Vitamin C is a water-soluble vitamin. It is
needed for normal growth and development.
Water-soluble vitamins dissolve in water. Leftover
amounts of the vitamin leave the body through the urine. That
means you need an ongoing supply of such vitamins in your diet.
Function
Vitamin C is needed for the growth and repair of tissues in all
parts of your body. It is used to:
•Form an important protein used to make skin, tendons, ligaments,
and blood vessels
•Heal wounds and form scar tissue
•Repair and maintain cartilage, bones, and teeth
•Aid in the absorption of iron
Vitamin C is one of many antioxidants. Antioxidants
are nutrients that block some of the damage caused by free radicals.
•Free radicals are made when your body breaks down food
or when you are exposed to tobacco smoke or radiation.
•The buildup of free radicals over time is largely responsible
for the aging process.
•Free radicals may play a role in cancer, heart disease,
and conditions like arthritis.
The body is not able to make vitamin C on its
own, and it does not store vitamin C. It is therefore important
to include plenty of vitamin C-containing foods in your daily
diet.
For many years, vitamin C has been a popular
remedy for the common cold.
•Research shows that for most people, vitamin C supplements
or vitamin C-rich foods do not reduce the risk of getting the
common cold.
•However, people who take vitamin C supplements regularly
might have slightly shorter colds or somewhat milder symptoms.
•Taking a vitamin C supplement after a cold starts does
not appear to be helpful.
Food Sources
All fruits and vegetables contain some amount of vitamin C.
Fruits with the highest sources of vitamin C
include:
•Cantaloupe
•Citrus fruits and juices, such as orange and grapefruit
•Kiwi fruit
•Mango
•Papaya
•Pineapple
•Strawberries, raspberries, blueberries, and cranberries
•Watermelon
Vegetables with the highest sources of vitamin
C include:
•Broccoli, Brussels sprouts, and cauliflower
•Green and red peppers
•Spinach, cabbage, turnip greens, and other leafy greens
•Sweet and white potatoes
•Tomatoes and tomato juice
•Winter squash
Some cereals and other foods and beverages are
fortified with vitamin C. Fortified means a vitamin or mineral
has been added to the food. Check the product labels to see how
much vitamin C is in the product.
Cooking vitamin C-rich foods or storing them
for a long period of time can reduce the vitamin C content. Microwaving
and steaming vitamin C-rich foods may reduce cooking losses. The
best food sources of vitamin C are uncooked or raw fruits and
vegetables. Exposure to light can also reduce vitamin C content.
Choose orange juice that is sold in a carton instead of a clear
bottle.
Side Effects
Serious side effects from too much vitamin C
are very rare, because the body cannot store the vitamin. However,
amounts greater than 2,000 mg/day are not recommended. Doses this
high can lead to stomach upset and diarrhea. Large doses of vitamin
C supplementation are not recommended during pregnancy. They can
lead to vitamin C deficiency in the baby after delivery.
Too little vitamin C can lead to signs
and symptoms of deficiency, including:
•Anemia
•Bleeding gums
•Decreased ability to fight infection
•Decreased wound-healing rate
•Dry and splitting hair
•Easy bruising
•Gingivitis (inflammation of the gums)
•Nosebleeds
•Possible weight gain because of slowed metabolism
•Rough, dry, scaly skin
•Swollen and painful joints
•Weakened tooth enamel
A severe form of vitamin C deficiency is known
as scurvy. This mainly affects older, malnourished adults.
Recommendations
The Recommended Dietary Allowance (RDA) for
vitamins reflects how much of each vitamin most people should
get each day. The RDA for vitamins may be used as goals for each
person.
How much of each vitamin you need depends on
your age and gender. Other factors, such as pregnancy and illnesses,
are also important.
The best way to get the daily requirement of
essential vitamins, including vitamin C, is to eat a balanced
diet that contains a variety of foods.
Dietary Reference Intakes for vitamin
C:
Infants
•0 to 6 months: 40* milligrams/day (mg/day)
•7 to 12 months: 50* mg/day
Children
•1 to 3 years: 15 mg/day
•4 to 8 years: 25 mg/day
•9 to 13 years: 45 mg/day
Adolescents
•Girls 14 to 18 years: 65 mg/day
•Pregnant teens: 80 mg/day
•Breastfeeding teens: 115 mg/day
•Boys 14 to 18 years: 75 mg/day
Adults
•Men age 19 and older: 90 mg/day
•Women age 19 year and older: 75 mg/day
•Pregnant women: 85 mg/day
•Breastfeeding women: 120 mg/day
Smokers or those who are around secondhand smoke
at any age should increase their daily amount of vitamin C an
additional 35 mg per day.
Women who are pregnant or breastfeeding and those
who smoke need higher amounts of vitamin C. Ask your health care
provider what amount is best for you.
Alternative Names
Ascorbic acid; Dehydroascorbic acid
References
Hemila H, Chalker E. Vitamin C for preventing and treating the
common cold. Cochrane Database Syst Rev. 2013: 31;1:CD000980.
PMID: 23440782 www.ncbi.nlm.nih.gov/pubmed/23440782.
Institute of Medicine. Food and Nutrition Board.
Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium,
and Carotenoids. National Academy Press, Washington, DC, 2000.
PMID 25077263 www.ncbi.nlm.nih.gov/pubmed/25077263.
Mason JB. Vitamins, trace minerals, and other
micronutrients. In: Goldman L, Schafer AI, eds. Goldman's Cecil
Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap
225.
Salwen MJ. Vitamins and trace elements. In: McPherson
RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management
by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders;
2011:chap 26.
Update Date 2/2/2015
Updated by: Emily Wax, RD, The Brooklyn Hospital
Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Isla
Ogilvie, PhD, and the A.D.A.M. Editorial team.
High-dose vitamin C does kill cancer
High-dose vitamin C does kill cancer—but
only when it’s given intravenously. It’s now just
a few steps away from being approved as a safe and effective cancer
treatment alongside chemotherapy and radiation.
Although researchers have tested the vitamin
as a cancer therapy many times, they almost always concluded that
it was ineffective—but they were guaranteeing failure by
giving it orally to patients.
When it’s given intravenously, it bypasses
the gut and goes directly into the bloodstream—where concentrations
of the vitamin are up to 500 times higher than when it’s
taken orally—and targets cancer cells, say researchers at
the University of Iowa.
The therapy is now going through the approval
process, and could soon be available as an alternative to chemotherapy
or radiation, the two conventional cancer treatments.
It’s been proved to be effective in animal
studies, and phase 1 trials have demonstrated that it’s
safe and well-tolerated.
Now doctors at the university are starting to
use it on patients with pancreatic cancer and lung cancer, and
are measuring their progress against other patients who will continue
to be given chemotherapy or radiation.
Biologist Garry Buettner, who works at the university,
has worked out just why vitamin C is so effective: the vitamin
breaks down quickly in the body, and generates hydrogen peroxide
that kills cancer cells. “Cancer cells are much less efficient
in removing hydrogen peroxide than normal cells, so cancer cells
are much more prone to damage and death from a high amount of
hydrogen peroxide”, he explained. “This explains how
very, very high levels of vitamin C do not affect normal tissue,
but can be damaging to tumour tissue.”
(Source: Redox Biology, 2016; 10: 274)
