How do protein substitutes compare with the real deal? Graihagh Jackson investigates by speaking to dietician Priya Tew, the Guardian’s Fiona Harvey and author Isabella Tree. This podcast was amended on 18 May 2019. An earlier version incorrectly claimed that vitamin B12 is also known as folate or folic acid. While folate/folic acid is also a B vitamin, it is not vitamin B12.. Help support our independent journalism at theguardian.com/sciencepod