Vitamin C plays key roles in immune, cognitive, cardiovascular, and skin health, as well as iron absorption and collagen synthesis.* But since the body can’t produce it spontaneously, we have to seek C out in food sources, and many people do a less-than-stellar job of meeting their daily needs: Almost half of American adults have a vitamin C gap in their diet1, and an estimated 108 million of us have insufficient vitamin C levels, per blood tests. (That’s 42% of the U.S. adult population2!) To guarantee you’re getting enough of the key vitamin and to leverage its full array of health benefits, a daily vitamin C supplement (preferably one that delivers an effective dose of vitamin C in a highly bioavailable form) is an effective solution.* In addition to personal differences in physiology (as well as stomach sensitivity, presence of a meal, etc.), the potential for stomach issues as a side effect is largely dependent on dose and form of vitamin C, which we discuss in detail here. General GI concerns, struggling to sleep deeply (perhaps by way of digestive distractions or due to vitamin C’s role in cellular energy production), and flushed skin are other potential side effects, says Christyna Johnson, M.S., L.D., RDN, registered dietitian and host of the Intuitive Eating for the Culture podcast. But even then, Michels reassures that “For many people, these side effects are mild and transient.” Each body is different, and there’s no dose that is definitively linked to side effects for everyone. That’s not how nutrition and our individual genetic makeup work. Michels says that even at the highest doses of vitamin C (again, above 2,000 milligrams daily), side effects often dissipate after a week as the body adjusts. Johnson also notes that GI concerns typically resolve once the vitamin C has been properly absorbed into the system. Taking a vitamin C supplement with adequate amounts of water can help aid digestion and absorption, as well as minimize the mild side effects that may come when unabsorbed leftovers need to be disposed of (i.e., via urine). But to further optimize absorption with intention, consider a highly bioavailable form of vitamin C —such as PureWay-C™, a vitamin-C-lipid-bioflavonoid complex featured in mbg’s vitamin C potency+. If side effects persist with vitamin C supplementation or any nutrition regimen, it’s always smart to consult your health care provider. “Once you have taken enough vitamin C that you are no longer at risk of deficiency, the remainder goes to antioxidant protection,”* Michels says. This manifests in supporting the immune, cardiovascular, and central nervous systems by delivering broadly protective actions against oxidative stress, or, in Michels’ words, “protecting you from free radicals that we encounter in our daily lives.”* Here are some specific health benefits you can expect when maintaining sufficient vitamin C status: Vitamin C not only plays a role in the production of white blood cells6 but also stimulates the creation of antibodies and helps T-cells reach maturity.* Researchers studying the link between immunity and vitamin C have found that leukocytes (the umbrella term for white blood cells, including T-cells, that help the body fight invading pathogens) use vitamin C to protect themselves from oxidative stress7.* As mbg’s vice president of scientific affairs Ashley Jordan Ferira, Ph.D., RDN, has previously explained, “You can’t even create the immune cells to fight for you without vitamin C.”* But the skin benefits don’t stop there. Topical approaches can go hand in hand (literally). In a 2015 study published by Clinical, Cosmetic and Investigational Dermatology, researchers found that topical vitamin C increased collagen production and made skin brighter9 in healthy female participants. According to a 2017 5Nutrients5 scientific review5, consuming vitamin C via both food and supplements has been associated with improved skin elasticity and texture, less wrinkling, and enhanced protection from unwanted effects of UV light.* Interestingly, while researchers found that topical vitamin C products demonstrate photoprotective properties against UV light, they noted that ingesting vitamin C may be more effective.* In a 2020 study from the Journal of Nutrition, researchers found higher vitamin C intake among older adults was associated with greater muscle mass11, especially in women.* Given the overwhelming scientific evidence that vitamin C levels decrease as we age, achieving sufficient vitamin C status becomes increasingly important later in life to promote whole-body health—and muscle mass and strength are pivotal to physical function and longevity.* While iron is found in plant-based sources like broccoli and spinach, plants only contain non-heme iron, which is much less bioavailable than heme iron—the kind found solely in animal sources. Luckily, vitamin C can enhance the absorption of nonheme iron, seriously increasing its bioavailability, Johnson explains.* So what are those minimum daily requirements? Per the National Academies, the recommended daily intake12 of vitamin C is 75 milligrams for women (85 and 120 milligrams if pregnant or lactating, respectively) and 90 milligrams for men, or about 1.5 oranges13. However, those baseline starting levels are debated. Michels says a daily minimum of at least 200 milligrams is actually needed to maximize blood concentrations of vitamin C. He recommends 400 milligrams daily, though evidence suggests that even higher doses can help bolster vitamin C status and promote optimal cardiovascular benefits14.* When it comes to safety, those taking higher potency vitamin C supplements shouldn’t worry—up to 2,000 milligrams of vitamin C daily is considered safe. Beyond that, the side effects listed above may begin to occur but are generally mild and short-lived, Michels says. That’s because vitamin C is water-soluble, meaning it’s transported through the bloodstream and doesn’t need another mechanism to move around, like a fat-soluble vitamin does. Thanks to vitamin C’s water solubility, “the body can easily remove any excess through the kidneys,” Michels explains. Additionally, people with certain health concerns should take extra care with higher-dose vitamin C supplements. Individuals with renal health concerns should talk to their health care provider before adding a vitamin C supplement to their regimen since, according to Michels, ascorbic acid can break down into oxalate (too much of which can affect kidney function). Those taking blood-thinning medications should also speak with their health care provider before taking a new vitamin C supplement since it may alter its effects. Those with very high levels of iron may also want to exercise caution since vitamin C can increase the amount of iron the body absorbs. Because vitamin C is a water-soluble vitamin, any excess is flushed out with urine. And while side effects may occur at very high doses, they’re likely to be mild. Of course, it’s always smart to check with your health care provider when introducing new supplements to your daily routine or experiencing any unwanted side effects. If you’re looking for a science-backed vitamin C supplement with the added benefits of citrus bioflavonoid phytonutrients, check out mbg’s vitamin C potency+ or peruse our list of the best vitamin C supplements on the market.*
