This week we're looking at what happens when the worlds of food and beauty collide. The BBC's Emily Thomas explores how the market for nutricosmetics - foods that have claimed beauty benefits - is growing by 10% every year.

A beauty blogger in Tokyo explains why she thinks these products are already popular in Asia, particularly Japan. In China, the concept of beauty from within sits comfortably with traditional medicine. One 'beauty food' that's been consumed for thousands of years is gelatin from donkey hide. We talk to the owner of a Beijing restaurant and the customers tucking in to his donkey hotpot.

Plus, we look at the rise of ingestible beauty in the West, and the products that have failed along the way. Could the food industry turn the beauty industry on its head? One company that thinks so invites us to take a look at their laboratory where they’ve created a small chocolate bar, which they say prevents ageing and promises all the goodness of 300g of Alaskan salmon. The promises made by these products are compelling - but is there enough science to back them up? We speak to an experts from Yale University in the US and a global collagen company in Europe.

Finally, we ask whether we should expect food to be the elixir of eternal youth, or if nutricosmetics feed an unhealthy pressure to be beautiful from the inside.

(Photo: A young woman eats strawberries in 1936: Credit: Fox Photos/Getty Images)