Vitamin D is one of those things which, when I was at medical school (only a decade ago), no one was really talking about, but now comes up regularly in conversations with patients at my surgery.
It is important for forming and maintaining healthy bones, and therefore particularly vital in pregnant women and children. Recent research has suggested it is essential for a healthy immune system and may also be protective against certain cancers.
The problem with vitamin D is that it comes from the sunshine, a commodity sadly lacking in the UK for most of the year. Eighty per cent of it comes from UVB light on our skin. This causes a particular problem in winter when we are exposed to very little UVB radiation.
But interestingly, inhabitants of countries such as Israel and Australia, soaked in sun all year round, are also suffering deficiencies: people there are so committed to wearing sunblock, they also block the vitamin D-making rays. So we in chillier climes don’t need to feel too sorry for ourselves.
There are very few foods that contain vitamin D. Liver, oily fish and egg yolk are good natural sources. By far the best natural source is sundried mushrooms, but these are not a common sight on your average dinner plate. Mushrooms contain a precursor to vitamin D and when they are sun-dried they make large quantities of it.
For the body to produce enough vitamin D, you need to be outside between April and September, for 15 minutes three times a week with your hands, arms and face uncovered. Then you can put your sunblock on.
Vitamin D deficiency causes vague symptoms of tiredness, aches and pains, muscle pains or muscle weakness, or bone pain in the back or legs. It is easily diagnosed on a blood test.
The treatment is vitamin D supplements, which your doctor will prescribe or recommend. There are different regimes depending on how low your levels are and whether or not your calcium levels are normal.
The high-strength capsules available often contain high levels of calcium or vitamin A as well, which means they may not be appropriate for everyone (particularly if you are pregnant)
North African dishes make for a colourful Mimouna table