This Misnamed Essential Can Accumulate to Dangerous Levels
To understand how to get enough vitamin D without poisoning yourself with too much, first you need to realize that this essential is not a vitamin at all. By definition, a vitamin must come from what you eat. Yet vitamin D is scarce or nonexistent in virtually all foods, unless artificially added.
Nature intended that humans manufacture their own vitamin D when certain ultraviolet rays from the sun strike skin. How do we know this? Because your skin cells have the ability to make D, and will do so whenever you allow them to. Humans thrived for eons before vitamin D supplements were available, so clearly these are not necessary for healthy life.
Vitamin D is actually a hormone, a necessary substance your body makes by itself. This essential was misnamed back in the 1920s, when researchers were first discovering vitamins. They had already named vitamins A, B, and C, so D became the mystery substance in cod liver oil that cured children with rickets. These children got rickets, a previously rare condition, because they lived in polluted cities that blocked the sun and spent their lives indoors. They did not get rickets because of a cod liver oil or other food or supplement deficiency.
To make all the vitamin D you need, store it effectively, and deliver and activate it as needed, you must keep many parts of your body healthy, including your skin, liver, kidneys, brain, and circulatory system. The process is complex and can become faulty at many points for many reasons.
The bottom line is that you need to stay healthy overall to make and use your own D the way nature intended. This assumes sufficient and the right kind of sunshine. The sun is the fuel that powers your vitamin D factory. And, as always, a whole foods, plant-based diet is the foundation of health.
D pervades your body in three forms, each one critical to its role.