(CNN) When a couple is having trouble getting pregnant, the focus often turns to a woman's health. But just as men are equal partners in conception, they can be contributors to fertility problems, too.
"It's important to appreciate that when you have a couple challenged with infertility, in about 40% to 50% of the time, we are able to attribute the male as the primary or contributory cause," said Dr. Natan Bar-Chama, director of the Center of Male Reproductive Health at RMA of New York and a board-certified urologist and male infertility specialist.
"People assume if a couple is having a hard time getting pregnant, it's the woman's responsibility to make the changes and it's her body that's not working right, but we're learning more and more that that's not the case," added Lauren Manaker, a registered dietitian and author of "Fueling Male Fertility," a guide that provides men with simple ways they can support a couple's goal of becoming pregnant, whether they are trying naturally or undergoing assisted reproduction.
Problems that can affect male fertility include low sperm count, sperm abnormalities and low testosterone levels. Additionally, evidence suggests that recurrent miscarriage may not be related only to female factors, yet the focus continues to be on the female partner when couples experience pregnancy loss, Manaker explained.
The promising news is, various lifestyle factors have been shown to support male fertility and improve chances of conception. But this requires men to be proactive about their role in conceiving a baby.
"Men don't access health care with the same seriousness as women do," Bar-Chama said, from his experience. "Women regularly visit their ob/gyn from early on in their reproductive life cycle ... but men are often neither proactive or preventative in their approach to medical care."
What's more, Manaker added, "men don't want to talk about apples and their sperm."
According to Bar-Chama, an initial fertility evaluation, which encompasses assessing lifestyle risk factors, along with an initial semen analysis is a simple first step to determine whether a problem exists.
Lifestyle factors affecting male fertility include diet, body weight, levels of exercise, stress and use of tobacco and drugs.
"There is a growing body of solid scientific data that correlates obesity, poor nutritional status, lack of exercise, smoking and marijuana usage ... with decreased semen parameters such as sperm concentration, motility and morphology," Bar-Chama said.
Lifestyle factors may affect sperm parameters, pregnancy and miscarriage rates, but Bar-Chama says that one of the most concerning issues is alterations in sperm that can be transferred to offspring and affect their development and long-term health.
"Sperm DNA from obese or marijuana-exposed animal models and men demonstrate alterations that are transferred to the progeny and can result in increased risk for cancer, effects on behavior, birth defects and overall long-term health repercussions," he said.
"Men need to appreciate that their lifestyle behaviors may not only affect their ability to initiate a healthy pregnancy but, just as importantly, affect the future well-being of their child -- something that has clear lifelong repercussions and that should be seriously considered prior to initialing fatherhood," he added.
Obese men are more likely to experience infertility. Their obesity also appears to put them at increased risk of a nonviable pregnancy.
Male obesity hurts fertility in a variety of ways. Increased fat in the scrotum can raise testicular temperature, which negatively affects sperm parameters and fertility, explained Paula C. Brady, assistant professor of obstetrics and gynecology at the Columbia University Irving Medical Center and reproductive endocrinologist at the Columbia University Fertility Center. Obesity can also cause several changes to sex hormones and their binding proteins that hurt sperm production.
Obesity is also associated with genetic changes in sperm that affect fertilization, embryo development and pregnancy outcomes, according to Brady. "One of these genetic changes -- sperm DNA fragmentation -- is associated with pregnancy loss."
Losing weight if a man is overweight is a good start. "You clearly see an improvement in semen parameters when men lose weight, and the more weight lost, the greater the improvement," Bar-Chama said.
Manaker often recommends the Mediterranean diet, which supports healthy weight loss in men and has been associated with improved sperm quality.
"The Mediterranean diet incorporates so many foods that have independently been studied and have been shown to correlate with male fertility parameters," Manaker said. For example, the diet is high in antioxidants and omega-3s and low in saturated fats and processed foods.
Breaking down diet a bit further, below is a list of nutrients that target many of the parameters that affect male fertility. Men should start to implement lifestyle changes at least three months before conception, which is the approximate length of time of the sperm life cycle.
Consume more antioxidants. Antioxidants combat oxidative stress, which can occur from a poor diet, obesity and smoking as well as pollution, radiation and other toxins and which is a mechanism by which damage to sperm occurs, Bar-Chama explained.
"When you cause damage to cell membranes, you are impacting the ability of the sperm to attach, penetrate and activate the complex fertilization process," he said.
Oxidative stress can also damage sperm DNA, which appears to be associated with infertility, failure of fertility treatments and pregnancy loss, according to Brady.
Complicating this issue is that, unlike other cells in the body, sperm cells lack cytoplasm, where defense mechanisms against oxidative stress occur, Bar-Chama explained. This means sperm are very dependent on external sources of antioxidants, including vitamin C, vitamin E, beta carotene, zinc, selenium, folic acid, lycopene and coenzyme Q-10, which are found normally in the seminal fluid and help prevent damage to sperm cells.
