidence that following a healthy dietary pattern can help couples improve their chances of conception. Eating a Mediterranean diet (e.g., higher intake of vegetables, fruit, whole grains, fish, poultry, nuts and olive oil) has been associated with improved fertility in women.
So has a “fertility diet” pattern, studied by researchers from Harvard Medical School. It’s comprised of more plant proteins such as beans and lentils, low glycemic carbohydrates such as whole grains, full-fat dairy foods, monounsaturated fats (found in olive oil, avocado, almonds) and supplements containing folic acid.
In men, the DASH diet, which features beans and lentils, nuts, whole grains, fruits, vegetables, fish, poultry and low-fat dairy, has been associated with improved sperm counts. On the other hand, a typical Western diet, higher in red meat, saturated fat and refined carbohydrates, has been tied to lower sperm quality.
Eating a diet that emphasizes whole grains, fruits and vegetables, plant proteins, fish, poultry and unsaturated fats, and limits refined starches and added sugars, red meat and saturated fat can help prevent overweight and insulin resistance.
While doing so isn’t a guarantee that you’ll be able to conceive naturally, eating this way has other benefits. It can also help guard against high blood pressure, high cholesterol, type 2 diabetes, heart disease, stroke and dementia.
Leslie Beck, a Toronto-based private practice dietitian, is Director of Food and Nutrition at Medcan.
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