Vitamin C
Research Reliability -
A potent antioxidant vitamin that strengthens immune defenses, supports collagen synthesis, and combats oxidative stress.
Appetite
Mood
Sleep
Vitamin C
Description
Vitamin C is one of the most well-researched nutrients in human health, serving as both a powerful antioxidant and an essential cofactor in collagen production. It enhances immune cell function, shortens the duration of illness, and helps regenerate other antioxidants like Vitamin E. Vitamin C also supports adrenal function under stress, improves iron absorption from plant sources, and promotes healthy skin and connective tissue. An essential daily staple for nearly everyone.
Effects
Same day
tissue saturation begins; supports immune load
First week
most useful during or ahead of a cold
Ongoing
steady antioxidant and collagen support
How it Feels
You generally will not feel vitamin C working. Large doses can loosen the stomach or cause mild cramping, which is your cue to lower the dose. Most people take it as insurance rather than for any felt effect.
Usage
Entry Dose
250mg
Standard Dose
500–1000mg
Max Dose
2000mg
Onset
Hours (acute immune); weeks (tissue saturation)
Combinations
Pairs well with
Synergistic
Zinc — synergistic immune support; C enhances zinc absorption
Iron bisglycinate — vitamin C dramatically increases non-heme iron absorption
Quercetin — C regenerates oxidized quercetin; mutual antioxidant recycling
Collagen — essential cofactor for collagen hydroxylation and crosslinking
Avoid combining
Contraindicated
High-dose copper — excess C competes with copper absorption at megadose levels
Chemotherapy agents — antioxidant activity may interfere with oxidative cancer treatments
Biomarkers to Track
Subjective
(Daily)
Frequency of colds or infections
Skin appearance and healing speed
Perceived energy levels (1–10)
Objective
(Quarterly)
Plasma ascorbate (vitamin C) level
hs-CRP (inflammation marker)
Iron absorption (serum ferritin)
Very safe and water-soluble, so excess is flushed out. The main issue is loose stools at high doses.
People with hemochromatosis (it boosts iron absorption) and those prone to oxalate kidney stones at very high doses.
Megadosing to the point of diarrhea and assuming more equals better once you are saturated.
Strong (human RCTs / meta-analyses)
Regular supplementation modestly shortens cold duration but does not prevent colds in the general population.
Hemila H, Chalker E (2013). Cochrane Database of Systematic Reviews. Meta-analysis (common cold). PMID: 23440782.