Can vitamin C and other ‘immune boosters’ help a cold?

Up close image of vitamin tablets with pill bottle in the background

When you feel a cold starting, are you tempted to reach for a bottle of vitamin C or an “immune booster” at the drugstore to fight off a sore throat or runny nose, thinking a boost of vitamins will help ward off additional symptoms or shorten the length of a cold?

The reality is that, for most people, taking a supplement like this doesn’t do a whole lot to help.

In fact, there are no studies that show that taking an artificial supplement like vitamin C for a cold has any benefit at all. But what I tell my patients is that if it makes you feel better, then there’s no harm in taking it — as long as I know about it so I can make sure it won't harm you.

What is vitamin C, and how does it affect your immune system?

People use vitamin C as an immune supplement. Your body needs vitamin C for several reasons, including the repair and growth of tissues. A severe deficiency in vitamin C can cause scurvy, a condition that causes weakness, gum disease and skin problems.

In your immune system, the vitamin also impacts prostaglandins, lipids that aid in the recovery of tissue damage or infection. Prostaglandins help control your body’s inflammatory and infection response and this is where people get the idea that taking a vitamin C supplement will help their cold.

Vitamin C also aids in:

  • collagen production in skin, bones and muscles providing strength and elasticity 
  • the transport of fatty acids in the blood for energy storage 
  • the function of neurotransmitters (brain chemicals) that tell your heart to beat, your lungs to breathe, and your stomach to digest. These brain chemicals affect mood, sleep and concentration.

Is it safe to take a higher dose of vitamin C when you have a cold? Are there side effects?

There are some side effects of taking a higher dose of vitamin C. You might end up with an upset stomach. In some cases, you might experience cramps and diarrhea. In extreme cases, you could end up with kidney stones. And very rarely, it's been associated with heart rhythm disruption.

If you want to take a daily vitamin C tablet (500 mg), that’s OK, but as your doctor, I should know about it. The way I approach all supplements is that if it makes you feel better, then it’s fine to take in appropriate amounts. But more is not necessarily better, and taking too much of any supplement can cause problems.

The bottom line is that taking an artificial supplement of any vitamin does not have as much benefit as getting the vitamin on your own through dietary and nutritional means.

Do immune supplements like Airborne, Emergen-C or zinc work to improve or treat cold symptoms? What about elderberry, or echinacea?

There are no studies that show these supplements will help treat or prevent a cold. But again, if it makes you feel better, then it won’t hurt you. The only thing it might hurt is your wallet.

What’s the best defense against a cold?

The most effective way to avoid getting sick is to wash your hands frequently and thoroughly with soap and water. While proper sleep and staying hydrated help, I can’t stress enough the importance of good hand hygiene.

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