Taking A Vitamin C Supplement? Look Out For These Side Effects

Whether taken orally for its immune health benefits or applied via a serum to promote glowing skin, vitamin C seems to always be trending—and for good reason!* 

While you can get varying amounts of vitamin C from fruits and vegetables (e.g., oranges, bell peppers, cruciferous vegetables, and kiwis), statistics demonstrate getting the essential vitamin from diet alone is not a foolproof strategy since 46% of U.S. adults3 are failing to consume just 60 to 75 milligrams of the water-soluble micronutrient daily (i.e., less than baseline daily requirements).

Stomach discomfort is one of the most common side effects observed by Alexander Michels, Ph.D., clinical research coordinator at Oregon State University's Linus Pauling Institute. "This is usually because people are consuming the acidic form of vitamin C—ascorbic acid—and for some, their stomach can't handle the extra acid."

Side effects like gas, bloating, and changes in regularity may occur at very high doses of vitamin C. According to Michels, this is most common when megadosing the vitamin (i.e., consuming beyond 2,000 milligrams in a short period of time)—which, for reference, is equivalent to approximately 40 small oranges4 and at least twice the dose of most high-potency supplements.

As for topical skin care, Michels warns that some products with vitamin C may cause mild irritation—especially if you go out in the sun right after applying them to your skin. Since vitamin C supplements can provide complementary skin health benefits5, you can always try vitamin C orally to sidestep or synergize topical approaches. 

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+.

Vitamin C may be best known as a first line of defense when you're feeling under the weather (a reactive approach we would highly recommend swapping for a more proactive one), but it plays a number of critical functions and provides a slew of whole-body benefits.* 

"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."*

This is arguably its most famous benefit; vitamin C is well known as an avid supporter of both innate and adaptive immunity—i.e., the immunity we're born with and the immune response that's triggered when unwanted microorganisms enter the body.* 

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.*

Another buzzworthy benefit of vitamin C is brighter, more youthful-looking skin.* Because the body requires vitamin C to produce collagen8—the body's most abundant protein that makes up skin and all connective tissues—getting enough vitamin C can help enhance skin elasticity (think bouncy, firm skin).*

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.

Collagen gets a lot of buzz for its skin benefits, but it plays an equally critical role in joint health, supporting everything from joint mobility to musculoskeletal integrity10.* Because vitamin C is a necessary prerequisite to collagen synthesis (and let's not forget the antioxidant benefits of vitamin C for collagen longevity), getting optimal levels of vitamin C is essential to comprehensively support musculoskeletal health.* 

While vitamin C is a useful, complementary strategy for optimizing iron absorption regardless of your dietary pattern, the synergy becomes even more important for vegetarians and vegans. For those who avoid animal products (especially meat), vitamin C can play a crucial role in ensuring adequate iron absorption.* 

Since nearly half of U.S. adults3 fail to consume the minimum requirements of vitamin C daily, it's unlikely that the average person will overdo it on vitamin C.

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. 

For the average person, the most notable interaction to look out for with vitamin C is its potential ability to weaken the effects of certain medications. Michels says that vitamin C can ​​increase excretion of certain products into the urine, which quickens the rate at which it leaves the body and shortens the amount of time you feel its effects. 

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.   

While vitamin C plays a number of critical roles in the body and provides a slew of joint, skin, and immune health benefits, most people don't get enough of the essential micronutrient, even in these modern times.* A high-quality vitamin C supplement (with bioavailable vitamin C rooted in absorption science and bioefficacy research) is a convenient and effective way to achieve and maintain sufficiency of this pivotal nutrient.* 

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.