I have a confession to make. I was a vitamin D supplementor – someone who quietly obsessed over my Vitamin D numbers, scrutinising blood tests and popping vitamin D daily. I believed that getting my vitamin D levels to a certain number would grant me a free pass to good health. Well, my health rebels, it’s time for a little rethink.

To start with, here are a few things you may not know…

Vitamin D supplementation is a multi-billion dollar industry. With a robust CAGR (compound annual growth rate) of 8.79% between now and 2030 – sales are estimated to reach USD 7.96 billion in just four years. From tablets to gummies to plant-based alternatives, it’s no wonder this market keeps expanding as we’re all warned to stay out of the sun.

So is this explosive growth based on scientific evidence that supports vitamin D’s role in health? Or is there a fundamental misunderstanding of how vitamin D actually works in our bodies?

Today’s TL;DL (too long, didn’t listen) takes us on a vitamin D journey with Carrie Bennett, starting with the very first question: what exactly are you taking and testing for?

The Real Story Behind Vitamin D and what you’re Taking

Here’s the reality check: that vitamin D blood test you’re getting only measures ONE form of vitamin D – what they call the “storage form” or 25(OH)D. But your body actually makes DOZENS of different vitamin D metabolites when sunlight hits your skin.

Testing just one is like judging an entire orchestra by hearing only the triangle.

When you pop that D3 supplement, it can become a couple of these metabolites, but it cannot become the dozens of vitamin D compounds that natural sun exposure creates – including powerful anti-cancer metabolites that you literally cannot get from a bottle.

So what are you actually taking? A synthetic version that hits maybe 10% of what your body can naturally produce. And what are you testing for? One isolated marker that doesn’t tell you anything about the other 90% of vitamin D activity happening in your cells.

It’s like trying to understand your entire financial health by only looking at your checking account balance while ignoring your savings, investments, and assets. You’re getting a fraction of the story, but making decisions based on that incomplete picture.

Why Supplements Keep Failing Us

Here’s where it gets really interesting. When UVB light hits the cholesterol in your skin, it creates previtamin D3, which then becomes dozens of different metabolites – including powerful anti-cancer compounds that you literally CANNOT get from a bottle.

This is why all those high-dose vitamin D studies keep disappointing researchers. A three-year study in JAMA found that people taking the HIGHEST doses of vitamin D actually had MORE bone loss than those taking smaller amounts. The opposite of what they expected!

Cancer prevention studies? “Not clear” if supplementation helps. Multiple sclerosis research? No evidence that supplements reduce severity. Dementia studies? “Unclear whether vitamin D supplementation could reduce risk.”

But here’s what DOES work: people with higher sun exposure consistently show reduced rates of cancer, autoimmune diseases, and all-cause mortality.

If Not Supplements, Then What?

We don’t have to throw the vitamin D baby out with the bath water – it’s not as if we can’t get vitamin D from other sources.

Our first source of vitamin D should always be healthy sun exposure. Then food sources.

When you get vitamin D from whole food sources, you’re not getting an isolated compound – you’re getting it packaged exactly as nature intended, with all the co-factors your body needs to use it properly.

Take cod liver oil, for example. When you take cod liver oil, you get both vitamin D and vitamin A together – the way they’ve existed in nature for millions of years. Your body recognises this combination and knows exactly what to do with it.

The Exception to the Rule

Carrie mentions one scenario where short-term supplementation might help (and I would definitely agree) – acute respiratory infections or perhaps time of acute illness. There are times where vitamin D supplementation may have a place, however, I would recommend doing this under the guidance of a trusted health professional. And you could always go for the cod liver oil instead at that time too.

The Bottom Line

Your body houses vitamin D metabolites in every single cell – including water-soluble forms that never get tested. Winter “deficiency” might actually be a natural metabolic switch, working alongside increased melatonin production.

Those concerning symptoms people get from long-term high-dose supplementation – hair loss, hypothyroid-like effects, feeling worse over time? They often resolve when people stop the supplements.

In the end you need to do what’s best for you – this isn’t medical advice. But here’s what I hope you’ll consider: maybe the health benefits you’re seeking can’t be found in a pill after all. You can’t supplement the sun.