Want stronger sperm? Consider taking up the hard hat.
Blue-collar workers with physically demanding jobs have almost 50% higher sperm counts than their white-collar office-bound counterparts, according to a new study by researchers at Harvard University and Mass General Brigham.
“We already know that exercise is associated with multiple health benefits in humans… but few studies have looked at how occupational factors can contribute to these benefits,” said reproductive epidemiologist and the study’s first author, Lidia Mínguez-Alarcón, in a news release on Tuesday.
“What these new findings suggest is that physical activity during work may also be associated with significant improvement in men’s reproductive potential,” she added.
For the study, Mínguez-Alarcón and her team at Brigham and Women’s Hospital analyzed 950 semen samples from 377 men, who were seeking fertility treatment between the years 2005 – 2019. The results, produced in collaboration with Harvard T.H. Chan School of Public Health, were published in the journal Human Reproduction.
The participants — who had an average age of 36 — were required to self-report their level of physical exertion at work and how often they lifted heavy objects while on the job.
The samples were collected at Massachusetts General Hospital Fertility Center, with a large number of respondents appearing to have swanky (and sedentary) white-collar jobs: 51% of the men had graduate degrees, while 76% described their physical exertion at work as “light.” By contrast, just 12% of participants reported having highly physical jobs, while 9% said they worked evening or rotating shifts.
Nevertheless, the latter group had significantly stronger sperm counts overall. Men who claimed to spend most of their day “lifting or moving heavy objects” had 46% higher sperm concentrations.
Meanwhile, those working evening or rotating shifts had 24% higher testosterone than men who only worked during the day.
Researchers were surprised to find that occupations associated with higher levels of testosterone also showed increased estrogen levels, leading them to believe that excess male hormone was being converted to the female hormone to keep their hormonal balance in check.
Mínguez-Alarcón noted in the report that the 377 participants were already seeking fertility treatment, meaning many of the men were already likely suffering from low sperm counts. Therefore, the results may not be entirely indicative of the general healthy population.
Indeed, numerous other studies have found that physical activity — not necessarily at work — has a positive impact on sperm count.
According to a 2013 study led by Harvard researchers, men who exercised for 15 or more hours weekly at a moderate to vigorous rate had a 73% higher sperm count than those who exercised less than 5 hours per week.
The same study found men who watched more than 20 hours of TV weekly had a 44% lower sperm count than those who watched almost no TV, suggesting a sedentary lifestyle is incredibly damaging for men trying to reproduce.
A separate study, published in 2016, found that just six months of frequent exercise can improve a man’s sperm quality.
Despite all we now know about boosting male fertility, last year the journal Human Reproduction Update reported that sperm counts globally have fallen at an alarming rate – dropping by more than 62% between 1973 and 2018.