  Why is
Vitamin C important?
Vitamin C is important to
all animals, including humans, because it's vital to the production of collagen.
Vitamin C is also important because it helps protect the fat-soluble vitamins A & E as well as fatty acids from oxidation.
I have to confess that until I got to college, I had only a vague idea what collagen was & why it was so important. Collagen is the
most ubiquitous substance in the body because it's the most abundant of the fibers contained in connective tissue.
Connective tissue gives
our body form & supports our organs. To give you an idea of how important collagen is, here's a list of the 5 types of
collagen & where they're used in the body.
- Type 1 - Connective tissue of skin,
bone, teeth, tendons, ligaments, fascia, organ capsules
- Type 2 - Cartilage
- Type 3 - Connective tissue of our
organs (liver, spleen, kidneys, etc.)
- Type 4, 5 - The separating layer
between epithelial & endothelial cells as well as between skeletal or smooth muscle cells (basal
lamina), kidney glomeruli, lens capsule & Schwann & glial cells of the nervous system.
As you can see,
collagen is everywhere in the body & vitamin C plays a role in the formation of collagen.
So, how is vitamin C involved in collagen synthesis?
When collagen
is produced, there's a complex series of events, some occurring inside of the cell & some outside of the cell. Vitamin C is active inside of the cell, where it hydroxylates (adds hydrogen & oxygen) to 2 amino acids:
This helps form a precursor
molecule called procollagen that is later packaged & modified into collagen outside
of the cell. Without vitamin C, collagen formation is
disrupted, causing a wide variety of problems throughout the body. (see
How Cells Work for more information
about the biochemistry of cells.)
Vitamin C - The Most Famous of Vitamins!
By David Leonhardt
We
call Vitamin C, also known as ascorbic acid, "the most famous of vitamins" because it really is the best known. It is the
first one schoolchildren learn. It is the most cited cure for the common cold. Most people can rhyme off at least a few foods
that contain vitamin C. And vitamin C is the single most searched nutrient on the Internet.
HISTORY: Nobel Prize winning
biochemist Dr. Albert Szent-Gyorgyi first isolated vitamin C in 1928. (As someone of Hungarian descent,
I find this a touch exciting.)
Vitamin C first got its reputation for beating the common cold in 1970, when fellow
Nobel Prize winner Linus Pauling published his bestselling book "Vitamin C and the Common Cold".
In it, he suggested that taking vitamin C at levels well above the USA RDA (now 60 milligrams per day) could strengthen the
immune system and help ward off the common cold.
BENEFITS: Vitamin C helps form collagen, a glue-like fibrous protein
in bone, cartilage, tendons and other connective tissue. Vitamin C helps give structure and maintain such body parts as bones,
cartilage, muscle, veins, capillaries and teeth.
But recent studies have also linked "adequate dosages" of vitamin
C to preventing a number of common cancers, of helping boost the nervous system, of prolonging life, of reducing the risk
of heart disease, of softening the symptoms of respiratory diseases such as asthma and cystic fibrosis, and of keeping skin
and glands healthy.
SOURCES: Most animals manufacture their own vitamin C. Primates, such as humans, gorillas, and
monkeys, have somehow lost this ability.
Which is why we need to get our vitamin C from our diets.
It is well
known that citrus fruits, such as oranges, lemons, grapefruits, tangerines, limes, mandarins and others contain vitamin C.
In fact, vitamin C comes almost exclusively from fruits and vegetables.
Other good sources are tomatoes, strawberries,
raspberries, broccoli, asparagus, brussels sprouts, cauliflower, cabbage, peas, rutabagas, cantaloupe, kiwi, papayas, potatoes
and watermelon.
One place that is NOT a good source are vitamin C pills, which the body just cannot absorb properly.
This is a water soluble vitamin best taken in its natural juice or in a liquid supplement.
OPTIMUM USAGE: Fortunately,
if you consume too much of a water soluble vitamin, your body will get rid of excess. It also means that your body does not
store it for long periods of time. You can't "stock up" on it, and you can reach a saturation point quickly; you need vitamin
C several times a day.
