This article is for general information only and is not medical advice. If you think you have an infection, speak to a pharmacist or your GP.
The short answer
There is no good evidence that vitamin C treats or prevents parasite infections in people. A few laboratory and animal studies have found interesting effects, which is why the idea gets repeated online, but that research is at an early stage. Vitamin C is still an essential nutrient, and most people can get all they need from food.
What vitamin C does
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. According to the NHS, it helps to protect cells and keep them healthy, maintains healthy skin, blood vessels, bones and cartilage, and helps with wound healing. A lack of vitamin C can lead to scurvy.
Unlike most animals, humans cannot make their own vitamin C, so we have to get it from food. Good sources include:
- citrus fruit, such as oranges and orange juice
- peppers
- strawberries
- blackcurrants
- broccoli
- Brussels sprouts
- potatoes
What the research on vitamin C and parasites shows
The studies that are usually quoted fall into three groups.
- Laboratory studies. In a 2021 study, vitamin C slowed the growth of Plasmodium falciparum, the parasite that causes the most dangerous form of malaria, in infected red blood cells in the lab. Infected cells took up more vitamin C than healthy ones, which appeared to put the parasite under stress.
- Animal studies. In a study in mice infected with Trypanosoma cruzi, the parasite that causes Chagas disease, mice given vitamin C had lower parasite counts. The researchers tested it alone and alongside the standard medicine benznidazole.
- Reviews. A review of vitamin C and infection describes effects on bacteria, viruses, parasites and fungi, again based mostly on laboratory work.
These findings are worth following, but they have clear limits. Cells in a dish and infected mice are not people, the amounts used do not translate directly into supplement doses, and the parasites studied are not the ones most people in the UK are worried about. We are not aware of any good-quality human trials showing that vitamin C clears gut worms, giardia or any other parasite infection. Nobody should use it in place of treatment for malaria or any other infection.
How much vitamin C do you need?
The NHS says adults aged 19 to 64 need 40mg of vitamin C a day, and that you should be able to get this from your daily diet. Vitamin C cannot be stored in the body, so you need it in your diet every day.
Taking large amounts (more than 1,000mg a day) can cause stomach pain, diarrhoea and flatulence. These symptoms should stop once you stop taking the supplements. The NHS says taking less than 1,000mg of vitamin C supplements a day is unlikely to cause any harm.
You will often see much higher doses recommended online, sometimes based on how much vitamin C other animals make. There is no good evidence that very high doses help with parasites, and they are more likely to upset your stomach.
Vitamin C and minerals
One well-established effect of vitamin C is that it helps your body absorb iron from plant foods. Tap vitamin C on our free Mineral Interaction Wheel to see which minerals it works with.
If you think you have a parasite
Parasite infections can be tested for and treated. See a pharmacist if you have small white worms in your poo that look like pieces of thread, or extreme itching around your bottom at night. See a GP if you find a large worm or a piece of worm in your poo, have sickness, diarrhoea or stomach ache for longer than 2 weeks, or are losing weight for no reason. Tell the GP if you have travelled abroad in the last 2 years.
Related reading
- Clove, black walnut hull and wormwood: what the research says
- How long does it take to get rid of parasites?