Evidence-based supplements for immune support

Immune claims are a graveyard of overpromises. These are the compounds with real evidence for reducing infection frequency or duration — with dosing that reflects what the trials actually used.

The short list

Frequently asked

Does vitamin D help immunity?
Yes — vitamin D deficiency is strongly associated with higher infection risk and more severe respiratory illness. Supplementation is most impactful for people with actually-low blood levels (<30 ng/mL).
Do zinc lozenges shorten colds?
Properly-dosed zinc lozenges (started within 24 hours of onset, used for 3–5 days) shorten cold duration by about a day on average. Most over-the-counter lozenges are underdosed.
Should I take vitamin C every day?
Routine high-dose vitamin C doesn't prevent colds in most people. It slightly shortens duration once you're sick. Dietary intake from food is sufficient for most adults.

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