All About Vitamin D

What is Vitamin D?

The term “vitamin D” refers to a group of molecules that are critical for the intestinal absorption of calcium and phosphorus. Significant vitamin D deficiencies, therefore, are generally diagnosed when a patient presents with weak bones (rickets in children, osteomalacia in adults). However, more recent research shows that vitamin D is part of a wide variety of other biochemical processes — and research suggests that, for these other processes, higher vitamin D levels should be maintained than we previously believed. Check out the new research!

The Sunshine Vitamin

Vitamin D is not an actual vitamin. A vitamin is a nutrient that is required for good health and that must be obtained, in small quantities, from the diet. Though vitamin D is required – a severe vitamin D deficiency can kill – it is not a required dietary nutrient. Humans, as well as many other life forms, can synthesize vitamin D given ample sun exposure – thus its nickname, the “Sunshine Vitamin.” However, vitamin D was discovered in the hunt for a dietary explanation to a disease known as rickets, and was named before researchers realized that our skin can potentially produce far more vitamin D than a person would normally get from the diet. In fact, vitamin D is only present in a very few foods. Read more about vitamin D sources here.

Despite what seems like an unbeatable source of vitamin D in the form of sunshine, vitamin D deficiency became a huge problem in the northern industrialized world. By the turn of the 20th century, a combination of factors, including lifestyle and pollution, had turned vitamin D deficiency into an epidemic which scientists were hard-pressed to find a solution to.

Forms of Vitamin D

Vitamin D actually comes in many different forms. The two base forms which are of main importance in human nutrition are ergocalciferol (vitamin D2) and cholecalicferol (vitamin D3). Ergocalciferol is produced in large quantities via irradiation of plants and fungi and is used to fortify milk and other food products. Cholecalciferol is the form created in our skin when sufficiently irradiated, such as with ample sun exposure. Cholecalciferol is the form most animals use, too, though not usually in large enough quantities to provide us with dietary vitamin D. Read more about the differences between cholecalciferol and ergocalciferol here.

These base forms of vitamin D are then metabolized twice before reaching their most biochemically active form. For most people, it’s the second stage of vitamin D metabolism that matters the most — that’s the one assessed to establish a person’s vitamin D levels, or vitamin D blood serum levels. If you’re trying to understand your vitamin D test results or all of the research on vitamin D, it’s important to understand these stages of vitamin D.