1. Men who drink at least a quart of cola daily have sperm counts almost 30 percent lower than men who drink no cola.
The Danish study that yielded this stat suggests that the caffeine in cola hinders sperm. “However, in a Petri dish, caffeine enhances sperm movement,” says obstetrician Niels Lauersen, co-author of Eat, Love, Get Pregnant: A Couple’s Guide to Boosting Fertility and Having a Healthy Baby. “So I would not discount the high-fructose corn syrup found in these drinks as possibly being the real culprit. First, studies show too much sugar can lead to insulin resistance, which disrupts fertility. Second, powerful pesticides used in America’s cornfields—including Atrazine—have been shown in studies to be endocrine disrupters. Male corn farmers who regularly work with Atrazine are found to have lower sperm counts.”
Tina Kold Jensen, et al. “Caffeine Intake and Semen Quality in a Population of 2,554 Young Danish Men.” American Journal of Epidemiology, 171 (8): 883-891.
2. Women who eat lots of low-fat dairy products face an 85 percent higher risk of ovulatory infertility than women who consume little or no low-fat dairy products.
Failure to ovulate is a common cause of infertility. The Harvard-affiliated study that yielded this stat found this condition strikingly high in women who consumed two or more daily servings of low-fat dairy products. Because past fertility studies on milk were inconclusive, “we compared low- and full-fat dairy products as an exercise in thoroughness,” says Jorge Chavarro, an assistant professor of medicine at Harvard University and coauthor of this study and of The Fertility Diet: Groundbreaking Research Reveals Natural Ways to Boost Ovulation and Improve Your Chances of Getting Pregnant. “These findings were extremely surprising,” Chavarro says, given that the government’s Dietary Guidelines for Americans recommend that adults consume three or more servings of low-fat dairy products daily.
J.E. Chavarro, et al. “A Prospective Study of Dairy Foods Intake and Anovulatory Infertility.” Human Reproduction, 22 (5): 1340-1347.
3. Men who eat large quantities of soy-based foods produce 32 percent less sperm per milliliter than men who consume no soy-based foods.
The Harvard-based study that yielded this stat examined the effects of 15 different soy-based foods on men whose partners were trying to become pregnant. “The very reason menopausal women find soy-based foods helpful—because they exert mild estrogenic effects—is the same reason they can be harmful to male fertility,” Lauersen says. “While including a few soy-based foods in your diet won’t affect most men, if a man’s sperm count is low, or even low-to-normal, soy foods could tip the estrogen/testosterone balance in the wrong direction and reduce sperm count further.”
J. E. Chavarro, et al. “Soy Food and Isoflavone Intake in Relation to Semen Quality Parameters Among Men from an Infertility Clinic.” Human Reproduction, 23 (11): 2584-2590.
4. Women who consume at least one daily serving of whole milk are more than 50 percent less likely to experience ovulatory infertility than are women who consume less than one serving of whole milk per week.
The same Harvard-based study that linked low-fat dairy products to one kind of infertility linked full-fat dairy products with the opposite effect: “Successively higher intakes of ice cream” show promising results, its authors write. Fat and cholesterol are building blocks for hormones, so eating full-fat dairy products while attempting to become pregnant “is sound advice,” says Alice Domar, an assistant professor of obstetrics at Harvard and author of Infertility Explained: The Complete, Authoritative Guide to Everything You Need to Know on Your Journey to Parenthood. “Is there anybody who doesn’t want to be told to eat more Häagen-Dazs?” But she warns against the sensationalism that such studies spark.
J.E. Chavarro, et al. “A Prospective Study of Dairy Foods Intake and Anovulatory Infertility.” Human Reproduction, 22 (5): 1340-1347.
5. Men who are exposed to large quantities of bisphenol-A (BPA), a chemical used in the manufacture of canned foods, have sperm counts about 23 percent lower than men with no BPA exposure.
Still crave Spaghetti-Os? When used in the linings of cans, BPA leaches into food. The University of Michigan-affiliated study that yielded this scary stat also found a 10 percent increase in sperm DNA damage among men exposed to large quantities of BPA. Widely used in many products since the 1960s, BPA is now the subject of investigations by the Food and Drug Administration as the agency seeks to calculate risks, reduce human exposure, and support the shift to alternatives.
