Vitamin D

Vitamin D helps the body absorb calcium and supports bones, teeth and muscle function. Your skin makes most of it when exposed to sunlight, and a smaller amount comes from foods such as oily fish, egg yolks and fortified products.

Despite year-round sunshine, studies in Gulf countries report that low vitamin D is common. Reasons include spending most of the day indoors, avoiding the midday heat, clothing that covers the skin, sunscreen use and darker skin tones.

A blood test of 25-hydroxyvitamin D shows your level. Whether you need a supplement, and how much, depends on your result, age and health, so it is best decided with a clinician. Very high doses over time can cause harm, including raised calcium levels, so avoid taking large amounts on your own.