Vitamin C is important, but experts warn against taking too much. Here's why.

It turns out, you can have too much of a good thing. While a huge swath of Americans are deficient in essential vitamins and minerals like potassium, calcium, and vitamin E, fewer are lacking ones like magnesium and vitamin A. One vitamin that nearly 50% of the country is deficient in, according to one analysis, is vitamin C. 

Though getting too much of a nutrient like vitamin C is generally preferred over getting too little, it is still important to keep one's daily intake in mind. "Too much of anything is never good," says Alexandra Volo, DO, a family medicine physician at NYU Langone Medical Associates, West Palm Beach, "and you can get too much vitamin C." 

Before diving into reasons not to get too much vitamin C, however, it's important to know that this vitamin packs many health benefits you don't want to miss out on. 

What are the health benefits of vitamin C?

"For years, vitamin C has been known to be a health benefit for the human body," says Volo. It plays a vital role in immune system health, cognitive function, cardiovascular health "and skin and eye health," she says. What's more, as ascorbic acid, vitamin C is a nutrient that aids many different parts of the body, including one's muscles, blood vessels, cartilage and bones.

The nutrient also serves as an antioxidant, "which helps protect your cells from destruction and promotes wound healing," says Jesse Bracamonte, MD, DO, a family medicine physician at Mayo Clinic in Arizona.

Are you getting enough vitamin C?And why it matters.

What is the recommended amount of vitamin C?

Because of these benefits, getting enough vitamin C is important. The Recommended Dietary Allowance for adults aged 19 years and older is 90 milligrams daily for men and 75 milligrams for women, per Harvard School of Public Health. For women who are pregnant or lactating, the suggested amount increases to 85 milligrams and 120 milligrams daily. And smokers need an extra 35 milligrams of vitamin C each day since smoking depletes vitamin C levels.

The upper limit recommendation for the vitamin is 2,000 milligrams per day, "with strong evidence of safety when taking 500 milligrams of vitamin C," explains Volo.

What are the best food sources of vitamin C?

Because the body doesn't produce vitamin C, it's important to get as part of a healthy diet. Vitamin C is abundant within citrus fruits, berries, peppers, parsley, tomatoes, cabbage, kale and spinach. Brussels sprouts and broccoli are particularly strong sources of vitamin C: Brussel sprouts pack about 75 milligrams of the nutrient, and one cup of broccoli contains 80 milligrams. 

Though food sources of vitamin C are preferred, supplementation may be necessary for some people. "If patients have certain gastrointestinal conditions, cancer, or a limited low-nutrient diet that does not regularly include fruits and vegetables, they are encouraged to take oral supplementation of vitamin C," says Volo. 

But any individuals who use vitamin C supplements in hopes of gleaning extra benefits beyond the recommended allowance are probably wasting their money. "Once the recommended intake level is met, it is unlikely additional vitamin C will result in a benefit," says Alice Lichtenstein, DSc, director of the Cardiovascular Nutrition Team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

Can you overdose on vitamin C?

That's especially true in the case of vitamin C, because, as a water-soluble nutrient, it's not well stored in the body so excess amounts are simply excreted in one's urine. That means vitamin toxicity related to vitamin C is rare. 

Still, taking too much vitamin C can cause some problems. "Like with any supplement or vitamin, having an excess is not better," says Bracamonte. Taking too much vitamin C may cause nausea, vomiting, heartburn, headaches, and diarrhea.

Over-supplementation can also affect some groups more than others. "For individuals with diabetes who monitor their urinary glucose levels, excess supplemental vitamin C may result in a false-negative result," says Lichtenstein.

For such reasons, Bracamonte says it's wise to stick to the Recommended Dietary Allowance of all vitamins, "and to ensure you are not duplicating any one as it may be found in a variety of vitamin compilations." 

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