the long history of experience and research with vitamin
C, dating back several centuries to the search for
the cause of scurvy among sailors on long voyages,
we still have much to learn about how it works in
the human body. We know that humans are one of the
few creatures on earth that don't make their own vitamin
C, but we don't know why.
Professor Linus Pauling proposed that humans' inability
to make ascorbic acid and the decrease in C content
of our diet over the years, particularly as early
humans shifted from an all vegetarian diet to a partly
meat diet, has placed us at risk for getting less
vitamin C than we need for optimum health. Some vitamin
C advocates are quick to point out that animals that
make their own vitamin C produce the human equivalent
of 10 to 20 per day. The average human diet, on the
other hand, contains only 30 mg per day. They also
point to apes, which get an average of 5 g of vitamin
C a day in the wild.
This theory is disputed by many nutritional experts,
who claim the humans' diet was probably never strictly
vegetarian and has always contained both meat and
vegetables. Conventional wisdom tells us that if the
ability to make vitamin C had been needed in our species'
early history, it would have been carried down to
today's human through own genes. Some evidence indicates
that animals make their own vitamin C in large amounts
because they use it up much faster than we do. Perhaps
humans are more efficient than most members of the
animal kingdom in that we efficiently absorb and can
store small amounts of vitamin C. why carry the machinery
to make vitamin C when you can let plants do it for
you? Both sides of this debate are pure speculation,
and no one can conclusively prove any of these points.
Nevertheless, as knowledge of the importance of antioxidants
in the diet grows, increasing vitamin C intake seems
like a good idea.
C is a modified sugar molecule that is water soluble.
One of the important functions of vitamin C is to
serve as a water-soluble antioxidant and free-radical
scavenger. It is one of the compounds in the body
that protects us from oxidative free-radical damage.
It is also known that vitamin C is necessary in the
synthesis of hydroxyproline and hydroxylysine. These
hydorxylated amino acids are building blocks of collagen,
the main supporting component in connective tissue,
which is the tissue that holds us together. Some types
of connective tissue are cartilage, tendons, and fibers.
A lack of vitamin C causes defects in the formation
of mucous membranes and interferes with the normal
healing of wounds. Without sufficient vitamin C, the
tissue that surrounds and supports capillaries breaks
down, and the capillaries themselves then break from
lack of support. This results in back - and- blue
bruise marks as blood leaks into tissue and clots
there. The hallmark of scurvy, the vitamin C deficiency
disease, is a lack of collagen synthesis.
Vitamin C also stimulates the adrenal glands to manufacture
cortisone and other body hormones involved in helping
us cope with stresses of daily life. Vitamin C levels
are high in the adrenal glands. Vitamin C is known
to participate in the hydroxylation of a chemical
called dopamine in the adrenal gland to form the neurotransmitter
norepinephrine. Norepinephrine is essential to life
because it affects many parts of the central nervous
system and all of our major organs. Another important
chemical in the body whose synthesis is dependent
on vitamin C is carnitine. Carnitine is needed to
move sugars into the mitochondria of the cells so
that they can be metabolized to yield energy.
Vitamin C increased the amount of iron absorbed from
non-meat sources through the intestines by chemically
reducing and chelating the iron. To be effective,
the vitamin C must be taken at the same time as the
iron. If you have iron-deficiency anemia, taking the
iron tablet simultaneously with 100 to 200 mg of vitamin
C will increase absorption by 30 to 40 percent. The
vitamin C is involved in the conversion of folic acid
to its active form, dihydrofolic acid, in the body.
In fact, one of the features of vitamin C deficiency
is an anemia similar to the kind found in people deficient
in folic acid. Small amounts of ascorbic acid are
also needed to break down cholesterol in the blood.
White blood cells contain relatively large amounts
of vitamin C, and it seems to be key to the ability
to these cells to attack and engulf invading bacteria.
Immune function is diminished in vitamin C deficiency.
Deficient individuals are more susceptible to viral
and bacterial infections. Interferon production by
cells is stimulated by vitamin C, which may account
for its importance in the defense against viruses.
