By Alicia Christians, RDN, LD


Now more than ever people are searching for ways to support or “boost” their immune systems. One of the most commonly marketed ways to support your immune system is by encouraging extra vitamin C in your diet. I’m sure most have heard to grab some extra citrus fruit or buy some vitamin C supplements at the store when they begin to feel sick to kick that cold to the curb. Is the extra vitamin C worth the hype?

Vitamin C has long been marketed as an immune-boosting, cure-all for illnesses such as the common cold and the flu after being discovered as the missing puzzle piece in what is called scurvy – the condition resulting from a deficiency in vitamin C.1The common ways that extra vitamin C has been marketed have either been as a supplement that can often contain over 1,000 milligrams of vitamin C in just one serving, or by encouraging the consumption of copious amounts of citrus fruits and citrus juices. To put into perspective just how heavily these products are often marketed, the sales of orange juice rose by nearly 40 million gallons in just one month during the 2018 flu season.2

“So is all this extra vitamin C helping my body and boosting my immune system? Does it actually cure or prevent my common cold?”

The simple answer for these questions is “sort of, but not really”. Years of research around this topic have shown that our bodies use vitamin C to support the normal functions of our immune system in addition to healing wounds and injuries, repairing blood vessels, and helping to form strong bones. Any extra and unused vitamin C in our body will be conveniently disposed of as waste. In short, a normal and healthily functioning immune system will utilize vitamin C to support itself, but cannot necessarily better or boost any of its functions with extra vitamin C taken in through the diet.3

“Well, how do I know if I’m getting enough vitamin C to support my normal immune system?”

Luckily, the perfect amount of vitamin C for a healthy adult has been figured out and it turns out that it’s pretty easy to get all the vitamin C you need from a regular, healthy, and balanced diet. The standards set ahead by the National Institute of Health for vitamin C consumption outline that women should be consuming 75 milligrams per day of vitamin C and men should be consuming 90 milligrams per day of vitamin C to maintain healthy functions. To put in perspective, just oneserving of a vitamin C rich fruit or vegetable is enough to fulfill this daily requirement.3Some great sources of vitamin C other than citrus fruit include bell peppers, strawberries, and even broccoli.3

In short, you are supporting a healthy immune system with your essential daily intake of vitamin C, but the enormous amounts of vitamin C taken in during the start of your cold is probably nothing but a placebo effect and extra waste for your body to eliminate.


1Hemilä H. Vitamin C and infections. Nutrients. 2017;9(4):338-367.