For people that have difficulty conceiving, it is, of course,
an incredibly important issue. Because men produce millions of sperm cells,
you might think that they're less likely to play a role
in the couple's fertility problems, but actually that's not true at all.
Generally speaking, when you look at a population
of couples that have failed to conceive without assistance and
they've started to go down the medical route - looking at medical options,
we generally see a fairly even split of male problems vs. female problems.
And that often comes as a surprise to people because for far too long now,
we've considered fertility issues has been largely a woman's problem.
And that isn't the case.
I asked Allan to walk me through the process of how sperm are actually made.
Well, sperm are made in the testicles and the testicles hang outside the body
in a bag of skin called the scrotum.
And that is the sperm production site of males.
The average age at when a man starts to produce sperm
is at about 13 and a half years old.
It's a very early event in puberty.
We generally think that it takes about three months
to produce a sperm from start to finish.
All sorts of things can go wrong during this three month window.
So to get a clearer picture of what's affecting each man, Allan
and his team have to look closely at the samples they provide.
We look at a number of different parameters in that sample.
We look at how voluminous the semen sample is.
We like to look at how well and how fast those sperm are swimming.
We like to count the sperm so we can work out
how many sperm there are per unit volume.
And then we look at sperm size and shape - that's called sperm morphology.
The more swimming sperm you have and the better size and shape they have, the better.
So when we think about men's lifestyle factors,
we have to think about the impact that they potentially have
on all of these parameters or perhaps one of these parameters.
So if I have a beer tonight, then will that affect my sperm?
Alcohol is an interesting one.
There's a lot of literature written on this,
and sometimes the answer is a little bit contradictory,
depending on how you ask the question.
There was a recent, very large epidemiological study actually looking
at whether or not drinkers were more or less likely to have a baby.
And the answer was that there was no difference between drinkers
and non-drinkers.
So that should be broadly reassuring.
In terms of whether it makes subtle changes to sperm,
that depends on the study.
The evidence suggests that moderate drinking probably doesn't alter sperm,
but binge drinking does.
So I think the advice to anyone really is there's no reason
to give up your alcohol consumption as long as it's moderate.
Okay. And what about coffee?
Does that have an impact on sperm production?
Lots of studies have been done looking at coffee
and caffeine taken through other routes.
So caffeine is probably the worrisome thing in coffee,
but you can also get caffeine from carbonated beverages,
fizzy drinks, that kind of thing. We know interestingly,
when you add caffeine to sperm, you can make them swim,
but that doesn't mean that it has the same effect if you drink it.
[There is] a tiny hint that high caffeine drinkers probably take longer to get a baby
than people who don't take caffeine through whatever route.
But I don't think the the difference is so great for it to be a concern.
OK, so coffee and alcohol don't really seem to have much of an impact.
Are there any other aspects of lifestyle that we know do affect sperm production?
Heat is is perhaps the most obvious one because
the whole reason that the testicles are in the scrotum is to keep them cool.
So that can manifest itself in a number of ways.
So we know that men who work in hot environments are less fertile
than men who had other occupations.
In a study that I did over 10 years ago now,
we looked at the lifestyle habits
of over two and a half thousand men in the United Kingdom,
and the single biggest risk factor for poor sperm production
was wearing of tight underwear as opposed to baggy underwear.
So is, I think, a classic example of how heat can cause
fewer sperm to be produced per unit time.
And I presume, we didn't do the measurements,
but I can only presume that men who wear tight underwear
have scrotums that are hotter because they're more tightly shoved up
to the base of the pelvis and they're kept warmer throughout the day.