The Mediterranean Diet And Its Relationship To Fertility

Opinion

Originally printed in the January 2019 issue of Produce Business.

The Mediterranean diet generally is described as a way of eating based on a foundation of fruits and vegetables, along with whole grains, legumes, nuts and healthy fats such as olive oil. It also includes moderate amounts of fish, seafood and dairy products and, on occasion, eggs and poultry. Red meat is limited. The health benefits of the Mediterranean diet — weight management, heart health, cholesterol reduction, lower blood pressure — are so well established that Oldways, a nonprofit food and nutrition education organization with a mission to inspire healthy eating through cultural food traditions and lifestyles, collaborated with Harvard to produce a Mediterranean Diet Pyramid as an alternative to the U.S. government’s version. The Dietary Guidelines for Americans 2015-2020 includes a Healthy Mediterranean-Style Eating Pattern. The USDA’s Healthy Mediterranean-Style Eating Pattern suggests a total of 2 cup-equivalents (c-eq) of fruits and 2 c-eq of vegetables each day. Vegetables are broken down into weekly recommendations for dark green (1 c-eq), red and orange (5 c-eq), starchy (5 c-eq) and other (4 c-eq).

Two studies from Greece suggest following a Mediterranean diet may offer an additional health benefit — boosting fertility in women and men.

In a study1 described in the January 2018 journal Human Reproduction, researcher Nikos Yiannakouris of Harokopio University and his colleagues evaluated the diet and lifestyle of 244 non-obese women between the ages of 22 and 41 years who underwent their first trial of in-vitro fertilization (IVF). The team used a measure called the MedDietScore to determine how closely the women were following a Mediterranean eating plan prior to IVF. They divided the women into three groups based on high, medium or low MedDietScore. Later, the team looked for associations between MedDietScore and fertility outcomes, including number of eggs, fertilization rate, implantation, clinical pregnancy and rate of live birth. Women under age 35 and with the highest MedDietScores during the six months before their first IVF were nearly three times more likely to become pregnant and have a successful pregnancy. Diet had no effect on the number of eggs, fertilization rate or implantation, and did not make a difference among women 35 and older.

Yiannakouris and his research team also studied2 the relationship between the Mediterranean diet and semen quality among 225 male partners from couples undergoing fertility evaluation. Men in the lowest one-third for MedDietScore were more likely than men with the highest scores to have abnormal sperm concentration, total sperm count and sperm motility.

Few studies to date have looked at the impact of healthy eating in general and the Mediterranean diet in particular on fertility, and these two studies show only an association, not a direct effect. Also, it’s important to note benefits were attributed to the overall diet rather than to individual foods such as fruits and vegetables. In a published interview, Yiannakouris offers several possible explanations — the high antioxidant content of fruit, vegetables and other Mediterranean diet foods may aid the health of the endometrium; healthy fats in foods such as olive oil and nuts could boost conception rates; and adherence to the Mediterranean diet is associated with a healthier body weight, which is linked to improved fertility and pregnancy outcomes.

The researchers say their findings cannot be generalized to all women trying to become pregnant, nor to obese women or women attending other infertility clinics around the world. They point out their findings show a Mediterranean diet is only linked to improved IVF outcomes, and they cannot show it improves the chances of pregnancy and birth.

Still, the numerous health benefits of the Mediterranean Diet suggest it’s never too early for women and men to start eating Mediterranean style, and particularly before trying to get pregnant. Although diet was not related to pregnancy outcome among women 35 years and older, healthy eating is equally important for its numerous health benefits as women get older.