In addition, vitamin C is involved in the manufacture
of a group of enzymes that are essential to the body's
ability to break down drugs and other chemicals the
body considers foreign.
about 10 mg a day of ascorbic acid is enough to protect
against scurvy, which is the disease resulting from
a deficiency of vitamin C. Nevertheless, the average
adult RDA for ascorbic acid has been set at 60 mg
to provide an extra margin of safety during times
of illness and stress. In the United States it is
estimated that 20 to 30 percent of adults consume
less than the RDA value. A current controversy is
whether levels of vitamin C over the RDA value are
needed for optimal health. Given the importance of
this vitamin as a water-soluble antioxidant we believe
that a higher levels would be beneficial. In considering
what intakes might be optimal, it is important to
note that 200 mg will provide about 80 percent of
complete saturation of blood. Because vitamin C is
"pumped" into cells by an enzymatic process,
blood cells and body tissues are completely saturated
at this dose. Doses of 500 mg to 1,000 mg will saturate
blood. Vitamin C intakes of RDA amounts will not saturate.
Thus if you believe that for optimum health, you want
to saturate your body with vitamin C, you will need
to take in more than 200 mg per day. If five portions
of fruits and vegetables were consumed each day, as
recommended by nutrition authorities, vitamin C intake
would be in the 100 to 300 mg per day range. Researchers
at the National Institutes of Health note that 100mg
to 200 mg of vitamin C daily will benefit most healthy
Americans. Intakes higher than 300 mg will be difficult
to achieve without taking supplements.
potatoes, and green vegetables are the best natural
sources of this vitamin. There is little vitamin C
in meats, cereals, grains, and the foods we normally
think of as being loaded with B vitamins. Interestingly,
the richest sources of vitamin C are not the citrus
fruits, as we have been led to believe, but rose hips,
broccoli, Brussels sprouts, and green peppers. Additional
good sources are listed in the accompanying table.
Vitamin C is chemically unstable and therefore presents
some problems in terms of storage and processing.
Drying fruits and vegetables destroys much of their
vitamin C content. In one experiment up to 54 percent
of the vitamin was destroyed by drying. Vitamin C
also breaks down after exposure to light and air.
In addition, long storage of fruits and vegetables
allow the vitamin to be broken down by natural enzymes.
Another problem unique to ascorbic acid is that if
fruits and vegetables are picked before they reach
their fully ripened state, they will not have produced
their full quota of vitamin C.
Freezing does not destroy the vitamin C content of
foods. A typical cup of freshly squeezed orange juice
contains 100 mg of ascorbic acid, while a cup of juice
reconstituted from frozen concentrate contains about
120 mg of the vitamin, probably because of a special
effort to concentrate ascorbic acid during the quick
freezing process and the fact that vitamin C is most
stable in an acid medium, such as fruit juice. However,
the vitamin in frozen orange juice can be broken down
by oxygen as soon as the juice is reconstituted and
warmed to refrigeration temperatures.
C (Ascorbic Acid) Content of Selected Foods
(Average adult RDA is 60 mg)
(Mg per 3 oz)
of actual cooking losses range between 30 and 60 percent,
although some procedures, such as blanching vegetables
and then cooking them in iron or copper pots, can
result in the destruction of almost all of the vitamin
C. In summary, the vitamin C content of foods is highly
variable. For optimal C content, consume fresh, uncooked
fruits and vegetables and drink reconstituted frozen
disease associated with vitamin C deficiency is scurvy,
which was common in sailors in the days before vitamin
C was known. Also hard hit were people in northern
climates who did not have access to fresh fruits and
vegetables during the long winter months. Now our
ability to transport fresh food over great distances
has dramatically decreased the amount of scurvy world
wide. Nevertheless, marginal vitamin C deficiencies
still exist in some people, even in Westernized countries.
It takes several months of a vitamin C - deficient
diet before scurvy develops. However, marginal deficiencies
can develop sooner.
basic descriptions of the symptoms of scurvy come
from the logs Jacques Cartier kept during long sea
voyages. Cartier's log, written in 1535, graphically
tells how severe the disease can be : "unknown
sickness began to spread itself amongst us at the
strangest sort that was ever heard or seen; inasmuch
that some did lose all their strength and could not
stand upon their feet; the did their legs swell, their
sinews shrunk and became black as coal. Others also
their skins spotted with spots of blood, of a purple
colour. It ascended up their ankles, knees, thighs,
shoulders, arms and neck. The mouth became stinking;
their gums so rotten that the flesh came away to the
roots of their teeth, which at last did fall out."
The latter symptom is a result of periodontal disease,
which can be caused by vitamin C deficiency as well
as other factors.
