June 1, 2014
By Sharon Palmer, RD., Speaker at the upcoming Enhancing Health with Plant-Based Nutrition Conference and Portland VegFest this September 26-28.
An estimated 10% to 15% of couples experience infertility, defined as one year of unsuccessful attempts at trying to conceive a baby. However, this is largely viewed as a “woman’s problem,” even though statistics show that male factors may be involved in one-third of infertility cases.1
A study by the Centers for Disease Control and Prevention analyzed data from the National Survey of Family Growth and found that 7.5% of all sexually experienced men reported a visit for help with fertility at some point in their lives. Of those who sought help, 18.1% were diagnosed with a male-related infertility issue, such as sperm or semen problems or varicocele (when veins in the testicles are too large, causing heat that can affect the number or shape of sperm).2
Semen quality has been on the decline over the past few decades.3 One of the latest strategies for battling male fertility is to enlist diet as a powerful ally. Fascinating research is emerging in this area, highlighting the techniques that dietitians may employ to help counsel men on preconception nutrition.
Nutrition and pregnancy expert Bridget Swinney, MS, RD, LD, author of Eating Expectantly, says, “I think people first think of the physical causes of male fertility rather than something simple like diet. Everyone I speak to on this topic is very surprised that a dad’s diet could really improve or hamper the likelihood of conception.”
Indeed, many RDs aren't aware of the importance of discussing a father-to-be’s diet to boost his chances for conception. However, fertility researchers agree it should be discussed. When consulting with hopeful mothers about the optimal preconception diet, it may be appropriate to bring in the male partner for a group consultation.
“There’s hope though, as talk about fertility hits pop culture,” Swinney says. She cites a recent episode of the television program Mike and Molly, in which the lead characters are thinking about getting pregnant. “Molly is shown skipping alcohol and going for a green smoothie instead, and Mike is hitting the home gym to get in shape. In that episode, we didn’t see Mike making any dietary changes, but hopefully that’s coming too,” she says.
Male Reproduction 101
To understand how nutrition can impact male fertility, it’s important to get back to the basics of the male reproductive system, which is designed to manufacture, store, and transport sperm—the microscopic genetic cells that fertilize a woman’s ovum. Sperm production begins when immature cells grow and develop in tubules inside the testicles. The sperm are carried out of the body through seminal vesicles via semen, a fluid composed of secretions from glands such as the prostate.1
To transport functional sperm, several specific events must occur in the male reproductive tract in perfect sequence. There are many things that can go wrong along the way, which can prevent the cells from maturing into sperm that can reach the woman’s fallopian tube to fertilize the ovum. These problems can include a diminished output of sperm by the testicles, abnormal sperm production, and structural abnormalities. Many factors can influence sperm problems, such as genetics, hormone imbalances, past childhood diseases, environment, physiology, and lifestyle—and this is where diet comes in.1
Diet and Conception
Throughout history, food has been linked to successful human reproduction. While we know that diet and nutrients are important for maternal conception, we don’t know as much about the role nutrition plays in paternal reproduction. However, the research world is beginning to show how diet can impact male fertility, according to Jorge Chavarro, SCD, MD, ScM, an assistant professor of nutrition and epidemiology at Harvard School of Public Health, who performs research in this area. “We’re starting to scratch the surface on diet and male fertility; in a few years we’ll have much more solid evidence,” adds Chavarro, who reports that several new scientific papers will be published in the coming months on diet and male fertility.
“A growing number of studies in rodents and other model organisms are showing that paternal diet at the time he produces offspring can affect his offspring’s health,” says Wendie A. Robbins, PhD, RN, FAAN, a professor and the Audrienne H. Moseley endowed chair at UCLA. “For example, a low-protein paternal diet changes lipid and cholesterol metabolism in his offspring; a high-fat paternal diet leads to beta-cell dysfunction in daughters; and paternal obesity has been shown to affect embryo development, pregnancy outcome, and body fat in offspring. Our lab had been focusing on factors such as smoking, pesticides, and air pollution that can damage sperm DNA, causing poor health in the offspring of exposed fathers. We thought about taking research in a different direction. We wondered what we could do to improve the quality of sperm at the time of conception. Just like women change their diets before conception, maybe men should, too.”
Studies have confirmed that environmental concerns, such as pesticides, exogenous estrogens, and heavy metals, negatively impact spermatogenesis.4 “Men should be particularly cautious in the child-bearing years about handling chemicals and also to be careful of environmental chemicals they come into contact with, like cleaning, body care products, air fresheners, and plastics that come into contact with food,” Swinney warns.
