Vitamin C
A potent antioxidant that supports collagen and immune defense.
Vitamin C is essential for collagen synthesis, immune function, and iron absorption. As one of the body's primary water-soluble antioxidants, it neutralizes free radicals and regenerates vitamin E. A European Prospective Investigation into Cancer and Nutrition (EPIC) study found that a 20 umol/L increase in plasma vitamin C was associated with a 20% reduction in all-cause mortality.
How Vitamin C affects aging
Vitamin C is the required cofactor for the enzymes that cross-link collagen — the protein scaffold of skin, blood vessels, tendons, and bone, and roughly a third of all protein in the body. Collagen quality degrades with age, showing up as thinning skin, stiffer arteries, and slower wound healing; without ascorbate, the hydroxylase enzymes that stabilize collagen's triple helix simply stop. This is why early deficiency looks like accelerated aging of connective tissue: bruising, bleeding gums, and wounds that will not close.
A newer and less appreciated role is epigenetic. Vitamin C is a cofactor for TET enzymes, which demethylate DNA, and for histone demethylases — the machinery that maintains a youthful gene-expression pattern. Age-related drift in DNA methylation is the basis of epigenetic clocks, and adequate ascorbate helps this maintenance machinery run properly, particularly in stem cells. Alongside this, vitamin C is the blood's primary water-soluble antioxidant, sacrificing itself to neutralize free radicals and then regenerating oxidized vitamin E back to its active form.
The immune system concentrates vitamin C deliberately: neutrophils and lymphocytes hold it at levels 10 to 100 times higher than plasma, using it for microbial killing, cell migration, and the orderly cleanup of spent immune cells. Plasma vitamin C tends to decline with age and drops sharply during infection and inflammation, exactly when demand rises. Since immunosenescence — the aging immune system's weaker defense and higher baseline inflammation — drives much of late-life disease, keeping immune cells saturated with vitamin C is a low-cost, well-grounded intervention.
Dosage
RDA: 90mg for men, 75mg for women; smokers need 35mg more
Optimal for longevity: Researchers suggest 200-500mg daily from food sources to maintain tissue saturation.
Food first works unusually well here: two kiwis or a bell pepper clear the RDA, and 200–500mg daily from food keeps tissues saturated. Absorption is dose-dependent — at intakes above about 200mg at once, uptake efficiency falls and the excess is excreted, so splitting doses beats megadosing. Plain ascorbic acid is as effective as expensive liposomal or ester forms for raising plasma levels; buffered forms are gentler on sensitive stomachs.
Vitamin C is water-soluble and non-storable, so consistency matters more than timing; taking it with iron-rich plant meals is a bonus, since it markedly boosts non-heme iron absorption. Safety is forgiving — the tolerable upper limit is 2,000mg per day, above which diarrhea and, in predisposed people, kidney stone risk appear. Smokers need at least 35mg extra daily. Heat destroys vitamin C, so favor raw or lightly cooked sources.
Deficiency signs
~7% of the US population is vitamin C deficient; ~30% have suboptimal levels
- Easy bruising
- Slow wound healing
- Bleeding or swollen gums
- Dry, rough skin
- Frequent infections
Top food sources
What the research shows
In 19,496 adults followed for about four years, mortality in the highest plasma vitamin C quintile was roughly half that of the lowest, and each 20 µmol/L increase — achievable with about 50g more fruit and vegetables daily — was associated with about 20% lower all-cause mortality. Blood levels, which reflect food intake, predicted lifespan; the study cannot separate vitamin C itself from everything else in produce.
The essential null result: in 14,641 male physicians randomized for eight years, 500mg of synthetic vitamin C daily did not reduce major cardiovascular events at all — event rates were virtually identical to placebo. Taken together with EPIC-Norfolk, the evidence favors food-level intakes and correcting low status over high-dose pills in well-nourished people.
This review details how vitamin C supports both innate and adaptive immunity — epithelial barrier integrity, neutrophil function, and B- and T-cell development — and notes that immune cells actively concentrate it. The authors conclude that prophylactic intakes of 100–200mg daily saturate plasma and support prevention, while active infections increase demand well beyond that.
Frequently asked questions
Does vitamin C actually prevent colds?
For most people, regular vitamin C does not prevent colds, but it modestly shortens their duration and severity. The clearer exception is people under heavy physical stress — marathoners, soldiers, skiers — where regular supplementation roughly halves cold incidence. Starting vitamin C after symptoms begin shows little effect.
How much vitamin C do I need per day?
The RDA is 90mg for men and 75mg for women, but tissue saturation — the sensible target — occurs around 200mg daily from food. That is roughly a bell pepper plus a kiwi. Smokers burn through vitamin C faster and need at least 35mg more.
Is liposomal vitamin C worth the extra money?
For raising blood levels at normal doses, no — plain ascorbic acid is absorbed well and the kidney excretes any excess regardless of form. Liposomal formulations may achieve somewhat higher plasma peaks, but there is no good evidence this translates into health outcomes. Spend the difference on fruit.
Can too much vitamin C cause kidney stones?
At high supplemental doses, possibly. Vitamin C is partly metabolized to oxalate, and doses of 1,000mg or more daily have been linked to higher kidney stone risk in men with a history of stones. Food-level intakes are not a concern; staying under the 2,000mg upper limit is prudent for everyone.
Does cooking destroy vitamin C?
A good share of it, yes — vitamin C is heat-sensitive and water-soluble, so boiling can cut content by half or more, with losses into the cooking water. Steaming briefly, microwaving, or eating sources raw preserves the most. This is one reason raw peppers, citrus, kiwi, and berries anchor the top-food lists.
Track your vitamin c intake
Biohack logs vitamin c alongside 22 other longevity nutrients in every meal.