Despite the unclear picture when it comes to the causes of male infertility, unproven solutions are being sold across social media.

Naturopath Lucas is one of the health influencers whose content includes warnings about fertility rates.

“We’re seeing a worldwide epidemic, a decrease in fertility across the board,” he tells the BBC.

But Lucas’s concern comes with some misleading claims – for example, he told his YouTube audience that men would be infertile in 33 years, which is unsupported by scientific evidence.

He sells online courses, provides 1:1 coaching, and sells supplements for men looking to increase testosterone and fertility.

His social media content, which promotes some unproven fertility protocols, has gone viral.

“I recommend to guys to apply an ice pack up against his underwear, two to three times a day for about 10 to 15 minutes,” he says, claiming clients have told him their partners have fallen pregnant after trying this.

“This is more preliminary. I do think that it’s a viable enough strategy to give it a shot,” he claims.

When questioned about the unproven nature of his advice, Lucas said he believed icing the testes was a “promising intervention” but added that he would like to see more research.

NHS guidance on low sperm count , externaldoes say tight underwear can increase the temperature of your testicles which may affect the quality of your sperm.

Lucas also advises followers and clients about healthy eating, sleep and exercise – steps which do have a strong evidence base.

Prof Jayasena recommends lifestyle changes to improve fertility.

“If there are any reversible things such as [quitting] smoking, such as [losing] weight and increasing physical activity,” he says, “that’s by far the best thing you can do.”