1. What is vitamin D?
  • A fat-soluble vitamin made in the skin when exposed to sunlight.

  • Important for bone health, calcium balance, and immune function.

  • Also thought to have effects on the cardiovascular system because vitamin D receptors are found in blood vessels, heart muscle, and immune cells.

  1. Why the interest in heart health?
  • Low vitamin D levels have been linked in observational studies to:

    • High blood pressure

    • Diabetes and metabolic syndrome

    • Coronary artery disease

    • Heart failure

    • Increased risk of death

  • These associations raised hopes that supplementing vitamin D might protect the heart.

  1. What the big trials show
  • Large randomised trials (like VITAL and others) have tested vitamin D supplements in tens of thousands of people.

  • The results: no clear reduction in heart attacks, strokes, or major cardiovascular events from vitamin D supplements in the general population.

  • In other words, low vitamin D is probably a marker of poor health rather than a direct cause of heart disease.

  1. Where it might still matter
  • Heart failure: some smaller studies suggest vitamin D supplementation may improve heart muscle function and reduce inflammation in people with deficiency, though the evidence is not yet conclusive.

  • Hypertension: vitamin D deficiency is associated with higher blood pressure, but supplements have shown only modest or inconsistent effects.

  • Deficiency states: correcting severe deficiency (<25 nmol/L or 10 ng/mL) is important for general health and may indirectly benefit the heart.

  1. Safety
  • Normal supplementation (e.g. 800–2000 IU daily) is generally safe.

  • Very high doses can cause calcium overload, kidney stones, and vascular calcification — which may harm the heart.

💡 Summary for patients:

Vitamin D deficiency is linked with a higher risk of heart problems, but large studies show that taking vitamin D supplements doesn’t prevent heart attacks or strokes in most people. The real benefit of vitamin D is for bone and muscle health. If you’re severely deficient, correcting that may help your overall health — and possibly your heart indirectly — but vitamin D does not thus far appear to be a magic pill for the heart.

 

Here is a video I have done on this subject:

https://youtu.be/5yaI5s_3K7o