Role of diet in causing problems with ovulation

It is estimated that about one in six couples will be faced with the problem of infertility at some point during their reproductive lifetime. Of those couples, problems with ovulation (making and releasing an egg in a regular fashion) can be identified in 18-30% of cases. Several factors have been found in medical studies to affect the likelihood of ovulation. Most commonly, extremes of body weight (both obese and underweight) have been associated with ovulation problems. Recently, evidence has begun to emerge that the type of diet a woman consumes may influence her risk for ovulation problems.

In a recent study, researchers used data from a large group of nurses known as the Nurses Health Study II. The Nurses’ Health Study II was started in 1989 when more than 116,000 female registered nurses aged 25–42 years completed a mailed baseline questionnaire. Participants have been followed every two years since then with mailed questionnaires. Finding women who were trying to get pregnant With each questionnaire, participants were asked if they had tried to become pregnant for more than 1 year without success since the previous questionnaire. They were also asked to identify whether they believed their inability to conceive was caused by blockage of their fallopian tubes, a problem with ovulation, endometriosis, cervical mucus factor, male factor, or was not found, was not investigated, or was due to another reason.

In order to determine how accurately, these nurses reported their actual diagnosis, the researchers conducted a “validation study” in which they reviewed the medical records of a small portion of the larger group. The researchers found that a diagnosis of an ovulation problem was correctly reported by the nurses 95% of the time.

Women were also asked if they became pregnant during the preceding 2-year period, including pregnancies resulting in miscarriages or induced abortions. Only married women without a history of infertility and with available information on diet, physical activity, height, and weight were eligible to enter the analysis.

In total, the researchers identified 17,544 women without a history of infertility who tried to become pregnant or became pregnant during the study period – which lasted eight years. 25,217 pregnancies and pregnancy attempts were estimated among this group. 3,209 nurses reported difficulty in becoming pregnant. Of these, 2,032 actually sought medical care for the diagnosis of infertility. Only 416 of the infertile women reported an ovulation problem as one of the reasons for their infertility.

Assessing the diet of these women In the mailed questionnaires, the nurses were also asked to report how often, on average, they consumed each of the foods, beverages, and supplements included in a “food frequency” diary during the previous year. The researchers were interested in several components of diet. Specifically, the categories were:

  • The amount of trans fats compared to “monounsaturated” fats
  • The amount of protein from animal sources (meat) compared to vegetable sources (beans)
  • The amount of carbohydrates from refined sources (white bread)
  • The use of multivitamins and specifically the amount of iron intake
  • The amount of “high fat” dairy products versus “low fat dairy products”

Within each category, a “fertility score” was given based on perceived benefit or harm. For example, a large amount of trans fats in the diet was thought to be bad and so this would be given a low score. Conversely, a high percentage of protein that came from vegetable sources was thought to be good and so was given a high score.

Fertility Diet Score


The results of this study showed that diet plays a role in causing ovulation problems. The higher a woman’s fertility score, the less likely she was to have an ovulation problem. Looked at in another way, if each category was considered a dietary habit, the more “good” dietary habits a woman had, the less likely she was to have problems with ovulation. It should be noted that these relationships still held up when the researchers compared women under age 35 to women over age 35 or for those who had pregnancies previously compared to those who didn’t  and for women who were normal weight or overweight.

Lowest to Highest Likelihood of having ovulation problems
1 Baseline
2 32% less likely compared to group 1
3 35% less likely compared to group 1
4 47% less likely compared to group 1
5 66% less likely compared to group 1

The study also confirmed what many other studies found: that extremes of weight are also associated with ovulation problems. The impact of weight was identified by using a calculated number (body mass index) which takes into account a woman’s height and weight. A normal body mass index is between 20 and 24.99. A number below 20 is considered underweight. A number of 25 or over is considered overweight. A number of 30 or over is considered obese.

  BMI Likelihood of having ovulation problems
Less than 20 38% more likely compared to normal weight
20-24.99 Baseline
25-29.99 32% more likely compared to normal weight
30 or more 35% more likely compared to normal weight


The results of this study should be interpreted with caution. First of all, the numbers are very small. From a group of over 100,000 nurses in the original group, only 416 were found to have ovulatory infertility. If is from these few hundred women that all the conclusions are based.

Furthermore, these recommendations only apply for women who have a problem with ovulation. The current study does not indicate associations with these diet parameters and other types of infertility. For example, this study did not address women with unexplained infertility. There is no evidence from this study to indicate that other causes of infertility are related to diet.

This study also did not attempt an experiment where the type of diet was changed to see if ovulation improved in women who previously had a problem. Although it might seem logical to assume that the changes in dietary habits from “bad” to “good” should result in lowering the rate of ovulation problems, this study did not attempt to prove that. There may be other factors related to diet that could be of importance. For example, the authors noted differences in the rates of alcohol use, caffeine use and smoking when comparing women with high fertility diet scores to women with low scores. These other factors may be important confounding factors.

On the other hand, with one exception, the type of diet that the authors claim is related to a lower risk of ovulation problems is generally considered to be a healthier diet overall. For example, much data points to the adverse effects of trans fats in the diet. The one exception is that increasing amounts of “high-fat” dairy items seems to be associated with less ovulation problems than “low-fat” dairy items for unknown reasons.

So keeping all this in mind, here are some general recommendations for women with ovulatory infertility:

1. Maintain a healthy weight (a body mass index of between 20 and 24.99).

Lose weight, if you’re overweight or obese and try to gain weight if you are underweight. Exercise may help with losing weight but, by itself, may not help improve the chances for ovulation.

