While it is possible to go overboard when taking vitamins, it's really tough to have too much vitamin C. "Vitamin C is an essential vitamin, which means we need to consume it from food because our bodies can't make it," Krista Linares, RDN, a registered dietitian nutritionist, tells Bustle. "It has many roles in the body including antioxidant function, collagen production, and immune function."
Unlike fat soluble vitamins, which can store up in the body and cause side effects, vitamin C is water soluble. Once your body has what it needs, you simply pee out the extra. "This is why very large doses of vitamin C in one sitting do not tend to produce any additional benefit," Linares says. "Also because it is not stored in the body, high doses of vitamin C do not tend to be toxic."
In order to get what you need, vitamin C-wise, you should have around 75 mg a day, which is possible through your diet, but can be boosted with supplements. The tolerable upper limit of vitamin C for adults is 2,000 mg, Linares says, meaning this is the highest possible intake that is likely to pose no risk or adverse effects. Anything more than that, and there is some evidence that it can cause nausea and diarrhea, she says.
Such a high level of vitamin C can be reached when throwing back immune boosting powders or "snacking" on sugary gummy vitamins, Christina Anderson, MS, RDN, CDE, CNSC, LD, a registered dietitian, nutritionist, and certified specialist in nutrition support, tells Bustle. "Too much vitamin C can cause tummy trouble," she says, and would likely put you off taking that much again.
It's also possible to consume over 2,000 mg a day if you aren't reading labels. "You might take too much vitamin C if you're taking various supplements that contain vitamin C (also called ascorbic acid) and/or vitamin C fortified foods," Bri Bel, RD, a registered dietitian, tells Bustle. Add it all up, and it might leave you feeling a bit nauseated.
Aside from digestive issues, some experts have pointed to a link between vitamin C and the formation of kidney stones. One study found that high-dose vitamin C could double a man's risk, while other studies have shown no connection between vitamin C and kidney stones in women, and others still have found no connection at all.
"Most kidney stones are made of calcium oxalate, which is why there is the idea that the oxalates in vitamin C could contribute to kidney stones," Dr. Kelly Bay, a certified dietician nutritionist, certified nutrition specialist, doctor of chiropractic, and health coach, tells Bustle.
Again, since you'll excrete any excess through your urine, it isn't guaranteed to be a problem. It's important to note, Bay says, that the oxalates produced from vitamin C may actually be from the sucrose and other additives used in these supplements rather than the vitamin C itself contributing to oxalates. It won't hurt to ask your doctor about this, as well as other ways vitamin C supplementation might impact your health.
For the most part, vitamin C is incredibly safe. And the good news is, "most people consuming vitamin C from food sources, such as fruits and vegetables, will have an appropriate amount of vitamin C," Linares says. "It is very rare for someone to get too much vitamin C from food alone. It is far more common to get too much vitamin C from supplements — think vitamin C powders for drinks, multivitamins, etc." So make sure you're reading labels, while trying to get most of your vitamin C from real foods.
"My top recommendation is to get vitamin C from fruits and vegetables every day, especially citrus, tomatoes, berries, and leafy greens," Linares says. "I only recommend adding supplements if for some reason you're not getting three to four servings of fruits and vegetables every day."
Other great food sources, according to Bay, are kiwi, broccoli, Brussels sprouts, bananas, plums, apples, spinach, red peppers, and winter squash. With all these options, you might not even want or need to take a vitamin C supplement.
Thomas, L. D. K., Elinder, C.-G., Tiselius, H.-G., Wolk, A., & Åkesson, A. (2013). Ascorbic Acid Supplements and Kidney Stone Incidence Among Men: A Prospective Study. JAMA Internal Medicine, 173(5), 386. doi: 10.1001/jamainternmed.2013.2296
Ferraro, P. M., Curhan, G. C., Gambaro, G., & Taylor, E. N. (2016). Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. American Journal of Kidney Diseases, 67(3), 400–407. doi: 10.1053/j.ajkd.2015.09.005
Krista Linares, RDN, registered dietitian nutritionist
Christina Anderson MS, RDN, CDE, CNSC, LD, registered dietician nutritionist and certified specialist in nutrition support
Bri Bel, RD, registered dietitian
Dr. Kelly Bay, certified dietician nutritionist, certified nutrition specialist, doctor of chiropractic, and health coach