In the United States, approximately 6 percent of married women up to 44 years old are unable to get pregnant after one year of trying, and about 12 percent of all women have difficulty getting pregnant or carrying a pregnancy to term, often known as “impaired fecundity.”
Fertility refers to the preconception period of a reproductive-aged woman — 15 to 49 years old, according to the World Health Organization — during which she is trying to get pregnant. A couple is considered to experience infertility if after 12 months or more of regular unprotected sexual intercourse, no pregnancy results. Since fertility in women is known to decline steadily with age (with each month of menstruation, women lose a portion of their ovarian reserve and egg quality may decline, making it harder to conceive), some health care providers will evaluate and treat women 35 or older after six months of unprotected sex without conception. Women under 35 are advised to try to conceive without the aid of fertility treatment for at least one year before pursuing fertility medicines, surgical procedures or assisted reproductive technologies, or ART, such as in vitro fertilization, or IVF.
However, infertility is not a woman’s disease. In about 35 percent of couples with infertility, male- and femalerelated factors are involved. And in 8 percent of cases, a male factor is the only identifiable cause. The causes of infertility vary, and there is no one-size-fits-all solution.
Causes of Female Infertility
Female infertility often reflects problems with ovulation that may be related to diseases or conditions affecting the female reproductive system, such as polycystic ovary syndrome, endometriosis, primary ovarian insufficiency, structural uterine abnormalities(such as a condition in which the uterus is shaped like a heart), blocked fallopian tubes, uterine fibroids, excess body weight and overactivity. Eating disorders, overactivity (which may cause female athlete triad, a combination of low energy availability, changes in menstruation and impaired bone health) and stress can cause a condition known as “hypothalamic amenorrhea” that often is associated with infertility. Also, conditions such as celiac disease that are left untreated can affect fertility.
Causes of Male Infertility
According to the Centers for Disease Control and Prevention, male infertility factors often are related to varicocele, a condition in which veins on a man’s testicle are too large and cause the testicle to overheat. This elevated temperature can affect the shape, movement and quantity of sperm. Other factors that can lead to male infertility include genetic conditions that affect sperm production, injury to the testicles and conditions such as cystic fibrosis.
Peer-reviewed, randomized control trials on male infertility, regardless of cause, remain sparse. Available research is predominately observational and review studies that rely on self-reported measurements, such as food frequency questionnaires and dietary recalls, leave room for errors and limitations.
Recommendations for Women
Many fertility researchers have relied on data from the Nurses’ Health Study II, a prospective cohort study that began in 1989 and evaluated nearly 20,000 responses from registered nurses to a questionnaire on diet and lifestyle habits and reproductive outcomes.
Researchers found that a high fertility diet, or an eating style that promotes fertility, for women consisted of:
- Low intake of trans fat and greater intake of monounsaturated fat
- Greater plant protein consumption and lower animal protein consumption
- Greater consumption of complex, high-fiber carbohydrates
- Consumption of full-fat dairy products rather than low-fat dairy foods
- Greater consumption of non-heme iron foods from plant sources.
Researchers found that women who followed these dietary recommendations had a 66 percent lower risk of ovulatory disorder infertility and a 27 percent lower risk of infertility due to other causes.
Regarding women using ART procedures such as IVF, studies have demonstrated success in the use of both the Mediterranean diet and a “pro-fertility” diet. For example, a study published in 2018 found that consuming more produce, seafood and healthy fats (such as olive oil and nuts) and less red meat decreased time to conception and increased likelihood of pregnancy in those undergoing ART.
Key Nutrients for Female Fertility
|Nutrient||Dietary Reference Intake (DRI)|
|Vitamin D||600 IU|
|Omega-3 fatty acids||1.1g*|
*denotes Adequate Intake (AI)
Similarly, an observational prospective cohort study published in 2019 found a fertility-promoting diet consisting of a higher intakes of supplemental folic acid, vitamins B12 and D, whole grains, dairy, soy products and seafood resulted in more positive ART outcomes, with improved odds of implantation and pregnancy.
That said, since participants in the 2019 study were undergoing ART, these supplement recommendations may not be applicable to all patients trying to achieve pregnancy. Registered dietitian nutritionists working with female patients or clients can encourage a food-first approach, including dark leafy greens, berries, whole grains, eggs, dairy products and seafood. Dietary supplements should be discussed as necessary based on individual patient needs.
Recommendations for Men
With fewer studies conducted on male fertility, more research is needed to confidently make recommendations for this population. However, a recent review found that “healthy” diets consistently improve semen quality across a range of populations.
In particular, increasing consumption of produce, seafood, poultry, whole grains and low-fat dairy products while decreasing consumption of red and processed meats, foods and beverages with added sugars, and high-fat dairy products may positively affect semen quality.
Increased seafood consumption parallels findings from a prospective observational study conducted on males attending a fertility clinic. Researchers found higher intakes of fish and lower intakes of processed meats may result in higher sperm counts and more normal sperm. Since sperm naturally contains omega-3 fatty acids from dietary intake and local metabolism, it is important for RDNs to educate male patients or clients on the role fish can play in improving fertility.
The trace mineral zinc receives widespread attention as a nutrient essential for reproductive health. The Recommended Dietary Allowance for men is 11 milligrams per day, which can be achieved through food sources including dairy, some seafood and whole grains; more research is needed on supplemental dosages.
As with women, men should focus on consuming nutrients from foods first, including fruits and vegetables, whole grains, low-fat dairy products, fish and shellfish, and always consult an RDN or physician before taking dietary supplements.
Other aspects of physical health, recreational behaviors and lifestyle can play a role in male and female fertility.
Body weight: For patients with overweight or obese BMIs, discuss dietary interventions and physical activity benefits to reduce risks associated with increased body mass and preconception health. For those with underweight BMIs, discuss the role proper nutrition can play in improving fertility and enhancing the health of their future baby.
Fitness: Discuss aiming for 150 to 300 minutes of moderate intensity activity per week with two days of strength training. The entire multidisciplinary treatment team should review individual fitness recommendations for female patients or clients undergoing ART cycles and those with (or who have a history of) low body weight, hypothalamic amenorrhea or eating disorders.
Alcohol, smoking and drug use: According to the American Society for Reproductive Medicine committee, men and women seeking improved fertility should abstain from smoking. It also is recommended to avoid alcohol or recreational drug use.
Caffeine: Female patients should consume no more than 200 milligrams of caffeine per day, roughly the amount in a 12-ounce cup of coffee. Research is inconsistent regarding male fertility and caffeine.
More research on the preconception period is needed to further identify the roles of nutrition and lifestyle habits, and specific recommendations likely will continue to evolve for both female and male fertility — as well as how to improve success rates of ART procedures.
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