But how can diet boost the chances of paternity? “There are several mechanisms involved,” Chavarro explains. “Oxidation is the most obvious, but there are other things going on. Sperm production is essentially very fast cell division. If you think of the nutrients that support cell division, they’re probably good targets for looking at semen quality. This can include folic acid and other nutrients involved in the metabolism of methyl donors, such as vitamins B6 and B12, given their involvement in DNA production and DNA methylation. Another area is dietary factors that impact the structure of sperm. The sperm membrane has a fatty acid composition different than other cells—it has a much higher concentration of polyunsaturated fatty acids [PUFAs] than other cells. So it may be important to look at factors involving fatty acid metabolism.”
Diet Patterns Make a Difference
According to US fertility researchers, dietary patterns may play a role in male fertility. The typical American diet has changed drastically over the past 50 years. Compared with diets in the 1950s, the typical US diet features higher intakes of total calories, meat, cheese, added fats, refined grains, and added sugars, which reflects a poorer diet quality.3,5
In the Rochester Young Men’s Study, a cross-sectional study from 2009 to 2010 at the University of Rochester, a total of 188 male subjects aged 18 to 22 were recruited on college campuses in the Rochester area. Both their diets and semen were analyzed. Two dietary patterns were identified: the Western pattern, which was characterized by high intakes of red and processed meat, refined grains, pizza, snacks, high-energy drinks, and sweets; and the Prudent pattern, which featured high intakes of fish, chicken, fruits, vegetables, legumes, and whole grains. Men in the highest quartile of the Prudent diet had an 11.3% higher “percent of progressively motile sperm” (measure of semen quality that evaluates sperm motility) compared with men in the lowest quartile.3
Body Weight Counts
“Body weight is probably the most solid area of research for diet and male fertility,” Chavarro says. “Many studies have been published looking at semen quality and BMI. It’s pretty convincing that both underweight and overweight or obesity is linked with low semen quality.”
The trend of lowered male fertility has coincided with the increase in the prevalence of overweight and obesity. Many factors may explain the relationship between overweight and poor sperm parameters, which includes alterations in hormones, such as decreased testosterone, increased estradiol, and elevated endorphins that can impact sperm production; hyperinsulinemia, which may mediate a decrease in sex hormone-binding globulin in obese men; a rise in scrotal temperature caused by fat tissue accumulation; and an increased accumulation of toxic substances in fatty tissue.6
An international team of researchers, which included Chavarro, performed a systematic review of studies on body weight and male fertility. A total of 21 studies were included in the meta-analysis, resulting in a sample of 13,077 men from the general population and fertility clinics. Compared with men of normal weight, the odds ratio for oligozoospermia (a low concentration of sperm in semen) and azoospermia (no sperm present in semen) was 1.15 for underweight, 1.11 for overweight, 1.28 for obese, and 2.04 for morbidly obese men.6
Dietary Fat Factors in Fertility
“There’s a broad base of literature that shows how fatty acid profiles change in spermatozoa over their maturation,” Robbins says. “The fatty acids are very important, in particular PUFAs. They’re necessary for membrane fluidity and flexibility.” Moreover, saturated and trans fats have been linked with decreased sperm quality, Chavarro says.
A study in Iran investigated omega-3 fatty acid levels in blood and spermatozoa in 78 fertile and 82 infertile men. The researchers found that proven fertile men had higher blood and spermatozoa levels of omega-3 fatty acids compared with infertile men. The ratio of serum omega-6 to omega-3 fatty acids was significantly higher in infertile men, and levels of arachadonic acid were higher and the omega-3 index (EPA and DHA) was lower in infertile men compared with fertile controls.7
This research led Robbins to select walnuts as an ideal food to study because they’re rich in omega-3 fatty acids as well as folate and selenium—nutrients that have been associated with sperm quality. Robbins’ team performed a randomized controlled trial, enrolling 117 healthy men aged 21 to 35 on the UCLA campus who ate a Western diet. The men were randomized to either continue eating their usual diet or to add 75 g of walnuts per day to their usual diet. During the course of the 12-week study, which captured one cycle of spermatogenesis, the scientists collected a 24-hour food recall every two weeks, and at the conclusion performed a diet history and physical assessment, and gathered blood and semen specimens.5
“The subjects were all nonsmokers, so there was no reason to believe they had fertility problems,” Robbins explains. “We wanted to test intervention in a healthy group to begin with. This was the first study like this looking at male reproductive outcomes. We found improved semen parameters, including improvement in sperm vitality [the number alive]; morphology [shape provides better motility as abnormal shape suggests problems with the cell]; and sperm motility. The men that had lowest motility at baseline showed improvement, and we also saw a decrease in sperm aneuploidy [chromosomal abnormalities] in the walnut group. It’s encouraging because all they did was add one thing, which had different avenues to improve the cell through fatty acids, selenium, and folate.”5
Micronutrients and Antioxidants
Certain micronutrients, such as folic acid, selenium, zinc, and vitamins C and E, also have been linked with sperm quality.5 For example, researchers in the Netherlands found that total normal sperm count increased after combined zinc sulfate and folic acid treatment in both subfertile and fertile men.8 And a dietary and supplement intake of zinc, folate, beta carotene, and vitamins C and E was associated with improved semen quality in men.9 Although these nutrients may possess various functions in the development of sperm, recent attention has been drawn to the antioxidant activity of many micronutrients.
