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Key Takeaways
- Vitamin C supports immune function and collagen production, but excess amounts are quickly excreted.
- Most adults can meet their daily vitamin C needs through a balanced diet.
- Consistent vitamin C intake matters more than occasional high doses because the body absorbs only limited amounts at a time.
Taking vitamin C during a cold won’t do much good. However, maintaining steady levels of vitamin C, also known as ascorbic acid, supports your immune system and helps your body raise its defenses when needed.
Vitamin C also helps your body produce collagen, a key building block for connective tissues such as skin, bones, muscles, tendons, ligaments, and cartilage. It’s important for vascular and bone integrity, wound healing, and the production of brain messengers.
How Does Your Body Absorb and Store Vitamin C?
Vitamin C is absorbed in the small intestine through specialized transporters. “It then quickly saturates blood and tissues. It shuttles to tissues where oxidative stress is high, like the brain, adrenal glands, and white blood cells,” said Gary Soffer, MD, director of the integrative medicine program at the Yale School of Medicine.
Transporters in the small intestine can only absorb so much vitamin C. “So, as intake rises, absorption efficiency fails,” Soffer added.
Since vitamin C is a water-soluble vitamin, any excess is excreted in the urine in a few hours.
How Much Vitamin C Do You Need?
Current U.S. recommendations call for 75 mg of vitamin C per day for adult women and 90 mg per day for adult men, with an additional 35 mg per day for people who smoke because smoking increases oxidative stress.
Pregnant people generally need more vitamin C to support fetal development, and people with obesity may require higher doses because they often have lower circulating levels of the nutrient. The upper recommended limit of vitamin C is 2,000 mg per day.
If you’re taking a vitamin C supplement, it’s important that you take it consistently, because the body uses what it needs and excretes the rest, said Talia Wall, PharmD, BCPS, an assistant professor of pharmacy practice at the Touro College of Pharmacy in New York City.
Can You Get Enough Vitamin C Through Diet Alone?
For most healthy adults, a balanced diet provides all the Vitamin C necessary. “There is even some evidence that food outperforms supplementation,” Soffer said, adding that frozen produce often retains more vitamin C than fresh fruits and vegetables that have been stored and shipped.
Vitamin C supplements at levels above 1,000 mg per day have been linked to an increased risk of kidney stones in some studies. Vitamin C supplements affect the kidneys more because high doses can overwhelm the body’s ability to process them, according to Debbie Petitpain, RDN, a registered dietitian in Charleston and a spokesperson for the Academy of Nutrition and Dietetics.
“That can lead to extra vitamin C breaking down into oxalate, which crystallizes with calcium to form kidney stones,” Petitpain told Verywell.
However, vitamin C from food sources doesn’t carry the same risk. “Foods provide much lower, gradual doses that the body uses without producing oxalate,” Petitpain said.