Coffee or cannabis - what's best for dad?

Large latte, please. Research from Brazil suggests that male coffee-drinkers are more fertile. 

A study of 750 men who attended Sao Paulo University's clinic for a vasectomy found that the sperm of coffee drinkers were better swimmers and so more likely to fertilise the female's egg.

Amid the general concern about lowering male sperm counts, the issue of  a lack of so-called sperm 'motility' has attracted particuar attention. Euan Paul, of the Coffee Science Information Centre, said: 'If sperm don't swim well, they tend to be more lethargic - they give up before they reach their goal. It seems caffeine makes them swim faster, which means they will also last longer.'

The conference of the American Society for Reproductive Medicine conference in San Antonio heard less good news for dope smokers. An admittedly small study of 81 men at Buffalo University in New York found that cannabis smokers had fewer sperm and that those they did have tended to wear themselves out too by swimming too fast at first.

Lani Burkman, the senior researcher, said: 'The sperm from marijuana smokers were moving too fast, too early. The timing was all wrong. These sperm will experience burn-out before they reach the egg and would not be capable of fertilisation.'