“If I had to choose a single nutrient that would help you ward off heart disease, cancer, diabetes, obesity, dementia, influenza, bacterial infections, depression, insomnia, muscle weaknesses, fibromyalgia, osteomalacia, osteoarthritis, rheumatoid arthritis, osteoporosis, psoriasis, multiple sclerosis, and hypertension, it would be vitamin D” – Dr. Michael Holick

As important as vitamin D is to your health, it is not an essential dietary vitamin. An ‘essential’ nutrient, like essential fatty acids, is a nutrient not synthesised by the body, therefore necessarily obtained from foods. Because vitamin D is synthesised by exposure to sunlight, it is not essential.

Even stranger, vitamin D is not even a true vitamin. It is a steroid hormone, also known as calciferol, manufactured in skin cells in direct action to solar radiation.

This is why it’s called the ‘sunshine’ vitamin.

Human Evolution and Vitamin D

It is generally agreed that our early ancestors first lived in equatorial Africa. Their dark skin served to protect against the intensive tropical sun. They also absorbed huge amounts of vitamin D. Man’s migration to northern latitudes caused skin pigmentation to lighten, a necessary adaptation to allow for absorption of the now-scarcer sunlight.

Vitamin D and Rickets

In today’s modern society where migration patterns have people with different skin colours living all over the world, the effects of latitude and exposure to sunlight has significant effect on vitamin D levels. This is especially true of people with dark pigmentation living in northern parts of the globe where their skin blocks the penetration of more limited sunlight, making the synthesis of vitamin D very difficult.

Evidence of the effects of this is becoming apparent. This lower production of vitamin D in African-Americans and other dark-skinned people living in northern climates is now thought a cause of higher rates of heart disease, diabetes, cancer, and hypertension.

Further evidence of the adverse effects of vitamin D deficiency was noted in Industrial Revolution times in the UK. This was a time of mass migration of populations from rural towns to large cities. While England isn’t exactly the sunshine travel destination, these new city dwellers now worked in factories (as opposed to farmers’ fields) in smoggy cities.

The British Medical Association reported in 1889 that rickets, a bone disease related to vitamin D deficiency, was widespread in industrial centres.