Some symptoms of marginal deficiency are fatigue,
shortness of breath, digestive difficulties, bleeding
gums, easy bruising, swollen or painful bone joints,
nosebleeds, anemia, more frequent infections, and
slow wound healing. Some nutrition experts claim that
people deficient in C who are at risk for heart attacks
or strokes are more likely to develop one of these
serious problems because of blood vessel weakness.
Vitamin C can be measured directly in the blood. The
symptoms of scurvy start to appear when the blood
level falls below 1 mg for every 100 ml of blood.
The vitamin can also be measured in white blood cells.
These levels are often taken as a better representation
of the amount of vitamin C in body tissues because
they are not as subject to variation as the blood
WHO MAY BENEFIT FROM SUPPLEMENTATION
C deficiencies have been found in seniors, particularly
those living in nursing homes or other health care
facilities. The reasons for this deficiency seem to
be inattention to diet. The loss of appetite, and
in some cases difficulty digesting foods rich in vitamin
C, many of which are also high in roughage. On the
basis of this information, we suggest that all people
over age sixty-five take a daily multivitamin containing
at least 60 mg of ascorbic acid. Of course, this does
not eliminate the need for a balanced diet, including
vitamin C-rich foods, but it does provide a measure
of protection against possible deficiencies.
women should supplement their daily vitamin C intake
because of the demands by the fetu's developing bones,
teeth, and connective tissue. Breast-feeding women
also bleed supplemental C because they must supply
enough vitamin C in their milk to support their baby's
rapid growth. Smokers women who take oral contraceptives,
and people under any kind of stress should supplement
their daily intake of vitamin C, but the amount does
not have to exceed 500 mg per day.
C is considered nontoxic in doses less than 1 g per
day. Over 1 g, less is known about long-term consumption.
However, large-scale clinical trials involving thousands
of volunteers who received between 1 and 30 g of vitamin
C per day revealed very few problems. Since the 1970s
large doses of vitamin C have been consumed by millions
in the United States with very few reports of adverse
effects. As discussed later, the body is saturated
at about 500 mg per day, and higher doses are simply
eliminated in the urine.
are scattered reports of a variety of adverse reactions
to vitamin C, including upset stomach and diarrhea,
but these are rare. Because vitamin C is metabolized
in the body to oxalic acid, which is relatively insoluble
in urine, high doses of C have the potential to contribute
to the formation of kidney stones. High doses can
also block the body's ability to eliminate urate,
which could be deposited in joints, causing gout.
The significance of these risks is controversial,
but if you have bladder problems, kidney stones, or
gout, we suggest not using large amounts of vitamin
C because of potential problems associated with crystal
Patients with iron overload conditions should avoid
large amounts of vitamin C because it will increase
iron absorption. Hemolysis has been reported in patients
having glucose-6-phosphate dehydrogenase deficiency.
This deficiency makes patients susceptible to hemolysis
from taking many common drugs. These patients need
to avoid high-dose vitamin C.
stoppages of large doses of vitamin C have been reported
to result in deficiency symptoms. This is called rebound
scurvy ; it is considered a very rare event and is
not well documented megadoses of vitamin C. They have
developed deficiency symptoms soon after birth, probably
because their body tissues had become used to very
large amounts of vitamin C in the blood circulating
from their mother. High doses of any vitamin or mineral
should be avoided during pregnancy because the risks
are simply not known.
C can interfere with certain urine and blood tests
for sugar and for the test for occult blood in the
C supplements may be given to counteract any of the
standard symptoms of vitamin C deficiency reviewed
earlier in this profile. However, such symptoms will
not be alleviated by vitamin C unless they are, infact,
caused by vitamin deficiency.
important role of vitamin C as a water-soluble antioxidant
and free-radical scavenger is discussed. Low dietary
vitamin C intake has been associated with increased
risk for cancer, especially cancer of the stomach,
throat, intestines, and lungs. Low intake also increases
the risk for heart disease, high blood pressure, and
C is often given after surgery to speed the healing
of surgical wounds. Vitamin C has an important role
in the synthesis of new connective tissue, and controlled
studies have shown that supplements speed up healing
of bedsores and experimentally administered cuts in
the mouth. Not all studies show benefit, however.
We suggest that supplements be used following any
significant injury or surgery in order to ensure ample
vitamin C to help speed the healing process. Doses
of 250 to 500 mg per day are sufficient for this effect.
claim that vitamin C will cure or prevent the common
cold is of obvious interest to everyone. This is not
a new idea, but it was popularized in 1970 with the
publication of vitamin C and the common cold, by Dr.