Chavarro says antioxidants may be a promising area in infertility, adding, “Sperm are very susceptible to oxidative damage, which is suggestive that antioxidants may benefit sperm quality.”
“Oxidative stress can affect many parameters of male fertility, including sperm motility, sperm number, and DNA damage,” Swinney says. “We tend to think of vitamin C and vitamin E as antioxidants, but zinc, folic acid, copper, and selenium have antioxidant properties as well. The best way to get this variety of nutrients is to eat a healthful diet containing a variety of protein sources, whole grains, nuts, fruits, and veggies.”
Studies also have examined the benefits of supplemental carnitine, arginine, vitamin E, glutathione, and coenzyme Q10; however, additional research in this area is needed to confirm results.4
Putting a Male Fertility Diet Into Practice
Diet may be a rich opportunity for health care professionals to provide intervention, considering that some risk factors for fertility problems, such as structural abnormalities, can’t be reversed. “I think that in the fertility and diet field there are specific nutrients that seem to be promising, though the mechanism behind all of this needs research,” Robbins says. “There’s enough [research] that we can say that diet can have an impact. Diet is the strongest thing for improving sperm quality that I’ve seen so far.”
So what diet should RDs advise future fathers to consume? “Men should get their body ready for pregnancy too by getting closer to ideal body weight,” Swinney advises. “Men should follow MyPlate and fill half their plate with fruits and veggies, emphasizing those rich in vitamin C. Fruits and vegetables are great sources of vitamin C, carotenoids, and other phytochemicals, which may enhance fertility. Following a heart-healthy diet that contains moderate fat, limited saturated fat, and some omega-3s can positively affect fertility.”
David Grotto, RD, LDN, author of The Best Things You Can Eat, recommends that men boost fiber-rich carbs, folate, antioxidants such as vitamin C and lycopene, and zinc-rich foods, such as oysters, crab, pork, beef, chicken, and turkey, to help sperm and testosterone production.
Robbins offers another consideration: The foods and dietary patterns that show promise for improved fertility—omega-3–rich foods, fruits, vegetables, essential micronutrients, healthy fats, and prudent diet patterns—also are those we recommend for better health and disease risk reduction. The diet that’s good for conception also is the same diet that’s good for helping ensure that the father is around to raise his children, too.
1. Male infertility: management. Urology Care Foundation website. http://www.urologyhealth.org/urology/index.cfm?article=29. Accessed March 18, 2013.
2. Anderson JE, Farr SL, Jamieson DJ, Warner L, Macaluso M. Infertility services reported by men in the United States: national survey data. Fertil Steril. 2009;91(6):2466-2470.
3. Gaskins AJ, Colaci DS, Mendiola J, Swan SH, Chavarro JE. Dietary patterns and semen quality in young men. Hum Reprod. 2012; 27(10):2899-2907.
4. Sinclair S. Male infertility: nutritional and environmental considerations. Altern Med Rev. 2000;5(1):28-38.
5. Robbins WA, Xun L, FitzGerald LZ, Esguerra S, Henning SM, Carpenter CL. Walnuts improve semen quality in men consuming a Western-style diet: randomized control dietary intervention trial. Biol Reprod. 2012;87(4):101.
6. Sermondade N, Faure C, Fezeu, L, et al. BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis. Hum Reprod Update. 2013;19(3):221-231.
7. Safarinejad MR, Hosseini SY, Dadkhah F, Asgari MA. Relationship of omega-3 and omega-6 fatty acids with semen characteristics, and anti-oxidant status of seminal plasma: a comparison between fertile and infertile men. Clin Nutr. 2010;29(1):100-105.
8. Wong WY, Merkus HM, Thomas CM, Menkveld R, Zielhuis GA, Steegers-Theunissen RP. Effects of folic acid and zinc sulfate on male factor subfertility: a double-blind, randomized, placebo-controlled trial. Fertil Steril. 2002;77(3):491-498.
9. Eskenazi B, Kidd SA, Marks AR, Sloter E, Block G, Wyrobek AJ. Antioxidant intake is associated with semen quality in healthy men. Hum Reprod. 2005;20(4):1006-1012.
This article was reprinted with kind permission from Sharon Palmer, RD and Today's Dietitian.