Being a water-soluble vitamin, you lose it when you boil foods. For instance, if you boil your
broccoli, you will lose the vitamin C. However, if you boil your broccoli in a soup, you will get the broccoli's vitamin C
in the broth.
Do not soak or store fruits or vegetables in water, for you can lose the vitamin C that way. In short,
the fresher cut the fruit or vegetable, and the less cooked, the more vitamin C you will get.
Like all vitamins and minerals,
Vitamin C is most effective when combined with other nutrients. For example, one of the big benefits of vitamin C is that
it helps the body digest and absorb iron, an essential mineral for good health.
This is one of the reasons it's so important to take vitamin supplements that contain as many
different nutrients as possible, so the body can absorb them together & enjoy the maximum benefits from each one.
Dosage: Most experts agree that the US RDA is only a fraction of what it should be & that
daily vitamin C levels up to 1,000 or even 2,000 milligrams per day are safe & healthy.
source: selfgrowth.com
What is "a good food source"?
A good food source of
vitamin C contains a substantial amount of vitamin C in relation to its calorie content & contributes at least 10% of
the U.S. Recommended Daily Allowance (RDA) for vitamin C in a selected serving size.
The U.S. RDA for
vitamin C is 60 milligrams per day. The U.S. RDA given is for adults (except pregnant or lactating women) &
children over 4 years of age.
The U.S. RDA for vitamin
C is the amount of the vitamin used as a standard in nutrition labeling of foods. This allowance is based on the 1968 RDA
for 24 sex & age categories set by the Food & Nutrition Board of the National Academy of Sciences. The 1989 RDA for
vitamin C has been set at 60 mg per day for women & men 19 to 50 years of age.
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Good
Sources of Vitamin C
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Food
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Serving Size |
Percentage of US RDA1 |
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Breads, Cereals & Other Grain Products
|
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Ready-to-eat cereals, fortified2
|
1 ounce |
++ |
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Fruits
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Apples: |
|
|
|
Baked, unsweetened |
1 medium |
+ |
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Raw |
1 medium |
+ |
|
Apple juice3 |
3/4 cup |
+++ |
|
Banana, raw |
1 medium |
+ |
|
Blackberries, raw |
1/2 cup |
++ |
|
Blueberries, raw |
1/2 cup |
+ |
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Cantaloupe: |
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|
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Frozen balls, unsweetened |
1/2 cup |
+++ |
|
Raw |
About 1/2 cup diced |
+++ |
|
Cranberry juice cocktail3 |
1 cup |
+++ |
|
Grapefruit, raw |
1/2 medium |
+++ |
|
Grapefruit juice, fresh, canned, or reconstituted
frozen, unsweetened |
3/4 cup |
+++ |
|
Grapefruit & orange sections, canned, unsweetened
|
1/2 cup |
+++ |
|
Grapefruit & orange juice, unsweetened
|
3/4 cup |
+++ |
|
Grape juice, unsweetened3 |
3/4 cup |
+++ |
|
Honeydew melon, raw |
About 3/4 cup diced |
+++ |
|
Kiwifruit, raw |
1 medium |
+++ |
|
Mandarin orange sections, canned or frozen,
juice-pack |
1/2 cup |
+++ |
|
Mango, raw |
1/2 medium |
+++ |
|
Nectarine, raw |
1 medium |
+ |
|
Orange, raw |
1 medium |
+++ |
|
Orange juice, fresh, canned, or reconstituted