To maximize antioxidants, aim to get five daily servings of fruits and vegetables that vary in color, Manaker advised. Canned tomatoes are an excellent source of lycopene, an antioxidant that has been associated with improved sperm morphology. The antioxidant selenium (found in Brazil nuts, tuna, halibut and sardines) and zinc (found in oysters, crab, dark-meat poultry and fortified cereals) are also beneficial for male fertility.
Though more studies are needed, research indicates that antioxidant supplements may improve sperm parameters, as well as outcomes of assisted reproductive therapy. According to Brady, coenzyme Q10 is a commonly used antioxidant with reasonable supporting data for its use, though optimal dosing has yet to be determined.
Incorporate at least two servings of low-mercury fatty fish per week. Fatty fish like salmon, trout, herring and sardines is rich in omega-3 fatty acids and has been associated with pregnancy success, according to Manaker.
In one study, couples who consumed eight or more servings of seafood per menstrual cycle required less time to achieve pregnancy compared with couples who ate only one or fewer servings per menstrual cycle. And couples who both consumed eight or more servings of seafood per week had even greater success, Manaker explained.
Omega-3s are a vital part of the sperm cell membrane, which is central to fertilization and fusion of the egg and sperm, Brady said.
Enjoy a daily handful of nuts -- or two. Nuts such as walnuts, almonds and hazelnuts are rich in fertility nutrients, including plant protein, omega-3s and antioxidants.
One study suggested that nuts may boost male fertility by improving sperm parameters. Although the research was industry-funded, "it was a well-designed study, and the results had statistical significance," Manaker said.
Limit or cut out processed meats, which can interfere with male fertility, according to research. On the flip side, replacing processed meats with poultry or fish may boost fertility.
Processed meats to avoid or minimize include bacon, sausage, ham, corned beef, beef jerky and salami, according to Manaker.
Limit caffeine and alcohol. If you consume caffeine, limit yourself to one or two cups of coffee per day. This amount has not been consistently associated with male infertility, according to Brady.
However, more than this amount does not bode well for fertility. "Results from many studies suggest that excessive caffeine intake has a negative influence on male fertility parameters and may lead to couples having a more difficult time becoming pregnant," Manaker said.
Limit alcohol intake to one serving per day, defined as 12 ounces of beer, 5 ounces of wine or 1.5 ounces of spirits. Excessive alcohol intake (more than two drinks per day) is associated with lower sperm quality and infertility, according to Brady.
And eliminate soft drinks. "What I found, with the research, is that sugary caffeinated beverages should be cut out," Manaker said.
Research suggests that moderate-intensity aerobic exercise can boost fertility. Resistance training has also been associated with improved markers of male reproduction and pregnancy rates.
But more exercise is not necessarily better. "Excessive exercise and endurance training have been associated with reduced sperm production and quality. And some aspects of exercising can be particularly deleterious, namely any activities that increase testicular temperature, like bicycling for five or more hours per week," Brady said.
To optimize fertility, stop any tobacco and drug use. Smoking has consistently been shown to negatively affect sperm parameters and pregnancy rates, while marijuana intake may be associated with lower sperm counts, according to Brady.
Yes, staying away from tight underwear or pants is advised, as it may elevate scrotal temperature. Manaker notes one well-designed study conducted in 2018 to get to the "bottom" of the controversy. In total, 656 men were evaluated for type of underwear worn and any correlation with sperm parameters. The results indicate that the men who wore boxer shorts had 25% higher sperm concentration and 17% higher total sperm count than men who did not wear boxer shorts.
And careful with cell phones: Manaker points out a meta analysis that found that mobile phone exposure negatively affects sperm quality. In one study, the amount of time spent talking on a cell phone correlated with reduced sperm concentrations and sperm count. Another study demonstrated a negative relationship between wireless internet use on a cell phone and sperm count.
And it may seem counterintuitive, but taking testosterone is usually harmful to male fertility by reducing intratesticular testosterone levels and sperm production, Brady explained.
Bar-Chama also cautions that exposure to heavy metals or excessive heat, like hot tubs or saunas, are modifiable factors that could affect a man's fertility. "I've had men seeking paternity who, unbeknownst to them, had elevated exposure to heavy metals -- and this was only diagnosed during their fertility evaluation and assessing their environmental and occupational risk."
Though a man changing his lifestyle may not guarantee conception, it could be the missing link that a couple needs.
"When equal efforts are made about enhancing fertility, couples appear to have an easier time getting pregnant," Manaker said. "It also sets the tone for the pregnancy -- that you are a team. You are equal partners. It starts the whole process on a nice foot."