How Much Vitamin C Is Safe to Take to Fight a Cold?

Hint: It's not as much as you think.

Cold and flu season is upon us. Wondering what you can do ward off the looming effects of this germy, sniffly and throat-irritating illness? Many reach for hefty doses of vitamin C via supplements or big glasses of OJ, but is there any science to back up this old wives tale? Here's the truth about vitamin C and colds.

Vitamin C Basics

Vitamin C is an essential nutrient involved in collagen formation, iron absorption and yes, immune health (but there’s more to the story). Vitamin C also works as a powerful antioxidant to protect cells and fight inflammation. Adults require about 60 milligrams of this vitamin each day. An orange contains 70 milligrams, one cup of strawberries or broccoli has 100 and a half-cup of red bell pepper has 95.

Can Vitamin C Fight a Cold?

A small amount of research from the 1970s suggested vitamin C was the answer to preventing and treating the common cold. For decades this has fueled the old wives’ tale that vitamin C “boosts” the immune system and can prevent illnesses such as cold and flu. Continuing research has indicated that this isn’t quite the case. While some data suggests that extra vitamin C may help those who partake in extreme exercise or are active in cold environments, it’s not the magic pill people many folks make it out to be. If you are falling short of your daily needs for vitamin C (which is not a hard bar to meet) you will potentially see better immune function when that deficiency is corrected. A study from 2017 determined that meeting needs for vitamin C would be enough to help prevent some infections from occurring while higher doses are needed to fight inflammation from existing infections.

The research is more compelling on how the antioxidant powder of vitamin C can fight inflammation and possibly shorten the duration of an illness when taken at the onset of symptoms. Newly published research continues to explore the antioxidant powder of vitamin c and both athletes and non-athletes. More importantly, this doesn’t translate to more is better. There is such thing as too much vitamin C.

How Much Is Too Much?

According to the dietary guidelines, the max amount of vitamin C that is safe to take each day is 1800 milligrams. Taking in more can cause stomach upset, nausea and diarrhea, which typically resolves quickly once the usage is discontinued. Some data suggests excessive intakes for long periods of time may be linked to kidney stones in people with existing kidney issues.

This may seem like an unattainable amount (who eats that much produce?!), but whether it’s a fizzy drink mix or chewable tablet, the average cold prevention supplement contains 1000 milligrams per serving. Many of these products recommend taking a dose multiple times a day, quickly exceeding the 1800 milligrams recommendation — and this is before you eat any vitamin C rich foods. It is also important to point out many of these products also include other vitamins and minerals, some of which may carry their own separate risks for toxicity or interactions with medications, so check labels carefully so you know what you are taking.

4 Tips to Optimize Immune Health

Sure, you can take in some vitamin C (preferably from food). If you really want to keep those germs away try these tips.

  • WASH. YOUR. HANDS.
  • Sleep: aim for 7 to 8 hours a night to keep your immune system strong
  • Eat a balanced diet to prevent any nutrient deficiencies.
  • Take steps to manage stress as it can wreak havoc on your system.

Dana Angelo White, MS, RD, ATC, is a registered dietitian, certified athletic trainer and owner of Dana White Nutrition, Inc., which specializes in culinary and sports nutrition. She is the author of four cookbooks First Bites: Superfoods for Babies and Toddlers, The Healthy Air Fryer Cookbook, The Healthy Instant Pot Cookbook and Healthy Quick and Easy Smoothies.

*This article was written and/or reviewed by an independent registered dietitian nutritionist.

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