Vitamin C: What It Does, and How Much Is Enough
Vitamin C is one of the most widely taken supplements in the world. Here is what the nutrient actually does in the body, how much adults generally need, and why very large doses are mostly wasted.
Vitamin C, or ascorbic acid, is a water-soluble nutrient the human body cannot make on its own. Unlike most animals, we have to get it from food or supplements.
What it is used for in the body
Vitamin C plays a role in several ordinary, continuous processes:
- •It is needed to make collagen, the protein that gives structure to skin, blood vessels, tendons, and gums
- •It works as an antioxidant, helping protect cells from oxidative stress
- •It supports the normal function of the immune system
- •It improves the absorption of non-heme iron, the form found in plant foods
That last point is genuinely useful in practice. Having a source of vitamin C alongside lentils, beans, or spinach helps your body take up more of the iron in them.
How much adults typically need
General reference intakes for adults sit in the region of 65 to 90 mg per day, with a commonly cited upper limit around 2000 mg. Smokers are usually advised to aim higher, as smoking increases turnover of the nutrient.
Because vitamin C is water-soluble, the body does not store it. Take considerably more than you can use and most of the excess leaves in your urine. Very large doses can also cause stomach upset and loose stools in some people.
Food first, where you can
Plenty of everyday foods are good sources, and several are inexpensive and widely available:
- •Citrus fruits such as oranges, lemons, and malta
- •Guava, which is unusually high in vitamin C
- •Amla
- •Capsicum and green chillies
- •Tomatoes, cabbage, and broccoli
Vitamin C degrades with heat and with long storage, so a fruit eaten fresh generally provides more than the same fruit boiled for a long time.
When people consider a supplement
Supplements are typically used when diet is limited, when fresh produce is hard to get consistently, or on the advice of a clinician. They are a way of covering a gap, not a replacement for eating well.
If you are taking other medication or have a history of kidney stones, it is worth checking with a pharmacist before taking high-dose vitamin C regularly.
This article is general information about nutrition, not medical advice. Food supplements are not intended to diagnose, treat, cure, or prevent any disease. If you are pregnant, breastfeeding, taking medication, or managing a health condition, speak to your doctor or pharmacist before starting a supplement.
