Winter is a good time to talk about vitamin D. In fact, it’s been precisely one year since we wrote a blog saying as much.

At no other time are blocked noses, hacking coughs, sneezing fits and sore throats quite so ubiquitous.

You may wonder how vitamin D ties into this roll call of seasonal symptoms, and if so, it’ll probably shock you to learn that vitamin D deficiency is at the very root of them.