Sex, drugs and rock and roll- the impact on a man’s sperm

We all know that infertility is a couples’ problem.  But did you know that male infertility accounts for up to 40% of the difficulties that couples experience. Let’s think about that for a moment. What does the man contribute to baby- making?  One sperm!  In contrast, the woman provides an egg and a womb and gives birth etc etc yet only 60% of infertility is from female causes.  That means in our twenty first century world we must be doing serious damage to our men’s sperm.  We know from Biology that sperm are very vulnerable little cells.  During their development they give up all their repair mechanisms so they can focus on just one goal- the marathon journey from ejaculation to reach the egg.  That’s about the same distance as you or me running to 40 miles and arriving in tiptop shape, able to perform the act of a lifetime- fertilizing the egg! Could you do it???!

And of course, once they get there the egg may be late! Typical female! So they may have to wait for another week to meet her, all the time using up their minimal reserves. That means that of the 500 million that started the journey maybe only 100 sperm survive to meet the egg.

Now, on top of all these unavoidable hazards we have added a few more lifestyle dangers for our sperm to combat! We have started to expose them to drugs, drink and smoke, to name but a few.


A few years ago we did some experiments in our lab; adding social and binge levels of alcohol to sperm and watching its effects on the way they swim. Well, you know how men can’t walk in a straight line with too much alcohol, neither can their sperm swim well. They swim round and round in circles! The good news is that the effect was reversible. Once we took the alcohol away, they swam normally again.  The more serious effects of chronic alcohol intake are impotence and testicular atrophy.   Too much alcohol can also reduce the number of sperm men produce and the amount of testosterone, the male hormone they secrete. The NICE guidelines report that safe limits for men are 3-4 units per day.


There are no safe levels of cigarette smoking on health. The effects of smoking are worse than the effects of alcohol on male fertility.  Back in 2004, The British Medical Association (not known for sensational comment) stated that ‘the sheer scale of smoke damage to fertility is shocking!’

120,000 men in the UK become impotent each year as a result of cigarette smoking.  And of course, as men have a cigarette in one hand they often have a drink in the other so the effects accumulate.   Sperm quality is impaired. And unlike alcohol, the damage caused by tobacco smoke is often not reparable. Smoking fathers can pass on genetic mutations to their children.   Surprisingly, the effects of fathers smoking on childhood illness are even worse than smoking mothers! So men, sorry but the message here is, for your general health’s sake – give up!

Recreational drugs


In 1998 when Viagra first arrived on the market it was aimed at older men with impotence problems. Most of these men weren’t interested in having babies so the effects of Viagra on fertility didn’t matter, but within its first fortnight on the market 6, 000 prescriptions were dispensed in the US alone. Realizing Viagra’s potential, the market widened and now anti impotence drugs are now being targeted at everyone for sexual enhancement, including women.  Our research group in Belfast has carried out a number of studies and found that Viagra speeds up the sperm.  This could be helpful to some men with slow sperm.  But it has a bad effect on another sperm function. Every sperm also has an ‘acrosomal’ cap filled with enzymes.  These enzymes help it to get inside the egg.  If they are released too early, before the sperm reaches the egg the sperm will be incapable of fertilization. Unfortunately Viagra makes them do this too.  So caution should be exercised in recreational use if couple are trying for a family.


Very few studies have been performed in this area.  Most of those cited in the literature are pre 1970; some have doubtful controls and basis technologies. Cannabis has been feared and denounced throughout history for its alleged powers to unleash uncontrollable sexual passions. In fact, there is no experimental evidence that substantiates or refutes these opinions.  Surveys from the summer of love in California 40 years ago suggest an enhanced enjoyment of sexual behaviour but it is not clear if this is specifically due to the drug or a reflection of a lifestyle of those previously using cannabis.  But old-fashioned animal studies suggest the opposite results. Male rats took longer to mount and longer to ejaculate and an inhibition of motor activity.  Maybe they are experienced decreased motivation as is typical of the drug. One point to note is that Cannabis on the streets is becoming more and more potent. The amount of active ingredient has increased about 3-4 fold.

We, in Belfast have been working on the effects of Cannabis on male fertility for some years now. Our first study, published in 2006 showed that   when sperm are exposed directly to Cannabis at recreational levels, their ability to swim and release their enzymes is damaged. It is the opposite to the effects of Viagra.   Where Viagra speeds them up, Cannabis makes sperm sluggish.  We have also investigated the effects of cannabis on sperm production. Again this has marked adverse effects and chronic use of cannabis can reduce the number of sperm produced.

So what’s the take home message to you men?

Having given you all this bad news, we also realize that going through infertility treatment can be very stressful and sometimes we need some help to relax.  The reason for this article is not to add guilt to your problems but just to make you aware of the pitfalls so you can take more control of your lifestyle and pick and choose those potential fertility enemies with care.

Know the enemy, protect our vulnerable sperm…….and create the healthy child




Direct effect of alcohol on the motility and morphology of human spermatozoa

G. P. Donnelly, N. McClure, M. S. Kennedy and S. E. M. Lewis Andrologia 31, 43-47 (1999)


Whan LB, West M, McClure N, Lewis SEM. The effects of Delta–9-Tetrahydrocannabinol, the primary psychoactive cannabinoid in marijuana, on human sperm function in vitro. Fertility and Sterility 2006 85(3):653-660.