1 Dimitrios Karayiannis, Meropi D Kontogianni, Christina Mendorou, Minas Mastrominas, Nikos Yiannakouris. Adherence to the Mediterranean diet and IVF success rate among non-obese women attempting fertility. Human Reproduction, 2018; DOI: 10.1093/humrep/dey003
2 Dimitrios Karayiannis, Meropi D. Kontogianni, Christina Mendorou, Lygeri Douka, Minas Mastrominas, Nikos Yiannakouris. Association between adherence to the Mediterranean diet and semen quality parameters in male partners of couples attempting fertility. Human Reproduction, 2016; DOI: 10.1093/humrep/dew288


Comments & Analysis

Many Other Variables To Consider In Fertility?

Jim Prevor, Editor-in-Chief, Produce Business

It has been widely accepted for some time that nutrition impacts fertility. These very specific studies are focused on a group of women, who are not obese, who are less than 35 years old and whom are seeking in-vitro fertilization (IVF) at a fertility clinic.

The studies retrospectively asks people to report on their diet and, using an analytic tool, determines the degree to which their diets approach the Mediterranean Diet. The findings are that women of this type who more closely approximate the Mediterranean Diet have greater success at having a successful birth through IVF.

The Mediterranean Diet is widely recognized as an optimal diet. Walter C. Willett, M.D., Dr. PH, is Professor of Epidemiology and Nutrition at Harvard T.H. Chan School of Public Health and Professor of Medicine at Harvard Medical School. In his widely praised book “Eat, Drink and Be Healthy,” Willett explained that the “main elements of the Mediterranean lifestyle are connected with lower risks of many diseases.”

Analyzing data from Harvard’s Nurses’ Health Study (NHS), a long-term study, Willett came to the conclusion that “heart diseases could be reduced by at least 80 percent by diet and lifestyle changes.”

Produce has a big role in this with these insights ultimately leading Harvard to develop its own Healthy Eating Plate, which calls for 50 percent of the plate to be fruits and vegetables but also emphasizes the importance of healthy oils and water:

This basic direction is now recognized by the USDA, which also calls for 50 percent of the plate to be fruits and vegetables. Indeed, it is interesting how the nutritional science has been developing. At a symposium in which this author shared a stage with Dr. Willett, he was asked his thoughts on potatoes. Dr. Willett responded by saying if you had asked him a number of years ago, he would have said the potatoes were fine, but the problem was what we did with them, such as frying. Today, he said, the best thing about French Fries is the oil. The problem, he explained, was the high glycemic load of the potato itself.

So, is it possible this optimal diet might help fertility? Sure. But these studies doesn’t tell us that. The most you can say about these studies is they raise an interesting possibility to be explored by more studies.

Perhaps women who more closely comply with the Mediterranean Diet are more health-conscious or better able or more willing to comply with health-oriented instructions.

After all, the reputation of the Mediterranean Diet is well known. So, perhaps women who more closely comply with the Mediterranean Diet are more health-conscious or better able or more willing to comply with health-oriented instructions. Perhaps they exercise properly, comply with medication instructions, de-stress, etc., and it may be these behaviors that make them more successful at IVF.

Many years ago, I moved into a new ocean front condo, and there were several young couples who had bought large homes in anticipation of raising families. They were unable to get pregnant and, after several years of trying, often with expensive medical assistance, each couple decided to abandon that dream. They sold their big suburban houses, moved to the ocean front condos and prepared to live the new life they had come to embrace.

Oddly enough, having given up the stress of focusing on having children, every one of these couples was pregnant within a year. The studies just don’t address these many other variables.

The same point goes with the association between the Mediterranean Diet and semen quality. Again, you can’t just pluck one variable out of a life and know you have something important.

One wonders if they had done these studies on a thousand other variables — frequency of swimming, educational level, having children previously, eating dark chocolate, owning a summer house… if they wouldn’t also have found associations.

It is important to also identify mechanisms that explain results. If the Mediterranean Diet has all these pro-fertility properties, why would they cease to exist when women hit the age of 35? Why would they not apply to obese women?

Of course, as Lao Tzu said, “A journey of a thousand miles begins with a single step,” so our Greek friends have given us just that…. a starting point for further exploration. Let us be grateful for that.

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