It’s the workhorse vitamin, reinforcing your bones, bolstering your immune system and easing harmful inflammation.

The latest evidence suggests that vitamin D may reduced respiratory infections, autoimmune diseases and even your risk of dying from cancer.

The NHS suggests that between March and September, you’re probably getting plenty from the sun – but after that, you’re at risk of deficiency.

If this is severe, you could develop symptoms such as muscle weakness, fragile bones and bone pain.

Aim to take 1000 IU (international units) each day. While 600 IU is enough to avoid deficiency, a little more may help you build up your blood level of vitamin D, so you can unlock its full disease-preventing potential.

Enzymes in your skin can convert UV rays into vitamin D, but the amount generated depends on your skin colour, where you live and the time of year. So, seek it out in food. Canned salmon (716 IU in a serving) and cooked trout (648 IU) will push you towards the goal. A portobello mushroom contains 316 IU, a glass of milk has 100 and an egg has about 40.

Prioritise these foods rich in vitamin D, as they also carry other disease-preventing benefits. However, taking a supplement will ensure you hit your IU target.