A Review of Vitamin C. — Are you taking enough?

Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. Unlike most mammals and other animals, humans do not have the ability to make their own vitamin C. Therefore, we must obtain vitamin C through our diet. Since it is water soluble and quickly secreted through the urine, vitamin C supplements are more effective if divided into a minimum of twice daily. Dividing the dosages into 4-6 hour increments is even better.

Vitamin C is required for the synthesis of collagen, an important structural component of blood vessels, tendons, ligaments, and bone. Vitamin C also plays an important role in the synthesis of the neurotransmitter, norepinephrine. Neurotransmitters are critical to brain function and are known to affect mood. Research also suggests that vitamin C is involved in the metabolism of cholesterol to bile acids (components of bile, which are formed by the metabolism of cholesterol, and aid in the digestion of fats), which may have implications for blood cholesterol levels and the incidence of gallstones.

Severe vitamin C deficiency has been known for many centuries as the potentially fatal disease, scurvy. Symptoms of scurvy include bleeding and bruising easily, hair and tooth loss, and joint pain and swelling. Such symptoms appear to be related to the weakening of blood vessels, connective tissue, and bone, which all contain collagen.

Disease Prevention

  • Vitamin C is useful in wound healing of all types. From cuts and broken bones to burns and recovery from surgical wounds, vitamin C taken orally helps wounds to heal faster and better. Applied topically, vitamin C may protect the skin from free radical damage after exposure to ultraviolet (UV) rays.
  • Common cold
  • Allergies
  • Role in Immunity
  • Cataracts
  • Coronary Heart Disease
  • Stroke
  • Hypertension
  • Cancer
  • Gout
  • Lead toxicity
  • Diabetes Mellitus

As shown in the table below, different fruits and vegetables vary in their vitamin C content, but five servings (2½ cups) of fruits and vegetables should average out to about 200 mg of vitamin C.



Vitamin C (mg)

Orange juice

¾ cup (6 ounces)


Grapefruit juice

¾ cup (6 ounces)



1 medium



½ medium



1 cup, whole



1 medium


Sweet red pepper

½ cup, raw chopped



½ cup, cooked



1 medium, baked



Vitamin C (L-ascorbic acid) is available in many forms, but there is little scientific evidence that any one form is better absorbed or more effective than another. Most experimental and clinical research uses ascorbic acid or sodium ascorbate.

Natural vs. synthetic vitamin C

Natural and synthetic L-ascorbic acid are chemically identical and there are no known differences in their biological activities.

Mineral ascorbates

Mineral salts of ascorbic acid are buffered and, therefore, less acidic than ascorbic acid. Some people find them less irritating to the gastrointestinal tract than ascorbic acid. Sodium ascorbate and calcium ascorbate are the most common forms, although a number of other mineral ascorbates are available. Sodium ascorbate generally provides 131 mg of sodium per 1,000 mg of ascorbic acid, and pure calcium ascorbate provides 114 mg of calcium per 1,000 mg of ascorbic acid.

Vitamin C with bioflavonoids

Bioflavonoids are a class of water-soluble plant pigments that are often found in vitamin C-rich fruits and vegetables, especially citrus fruits. There is little evidence that the bioflavonoids in most commercial preparations increase the bioavailability or efficacy of vitamin C.

Ascorbate and vitamin C metabolites

One supplement, Ester-C® contains mainly calcium ascorbate, but also contains small amounts of the vitamin C metabolites dehydroascorbate (oxidized ascorbic acid), calcium threonate, and trace levels of xylonate and lyxonate). Don’t try to remember these. Although the metabolites are supposed to increase the bioavailability of vitamin C, the only published study in humans addressing this issue found no difference between Ester-C® and commercially available ascorbic acid tablets with respect to the absorption and urinary excretion of vitamin C. Ester-C® should not be confused with ascorbyl palmitate, which is also marketed as "vitamin C ester."

Ascorbyl palmitate

Ascorbyl palmitate is actually a vitamin C ester (i.e., vitamin C that has been esterified to a fatty acid). In this case, vitamin C is esterified to the saturated fatty acid, palmitic acid, resulting in a fat-soluble form of vitamin C. Ascorbyl palmitate has been added to a number of skin creams due to interest in its antioxidant properties as well as its importance in collagen synthesis. Although ascorbyl palmitate is also available as an oral supplement, it is likely that most of it is hydrolyzed (broken apart) to ascorbic acid and palmitic acid in the digestive tract before it is absorbed. Ascorbyl palmitate is also marketed as "vitamin C ester," which should not be confused with Ester-C® (see above).

Tolerable Upper Intake Level (UL) for Vitamin C

Age Group

UL (mg/day)

Infants 0-12 months

Not possible to establish*

Children 1-3 years


Children 4-8 years


Children 9-13 years


Adolescents 14-18 years


Adults 19 years and older


*Source of intake should be from foods or formula only.


Linus Pauling Institute Recommendations

For healthy men and women, the Linus Pauling Institute recommends a vitamin C intake of at least 400 mg daily—the amount that has been found to fully saturate plasma and circulating cells with vitamin C in young, healthy nonsmokers. Consuming at least five servings (2½ cups) of fruits and vegetables daily provides about 200 mg of vitamin C. Most multivitamin supplements provide 60 mg of vitamin C. To make sure you meet the Institute’s recommendation, supplemental vitamin C in two separate 250-mg doses taken in the morning and evening is recommended.

Older adults (65 years and older)

It is not yet known with certainty whether older adults have higher requirements for vitamin C than younger people. A vitamin C intake of at least 400 mg daily may be particularly important for older adults who are at higher risk for chronic diseases. Because maximizing blood levels of vitamin C may be important in protection against oxidative damage to cells and biological molecules, a vitamin C intake of at least 400 mg daily is particularly important for older adults who are at higher risk for chronic diseases caused, in part, by oxidative damage, such as heart disease, stroke, certain cancers, and cataracts.



2 Responses

  1. Wow! Great info! And thanks for the excellent reminder about breaking it up into two or more times each day. I’m fighting the sniffles to keep them from getting worse, and this reminded me to go take my second dose. 🙂 Have a blessed week!

  2. Hi Dr.Thomas, known as our beloved friend, David. I am very pleased that you have shown from a scientific view the importance of Vitamin C, and that the compound is no different from Natural food.

    My big concern right now is for Pam. What is happening with, and for, her? Please keep us updated.

    We have grown to care very much for you and Pam, so would appreciate knowing the latest.

    Love a lot,

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