Poor lifestyle choices linked to obesity have been blamed for the halving of sperm counts among men, including New Zealanders.
An international study published in journal Human Reproduction Update has found sperm counts have dropped by more than 50 percent in less than 40 years among men in North America, Europe, Australia and New Zealand
The most likely cause of this halving of sperm counts is obesity, Kelton Tremellen Professor of Reproductive Medicine at Flinders University says.
"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."
Maintaining a healthy weight and 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 says.
Researchers found a 52.4 percent decline in sperm concentration and a 59.3 percent 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.
The study is an urgent wake-up call for researchers and health authorities around the world to investigate the cause, given the importance of sperm counts for male fertility and human health, lead author Dr Hagai Levine says.