Vitamin D3

vitamins

★★★★★

Essential fat-soluble vitamin produced by the skin in response to sunlight. Widespread deficiency in the UK, especially during winter months.

Benefits

✓Bone health and calcium absorption

✓Immune system support

✓Mood regulation and mental health

✓Muscle function

✓May reduce risk of respiratory infections

Dosage

Typical Dose

1,000-4,000 IU daily

Upper Limit

10,000 IU daily (short-term)

Timing

With a fat-containing meal for best absorption

Forms & Bioavailability

Cholecalciferol (D3)

High — preferred form, same as body produces

Ergocalciferol (D2)

Lower — plant-derived, less effective at raising blood levels

Side Effects

⚠Rare at normal doses

⚠Hypercalcemia at very high doses (>10,000 IU/day long-term)

⚠Nausea, vomiting if severely overdosed

Interactions

⚡Increases calcium absorption — monitor with calcium supplements

⚡May interact with thiazide diuretics

⚡Statins may reduce vitamin D levels

Research Summary

Strong evidence for bone health and immune function. The VITAL trial (25,000 participants) showed reduced autoimmune disease risk. UK government recommends supplementation for everyone during autumn/winter.

Disclaimer: This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement, especially if you have existing health conditions or take medication.