Vitamin D: who needs it and how much

Vitamin D3 supports bones, muscle strength and immunity. In Uzbekistan it often runs low in winter and in people who get little sun.

• For prevention, usually 1000–2000 IU (25–50 mcg) a day.
• Take it with a meal containing fat for better absorption.
• Don't exceed 4000 IU a day without a doctor: vitamin D is fat-soluble and builds up.
• A 25(OH)D blood test shows the right dose; treatment doses for a real deficiency come from a doctor.

Pairing with K2 is popular but optional. With kidney stones, sarcoidosis or high calcium, see a doctor first.