Linus Pauling. Incredibly, surveys have shown that
as many as half the American people have, at sometime,
taken extra vitamin C to prevent or treat the common
cold, an illness responsible for billions of dollars'
worth of lost time and productivity each year. Advocates
of this treatment claim that between 1 and 5 g a day
of ascorbic acid will prevent the common cold and
that still higher doses are useful in treating cold
symptoms, if you are unlucky enough to get sick in
spite of the prevention regimen.
What is the evidence ? Vitamin C advocates usually
cite the results of studies conducted in the 1940s
and 1950s, but most of these early studies are technically
incorrect and have been criticized for that reason.
The publication of Linus Pauling's book and the increased
popularity of vitamin C have sparked careful evaluation
by a number of reputable investigators. At least ten
careful, technically correct studies have appeared
in the literature since 1970. What emerges from these
investigations is a picture far less optimistic than
that presented by advocates. In these large, controlled
studies, vitamin C does not seem to have much of an
effect in preventing the cold but has a small effect
in decreasing its severity.
One study worth nothing was conducted using school-age
twins as subjects. One twin from each pair was given
vitamin C , while the other was given a placebo with
the same appearance and taste of the vitamin C. As
the twins lived in the same household, they were exposed
to all the same factors, such as diet and contact
with others, that could potentially influence a cold.
Technically, this was a nearly ideal experiment. The
results of this study were similar to those reported
by other investigators: The children taking vitamin
C had some what less severe colds, but the number
of colds was essentially the same as experienced by
those taking placebo.
Despite the evidence from the large clinical trials,
many claim to benefit from taking vitamin C during
the winter months. Probably everyone has friends and
coworkers who swear by vitamin C and claim. "
I never get a cold while I take vitamin C." It
is difficult to evaluate these claims of success.
The evidence shows otherwise. There may be a subset
of the population that strongly benefits, but their
response does not show up in the large trials. On
the basis of the evidence, you might expect a mild
reduction in cold symptoms, although the high doses
usually suggested do not seem to be necessary. Studies
have been conducted in which a dose of between 80
and 200 mg per day was sufficient to produce this
effect. It is possible that a small number of people
are deficient in vitamin C or need unusually large
amounts. Taking extra vitamin C will help these few
people. We believe that a saturation - level dose
of vitamin C is enough to provide excellent antioxidant
and free-radicals scavenging activities and will optimize
the immune system to fight infection such as the common
the 1970s there was some enthusiasm for using very
high doses of vitamin C in the treatment of cancer.
Interest has waned, however, as the results from several
trials did not show benefit. Now most attention is
focused on the antioxidant properties of vitamin C
and the connection between supplementation with antioxidants
and protection against cancer. As discussed in Vitamin
C is an important link in the antioxidant sequence,
but vitamin E may be the most important antioxidant
vitamin with respect to cancer and heart disease prevention.
Consumption of fruits and vegetables high in vitamin
C is protective, and this is the best step you can
take to decrease risks. Additionally, we recommended
daily consumption of 200 to 500mg of vitamin C to
optimize antioxidant and free radical protection.
Alcoholics and Drug Abusers
are small number of unverified reports attesting to
the usefulness of enormous doses of ascorbic acid,
in some cases given by injection, in drying out alcoholics
and detoxifying people addicted to narcotics and tranquilizers.
People treated with vitamin C are given massive doses
and are supposed to experience fewer of the adverse
effects normally associated with drug withdrawal :
cramps, nausea, generalized discomfort. This application
of vitamin C should be considered unproven, although
future research may shed some light on a possible
role for this vitamin in this regard.
and Lipid Lowering
story of vitamin C and blood lipids is riddled with
conflicting information. While there is agreement
that ascorbic acid will lower blood cholesterol in
vitamin -deficient patients, it does not necessarily
follow that cholesterol levels in other people will
be affected. In fact, studies have shown that people
with high blood cholesterol who are otherwise healthy
are not affected by vitamin C. There are better drugs
to lower cholesterol.
stroll down the vitamin aisle of your local pharmacy,
health food, or vitamin store will soon make you aware
that ascorbic acid is available in just about every
possible dosage form and strengths. The combination
of vitamin C with bioflavonoids improves vitamin C
absorption somewhat, but these products are more expensive,
and at doses of over 500 mg per day, the small extra
amount absorbed is probably not important. Timed-released
products are poorly absorbed. Synthetic vitamin C
tablets are fine and are inexpensive.