Deficiency/Immunity/Heart

Vitamin C

Water-soluble vitamin that prevents deficiency, modestly shortens colds, and best helps adults with low produce intake.

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Quick Take

Worth it if your diet is light on fruit and vegetables or you want a small reduction in cold duration.

Vitamin C is a water-soluble vitamin found in citrus, kiwi, berries, peppers, broccoli, and potatoes. It acts as an electron donor and enzyme cofactor for collagen, carnitine, and catecholamine synthesis, while helping regenerate other antioxidants. Best-supported uses are correcting deficiency and modestly shortening common colds; smaller benefits may include slight improvements in blood pressure and vascular function. It helps most when fruit and vegetable intake is low or smoking increases needs.

Potential benefits

Corrects deficiency/scurvy

Shortens common cold duration

Lowers blood pressure modestly

May improve vascular function

Protocol

Amount

200-500 mg

Frequency

Once daily

When

Any time of day — consistency matters more than timing; take with food if you get stomach upset.

Onset Time

Days to weeks for deficiency; cold benefits require regular daily use.

Who Should Consider

Adults with low fruit and vegetable intake

Smokers or frequent secondhand smoke exposure

Older adults with limited diet variety

People who want a modest reduction in cold duration

Adults on restrictive or low-calorie diets

Food Sources

Red bell pepper (~95 mg per 1/2 cup raw)
Kiwi (~65 mg each)
Orange (~70 mg each)
Strawberries (~85 mg per cup)
Broccoli (~50 mg per 1/2 cup cooked)
Potato (~20 mg per medium potato)

How It Works

Vitamin C donates electrons to neutralize reactive oxygen species and helps regenerate oxidized vitamin E. It is also a required cofactor for enzymes that make collagen, carnitine, and norepinephrine, and it supports leukocyte migration and barrier integrity.

Updated 5/19/2026