Is Vitamin C REALLY effective against 'Colds'?

Updated: Mar 11, 2020

A common belief is that vitamin C (supplementation) can prevent you from getting a cold and, if you do contract a cold, vitamin C (supplementation) can make you recover quicker.

This article will explore if there is any truth to these claims.

Vitamin C, in respect to preventing and treating the common cold, has actually been a subject of controversy for over 70 years. (1)

In order to find out the truth, the following topics will be discussed:

  • What is vitamin C?

  • Is therapeutic vitamin C (supplementation) effective? In other words, does taking vitamin C, when symptoms first arise, shorten the duration of a cold?

  • Can vitamin C (supplementation) prevent a cold from occurring?

  • Are there risks to vitamin C supplementation?

  • Foods with the highest concentrations of vitamin C

What is vitamin C?

As we've discussed in The Best Ways to Protect Yourself Against Virus Infections Part 2, vitamins are essential nutrients that your body requires to perform various processes in the body. You need sufficient vitamins and minerals to keep a healthy immune system among others. (2), (3)

What about vitamin C?

For most of us, this vitamin comes to mind first when it comes to warding off colds and keeping a healthy immune system.

How does it impact our health defense system?

Vitamin C is known as an antioxidant that protects the body from free radical damage.

Free radicals are formed internally (in the body) due to natural processes.

Pollutants and toxins contribute as external sources.

Free radicals can cause damage to our cells. (4), (5), (6)

And we need our cells to let our bodies function properly. Therefore we need a constant supply of things that can stabilize the free radicals and offer protection to cells. (7) Unless of course, we enter some kind of android era, where we will become part machine.

One of these protectors is vitamin C.

Until we become androids, we need a constant supply of antioxidants, like vitamin C.

Vitamin C protects the immune system, reduces the severity of allergic reactions and helps to fight off infections.

The body further requires vitamin C for normal physiological functions. It helps in the synthesis or metabolism of other vitamins, minerals, amino acids and cholesterol.

When you aren't getting enough vitamin C, your immune system will obviously be affected.

That's not all though. Deficiency of this vitamin is often associated with anemia, infections, bleeding gums, poor wound healing and last but not least, scurvy. (8)

The term 'scurvy' is used for the disease resulting from prolonged vitamin C deficiency. It was a common problem in the world's navies, due to the lack of fresh produce on board, and is estimated to have affected 2 million sailors!

Symptoms of scurvy include loosening of the teeth, poor wound healing, emotional changes and depression and scurvy eventually leads to death. (9)

In 1747, James Lind conducted a trial of six different treatments for 12 sailors with scurvy: only oranges and lemons were effective in treating scurvy. (10)

Most of us are well aware that citrus fruits are a good source of vitamin C, so not surprising that those sailors recovered by eating citrus fruits.

Is therapeutic vitamin C effective?

In other words, does taking vitamin C, when symptoms of a cold first arise, speed up your recovery?

When you are getting your first symptoms of a cold and start taking vitamin C trying to treat your cold, it can be seen as 'therapy'. That's why we are speaking about therapeutic vitamin C.

The biggest review to date, that looked at all the studies done on vitamin C in relation to colds, looked at the efficiency of therapeutic vitamin C.

Therapeutic doses of 1.5 to 4 g/day of vitamin C, given after cold symptoms appeared, did NOT influence recovery time, but for some reason there was a 12% decrease in people missing out on work or staying indoors. (11)

This is quite a high dose of vitamin C, hard to get with food alone, unless you stuff yourself with bell peppers three meals a day.

Most advisory organs worldwide advise a maximum intake of 2 g of vitamin C per day.

Compare that to the recommended intake of anywhere from 40 - 110 mg. (12)

Now, the recommendations are on the low side and are basically in place to prevent you from getting scurvy.

Although that's awfully considerate, research has previously shown that 200 mg may be a more ideal number for the average person, because below 200 mg the body can still utilize vitamin C. (12)

Vitamin C still has protective properties to share with you, if you go above the recommended intake. Smokers and lactating women always have a slightly higher requirement, so they would need to take a little more. (12)

Also, we haven't mentioned people that have reduced absorption of vitamin C in the gut due to stress, alcohol intake, fever or other viral illnesses, usage of antibiotics (vastly underrated in my experience), pain killers, heavy metals toxicity and so on. (8)

Looking at the whole picture, that recommended intake seems therefore far from an ideal intake.

A higher therapeutic dose may still work

In a SINGLE study done among adults, a one-time therapeutic dose of 8 g of vitamin C administered on the first day cold symptoms appeared, seemed to have the ability to shorten the duration of the cold by 19%. (11) That's like being sick for 4 days, instead of 5. That may seem worth the trouble.

