The Dangers of Excess Vitamin C (COVID-19)

What this article is all about: Vitamin C is the go-to vitamin during COVID-19.  Supplement brands are going into overdrive with their marketing and Aunties on WhatsApp are sharing Vitamin C stories like there’s no tomorrow. I tell you what to watch out for with Vitamin C, especially when it comes to supplementation.

Vitamin C, also known as ascorbic acid, is arguably the king of all vitamins, given its biological properties, the number of processes it is involved in and, of course, its popularity. 

I spent quite a lot of time researching Vitamin c for my BSc Honours project in nutritional physiology 16 years ago.

I found Vitamin C so beneficial to what I was examining (the body’s absorption of the mineral Iron), that I called it a “knight in Shining Armour” in the title of my thesis (Determinants of Bioavailability in Iron Nutrition: ascorbic as a knight in shining armour).

That’s indeed a crazy title to give to a thesis!

Vitamin C, the Immune Vitamin

Vitamin C is no doubt needed by the body to maintain immune function. Various cells of the immune system need vitamin C to function.

With regard to infections by viruses, vitamin C is known to make the symptoms less severe.

However, vitamin C won’t prevent viruses from entering the body.

While Vitamin C is involved in the maintenance of normal immune function, taking more vitamin C than what your body needs does not mean a stronger immune system.

Here’s the important stuff you need to know:

  • If you are not consuming enough Vitamin C on a daily basis then your immune system is not obtaining what it needs. 
  • Ensuring an adequate daily intake of Vitamin C gives your immune system getting the nutritional support that it needs, at least with regard to Vitamin C. It needs many other nutrients, of course. 
  • Taking more than what is needed won’t “boost” your immune system further.

Vitamin C and COVID-19

Given Vitamin C’s track record in the management of cold and flu symptoms, it goes without saying that it would be tested during the present COVID-19 situation.

Vitamin C has been found effective in hospitalised COVID-19 patients in China. These patients were given Vitamin C intravenously. They received quite hefty doses of 100-200mg per kilogram of body weight per day. That’s 10-20g intravenously for a 100kg individual. 

Mind you, we are not talking about chewables, tablets or raspberry-lemonade vitamin C drink here, but a serious clinical intravenous administration under medical supervision. 

At present, it is not known whether the average oral Vitamin C supplement, will even help if you get COVID-19.

So, don’t let any supplement make reference to the Chinese study to sell you stuff.  

The dangers of excess Vitamin C

There is little evidence that megadoses of vitamin C (above 2g/ day) or any vitamin will confer any additional benefit.

As we will see below, the possibility of an overdose is real for some supplement forms (e.g. pure powders). It can make you run to the toilet.

However, there can be more severe consequences, especially in the long run.

As I reviewed in my thesis, Vitamin C does (not can or may. but does) boost the absorption of Iron in the body. An excess Iron absorption can lead to a buildup of Iron levels to dangerous levels (Iron overload).

Iron overload can lead to dysfunction of the heart, liver, and pancreas. In extreme cases, it can cause arrhythmia, heart failure, and death. The risk is higher in those who eat red meat frequently because of the iron content of these foods.

There you have it.

Must you take 1000% of the Recommended Daily Allowance?

It is time to do away with the “if a little is good then more must be better” mindset.

The same applies for any other supplement, by the way. You never know what kind of effect that nutrient excesses may be having in the body. That is why one has to be very careful when formulating and recommending supplements to others. You also need to be careful who you are taking advice from.

Indiscriminate use of supplements especially in high doses can have a myriad of effects on other body systems or medications. That’s the reason why I am not in favour of those high dose vitamin-mineral “mega-packs”.

Sure, many vitamins (especially water-soluble ones) cannot be stored in the body and need to be taken daily. However, between the time we ingest them in megadoses to the moment we “pee out” the excess you never know what they could have done to the body.  

Moderation is key! ...

What to watch out for regarding Vitamin C supplements.

I preach a food-first approach when it comes to micronutrients.  You get a lot more from food. A Vitamin C tablet may contain the Vitamin C equivalent of say 10 oranges but oranges kick the butt of the tablet in many other departments (see below).

Also, do we need 10 oranges’ worth of Vitamin C in one go?

Vitamins and minerals of orange fruit. Orange nutrition facts ...

Supplement Type A: Vitamin C pure powders

Pure powders are a cost effective way to supplement with Vitamin C. Proceed with caution when supplementing and don’t go overboard. You can easily overdose with this form. More than 2 grams can send you to the toilet as they can cause diarrhea. 

vitamin c powder

Supplement Type B: Vitamin C drinks

Vitamin C drinks are popular but aren’t cost effective at all. I have seen drinks that sell for about R14 for a single (high) dose. I can get a fairly large bag of oranges for twice that price. You see what I am saying!

Furthermore other issues with these drinks are as follows:

  • Excessive dosages: drawbacks already discussed above.
  • Sugar content: some brands are pushing their sports drinks because they contain Vitamin C. If you are training hard enough (especially during lock-down) to warrant the ingestion of sugars, you can use them. Otherwise, take the sugar content into consideration. 
  • Artificial ingredients: many of these drinks contain artificial ingredients like preservatives and artificial food dyes. I have seen drinks containing Allura Red and Brilliant Blue. These can give issues like hyperactive behaviours in susceptible kids. In the UK (not in SA), drinks containing artificial food dyes must carry a warning about this very issue. 
  • Stability: vitamin C is relative unstable in liquids. It can degrade with time, especially when exposed to light and temperature variations. 


  • Hygiene and social distancing can decrease your risk of infection with the novel coronavirus.
  • If you suspect that you have COVID-19, speak to a doctor rather than try to self medicate or take supplements.
  • Prioritise good nutrition and healthy practices (exercise, rest, sex, meditation, etc.).
  • Vitamin C supplements won’t cure COVID-19 as far as what scientists know.
  • If you catch a cold you may supplement with Vitamin C to reduce the severity of your symptoms so that people don’t look at you funny when you sneeze or blow your nose in public.
  • Choose your supplement wisely. Supplement within limits.

Thank you for your attention!

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Medical disclaimer
The information presented on this website is intended for adults 18 or over. Its aim is purely educational and does not constitute medical advice. Please consult a medical or health professional before you begin any program related to exercise, nutrition, or supplementation especially if you have a medical condition. If you consume any product mentioned on our site, you do so on your own free will, and you knowingly and voluntarily accept the risks.  © 2020. Veeraj Goyaram

About the author

Veeraj Goyaram, MSc Med (Exercise/ Nutr. Science)

My name is Veeraj Goyaram. I am a full time supplements guy and make my living in the world of nutritional supplements.

I am a nutritional product scientist by profession, meaning I create innovative nutritional supplements in the lab (food technology side) based on what I know about the human body and nutrients that affect it.

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