What happens when you supplement too much vitamin C?

Vitamin C (ascorbic acid) is necessary for growth, development and repair of tissues in the body. Because the body does not store vitamin C, it needs to be supplemented through foods such as oranges, tangerines, strawberries, bell peppers or functional foods when needed. Vitamin C supplements are safe for most people, but high or prolonged doses can cause some health side effects.

Kidney stones

High doses of vitamin C can increase urinary oxalate levels – a substance that can combine with calcium to form kidney stones. The process of converting excess vitamin C into oxalate, of concern to people with a history of kidney stones, chronic kidney disease or high oxalate levels, increases the risk of stone formation.

Digestive disorders

One of the common side effects of high doses of vitamin C is digestive upset, including stomach cramps, nausea, diarrhea and bloating. Vitamin C has acidic properties and osmotic activity. When used in excess, it will absorb water into the intestines, irritate the mucosa and cause discomfort. These symptoms usually appear when consuming more than 2,000 mg per day.

Iron overload

Vitamin C increases the absorption of non-heme iron in plants. But high doses can be harmful to people with hemochromatosis – a genetic disorder that causes the body to store excess iron. In these people, high doses of vitamin C worsen iron overload, increasing the risk of liver damage, heart damage, and diabetes. People with iron metabolism disorders should avoid taking high doses of vitamin C unless recommended by a doctor.

False test results

Excess vitamin C may cause errors in certain tests such as blood glucose meters, urine creatinine tests, and tests using oxidation-sensitive reagents. False results can affect diagnosis and treatment.

Worn tooth enamel

Chewable or gummy vitamin C supplements are often acidic, which can erode tooth enamel over time, leading to tooth sensitivity, discoloration, and increased risk of tooth decay. To reduce the risk, rinse your mouth with water after use and avoid brushing your teeth immediately afterward.

Increased oxidative stress

Although vitamin C has antioxidant properties, high doses and in the presence of free metal ions such as iron or copper, can act as an oxidant. This increases oxidative stress – an imbalance between antioxidants and free radicals, which can damage cells. Research shows that very high concentrations of vitamin C can form free radicals in the presence of metals, potentially causing cell damage and risks when used in large doses.

Recommended daily intake (RDA) depends on age, gender and stage: men 90 mg/day, women 75 mg/day, pregnant women 85 mg/day, breastfeeding women 120 mg/day. The maximum intake for adults is 2,000 mg/day. Exceeding this amount, especially over long periods of time, increases the risk of side effects.

Groups susceptible to side effects of vitamin C include people with kidney disease, iron overload disorders, diabetes, or undergoing chemotherapy and radiation therapy. For safe use, stick to the recommended daily dose, unless directed by your doctor. Tell your doctor about all supplements you are taking, especially before surgery or tests. People with persistent abdominal pain, blood in the urine or signs of kidney stones should see a doctor.