And it only took the amount of vitamin C found in about 420 kg of beef liver, 90 kg of white potatoes, 9 kg of broccoli, 125 green kiwis, 80 large oranges, 61 golden kiwis, 50 red bell peppers OR 24 large yellow bell peppers.

As you can see that dosage is slightly high, even for competitive eaters.

In addition, it has only been studied a single time. Whether it will work for a large group of people isn't clear at this stage.

Further down we will see if there are any risks involved with large doses of

vitamin C.

Can vitamin C supplementation prevent a cold from occurring?

The same review that looked at therapeutic intake of vitamin C also looked if vitamin C could prevent colds from happening in the first place, if people were already on a daily regime of vitamin C. They also looked at how well people recovered in case they managed to get a cold anyway.

Regular vitamin C intake did NOT change how often one got a cold, but it did do something else.

Adults and children, who regularly took at least 1 g of vitamin C daily, reduced their total time indoors, off work and off school by 13,6% on average and their symptoms were 12,8% less severe on average. (11)

That doesn't say exactly how fast they recovered completely.

How fast did they recover exactly?

Adults, who already got a cold and who took a minimum of 1 g of vitamin C daily recovered on average 8% faster, which was about 0,4 days.

Children, who already got a cold and who took a minimum of 1 g daily recovered faster as well. They recovered 18% faster on average, which was about 1 day. (11)

Vitamin C probably will have 0% effect though, on children who pretend to be sick.

That goes for adults too, who want to skip out on work.

You can't expect vitamin C to have it all.

Despite the results of the studies, the authors don't feel that regular supplementation for the general public is justified, because of the diversity of the studies themselves, which makes it more difficult to properly analyze the findings. What it does say, is that it might work for some people. (11)

The people who seem to benefit most though are the ones who do intense physical exercise.

They had about 50% less chance of getting a cold. (11)

If you remember from The Best Ways to Protect Yourself Against Virus Infections Part 1, very intense exercise may make you more susceptible for getting a cold, so the reduced risk makes sense in this context.

Children may benefit more than adults, but most of the studies were done on adults, so it's hard to say if the benefits will transfer over to the average child.

Are there risks to vitamin C supplementation?

A common belief that still persists to this day is that you simply pee out all the excess vitamin C your body can't use. Therefore, there is no such thing as taking too much.

But that is not really true.

Accumulating evidence shows that vitamin C supplements may double the risk of getting a kidney stone. (13)

Let's put that in more perspective.

About 1 in 680 people experience kidney stones every year. So double the risk would mean 1 in about 340 people would experience kidney stones every year.

Knowing the reason why this happens may be helpful in deciding whether you'd like to supplement vitamin C for longer periods of time or not.

Vitamin C or ascorbic acid is partly metabolized to something called oxalate and is then excreted in the urine.

The amount of oxalate excreted in urine plays an important role in the formation of kidney stones, because they are partly made up of these so called oxalates. (14)

Our microbiome plays a big role in the degradation of oxalates, (15) so if you have underlying gut issues or have a variety of food sensitivities, it could indicate your microbiome is imbalanced.

If your microbiome is imbalanced, your body's ability to degrade oxalates may be somewhat impaired. You could benefit from at least minimizing very high oxalate foods.

Foods with the highest concentrations of vitamin C

Citrus fruits may be well known for their high vitamin C content, but there are foods with relatively more vitamin C.

Take a look down here at some of the foods with the highest vitamin C content.

Kiwis are standard size, oranges and bell peppers are medium size and strawberries are calculated per 1 cup.

As you can see the difference can be quite substantial.

Bell pepper clearly stands out when it comes to vitamin C.

One yellow bell pepper even takes you well over the recommended range into the more ideal territory of around 200 mg.

Summary & Conclusion

Taking vitamin C preventatively may work for some people, but it is not a guarantee to stave off a cold or let you recover faster from your cold or respiratory tract infection.

If you think it's worth a shot, then you could of course try taking a vitamin C supplement daily and observe if it makes a difference for you.

Evidence for vitamin C supplementation, protecting you against a cold, is stronger however if you exercise intensely.

Regardless, there is an increased risk of kidney stones.

This depends on your body's ability to break down oxalates, which naturally occur in a variety of foods. Your gut health plays a huge role in the breakdown of oxalates. You may want to avoid very high oxalate foods, if you think you have any underlying issues.

You can also consider a high therapeutic dose of 8 g on the first day you experience cold symptoms. This may aid you in recovery, but not put you at an increased for kidney stones.

Take into consideration, that your body may need more vitamin C because of things like stress, alcohol intake, fever or other viral illnesses, (past) usage of antibiotics, pain killers, heavy metals toxicity, which can all impair vitamin C absorption.

Ideally, you cover your vitamin C with your food intake.

Don't worry about getting too much vitamin C through food. It might be easier to get scurvy than eating too much vitamin C containing food.

















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