Vitamin C is water-soluble and not stored in your body. It means that it dissolves in water.
In contrast to fat-soluble vitamins, water-soluble vitamins do not get stored within the body. Instead, the vitamin C that you consume gets transported to your tissues via body fluids, and any extra gets excreted in the urine.
Since your body does not store vitamin C or produce it on its own, it’s important to consume foods that are rich in vitamin C daily. However, supplementing with high amounts of vitamin C can lead to adverse effects, such as digestive distress and kidney stones. That’s because if you overload your body with larger-than-normal doses of this vitamin, it will start to accumulate, potentially leading to overdose symptoms.
It’s important to note that it’s unnecessary for most people to take vitamin C supplements, as you can easily get enough by eating fresh foods, especially fruits and vegetables.
Vitamin C Benefits
Vitamin C is a strong antioxidant that can boost your blood antioxidant levels. This may help reduce the risk of chronic diseases like heart disease.
Its supplements have been found to lower blood pressure in both healthy adults and those with high blood pressure. They have been linked to a reduced risk of heart disease.
These supplements may lower heart disease risk factors, including high blood levels of LDL (bad) cholesterol and triglycerides. Vitamin-C-rich foods and supplements have been linked to reduced blood uric acid levels and lower risk of gout.
Vitamin C may reduce the risk of iron deficiency. It may boost immunity by helping white blood cells function more effectively, strengthening your skin’s defense system, and helping wounds heal faster.
Low vitamin C levels have been linked to an increased risk of memory and thinking disorders like dementia, while a high intake of vitamin C from foods and supplements has been shown to have a protective effect.
Symptoms of Taking Too Much Vitamin C
It is usually safe to frequently eat foods high in vitamin C as they should not lead to any health issues. Taking too much vitamin C through supplements can, however, cause side effects.
In adults, the recommended dietary allowance (RDA) of vitamin C is 90 milligrams (mg) for males and 75 mg for females. Adults who take more than 2,000 mg of vitamin C per day may experience side effects.
When a person takes more than the recommended limit of vitamin C, they may experience mild digestive disturbances. These can occur if the vitamin C that the body does not absorb irritates the gastrointestinal tract.
Common mild side effects of too much vitamin C include diarrhea, nausea, vomiting, stomach cramping, bloating and general abdominal discomfort. Megadoses of vitamin C supplements might cause diarrhea, nausea, vomiting, heartburn, abdominal cramps, headache and insomnia.
The body does not absorb all of the vitamin C that it gets from supplements. For example, if a person takes 30–180 mg of vitamin C each day, their body absorbs about 70–90% of this vitamin.
If a person takes more than 1 gram of vitamin C per day, the body absorbs less than 50% of the vitamin, which reduces the risk of negative side effects. The excess leaves the body in the urine.
How Much Vitamin C is Too Much?
As vitamin C can cause unpleasant symptoms if a person takes too much. The upper limit for vitamin C intake in people aged 19 years and over is 2,000 mg in males and females. The limit remains the same for pregnant or breastfeeding women.
The upper daily vitamin C levels for children and infants are as follows:400 mg for infants aged 1–3 years, 650 mg for children aged 4–8 years, 1,200 mg for children aged 9–13 years, 1,800 mg for teenagers aged 14–18 years and 1,800 mg in pregnant or breastfeeding teenagers aged 14–18 years.
There are exceptions to these limits, which only apply if a person’s doctor has not specified a different intake. Some people may have to take larger amounts of vitamin C for medical treatments.
Less commonly, people may experience severe side effects from taking too much vitamin C. Long-term intake above the recommended levels increases the risk of these negative effects.
Kidney stones are a possible consequence of too much vitamin C supplementation. Too much vitamin C supplementation could result in a person excreting the compounds oxalate and uric acid in their urine. These compounds could lead to kidney stone formation.
Taking high doses of vitamin C supplements, such as 500 mg or more a day on a regular basis, has been shown to increase the risk of developing kidney stones in some people. This is particularly true in people who have had calcium oxalate stones in the past or who have a family history of these stones.
The reason for this may be that, at high doses, a significant amount of vitamin C is converted to oxalate in the body. A large amount of oxalate would then be present in the urine where it could combine with calcium to form calcium oxalate stones.
Eating foods that are high in oxalate may also trigger kidney stone formation in people who are prone to develop calcium oxalate stones.
The following foods have been shown to increase oxalate in the urine, and they should be avoided by these individuals: spinach, beets, nuts (including peanut butter), chocolate, tea, wheat bran and strawberries.
Another concern regarding excessive vitamin C intake is that it can impair the body’s ability to process other nutrients. For example, vitamin C may reduce the levels of vitamin B-12 and copper in the body.
Taking vitamin B-12 with vitamin C might reduce the available amount of vitamin B-12 in your body. To avoid this interaction, take vitamin C two or more hours after taking a vitamin B-12 supplement.
Vitamin C May Cause Iron Overload
Vitamin C is known to enhance iron absorption. It can bind to non-heme iron, which is found in plant foods. Non-heme iron is not absorbed by your body as efficiently as heme iron, the type of iron found in animal products.
Vitamin C binds with non-heme iron, making it much easier for your body to absorb. This is an important function, especially for individuals who get most of their iron from plant-based foods.
One study in adults found that iron absorption increased by 67% when they took 100 mg of vitamin C with a meal. However, individuals with conditions that increase the risk of iron accumulation in the body, such as hemochromatosis, should be cautious with vitamin C supplements.
Under these circumstances, taking vitamin C in excess may lead to iron overload, which can cause serious damage to your heart, liver, pancreas, thyroid, and central nervous system.
Iron overload is highly unlikely if you don’t have a condition that increases iron absorption. Additionally, iron overload is more likely to occur when excess iron is consumed in supplement form.
Osteoblasts are specialized mesenchymal cells that synthesize bone matrix and coordinate the mineralization of the skeleton. These cells work in harmony with osteoclasts, which resorb bone, in a continuous cycle that occurs throughout life.
Cell studies showed that vitamin C was able to induce osteoblast and osteoclast formation. However, high-dose vitamin C might increase oxidative stress and subsequently lead to cell death.
Vitamin C-deficient animals showed impaired bone health due to increased osteoclast formation and decreased bone formation.
Vitamin C supplementation was able to prevent bone loss in several animal models of bone loss. Human studies generally showed a positive relationship between vitamin C and bone health, indicated by bone mineral density, fracture probability and bone turnover markers.
One study found that the presence of very high vitamin C levels in the body increased the likelihood of a person developing painful bone spurs.
People with low levels of vitamin C had a higher risk of developing rheumatoid arthritis, a painful inflammatory joint condition. These facts emphasize the need for appropriate vitamin C supplementation that provides neither too much nor too little.