Vitamin D’s Supporting Actors

Vitamin D Overdose: Can You Take Too Much?

If nutrition had the Oscars, vitamin D would win best actor in a leading role hands down, and with good reason, as a pro-hormone, vitamin D is a stand out when it comes to promoting health. There are an estimated 2700 vitamin D binding sites on our DNA and those binding sites are located near genes involved if nearly all know chronic diseases.

Great actors however don’t work alone and are only as good as their supporting cast. This is no less true for vitamin D; it too needs help. Nutrients act synergistically, in other words, a nutrient’s effectiveness is either enhanced or hindered depending on whether or not other needed nutrients are present in the body in sufficient amounts. Vitamin D’s main supporting nutrients, or cofactors, include minerals magnesium, zinc, and boron and vitamins A and K2, the minerals zinc, magnesium and boron.

While it’s true that most people are not getting enough vitamin D, it’s important to note that it’s not wise nor effective to simply increase your intake of vitamin D without making sure you getting enough cofactors as well; without which, vitamin D cannot play it’s part well.


The fourth most abundant mineral in the body, magnesium helps to the body to use vitamin D. Magnesium is involved in over 300 enzymatic reactions, one of which is to convert the vitamin D from food, the sun and supplements into it’s active hormone form. Regarding bone health, magnesium is absorbed onto the surface of bone tissue and directs calcium to be deposited. Without adequate magnesium, calcium ends up in the blood vessels.


Zinc is a mineral that is involved in over 200 metabolic reactions and one of its roles is to oversee the active form of vitamin D’s (1,25(OH)D3) interaction with DNA so that vitamin D can positively influence those genes that are involved in chronic diseases. Zinc also ensures that the vitamin D receptors in the intestines are active so that calcium can be absorbed and transported throughout the body.


Boron is a trace mineral that is involved in the metabolic activity of many enzymes that help with the metabolism of calcium, magnesium and vitamin D making it a critical player. Boron also participates in the mineralization of bone.

Vitamin A

Vitamin A (retinol and its other forms) is absolutely essential for health. Beta-carotene is not the same thing as preformed vitamin A and the body is much less efficient at converting beta-carotene to vitamin A than once thought. Vitamin A is an essential cofactor in the metabolism of vitamin D and vitamin A is necessary to prevent any risk of vitamin D toxicity. Vitamin A works with vitamin D to optimize calcium and phosphorus absorption in the gut and adequate amounts of vitamin A are needed to prevent excess loss from bone (or bone resorption).

Vitamin K2

There are several different forms of vitamin K. In the context of vitamin D metabolism, it’s K2 that is key. Vitamin D enhances calcium absorption, which is desirable, but we want calcium to be deposited into bone and teeth. Vitamin K2-dependent proteins help to do this. Vitamin K2 and D work together to promote proper bone formation and to maintain bone density.

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Doug Cook, RD MHSc is a Registered Dietitian Nutritionist and Diabetes Educator who uses a holistic and science-based approach to his practice.