Poor lifestyle choices linked to obesity have been blamed for the halving of sperm counts among Australian men.
An international study published in journal Human Reproduction Update has found sperm counts have dropped by more than 50 per cent in less than 40 years among men in North America, Europe and Australia.
Australian reproductive expert Kelton Tremellen, Professor of Reproductive Medicine at Flinders University, says the paper confirms previous observations and should act as a "wake-up call" to men.
The most likely cause of this halving of sperm counts, he says, is obesity.
"Poor diet and lack of exercise, both endemic in the western world, has resulted in two-thirds of men being overweight or obese, and obesity is known to be a significant risk factor for both low testosterone levels and sperm count," Prof Kelton said.
"By maintaining a healthy weight, plus eating plenty of good foods like fish, nuts, fresh fruit and vegetables, while avoiding high-fat and sugary foods, will help maintain both a healthy sperm count and good overall health," he said.
Researchers from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai conducted meta-analysis of 185 studies between 1973 and 2011.
They found a 52.4 per cent decline in sperm concentration and a 59.3 per cent decline in total sperm count among men from North America, Europe, Australia and New Zealand, who were not selected based on their fertility status.
No significant decline was seen in South America, Asia and Africa.
The authors say the findings warrant rigorous investigation.
"Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention," said lead author Dr Hagai Levine.