2. Avoid trans fats completely.

Trans fat is typically found in stick margarine, fried foods, and yes, Girl Scout cookies. Foods in the United States are required to list their trans fat content on the package. If trans fat is not listed, look at the ingredients and avoid foods that contained “partially hydrogenated” oils.

Computer models of the nurses’ diet patterns indicated that eating a modest amount of trans fat (2 percent of calories) in place of other, more healthful nutrients like polyunsaturated fat, monounsaturated fat or carbohydrate would dramatically increase the risk of infertility. To put this into perspective, for someone who eats 2,000 calories a day, 2 percent of calories translates into about four grams of trans fat. That’s the amount in two tablespoons of stick margarine, one medium order of fast-food french fries or one doughnut.

The total amount of fat in the diet wasn’t connected with ovulatory infertility once weight, exercise, smoking and other factors that can influence reproduction had been accounted for. The same was true for cholesterol, saturated fat and monounsaturated fat—none were linked with fertility or infertility.

3. Stop eating excessive sugar and refined carbohydrates like white bread.

Not that long ago, carbohydrates such as bread, pasta, rice, and potatoes made up more than half of our calories. Then came the no-carb diet craze. Like all diet fad, the no-carb craze lost its luster and faded from prominence. However, it did result in studies being performed which allowed us a greater understanding of the role of carbohydrates in our diets.

Women should try to avoid easily digested carbohydrates such as sugary breakfast cereals, white bread, white rice, potatoes and sugar containing sodas. A better choice are the slowly digested carbohydrates that are rich in fiber such as brown rice, pasta, whole grains, beans, vegetables, whole fruits and dark bread.

A very important point to remember is that this study found that the total amount of carbohydrate in the diet wasn’t connected with ovulation problems. Women in the low-carb and high-carb groups were equally likely to have had ovulation problems.

4. Consume more protein from vegetables rather than from animals.

This means decreasing the amount of meat in your diet. Good sources of vegetable protein include beans (all types) and lentils.

Using computer models of the data from the study, the researchers found that when total calories were kept constant, adding one serving a day of red meat, chicken or turkey predicted nearly a one-third increase in the risk of ovulatory infertility. And while adding one serving a day of fish or eggs didn’t influence ovulatory infertility, adding one serving a day of beans, peas, tofu or soybeans, peanuts or other nuts predicted modest protection against ovulatory infertility.

Swapping 25 grams of plant protein for 25 grams of carbohydrates shrank the risk of ovulation problems by 43 percent. Replacing 25 grams of animal protein with 25 grams of plant protein was related to a 50 percent lower risk of ovulatory infertility.

5. Consume more than 54 mg of iron daily

Of course, animal protein is typically high in iron but the previous recommendation is to limit meat. Therefore, you need to try to get your iron from other sources. Prenatal vitamins contain iron but different brands contain different amounts ranging from 27 to 90 milligrams per tablet. Higher iron content may cause you to have stomach upset or constipation. Other non-animal sources of iron are listed here:

List of Grains Rich in Iron Iron (mg.)
Brown rice, 1 cup cooked 0.8
Whole wheat bread, 1 slice 0.9
Wheat germ, 2 tablespoons 1.1
English Muffin, 1 plain 1.4
Oatmeal, 1 cup cooked 1.6
Total cereal, 1 ounce 18.0
Cream of Wheat, 1 cup 10.0
Pita, whole wheat, 1 slice/piece, 6 ½ inch 1.9
Spaghetti, enriched, 1 cup, cooked 2.0
Raisin bran cereal, 1 cup 6.3
List of Iron Rich Legumes, Seeds, and Soy:     
Sunflower seeds, 1 ounce 1.4
Soy milk, 1 cup 1.4
Kidney beans, ½ cup canned 1.6
Chickpeas, ½ cup, canned 1.6
Tofu, firm, ½ cup 1.8
Soy burger, 1 average 1.8 to 3.9*
List of Vegetables Rich in Iron:   
Broccoli, ½ cup, boiled 0.7
Green beans, ½ cup, boiled 0.8
Lima beans, baby, frozen, ½ cup, boiled 1.8
Beets, 1 cup 1.8
Peas, ½ cup frozen, boiled 1.3
Potato, fresh baked, cooked w/skin on 4.0
Vegetables, green leafy, ½ cup 2.0
Watermelon, 6 inch x ½ inch slice 3.0

6. Consider starting a prenatal multivitamin.

Ask your doctor for a prescription prenatal versus one that you get over the counter. This does not have to do with ovulation problems; instead, the prescription prenatal vitamins have higher amounts of folic acid which have been found to reduce the risk of certain types of birth defects. Also, many prescription prenatal vitamins now contain an “unsaturated” fatty acid called DHA. DHA has been found to improve fetal brain development and has numerous health benefits for the women taking them regularly.

7. Consume one daily serving of full-fat dairy.

For example, 1 cup whole milk, full-fat yogurt, or 1-2 ounces cheese. In a previous study, the researchers found that women eating a half cup of ice cream two or more times a week had a 38% lower risk of ovulation problems than women consuming ice cream less than once a week. But, of course, ice cream contains refined sugar and calories!

In addition, whole milk has nearly double the calories of skim milk. If you are drinking three glasses of milk a day, trading skim milk for whole means an extra 189 calories a day. That could translate into a weight gain of 15 to 20 pounds over a year if you don’t cut back somewhere else. Remember that being overweight can reduce fertility and might therefore negate the potential benefits of the whole fat dairy in the first place.

Once you are pregnant, you can cut back to the low fat dairy again.