Vitamin C (Ascorbic Acid)

Vitamin C (Ascorbic Acid)

Vitamin C is a water-soluble vitamin and an antioxidant. The body needs it to produce collagen, heal wounds, make carnitine and neurotransmitters, and keep the immune system working. Humans cannot make it, so we must get it from food or a supplement.

“Water-soluble” doesn’t mean you can take any amount without risk. The body regulates absorption and excretes some of the excess in the urine, and at high doses digestive side effects become more common.

How much you need per day

The upper limit for adults is 2,000 mg per day from all sources. It is not a target but the level above which the risk of side effects increases. The recommendations for children are lower and depend on age.

Dietary sources

A diet that includes fruits and vegetables every day usually meets the requirement without a supplement. Heat, water and long storage reduce the amount; steaming or brief cooking in a little water preserves it better than long boiling. Food frozen soon after harvest can be a good source, and there’s no need to eat everything raw.

Benefits and roles

• Collagen production: vitamin C is needed by the enzymes that stabilize collagen in the skin, blood vessels, bones, cartilage and tendons. Severe deficiency causes scurvy, which shows up among other things as bleeding gums, bruising and poor wound healing.
• Iron absorption: it improves the absorption of non-heme iron from plant foods. Combining legumes or tahini with pepper, tomato or citrus fruit is especially helpful for people whose iron intake is borderline.
• Antioxidant: vitamin C can neutralize oxidants and recycle vitamin E, but a biochemical result does not mean that a high-dose supplement prevents chronic disease.
• Preventing deficiency: a supplement is effective when intake is inadequate or there is an absorption problem, based on a professional assessment.

Colds: prevention or shortening

For most of the population, taking vitamin C regularly does not prevent colds. It may slightly shorten the illness or slightly reduce its severity. Starting a supplement only after symptoms appear has not shown a consistent benefit. In people exposed to extreme physical exertion and cold, such as marathon runners in harsh conditions, some studies found a lower incidence.

Vitamin C is not a treatment for flu, COVID or a bacterial infection, and a high dose is no substitute for vaccination or medical treatment.

Deficiency and risk groups

Severe deficiency is rare when there is access to a varied diet, but the risk rises with a very restricted diet, smoking, alcohol or drug dependence, malabsorption and certain diseases. Babies fed evaporated or boiled cow’s milk instead of suitable infant formula are also at risk.

Fatigue is not a specific sign of vitamin C deficiency. A diagnosis of deficiency should be based on diet, symptoms and a medical assessment, not on a single symptom.

Supplements: dose, form and side effects

Plain ascorbic acid is the most studied and cheapest form. There is no clear evidence that liposomal, “natural” or Ester-C versions give a clinical advantage for most people. A dose of 100–200 mg is well absorbed; as the dose goes up, the absorption rate goes down.

High doses can cause diarrhea, nausea and abdominal cramps. There is concern about increased urinary oxalate and kidney stones, mainly in people who are prone to them or have kidney disease, although the studies are not consistent. In hemochromatosis or iron overload conditions, boosting iron absorption can be harmful. Vitamin C may also affect certain lab tests and cancer treatments, so it’s important to report a high-dose supplement.

Practical use

• Eat at least one fruit or vegetable rich in vitamin C every day, preferably several kinds over the week.
• To improve absorption of plant iron, add a fresh source of vitamin C to the same meal.
• There’s no need to “load up” on grams before a flight, a workout or the winter. If you choose a supplement, a moderate dose is usually enough.
• Store powder and tablets in a dry, dark place. A solution or cut fruit loses vitamin C faster when exposed to air, light and heat.

Summary

Vitamin C is essential, but it is relatively easy to get from food. It is needed for collagen and improves absorption of plant iron; a regular supplement may slightly shorten colds but usually doesn’t prevent them. Megadoses give no proven advantage for most people and raise the risk of digestive side effects and of problems in certain populations.