Treating hair with caffeine products can stop men from going bald, according to a new German study.

Professor Peter Elsner, part of the team at the Jena University, said that the stimulant has the most effect on men whose hair roots were very sensitive to testosterone, one of the causes of hair loss.

But the research does not mean that coffee drinkers will be spared a bald head in later life, only those who smear it directly on their heads.

Adolf Klenk of Kurt Wolff cosmetic research said: "One would have to drink between 60 and 80 cups of coffee a day for the necessary amount of caffeine to reach the roots."

He said that men who are frightened that they may lose their hair should start treating their scalps with caffeine while they are still young.