What is Vitamin C?
Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Humans, unlike most animals, are unable to synthesize vitamin C endogenously, so it is an essential dietary component .
Vitamin C is required for the biosynthesis of collagen, L-carnitine, and certain neurotransmitters; vitamin C is also involved in protein metabolism. Collagen is an essential component of connective tissue, which plays a vital role in wound healing. Vitamin C is also an important physiological antioxidant and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol (vitamin E).
What is the recommended Intake of vitamin C?
Intake recommendations for vitamin C and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) of the National Academies (formerly National Academy of Sciences). DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender, include:
Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.
| Recommended Dietary Allowances (RDAs) for Vitamin C | ||||
| Age | Male | Female | Pregnancy | Lactation |
| 0–6 months | 40 mg* | 40 mg* | ||
| 7–12 months | 50 mg* | 50 mg* | ||
| 1–3 years | 15 mg | 15 mg | ||
| 4–8 years | 25 mg | 25 mg | ||
| 9–13 years | 45 mg | 45 mg | ||
| 14–18 years | 75 mg | 65 mg | 80 mg | 115 mg |
| 19+ years | 90 mg | 75 mg | 85 mg | 120 mg |
| Smokers | Individuals who smoke require 35 mg/day more vitamin C than nonsmokers. |
* Adequate Intake (AI)
Can I take Vitamin C at night?
The recommended time to take vitamin C is in the morning because taking it in the night is likely to increase side effects such as upset stomach, heartburn, cramps, and headaches in some people.
In addition, taking vitamin C supplements at night isn’t advisable because digestion slows down during sleep, so taking your nutrient supplement late at night would not be associated with an efficient absorption. Spacing the doses out will increase the overall absorption. You can take vitamin C every few hours.
Oral vitamin C produces tissue and plasma concentrations that the body tightly controls. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1 g/day, absorption falls to less than 50% and absorbed, unmetabolized ascorbic acid is excreted in the urine.
Results from pharmacokinetic studies indicate that oral doses of 1.25 g/day ascorbic acid produce mean peak plasma vitamin C concentrations of 135 micromol/L, which are about two times higher than those produced by consuming 200–300 mg/day ascorbic acid from vitamin C-rich foods . Pharmacokinetic modeling predicts that even doses as high as 3 g ascorbic acid taken every 4 hours would produce peak plasma concentrations of only 220 micromol/L .
The total body content of vitamin C ranges from 300 mg (at near scurvy) to about 2 g. High levels of vitamin C (millimolar concentrations) are maintained in cells and tissues, and are highest in leukocytes (white blood cells), eyes, adrenal glands, pituitary gland, and brain. Relatively low levels of vitamin C (micromolar concentrations) are found in extracellular fluids, such as plasma, red blood cells, and saliva.
