W hen Eva Humphries first started working as a nutritionist, she met a client who had just found out he had high blood pressure and high cholesterol, and was on the verge of type 2 diabetes. He had no idea how to change his diet or lifestyle.

The man broke down and cried for 45 minutes, leaving Humphries with “no idea of what to do”, she says. In the final 15 minutes of the session, scrambling for a quick but helpful message, she finally said: “When you look at a plate of food, can you just make half of it veg for me?”

The client came back two months later and “the colour was back in his cheeks”, she says. He told her that adding the veg had “started to [make him] feel really good”.

It’s a simple approach to eating more plants – and one we might all need to start emulating, sooner rather than later. Earlier this month, a new report found that , due to deteriorating soil quality, crops including carrots, apples and peas are now 20% to 50% less nutritious than they were in the 1960s.…