It?s one of the most talked-about cosmetic products but what?s the evidence that collagen supplements really do slow the visible signs of the ageing process?

Listener Jo got in touch wanting to know if the collagen supplement she?s spending ?53 per month on will live up to its claim of reducing wrinkles, while promoting ?glossy hair and plump dewy skin.?

Other listeners asked whether it can help with joint aches and pains, or strengthen nails?

Greg Foot sets out to answer all these questions by speaking to a leading consultant dermatologist as well as the co-founders of two of the biggest companies selling collagen supplements, Absolute Collagen and Ingenious Beauty.

This series, we?re testing and investigating your suggested wonder-products. If you?ve seen an ad, trend or fad and wonder if there?s any evidence to back up a claim, drop us an email to sliced.bread@bbc.co.uk or you can send us a voice note to our new WhatsApp number: 07543 306807.

PRESENTER: Greg Foot PRODUCER: Simon Hoban

Government Secrecy with Matthew J. Connelly