Thinking about the existence of side effects of vitamin C is difficult, although they exist. They are rare and are associated, above all, with the interaction of the vitamin with other compounds.

Side effects of vitamin C in the body may appear, although in minimal proportion. Much more is known about the beneficial effects of this substance on the body, than of the possible complications that the indiscriminate intake of it can bring.

Let’s start by remembering that vitamin C is a necessary nutrient for body tissues. All the vitamin C that is needed must be acquired from the outside since the human body is unable to synthesize it by its own means.

The main source is food. This vitamin is water-soluble, that is, it dissolves in water. And, once it enters the body, it is used until the necessary amount is used. What is left over is eliminated in the urine?

It is this mechanism of automatic renal elimination that makes the appearance of adverse effects unlikely. Large amounts of vitamin C should be ingested to notice side effects, while there should be a problem with renal excretion.

Vitamin C functions

Vitamin C has the essential function of repairing and accompanying tissue growth, especially in the skin and in the osteoarticular system. 

The most important functions of vitamin C are:

• Formation of proteins involved in the construction of skin and tendons.
• Creation of materials from tendon tissues and ligaments.
• Scarring: scar tissue depends, to some extent, on the existence of good levels of vitamin C in the body.
• Adjuvant in the intestinal absorption of iron.

Science has shown that vitamin C is a powerful antioxidant. Antioxidants are substances that inhibit part of the effects that free radicals have on cells.

Free radicals are constantly formed during body metabolism, especially in the process of absorption of nutrients and energy from food. As free radicals accumulate, cell damage and tissue aging increase.

It has been postulated that free radicals are involved in the generation of some cancers, heart disease, and osteoarthritis. The possibility that vitamin C partly blocks the harmful effects of this aging process is good news. Vitamin C plays very important functions in the body. It is rare to cause adverse effects.

Sources of Vitamin C

The adverse effects of vitamin C would appear when the intake is excessive. The main sources of this vitamin are fruits and vegetables, and citrus in greater proportion. Other fruits with a good dose of vitamin C are:

• Kiwi
• Pineapple
• Red fruits: raspberries, blueberries, strawberries
• Cantaloupe
• Watermelon

Among the vegetables, the green ones are the richest in this substance. We can mention broccoli, cauliflower, spinach, and cabbage. Peppers and tomatoes are also good sources.

In some countries, there are laws that oblige food producers to add vitamin C to their products. These are known as fortified or fortified foods.

The cooking process that is applied to foods rich in vitamin C can alter its availability. Both cooking and exposure to sunlight are capable of altering the number of vitamins that the food offers to the body.

Adverse effects of Vitamin C

We arrived at this, after analyzing what functions it performs in the body and where we obtain it, from the side effects of vitamin C. They appear when amounts in excess of two thousand milligrams per day are ingested.

The first adverse effect that manifests itself is gastrointestinal. High doses of vitamin C generate acidity, heartburn, and even diarrhea. In pregnancy, huge amounts of vitamin C are not recommended because they affect the baby.

Another side effect of vitamin C is the formation of kidney stones. It has been observed that, in excess, the metabolism transforms it into oxalate, and the oxalate attempts to exit through the urinary tract, accumulating in the urine and manufacturing renal lithiasis.

When there is a preexistence of certain diseases, the body may react poorly to vitamin C overdose. Patients with G6PD deficiency suffer from hemolysis – the destruction of red blood cells – in high vitamin contexts, while patients with hemochromatosis may get worse. Excessive consumption of vitamin C can cause unwanted side effects. It is important to avoid doses greater than two thousand milligrams per day.

Adverse effects of vitamin C by interactions

Apart from the adverse effects of vitamin C due to excessive intake, we have to consider the interactions of the substance with others:

• Chemotherapy: in cancer patients, there is a scientific suspicion that vitamin C could reduce the effectiveness of treatment.
• Estrogens: Vitamin C has been shown to increase the blood availability of estrogens, which would interact with oral contraceptives, for example, and with hormone replacement therapies for menopause.
• Aluminum: there are cases of kidney patients who use medications with aluminum. If at the same time they consume high amounts of vitamin C, aluminum can increase its adverse effects.
• Anticoagulants: Warfarin, mainly, which is an anticoagulant, is reduced in its ability to act in the presence of elevated vitamin C.

It is rare that adverse effects occur due to the consumption of vitamin C; however, it can happen. In addition, in some cases, this vitamin has significant interactions with other substances.

Bibliographic References: 

• Manela-Azulay, Mônica, et al. “Vitamin C.” Anais brasileiros de dermatologia 78.3 (2003): 265-272.
• Lanyau Dominguez, Yeneisy, and Consuelo Macías Matos. “Vitamin deficiency and Alzheimer’s disease.” Cuban Journal of Public Health 31.4 (2005).
• Serra, Horacio Marcelo, and Thamara Analía Cafaro. “Ascorbic acid: from chemistry to its crucial protective function in the eye.” Latin American Clinical Biochemical Act 41.4 (2007): 525-532.