Sperm Count Down: What's Killing Off America's Semen?

(Aug. 11) -- Young men of America: Your semen is dying off.

That's the ongoing warning from researchers across the country, as science continues to pile new studies onto a growing heap of evidence counting against the reproductive potential of today's 20-somethings.

Obesity is the latest health woe being blamed for low sperm counts among men of child-rearing age, according to research published today. So in a bid to keep American men healthy and virile, Surge Desk offers up a handy guide on what not to do if you want to -- someday -- successfully produce an heir.

Body Fat: A Threat to Future Babies?

Maybe, at least according to a study on 2,157 young men published in this month's Fertility and Sterility.

Men with higher body mass indexes also had lower sperm counts, although still within the normal range. And BMI doesn't necessarily offer an accurate indicator of body fat levels -- although previous studies have already found a link between men's body fat distribution and poor semen quality.

BPA: A Sperm Killing Chemical?

The oft-maligned chemical compound, found in everyday plastics and blamed for a growing list of ailments, might also affect male sperm.

Just last week, a study out of the University of Michigan warned that urinary concentrations of BPA were linked to lower sperm counts. Men with the highest BPA levels had sperm counts that were 23 percent lower than those of men with the least BPA.

21st-Century Tech: For Optimal Sperm Count, Avoid It

Laptops and cell phones -- both are mainstays among most young men. But for top-notch sperm, the two might best be avoided, according to recent research.

Last year, researchers warned that the heat from laptops was a threat to the sperm health of young men and might make efforts at conception difficult.

And in 2008, a study on 361 men found a "strong association" between cell phone use and sperm count, noting that those who talked four or more hours also had fewer, and weaker, swimmers.

Soy-Lovers With Unlovable Sperm

Tofu aficionados -- not to mention the soy industry -- will be quick to tell you otherwise. But take note of a 2008 study, the largest ever in humans, that concluded that half a serving of soy a day was enough to harm a man's fertility.

"What we found was men that consume the highest amounts of soy foods in this study had a lower sperm concentration compared to those who did not consume soy foods," Dr. Jorge Chavarro of the Harvard School of Public Health told Reuters.

Men who ate the most soy had 41 million sperm per milliliter less than men who eschewed soy products.

Bud and Booze: Just Stating the Obvious

Assuming you've already done away with your cell phone, purged the fridge of tofu and started a rigorous running routine, there's still one more sperm hazard to keep it mind: recreational activities.

Pot and excessive alcohol consumption can decrease both the quantity and quality of semen. Marijuana use can also lead to sperm burnout: In a 2003 study out of Buffalo University, researchers found that men who smoked pot around 14 times a week for at least five years suffered serious fertility problems, including fatigued semen.

"The sperm from marijuana smokers were moving too fast too early," Dr. Lani Burkman, the study's lead author, told the BBC. "These sperm will experience burnout before they reach the egg and would not be capable of fertilization."