Why is vitamin D so important?
- It helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy. A lack of vitamin D can lead to bone deformities such as rickets in children and bone pain caused by osteomalacia in adults.
- It is widely thought that vitamin D reduces the amount of 'stress hormone' cortisol within the body. Cortisol is linked to high blood pressure, in turn increasing the risk of cardiovacular disease.
- There is some evidence from small studies that vitamin D may give some protection against Covid-19.
Sources of vitamin D
The main source of vitamin D for humans is sunlight, the level of which varies over the world. Around the equator, sunlight levels are high year round. As you travel north or south, the level of sunlight varies over the year, with lowest levels in the winter season. Natural sources of vitamin in the diet are oily fish, red meat, liver and egg yolks, though these contain limited quantities.
Ethnicity
People with dark skin are especially vulnerable to vitamin D deficiency due to their high melanin levels, which inhibit vitamin D production and protect against skin cancer. The level of vulnerability varies with the amount of melanin, so those with the darkest skin are the worst affected. As more people with dark skin ethnicity move to live or work in lower sunlight areas of the world, their vitamin D levels are not enough; a finding which is supported by some research in the US. Note this research was carried out some years ago, and uses the terms "black people" and "white people".
- One study found that 97% of "black" people and 70% of white people had vitamin D deficiency.
- Another study found that "blacks" have half the vitamin D levels of white people.
- Workers on permanent might shift will spend less time in sunlight.
- In some strict Muslim areas, women are kept indoors for much of the time.
- Some cultures rate paler skins as being more beautiful; people may therefore restrict time spent in full sunlight, and/or cover most of the skin with clothing when outdoors.
Supplements
Therefore people (especially those with dark skins) in countries with big seasonal variations are advised to take supplements of the vitamin. A dose of 10 micrograms a day will be enough for most people. Taking too many supplements over a long period of time can cause too much calcium to build up in the body (hyercalcaemia) , which can weaken bones and damage kidneys and heart.
Sources: various
