Vitamin C

Strong evidence for immune support and deficiency prevention. Megadose claims are mostly unsupported. Regular intake may modestly reduce cold duration.

A rough internal score reflecting quantity, quality, and consistency of human evidence. Not a clinical recommendation.

Cochrane reviews show regular supplementation reduces cold duration by 8% in adults. Essential for collagen synthesis, carnitine production, and neurotransmitter synthesis. Megadose IV vitamin C studied in sepsis and cancer with mixed results.

• Essential antioxidant and collagen cofactor
• Modestly reduces cold duration with regular use
• Enhances non-heme iron absorption
• Supports immune cell function

RDA is 75–90 mg. Common supplemental doses: 250–1000 mg daily. Upper limit is 2000 mg/day.

• Osmotic diarrhea at high doses
• Kidney stones in susceptible individuals
• GI discomfort

High doses (>2 g/day) increase kidney stone risk in susceptible individuals. Osmotic diarrhea at high oral doses. May interfere with certain lab tests.

Plasma saturation occurs around 200 mg/day. Doses above 400 mg/day provide diminishing absorption returns.

• Immunity65
• Recovery45
• Longevity45