John Meeker, et al. “Semen Quality and Sperm DNA Damage in Relation to Urinary Bisphenol A Among Men From an Infertility Clinic.” Reproductive Toxicology, 30 (4): 532-539.
6. Vegan women are only one-fifth as likely to have twins as are vegetarian and omnivorous women.
Published in the Journal of Reproductive Medicine, the study that yielded this stat suggests that the difference is driven by insulin-like growth factor (IGF), a protein released by the liver in response to growth hormone. IGF levels are much lower in vegans than in non-vegans. “Diets including dairy products, especially in areas where growth hormone is given to cattle, appear to enhance the chances of multiple pregnancies,” writes the study’s author.
Steinman, Gary. “Mechanisms of Twinning: VII. Effect of Diet and Heredity on the Human Twinning Rate.” Journal of Reproductive Medicine, 51(5): 405-10.
7. Men with high concentrations of trans-fatty acids in their semen have 96 percent fewer sperm than men with low concentrations of trans-fatty acids in their semen.
Eat donuts, shoot blanks. Trans-fatty acids are commonly found in fast food and junk food; their presence in a man’s semen proves that he ate foods containing them. The Harvard-affiliated study that yielded this stat confirmed previous rodent studies suggesting that “trans-fatty acids can affect spermatogenesis profoundly,” the authors write. High TFA in men’s drastically lower sperm counts raise stark questions, as the researchers were unable to determine the timespan over which TFA accumulates in the testes and/or how long it stays there. Potentially, it could last a lifetime.
J.E. Chavarro, et al. “Trans-Fatty Acid Levels in Sperm Are Associated With Sperm Concentration Among Men From an Infertility Clinic.” Fertility and Sterility, 95(5): 1794-1797.
8. Women who consume at least one alcoholic beverage per day have a nearly 50 percent greater risk of ovulatory infertility than women who drink no alcohol.
The Harvard-based study that yielded this stat followed 18,555 women for eight years as they attempted to become pregnant. “Alcohol hinders the liver’s ability to metabolize hormones,” says licensed acupuncturist Randine Lewis, author of The Infertility Cure: The Ancient Chinese Wellness Program for Getting Pregnant and Having Healthy Babies. “Most ovulatory infertility includes hormonal imbalances that are worsened by hepatic congestion. Hormonal excesses in the blood require a clean and healthy liver to metabolize and excrete. The body cannot rid itself of excess hormones when it is busy metabolizing alcoholic beverages.”
J.E. Chavarro, et al. “Caffeinated and Alcoholic Beverage Intake in Relation to Ovulatory Disorder Infertility.” Epidemiology, 20(3): 374-81.
9. Women who are exposed to large quantities of perfluorooctanoic acid (PFOA), a synthetic chemical used in the linings of microwave-popcorn bags, face an infertility risk ranging from 70 percent to 134 percent higher than that of women with the least amount of PFOA exposure.
Also used in candy wrappers, fast-food wrappers, and pizza boxes, PFOA has also been linked with breast and prostate cancers. The UCLA-based study that yielded this stat examined whether industrial pollutants might explain why “a remarkable decline in fertility rates has been observed in developed countries,” according to its authors, who found associations between high PFOA exposure and irregular menstrual periods, among other troubling effects.
Chunyuan Fei, et al. “Maternal Levels of Perfluorinated Chemicals and Subfecundity.” Human Reproduction, 24 (5): 1200-1205.
10. Men who eat a traditional Dutch diet have sperm counts nearly twice as high as do men who eat a fish-and-produce-based diet.
A study affiliated with Rotterdam’s Erasmus University examined the semen of men whose female partners were trying to become pregnant. One group of men ate the meat-and-potatoes-based diet that the study’s authors call “Traditional Dutch”; the other ate what the authors call a “Health-Conscious” diet high in produce and fish. The Dutch diet’s beneficial factor “might not be the meat and potatoes,” Chavarro speculates. “The Dutch diet is also very high in fatty sauces and mayonnaise, which is a strong source of omega-3 fatty acids”—which many studies link with increased fertility in both women and men.
M.Vujkovic, et al. “Associations Between Dietary Patterns and Semen Quality in Men Undergoing IVF/ICSI Treatment.” Human Reproduction, 24 (6): 1304-1312.
