Vitamin C
The body's master water-soluble antioxidant. Essential for collagen synthesis, immune function, and the regeneration of other antioxidants like vitamin E and glutathione.
Rock solid as an enzyme cofactor — without enough vitamin C, collagen synthesis fails (scurvy). Strong for shortening the duration of a cold (~10%), immune-cell function, iron absorption. Mixed evidence for preventing colds in the general population (does prevent in athletes / cold-stressed populations).
Ascorbic acid is required for collagen production (skin, blood vessels, tendons, bone matrix), immune cell function (neutrophil and T-cell activity), neurotransmitter synthesis (dopamine → norepinephrine), and the regeneration of glutathione and vitamin E from their oxidised forms. Humans are one of the few mammals that can't make our own — we have to eat it. Easy to hit RDA from food, but therapeutic uses (acute infection, post-surgery healing, heavy exercise) call for higher doses than diet typically delivers.
- Form
- Ascorbic acid is the standard form and works fine. Liposomal vitamin C for higher doses with less GI upset (significantly better absorption). Sodium ascorbate is buffered and gentler on the stomach. Ester-C is calcium ascorbate, marginally gentler. IV vitamin C delivers blood levels you can't achieve orally (used in cancer-adjunct protocols).
- Dose
- 500–1,000 mg/day for general support. 2–3 g/day during acute illness or for therapeutic effect. Up to 6–10 g/day in divided doses for heavy infection — bowel tolerance is the upper limit.
- Timing
- Anytime. Split doses for higher amounts (the body absorbs ~70–80% from a single 500mg dose, much less from larger boluses). With or without food.
- Schedule
- Daily for baseline. Pulse to high doses at first sign of illness.
- Side effects
- GI upset and loose stools above ~2 g in one dose. The kidney-stone concern is overstated for healthy adults but real for those with a history of oxalate stones.
- Interactions
- Improves non-heme iron absorption — useful normally, watch with iron-overload conditions (hemochromatosis). Can interfere with some lab tests (occult blood, glucose meters). May reduce the efficacy of some chemotherapy (debated).
- Contraindications
- Hemochromatosis (iron overload). G6PD deficiency at very high doses (hemolysis risk). History of oxalate kidney stones — keep dose moderate.
- Lab markers
- Plasma vitamin C (rarely tested — body keeps levels stable until severe deficiency). Symptoms of deficiency: bleeding gums, slow wound healing, easy bruising.
- Food sources
- Citrus (oranges, grapefruit, lemons), bell peppers (red especially — more than oranges), strawberries, kiwi, broccoli, brussels sprouts, kale, parsley, papaya, guava. Heat-sensitive — raw or lightly cooked preserves more.
Pairs with
Iron — vitamin C taken with iron-rich foods or iron supplements doubles absorption. Collagen peptides (vitamin C is the cofactor for collagen synthesis). Glutathione / NAC (network antioxidant synergy). Vitamin E (regenerates oxidised E).
within Vitamins