frozen, unsweetened |
3/4 cup |
+++ |
|
Papaya, raw |
1/4 cup |
+++ |
|
Peaches: |
|
|
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Frozen, unsweetened3 |
1/2 cup |
+++ |
|
raw |
1 medium |
+ |
|
Pear, raw |
1 medium |
+ |
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Pineapple: |
|
|
|
Canned, chunks, juice-pack |
1/2 cup |
+ |
|
Raw |
1/2 cup |
+ |
|
Pineapple juice, canned, unsweetened |
3/4 cup |
++ |
|
Pineapple-grapefruit juice, canned or reconstituted
frozen, unsweetened |
3/4 cup |
+++ |
|
Pineapple-orange juice, canned or reconstituted
frozen, unsweetened |
3/4 cup |
+++ |
|
Plum, raw |
1 medium |
+ |
|
Pomegranate, raw |
1 medium |
+ |
|
Raspberries: |
|
|
|
Frozen, unsweetened |
1/2 cup |
++ |
|
Raw |
1/2 cup |
++ |
|
Strawberries, raw, frozen, or canned, unsweetened
|
1/2 cup |
+++ |
|
Tangelo, raw |
1 medium |
+++ |
|
Tangerine, raw |
1 medium |
+++ |
|
Watermelon, raw |
About 1 3/4 cups diced |
+++ |
|
|
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Vegetables
|
|
Artichoke, globe (French), cooked |
1 medium |
+ |
|
Asparagus, cooked |
1/2 cup |
+++ |
|
Beans, green or yellow, cooked |
1/2 cup |
+ |
|
Beans, lima, cooked |
1/2 cup |
+ |
|
Bean sprouts, raw or cooked |
1/2 cup |
+ |
|
Broccoli, raw or cooked |
1/2 cup |
+++ |
|
Brussels sprouts, cooked |
1/2 cup |
+++ |
|
Cabbage: |
|
|
|
Chinese, cooked |
1/2 cup |
++ |
|
Green, raw or cooked |
1/2 cup |
++ |
|
Red, raw or cooked |
1/2 cup |
+++ |
|
Cauliflower, rare or cooked |
1/2 cup |
+++ |
|
Chard, cooked |
1/2 cup |
+ |
|
Collards, cooked |
1/2 cup |
+ |
|
Endive, chicory, escarole, or romaine, raw
|
1 cup |
+ |
|
Dandelion greens, raw |
1/2 cup |
+ |
|
Kale, cooked |
1/2 cup |
+++ |
|
Kohlrabi, cooked |
1/2 cup |
+++ |
|
Mustard greens, cooked |
1/2 cup |
++ |
|
Okra, cooked |
1/2 cup |
+ |
|
Onion, spring: |
|
|
|
Cooked |
1 large |
+ |
|
Raw |
1 medium |
+ |
|
Parsnips, cooked |
1/2 cup |
+ |
|
Peas, green, cooked |
1/2 cup |
+ |
|
Pepper, sweet, green or red, raw or cooked
|
1/2 cup |
+++ |
|
Plantain, green or ripe, boiled |
1 medium |
+++ |
|
Poke greens, cooked |
1/2 cup |
+++ |
|
Potato, with skin: |
|
|
|
Baked |
1 medium |
++ |
|
Boiled |
1 medium |
++ |
|
Pumpkin, cooked |
1/2 cup |
+ |
|
Radishes, raw |
6 large |
+ |
|
Rutabagas, cooked |
1/2 cup |
++ |
|
Snow peas, raw or cooked |
1/2 cup |
+++ |
|
Spinach: |
|
|
|
Cooked |
1/2 cup |
+ |
|
Raw |
1 cup |
+ |
|
Squash: |
|
|
|
Summer, yellow, raw |
1/2 cup |
+ |
|
Winter, cooked, mashed |
1/2 cup |
+ |
|
Sweet Potato, baked or boiled |
1 medium |
+++ |
|
Tomatoes: |
|
|
|
Canned |
1/2 cup |
+++ |
|
Cooked |
1/2 cup |
++ |
|
Raw |
1 medium |
++ |
|
Tomato juice or tomato vegetable juice cocktail,
canned |
3/4 cup |
+++ |
|
Turnip greens w/turnips, cooked |
1/2 cup |
+ |
|
Turnips, cooked |
1/2 cup |
+ |
|
Watercress, raw |
1/2 cup |
+ |
|
|
|
|
|
Meat,
Poultry, Fish & Alternates |
|
Liver, braised: |
|
|
|
beef or pork |
3 ounces |
++ |
|
chicken |
1/2 cup diced |
+ |
|
|
|
|
|
Fish
& Seafood |
|
Clams, steamed, boiled, or canned, drained
|
3 ounces |
+ |
|
Mussels, steamed, boil, or poached |
3 ounces |
+ |
|
1 A selected serving size contains:
+ 10-24% of
the US RDA for adults & children over 4 years of age
++ 25-39% of
the US RDA for adults & children over 4 years of age
+++ 40% or
more of the US RDA for adults & children over 4 years of age
2 See section on fortified foods.
3 Contains added vitamin C. |
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nutritional navigation here at changes!
