However, Prof Lewis said that it was not possible to say from this current study whether the DNA damage caused by diabetes would have the same effect on mens fertility and the health of future children as DNA damage caused by other factors such as smoking.

"This is just one, relatively small study that highlights a possible concern. Further studies need to be carried out in order to understand the precise nature of the diabetes-related damage, the causal mechanisms and the clinical significance. Given the global rise in the prevalence of diabetes, it is also vital to examine the reproductive outcomes of pregnancies fathered by diabetic men, and the prevalence of diabetes amongst men attending for infertility treatment," she concluded.