cancer, heart disease, the common cold, cataracts, and
many other diseases.
High dose vitamin C may be used to treat or pre-
vent urinary tract infections. High levels of vitamin C
increase the acidity of urine, creating an unhospitable
environment for bacteria growing in the urinary tract.
Description
Long before people knew what vitamin C was,
they understood that eating certain foods, especially
citrus fruit, would prevent a severe disease called
scurvy. Vitamin C turned out to be the essential
health-promoting compound in these foods. This vita-
min was isolated in the early 1930s, and by 1934, a
synthetic version of vitamin C was produced by the
pharmaceutical company Hoffman-La Roche.
All animals need Vitamin C, but most animals can
make their own. However, humans, along with apes,
guinea pigs, and a few other animals, have lost that
ability. In humans, this occurs because of a gene muta-
tion that controls an enzyme needed to make vitamin C.
As a result, humans are completely dependent on get-
ting enough of the vitamin from foods in their diet. In
addition, vitamin C cannot be stored in the body. It is a
water-soluble vitamin, and any amount that cannot be
used immediately is excreted in urine. Vitamin C is not
evenly distributed throughout the body. The adrenal
glands, pituitary gland, thymus, retina, brain, spleen,
lungs, liver, thyroid, testicles, lymph nodes, kidney, and
pancreas all contain much higher levels of vitamin C
than are found in circulating blood.Vitamin C’s role in health
Vitamin C functions as an antioxidant and as a
coenzyme. Molecules called free radicals are formed
during normal cellmetabolismand with exposure to
ultraviolet light or toxins such as cigarette smoke. Free
radicals cause damage by reacting withfatsand pro-
teins in cell membranes and genetic material. This
process is called oxidation.Antioxidantslike vitamin
C are compounds that attach themselves to free radi-
cals so that it is impossible for the free radical to react
with, or oxidize, other molecules. In this way, antiox-
idants protect cells from damage. The antioxidant
properties of vitamin C are the basis for many of the
controversial health claims made for it.
Vitamin C also functions as a coenzyme. Coen-
zymes are small molecules that make it possible for
metabolic activities to occur in cells. They are needed
to break down food into its building-block molecules,
build up new molecules from these building blocks, and
convert nutrients into energy in cells. Vitamin C func-
tionsasacoenzymeinreactions that create collagen.
Collagen is aproteinthat is found in cartilage, ligaments,
tendons, bones, skin, and blood vessels. Vitamin C also
is required to make the neurotransmitters dopamine,
norepinephrine (noradrenaline), and epinephrine (adre-
naline). Neurotransmitters are molecules that carry
chemical messages from one nerve to another. Epinephr-
ine is also made in the adrenal gland in response to stress.
It prepares the body for a fight or flight response. Vita-
minCmayalsobeinvolvedincholesterolmetabolism.Normal vitamin C requirements
The United States Institute of Medicine (IOM) of
the National Academy of Sciences has developed val-
ues calledDietary Reference Intakes(DRIs) forvita-
minsandminerals. The DRIs consist of three sets of
numbers. The Recommended Dietary Allowance
(RDA) defines the average daily amount of the
nutrient needed to meet the health needs of 97–98%
of the population. The Adequate Intake (AI) is an
estimate set when there is not enough information to
determine an RDA. The Tolerable Upper Intake Level
(UL) is the average maximum amount that can beVitamin CRecommended Dietary Tolerable Upper
Age Allowance (mg) Intake Level (mg)
Children 0–6 mos. 40 (AI) Not established
Children 7–12 mos. 50 (AI) Not established
Children 1–3 yrs. 15 400
Children 4–8 yrs. 25 650
Children 9–13 yrs. 45 1,200
Boys 14–18 yrs. 75 1,800
Girls 14–18 yrs. 65 1,800
Men 19 yrs. 90 2,000
Women 19 yrs. 75 2,000
Men who smoke 125 2,000
Women who smoke 110 2,000
Pregnant women 18 yrs. 80 1,800
Pregnant women 19 yrs. 85 2,000
Breastfeeding women 19 yrs. 120 2,000
Food Vitamin C (mg)
Pepper, red bell, raw, ½ cup 141
Papaya, 1 94
Strawberries, 1 cup 82
Orange juice, ¾ cup 75
Orange, 1 med. 70
Broccoli, steamed, ½ cup 62
Grapefruit juice, ¾ cup 60
Grapefruit, ½ med. 44
Cauliflower, boiled, ½ cup 27
Potato, baked, 1 med. 26
Tomato, 1 med. 23
AI Adequate Intake
mg milligram(Illustration by GGS Information Services/Thomson Gale.)
Vitamin C