11. Women who eat large quantities of omega-3 fatty acids are 22 percent less likely to be diagnosed with endometriosis—a common cause of infertility—than women who eat little or no omega-3s.
“Consuming each additional 1 percent of energy from omega-3 fatty acids”—say, from mackerel, flaxseed, or supplements—“rather than from saturated, monounsaturated or omega-6 polyunsaturated fats was associated with approximately a 50 percent lower risk of endometriosis,” write the authors of the Harvard-affiliated study that yielded this stat. Powerful anti-inflammatories, omega-3s “are probably the single most important fertility nutrient,” says Lauersen, adding that omega-3s “not only can help control emdometriosis symptoms, but can also reverse some of the fertility-related damage” that endometriosis causes.
Stacey Missmer, et al. “A Prospective Study of Dietary Fat Consumption and Endometriosis Risk.” Human Reproduction, 25 (6): 1528-1535.
12. Women who consume large quantities of non-heme iron—the kind found in lentils, spinach, and supplements—have a 40 percent lower risk of ovulatory infertility than women who consume little or no non-heme iron.
“The kind of iron that is found in meats is essentially not related to fertility,” says Chavarro, who led the Harvard study that yielded this stat. “Instead, the strong association is the kind of iron that comes from either supplements or vegetable sources.” Can lentils help you get pregnant? No one knows—yet. Of the many infertility-causing conditions, ovulatory disorders are the ones that studies show respond most strongly to dietary changes, Chavarro says. Yearning to learn more, his team is soliciting participants for a huge new fertility study.
J.E. Chavarro, et al. “Iron Intake and Risk of Ovulatory Infertility.” Obstetrics & Gynecology, 108 (5): 1145-1152.
13. Women who consume at least 5 percent of their daily calories in the form of vegetable protein rather than meat protein have a 50 percent lower risk of ovulatory infertility than women who consume only meat protein.
Replacing chicken and red meat with vegetable sources of protein might reduce the risk of ovulatory infertility, write the authors of the Harvard-based study that yielded this stat. “Red meat contains arachidonic acid that can cause or worsen internal inflammatory reactions,” Lewis explains. “When the body is in a state of internal reactivity, it is in a state of ‘dis-ease,’ and has less energy available for housekeeping functions like procreation.”
J.E. Chavarro, et al. “Protein Intake and Ovulatory Infertility.” American Journal of Obstetrics and Gynecology, 198 (2): 210.
14. The sperm of men who consume very low quantities of antioxidants is only two thirds as motile as the sperm of men who consume high quantities of antioxidants.
The UC Berkeley-affiliated study that yielded this stat found that high antioxidant intake increased not only sperm motility—that is, their swimming strength—but also sperm count. While it’s tempting to think that quaffing green tea leads straight to parenthood, “I don’t think there are any foods you can eat to make you fertile, nor are there any foods you can eat to make you infertile,” Domar says. “Wouldn’t it be great if grapes made you infertile? Then we wouldn’t need birth control.” Her best advice is to “eat exactly as your grandmother told you to eat. Have meatloaf and lots of fruit and vegetables. Don’t drink soda. And take prenatal vitamins.”
B. Eskenazi, et al. “Antioxidant Intake Is Associated With Semen Quality in Healthy Men.” Human Reproduction, 20 (4): 1006-1012.
15. Men whose mothers ate beef at least seven times a week while pregnant with them are three times as likely to have low sperm counts as men whose mothers ate less beef while pregnant.
Did Mom bolt brisket? “To look at possible long-term risks from anabolic steroids and other xenobiotics in beef, we examined men’s semen quality in relation to their mothers’ self-reported beef consumption during pregnancy,” write the authors of the University of Rochester-affiliated study that yielded this stat. Their conclusion? “Sperm concentration was inversely related to mothers’ beef meals per week.” These findings “suggest that maternal beef consumption, and possibly xenobiotics in beef, may alter a man’s testicular development in utero and adversely affect his reproductive capacity,” the authors write.
S.H. Swan, et al. “Semen Quality of Fertile U.S. Males in Relation to Their Mothers’ Beef Consumption During Pregnancy.” Human Reproduction, 22 (6): 1497-1502.