It’s important for bone health and the immune system

The British Nutrition Foundation estimate that one in five of us are deficient in vitamin D - its main role being to regulate the amount of calcium and phosphate in the body. As a result, Public Health England guidelines say everyone aged five and above should be getting 10 micrograms of vitamin D daily.

“In the summer it’s not a problem, because you can get some vitamin D from just being outside face, backs of hands, neck, even if it’s not a sunny day, because UV rays would still get to your skin, so you’d start to make some vitamin D,” says Prof Susan Lanham-New, head of nutritional sciences at the University of Surrey and a member of The Scientific Advisory Committee on Nutrition (SACN) and the vitamin D working group.

In the winter months, food is often the only natural source. However, LanhamNew says it’s “really hard” to get enough from diet alone, as nature’s sources are pretty limited.

“You’re not going to get more than three or four micrograms, unless you really love your fish and eggs,” she explains. “A lot of breakfast cereals are fortified, but you’d have to eat quite a lot of them! The only plant source is mushrooms, either safe wild mushrooms or mushrooms that have had UV radiation.” She advises putting button mushrooms on a windowsill on a sunny day.

So even if you eat a healthy diet, you could still be deficient. “The bottom line is that people are nowhere near that 10 micrograms during the winter,” says Lanham-New. Which is why it’s advised we take a supplement from October to March.

If millions of us are unknowingly deficient in vitamin D, does that mean it’s symptomless? “No, not at all,” says LanhamNew. “When people feel really tired, have muscle ache or lethargy, these are symptoms people just associate with winter. It’s dark, it’s cold and wet, and while that might be a contributor, those are absolutely symptoms of what we would call mild osteomalacia,” which can cause bone softening over time.

“It’s the adult form of rickets; it presents itself as aches or feeling really tired.”

Secondly, vitamin D is important to the immune system, which can often be more run down in winter. “We always associate winter and the common cold with [needing] vitamin C, but actually, it can have as much to do with vitamin

“There’s data starting to come out also for diabetes risk. So what we call pancreatic beta cells, what we use to produce insulin, they need vitamin D to be at optimal working. So, of course, if you don’t have enough vitamin D, that’s going to be an issue,” says Lanham-New.

You’ll find vitamin D supplements, and multivitamins that contain vitamin D, in most major pharmacies.

For more information, visit the British Nutrition Foundation at Nutrition. org.uk.