Vitamin D isn't really a vitamin. It's a hormone. And it controls over 1,000 genes in your body — including the ones that run your immune system.

One thousand genes.

When your vitamin D is low, your immune system is running blind. T-cells, B-cells, natural killer cells — they all have vitamin D receptors. Without adequate levels, they can't activate properly.

Over 40 percent of the global population is deficient. In northern climates and among people who work indoors, it's closer to 70 percent.

Your body makes vitamin D from sunlight. But you'd need 20 to 30 minutes of midday sun on bare skin most days. For most people, that doesn't happen.

From my training in longevity science, the target is 5,000 IU of vitamin D3 daily. Not the government's minimum of 600 IU — that prevents rickets. You're not trying to prevent rickets. You're trying to optimise a hormone.

But here's what almost nobody tells you. Vitamin D increases calcium absorption. Without direction, that calcium can end up in your arteries instead of your bones.

This is where K2 comes in. Vitamin K2 — specifically MK-7 — activates osteocalcin, which directs calcium into bones. And it activates matrix GLA protein, which pulls calcium out of arteries.

200 micrograms of K2 MK-7 daily, alongside your D3. They're a pair. Taking D3 without K2 is an incomplete protocol.

Take both with food that contains fat. They're fat-soluble. No fat, poor absorption.

D3 and K2 build the foundation. But your immune system needs frontline soldiers too — and the most powerful antioxidant for that job is simpler than you think.

Ask me about Vitamin C next. The liposomal form changes everything.