By John M. Norian, MD FACOG Reproductive Endocrinology and Infertility
Nutrition affects women and men’s health in many ways and has now been demonstrated to affect our chances at pregnancy. Particularly, the types of carbohydrates, fats, and proteins that we eat or drink can each have an impact on how regularly women ovulate (the release of mature eggs from the ovary). In addition, lifestyle choices that we make each day, such as exercising, drinking caffeine or alcohol, or smoking cigarettes also impact the likelihood of getting pregnant and also the developing fetus (the growing baby inside).
We have learned from the Nurse’s Health Study (NHS) and also through other researchers that all carbohydrates are not created equal especially when it comes to infertility. More than any other nutrient, carbohydrates determine a person’s blood-sugar and insulin levels. When these rise too high repeatedly, our bodies become insulin resistant, thus disrupting the finely-tuned balance of hormones needed for reproduction and menstruation (having a monthly period).
Studying a group of over 18,000 female nurses with detailed histories every two years, women who ate highly-refined carbohydrates or fast carbs (such as white rice, corn flakes and French fries) were 92 percent more likely to have had ovulatory infertility than the women who ate slow carbohydrate rich meals (such as brown rice, oatmeal and dark bread) after accounting for age, smoking, how much animal and vegetable protein they ate and other factors that can influence fertility. Specifically, fast and slow carbs vary by their glycemic loads (www.glycemicindex.com) which determines how quickly certain carbs are turned into blood sugar. Interestingly, the total amount of carbs was not connected with ovulatory infertility rather than the type of carbs.
Proteins have been a mainstay of the modern human diet. Beef, chicken and pork are Americans’ favorites, trailed by fish. Beans, nuts and other plant-based proteins have lagged far behind. The NHS found that consuming more protein from plants and less from animals resulted in less ovulatory infertility. Consuming five percent of total energy intake as vegetable protein rather than as animal protein was associated with a more than 50 percent lower risk of ovulatory infertility.
Several different types of fats exist and influence our fertility in different ways. Fats do more than just carry calories or provide the building blocks for hormones or cellular machinery. They can have biological effects themselves by turning genes on or off, revving up or calming inflammation and influencing cell function. Unsaturated fats (those found in vegetable oils such as olive oil) can improve fertility by improving insulin sensitivity while trans-fats do the opposite.
Trans-fats are unsaturated that are typically found in many commercially prepared products and fast food. They increase the risk of heart disease by increasing LDL levels (“bad” cholesterol) and lowering levels of “good” HDL cholesterol. Among the 18,555 women in the Nurse’s Health Study, similar to carbohydrates, the total amount of fat in one’s diet was not connected with ovulatory infertility once weight, exercise, smoking, and other factors that can influence reproduction had been accounted for. But rather, the type of fats consumed had either a negative or positive impact upon a woman’s fertility; diets rich in trans-fats were particularly bad for ovulation and conception.
Two recent studies have noted that women who consume a typical Mediterranean diet (abundant fruits and vegetables, fish, legumes, olive oil, and a moderate amount of dairy foods and wine) had improved fertility. The observational study demonstrated that couples undergoing in-vitro fertilization who adhered to a Mediterranean diet were more likely to be pregnant than those who ate a “health conscious – low processed foods” diet that had decreased amounts of vegetable oils (especially those rich in linoleic acid) and vitamin B6. A case controlled study showed that infertile women who consumed a Mediterranean diet compared to a “Western-type” diet had less difficulty getting pregnant. Results of these two studies are interesting and warrant further investigation.
Micronutrients (Vitamins and Minerals)
Despite the high rates of over-nutrition and obesity, Western diets (typified by snacking, breakfast skipping, fast foods, soft drinks, and convenience foods) are nutritionally unbalanced and the intake of micronutrients (vitamins and minerals) in general fails to meet recommended daily allowance (RDA) values. Especially in couples hoping to conceive, supplementation with a multivitamin may increase the chance of pregnancy while decreasing other pregnancy related complications.
Numerous researchers from around the world have demonstrated that folic acid intake decreases the incidence of neural tube defects (such as spina bifida) in developing fetuses. In addition, folic acid and other B vitamins improve the likelihood of ovulation and fertility. Furthermore, women who consumed iron supplements or diets rich in non-heme iron (primarily found in fruits, vegetables, and beans and not from animal sources) also had decreased rates of ovulatory infertility. Numerous studies suggest that vitamin D deficiency may be detrimental to reproduction although the exact mechanism is unknown.
