What is it?
We call vitamin D a vitamin because we need it for life, but actually, it’s a hormone. Every cell in the body pays close attention to vitamin D.
So why do we call it “the sunshine vitamin”? Because just by shining onto — and into — the skin, those lovely rays awaken slumbering molecules that are just waiting to be transformed into active D.
Where is it from?
Vitamin D doesn’t actually travel at light speed through interstellar space, but the sun puts out just the right light spectrum that the human body craves — as do plants, animals, and microbes — for making active D. Before dietary supplements and food fortification provided vitamin D, it wasn’t uncommon for people, especially little kids, to experience bone pain and malformation from severe deficiency.
Besides supplements, some of the better food sources of vitamin D include cod liver oil, cod, carp, mackerel, catfish, trout, halibut, and mushrooms.
BTW, it’s estimated that at least a billion of us still don’t get enough vitamin D — especially during winter, and in those who are obese, older, darker-skinned, living at higher latitudes, have inflammation, or are pregnant or nursing.
What does it do?
Hoo boy, we’d need a whole website to explain everything that vitamin D does for us. Here are a few things worth highlighting:
- Vitamin D is one of the chief executives of immunometabolism, and works closely with vitamin A to keep the right balance of experienced immune cells at the ready.
- D status (meaning whether or not your blood levels reach the 30-60 ng/ml now recommended by some seriously well-informed experts) can impact how well you hold onto muscle over time, your risk for cardiovascular conditions, your mood and brain function, your chances of getting autoimmune or inflammatory diseases, and even how much longer you live.
- There is no substitute for vitamin D in building — and remodeling — bone throughout your life.
Each of us has a combination of genes the world has never before seen. This genetic uniqueness means that our vitamin D receptors don’t all have the same priorities in life, and they don’t all work with the same efficiency.
Because so many genes respond to D, researchers are now compiling data to figure out who is a high, medium, or low responder to food-based and sunlight-activated vitamin D, which will make personalized nutrition and sun exposure recommendations more precise. Here’s a study about a “personal vitamin D response index” for further reading.