In Vol. 1, I stated that the endogenous production of vitamin D depended upon the availability of seven nutrients: B2, B6, C, E, Boron, Magnesium and Zinc. A deficiency of any of these could, therefore, lead to a deficiency of vitamin D. I also discussed in detail the deleterious effects of vitamin D supplementation on the balance between calcium and magnesium.

In the second part of the article, i’m going to explain the negative effect that vitamin D supplementation can have the levels of other essential nutrients, and how this could impact our overall health.


Vitamin D supplements appear to deplete the body of potassium. In fact, it is common to see the potassium level on a hair test disappear completely after a short period of using them. This may be because vitamin D instructs the kidneys to waste potassium [1]. In conjunction with this, it raises the serum calcium level (as discussed in Vol. 1), which drastically increases the calcium to potassium ratio on a hair test.

In Hair Tissue Mineral Analysis (HTMA), the calcium to potassium ratio is used as an indicator of thyroid function; people with a high ratio are invariably hypo-metabolic. Mark Starr wrote a book (“Hypothyroidism Type 2: The Epidemic”) in which he lists the all possible symptoms of hypothyroidism. If I remember correctly, the list was 87 pages long! Thyroid function affects everything. It’s not something you want to impair. By elevating the calcium to potassium ratio, this is a theoretical risk of vitamin D supplements.

As an aside, it’s extremely common to suffer hypothyroid symptoms while having adequate levels of thyroid hormones in the blood. In this case, cellular sensitivity to thyroid hormone is impaired, which may be due to low levels of intracellular potassium.


Much like with potassium, vitamin D supplements cause boron to completely disappear from a hair test. Unlike with potassium, i’m not sure why this is, but I am sure that it isn’t a good thing.

Boron is a cool mineral. It improves low testosterone levels, beneficially effects oestrogen levels, reduces inflammation, kills yeast, improves cognitive function and, most importantly, hugely increases the retention of calcium and magnesium, while helping to assure their deposition in the bones [2]. Countries with high levels of boron in the soil are remarkably free of arthritis. The inverse is also true. People have successfully treated this condition with boron supplements [3].

How ironic that Vitamin D, widely touted for its bone protective effects, would deplete a nutrient of such benefit to bone health.

But the irony doesn’t end there. As I mentioned in the introduction, boron is required for the body to be able to produce vitamin D. Therefore, supplementing vitamin D may actually impair your body’s ability to produce it for itself. In the light of this, it’s unsurprising that a recent review found that the purported benefits of vitamin D supplements were little more than marketing hype [4].  


Since zinc is known to be antagonised by excessive calcium [7, 8], vitamin D supplementation, by increasing the intestinal absorption of calcium, may actually contribute to a zinc deficiency.

Again, there is a sense of irony about this, as zinc is required for the expression of the vitamin D receptor [5,6], so by taking vitamin D, we may contribute a situation in which vitamin D is unable to exert its effects on our cells.

Vitamin C, Vitamin E & Hepcidin

Vitamin D supplements lower the hormone hepcidin [9], which is responsible for regulating the amount of iron in circulation. Lowering hepcidin, therefore, is likely to result in more iron entering the system than the body might have liked.

Vitamin C and Vitamin E are essential for the metabolism of iron. They help to protect iron from oxidation, make tissue stores of iron available for use, and prevent iron’s excessive accumulation in the liver. Both these vitamins are at epidemic levels of deficiency [10], which is contributing to the prevalence of iron overload & dysregulation.

Vitamin C and vitamin E are also essential for the production of vitamin D, so we may not produce enough if we are deficient in them. We will also be more likely to struggle with iron overload. If this is the case, supplementing vitamin D will accentuate the problem by lowering hepcidin, leading to more iron being absorbed, further depleting ourselves of vitamins C and E, and thereby rendering ourselves less capable of producing vitamin D internally. Have you spotted the pattern yet?!

Where does this leave us?

Firstly, I want to make it clear that I don’t think the vitamin D that our body naturally produces is bad for us. Quite the opposite. I think that producing enough vitamin D is essential. It’s only the supplements which are problematic.

We have seen numerous examples of how the supplementation of vitamin D can overwhelm our body’s ability to regulate the levels of calcium and iron in circulation. We have also seen how low levels of vitamin D can be a symptom of deeper nutrient deficiencies, and how seeking to treat the symptom rather than addressing the cause can create vicious cycles, exacerbating the underlying issue.

It has often been said that a lie repeated often enough becomes the truth. Never is this truer, than in the field of nutrition. Our beliefs about vitamin D supplements are no exception.

If you have low levels of vitamin D and are interested in addressing the root cause of this problem, or would like to optimise the levels of any of the nutrients mentioned in this article, then you can contact me via my email ( or via the contact page on my website.