Overview

Also known as the “sunshine” vitamin, Vitamin D has several functions in the body. Before I get into its many uses, lets breakdown how it is made. When the sun’s rays make contact with the skin it interacts with a form of cholesterol to form cholecalciferol. It is then transferred to the liver and converted to calcidiol. Calcidiol, from the liver, is then sent to the kidneys for it’s conversion into 125-dihydrixycholecalciferol also known as D3. When ingested, this fat soluble vitamin is absorbed through the intestinal wall with other fats and with the help of bile. In saying that, it is important to take this vitamin with food that contains fat for optimal absorption.

Fun fact: Vitamin D is actually more like a hormone than a vitamin – it is closely related, structurally, to the hormones estrogen and cortisone.

Functions

Vitamin D helps increase calcium absorption in the small intestine and decreases excretion from the kidneys.  Along with vitamin K2, it helps put minerals like calcium and phosphorus into bones and teeth. Vitamin D helps to maintain normal blood levels of calcium by regulating its metabolism, which are all important for heart and bone health. Without sufficient amounts of vitamin D and K2, you run the risk of calcium build up in the arteries and poor calcification of our bones. Vitamin D is best utilized by the body with Vitamin A. Taken together they may help with muscle spasms, asthma, arthritis, menopausal symptoms, skin problems, and many other ailments.

Now more than ever, we need all the immune support we can get. With viruses, environmental pollutants, toxins, stress, and many other factors that can impact our immune systems functionality, it is critical that we make sure we are getting enough of this vital nutrient. Research shows that vitamin D is very important for modulating the immune and inflammatory responses. It can be synthesized by immune cells like macrophages which help destroy damaged and dead cells and other harmful organisms (1).

Did you know? If Vitamin D is low, blood levels of calcium and phosphorus decrease, and the body will pull these minerals from the bones. 

Sources

Taken in a supplement form, you have a plant based and animal based option. As mentioned above, Vitamin D needs cholesterol to convert into it’s active form. Plants do not have cholesterol, but they have a similar steroid molecule called ergosterol that converts the same way as the animal based option. However, this version of vitamin D2 from plants, does not appear to have the same functions as the cholesterol-based vitamin D3. Good news for vegans is that they now have some great D3 options on the market, both plant based and synthetic. Whatever source you ultimately choose, make sure it is the D3 form.

Other sources of vitamin D can be found in fish/cod liver oil (naturally occurring). Tip: Make sure you choose a good quality fish/cod liver oil that tests for heavy metals like mercury as those levels can be high in larger fish. Butter, egg yolks, oily fish like mackerel, salmon, and liver contain small amounts as well. If you are vegan, there are now a lot of fortified plant based mylks and cereals that contain vitamin D.

Did you know? According to research from the University of Calgary, 100% of all Canadians are Vitamin D deficient during some part of the year when the sun is scarce.

Requirements

The daily recommended amount of Vitamin D is 400 - 1000 IU (International Units). The requirements vary from person to person as we factor in age, health status, etc. Because it is a fat soluble vitamin, there is a risk for toxicity. If you are taking more than the above amount or unsure what amount you should be taking, it is strongly advised to check with a practitioner.

As we can see, Vitamin D plays a major factor in our overall health. From immune system function to calcium metabolism, this nutrient is involved in almost every function in the body. Which is all the more reason to make sure that we are getting enough! See below for my top picks and CNF verified products, for your convenience – liquid and capsules options included!

1. Current perspectives on vitamin D, immune system, and chronic diseases - Maria C. Borges M.D., Lígia A. Martini Ph.D., Marcelo M. Rogero Ph.D. *