The vital nutrient you aren't getting enough of - and why you need to fix it

There is only one supplement that the NHS recommends almost everyone to take: vitamin D.

That’s because a third of us are deficient in this nutrient over winter, when British sunshine is too weak for our skin to manufacture it. Even in summer, many spend too much time indoors in an office, or covered up, for it to reach adequate levels in the body.

“It’s shocking what the average vitamin D level is,” said Professor Cathie Martin, a nutrition researcher at the John Innes Centre.

Vitamin D’s best-known benefit is to our bones because it helps the gut absorb calcium, a crucial mineral needed for the skeleton. When children become deficient, they may get rickets, with bowed legs.

But vitamin D has several other health benefits, with two pieces of research out this week adding to the list. Here’s the science behind it.