Other studies have also demonstrated a link between caffeine and infertility. A report published in 1998 in Reproductive Toxicology revealed that women who drank between 300 to 700 milligrams of caffeine a day suffered a 12 percent lower chance of achieving pregnancy. Drinking even more lowered the chance of conceiving by 37 percent. And in 2008, Dutch researchers announced that in their study of nearly 9,000 women with fertility issues, those who drank four or more cups of coffee, or some other kind of caffeinated drink, on a daily basis were 26 percent less likely to get pregnant. "We're relatively conservative and recommend a limit of 50 mg of caffeine a day," says Chen, "which means one 6-ounce cup of brewed coffee or two teas. Decaffeinated drinks should be okay, but the healthiest thing to drink is water, and lots of it."
Go gluten-free. "A little-known cause of infertility in both men and women is celiac disease or gluten sensitivity," says Trudy Scott, a certified nutritionist based in Rancho Cordova, Calif., and author of The Antianxiety Food Solution. Celiac disease, an autoimmune disorder triggered by a reaction to gluten, a protein found in wheat, rye, and barley, was diagnosed in over 5 percent of women suffering from unexplained fertility in an infertility clinic, says a study published in 2011 in the Journal of Reproductive Medicine. Another 2011 research report in the Journal of Obstetrics and Gynaecology Research found a greater prevalence of celiac disease in infertile couples than in couples reporting no reproductive problems.
Women with celiac disease often suffer from menstrual disorders such as secondary amenorrhea, where a woman who typically has normal menstrual cycles experiences a prolonged absence of her period. Conditions like this can lead to fewer ovulations. And men with celiac disease may have lower testosterone levels and abnormal sperm. "Gluten issues should always be considered as just one of the many factors that can contribute to infertility," says Scott.
Avoid mercury. If you're fond of fish, you might want to think about what kind you eat. In 2002, the British Journal of Obstetrics and Gynaecology published a study showing that among a group of 150 infertile couples, over a third of the men had abnormally high concentrations of mercury in their blood, while 23 percent of the women did also. The study was done in Hong Kong where consumption of seafood from polluted waters is high. "Fish can be eaten in moderation and does have health benefits, including providing omega acids, but we advise women to avoid fish at the top of the food chain such as shark, tilefish, and mackerel, [which have the highest mercury,]" says Scotchie.
Trim the fat. According to a new study published in March in Human Reproduction, among the men surveyed in a fertility clinic, those who ate the most saturated fat had 35 percent fewer sperm than men who ate the least. Saturated fat is found in foods such as processed meats, butter, and dairy. Says Jill Attaman, a fertility specialist at Darmouth-Hitchcock Medical Center in New Hampshire and lead author of the study: "The magnitude of the association between saturated fat intake and sperm concentration is quite dramatic." The good news, the study shows, is that men can improve their sperm quality by eating omega-3 fatty acids, which can be found in foods such as cold water fish, flax seeds, and nuts or supplements, says Attaman.
So what foods should both men and women trying to conceive eat? Julie Matthews, a certified nutrition consultant based in San Francisco and author of Nourishing Hope for Autism, suggests a diet containing lots of vegetables, grass-fed animal meat and milk, whole-fat milk, pastured eggs, fruits, nuts, and whole, gluten-free grains.
Chen recommends The Fertility Diet, a book that's based on a landmark Harvard collaboration on women's health known as the "Nurses' Health Study." Data from that epidemiological study has shown that fertility foods for women include vegetable proteins like beans, peas, and nuts; extra iron from plants such as spinach, tomatoes, and beets; unsaturated vegetable oils from seeds and fish like salmon and sardines; whole milk; and carbohydrates rich in fiber like whole grains and fruits. And avoid sugary drinks like soda and artificial sweeteners, says Chen.