Ascorbic acid, commonly known as Vitamin C, is a water-soluble organic compound that plays a fundamental role in human health. Unlike many animals, humans cannot produce this nutrient internally, making it an indispensable part of the diet. Its name, “ascorbic,” originates from its ability to prevent scurvy, a disease caused by its deficiency.
It dissolves readily in water, forming mildly acidic solutions. This chemistry allows it to participate in various biological reactions throughout the body.
Key Roles in the Body
Ascorbic acid acts as an antioxidant, protecting cells from damage caused by free radicals. These unstable molecules are byproducts of the body’s energy conversion processes and can also form due to exposure to pollutants or radiation. Antioxidants like vitamin C neutralize these free radicals, which helps to mitigate cellular damage and may reduce the risk of certain chronic conditions.
The nutrient is also involved in collagen synthesis, a protein that forms the basis of connective tissues like skin, bones, blood vessels, and cartilage. Adequate vitamin C intake supports skin integrity, promotes wound healing, and helps maintain the strength and elasticity of these tissues.
Vitamin C also supports immune system function by stimulating the activity of white blood cells, which are important for fighting infections. It also enhances the absorption of non-heme iron, the type of iron found in plant-based foods, by converting it into a more absorbable form. This is particularly beneficial for individuals consuming vegetarian or vegan diets, helping to prevent iron deficiency.
Sources and Supplementation
Many fruits and vegetables are excellent sources of ascorbic acid. Citrus fruits like oranges and grapefruits, as well as strawberries, kiwi, and papaya, are high in vitamin C. Vegetables such as red and green bell peppers, broccoli, Brussels sprouts, and cantaloupe also provide this nutrient.
The vitamin C content in foods can decrease with prolonged storage or cooking due to its water-soluble nature and sensitivity to heat. Because the human body cannot store vitamin C for extended periods, a consistent dietary intake is necessary.
For individuals who may not get enough through diet, vitamin C supplements are widely available in various forms, including tablets, capsules, and powders. Most supplements contain ascorbic acid, which is chemically identical to the naturally occurring form and has similar bioavailability. Other forms, such as sodium ascorbate or calcium ascorbate, may be used to reduce acidity for those with sensitive stomachs.
Considerations for Use
The recommended daily allowance for vitamin C is around 75 milligrams for adult women and 90 milligrams for adult men. Smokers may require an additional 35 milligrams daily due to increased oxidative stress. Most people can meet these requirements through a balanced diet.
While safe, consuming high doses of vitamin C supplements can lead to side effects, primarily gastrointestinal distress like stomach cramps, nausea, or diarrhea. These symptoms occur with doses exceeding 2,000 milligrams per day, which is considered the tolerable upper intake level.
High doses of vitamin C can also increase the amount of oxalate in urine, which may contribute to the formation of kidney stones in susceptible individuals. This risk is more pronounced with supplemental intake, particularly doses of 1,000 milligrams or more per day in men, rather than from dietary sources. Individuals with a history of kidney stones or certain kidney conditions should consult a healthcare professional before taking high-dose vitamin C supplements.