You’ve almost certainly heard that it’s a good idea to “eat your greens” and we’re increasingly being made aware that eating other colours of fresh plant foods is a good idea too – “eat a rainbow” is today’s advice for those wanting as much benefit as possible from their daily fare.

But do you know why it’s a good idea to “eat a rainbow”?

An obvious initial reason is that to do so almost certainly means eating a wide variety of fruit and vegetables which are filling and low in calories andfa...