THE global collagen market could be worth £7BILLION a year by 2023, as women – and increasingly men – battle to banish visible signs of ageing.Production of collagen, a natural protein in the body, drops as we age, leaving skin duller.And getting more can help our health as well as our looks.But with so many ways – from supplements to drinks – which is the best?Here, work pals Naomi Snelling, 42, and Claire Dison, 40, pit a collagen-boosting diet against beauty products.For two weeks, mum of two Naomi tried the collagen diet, while Claire used various lotions for suppler skin and both gave their verdicts to JULIA ETHERINGTON. NAOMI, mum to daughters Arielle, eight, and Amelie, six, followed an eating plan designed to maximise her body’s collagen levels.She says: “I have very fair skin and growing up we holidayed in the UK so used sun lotion pretty haphazardly.”I still get caught out wearing SPF15 at the beach and get burnt, which I know can contribute to ageing.”I’ve become more conscious of wrinkles since going through a divorce last year. It really affected my self-esteem, so I decided to focus on looking after myself.”I started to notice wrinkles after hitting 40…