Nutrition for Males
Approximately 40 percent of couples struggling with infertility have a contributing male factor. Men can help to optimize their fertility by maintaining a healthy weight; men who are obese (body mass index (BMI) >30 kg/m2) have lower testosterone levels, increased insulin resistance and decreased semen
parameters. Higher levels of trans-fats are seen in men with lower sperm concentrations.
Men are also encouraged to take a multivitamin daily. The role for antioxidant therapies (such as vitamin C, vitamin E, co-enzyme Q-10, and pycnogenol) has been demonstrated to improve various semen parameters; however, their direct impact upon increased live birth rates remains to be proven. Similar to women, not smoking, avoiding excess alcohol, and eating a healthy diet are also important for male fertility.
Weighing too much or too little can interrupt normal menstrual cycles, interrupt ovulation or stop it altogether. A person’s body mass index (BMI) is a common measure (nhlbisupport.com/bmi/) that compares one’s height and weight. The NHS demonstrated that women with the lowest and highest BMIs
were more likely to have had trouble with ovulatory infertility than women in the middle. Infertility was least common among women with BMIs of 20 to 24, with an ideal around 21. Of interest, women who are overweight (BMI >25) or obese (BMI >30), losing just five to 10 percent of your current weight is often enough to improve ovulation.
In addition, having a high BMI ( >30) increases the chances of miscarriage, puts a mother at risk during pregnancy of developing high blood pressure (pre-eclampsia) or diabetes, and elevates her chances of needing a Cesarean section. New studies suggest that the sons and daughters of obese pregnant mothers may have increased rates of heart disease when they are adults because of the genetic programing that goes on in the womb.
Things to Avoid
An occasional glass of wine or beer likely will likely not hurt your chances of conceiving. Once your pregnancy test is positive, avoiding alcohol will prevent any potential harm to your developing fetus. No adequately designed study has looked at alcohol consumption and the time between ovulation and a woman’s missed period, so it’s best to keep alcohol consumption to a minimum. In couples under-going in-vitro fertilization, a recent retrospective study has demonstrated improved results when alcohol is avoided completely.
Large amounts of caffeine (greater than 500 mg or five cups of coffee/day) have been demonstrated to decrease one’s fertility. During pregnancy, caffeine consumption over 200 to 300 mg/day may increase the risk of miscarriage but does not increase the risk for congenital anomalies. Overall, moderate amounts of caffeine consumption (one or two cups of coffee/day) have no apparent adverse impact on fertility or pregnancy outcomes.
Numerous large studies have demonstrated that cigarette smoking increases rates of infertility. In addition, women who smoke cigarettes are more likely to have a miscarriage and also an earlier menopause. Second-hand smoke, particularly from male partners, negatively impacts fertility even though the association may not be as strong.
Herbal supplements (such as saw palmetto or black cohosh) and bio-identicals can negatively impact one’s chance of pregnancy as they have hormonal activity themselves. In addition, because these classes of supplements are not regulated, contamination is more likely. Complementary therapies such as acupuncture or other stress reduction techniques may increase pregnancy rates in select patients although the data is conflicting.
The multitude of factors that go into having a menstrual period and to getting pregnant is remarkable. Modifying one’s lifestyle to optimize the likelihood of conception and also to decrease the chance of pregnancy related complications is an essential step in the process of starting a family. HRC physicians continually strive to improve fertility treatment and pregnancy outcomes in a patient centered fashion.
• Increase your slow carbohydrates
• Eat less animal protein & more plant-based protein
• Some fat is good, but avoid trans-fats
• Take your folic acid, the B vitamins and iron
Cetin I, Berti C, Calabrese S. Role of micronutrients in the periconceptional period. Human Reproduction Update 2010; 16(1): 80-95.
Chavvarro J, Willett W, Skerrett P. The Fertility Diet. New York, NY: McGraw-Hill, 2008.
Chavarro JE, Rich-Edwards JW, Rosner BA, Willett WC. Caffeinated and alcoholic beverage intake in relation to ovulatory disorder infertility. Epidemiology 2009; 20:(3)374-81.
Chavarro JE, Rich-Edwards JW, Rosner BA, Willett WC. 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.
Rossi BV, Berry KF, Hornstein MD, Cramer DW, Ehrlich S, Missmer SA. Effect of alcohol consumption on in vitro fertilization. Obstetrics & Gynecology 2011; 117(1): 136-42.
Wathes DC, Abayasekara DR, Aitken RJ. Polyunsaturated fatty acids in male and female reproduction. Biology of Reproduction 2007; 77: 190-201.