vitamins
vitamin c - you are here!
minerals
What about taking vitamin C supplements?
One way an individual can
up their intake of vitamin C is thru the consumption of vitamin
C supplements.
A report issued by the Food
& Nutrition Board in 2000 sets the upper intake level for vitamin C at 2,000 mg a day
for adults. This dosage recommendation includes vitamin C obtained from both the the consumption
of food & supplements containing vitamin C.
Where do we get vitamin
C?
In 1990, 93% of the vitamin C in
the diets of Americans came from fruits & vegetables. Citrus fruits & tomatoes contributed almost 1/2 of the vitamin C provided by the fruits & vegetables group.
Foods that contain small amounts of vitamin C
but aren't considered good sources can contribute significant amounts of vitamin C to an
individual's diet if these foods are eaten often or in large amounts.
Average intake of vitamin C in the
typical American diet. The "Other Foods" category includes legumes, nuts, & soy (0.1%) & miscellaneous foods (0.8%).
Source: Gerrior
SA, Zizza C. 1994 Nutrient Content of the U.S. Food Supply, 1909-1990. Home Economics Research Report No. 52. U.S.
Department of Agriculture, Washington, D.C.
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Why do we need vitamin C?
Vitamin C, a water-soluble vitamin,
is important in forming collagen, a protein that gives structure to:
- bones
- cartilage
- muscle
- blood vessels
Vitamin C also helps
maintain:
- capillaries
- bones
- teeth
- aids in the absorption of iron
Do
we get enough vitamin C?
According to recent surveys of the U.S. Dept. of Agriculture (USDA),
the average intake of vitamin C by Americans 20 years of age & older was over the RDA
for vitamin C.
Women tended to consume less than men of the same age. Most nutrition scientists
believe that there are no known advantages in consuming excessive amounts of vitamin C.
A deficiency of vitamin C causes the disease Scurvy. Scurvy is rarely seen today except in alcoholics who receive their entire
calorie intake from alcohol.
Scurvy causes bleeding &
inflamed gums, loose teeth, poor wound healing (purplish spots called petechiae),
easy bruising, bumps of coiled hair on the arms & legs, pain in the joints, muscle wasting & many other problems.
It was a Scottish physician
named James Lind back in 1753 that first advocated fresh vegetables & ripe fruits to prevent Scurvy. The British Navy
adopted his advice some 40 years later. The navy men were ever after nicknamed "Limeys" because they took lime juice on long
sea voyages to ward off Scurvy.
How can we get enough vitamin
C?
Eating a variety of foods that contain vitamin
C is the best way to get an adequate amount. Healthy individuals who eat a balanced diet rarely need supplements.
The list of foods on the left will help you select those foods that
are good sources of vitamin C as you follow the Dietary Guidelines. This list of food sources
was derived from the same nutritive value of foods tables used to analyze information for recent food consumption surveys
of the USDA.
Vitamin C is found in citrus fruits such as oranges, limes & grapefruit
& vegetables including tomatoes, green pepper, potatoes & many others.
Vitamin C is easily damaged during the food preparation stage, such
as during chopping, exposure to air, cooking, boiling & being submerged in water. The amount of
Vitamin C is high enough in most foods that the quantity that remains after processing is usually more than enough
for a daily supply.
The recommended dietary allowance
(RDA) of vitamin C is 60 to 90 milligrams per day. Men should consume more vitamin C than women & individuals who smoke cigarettes are encouraged to consume 35 more mg of vitamin C than average adults.
This is due to the fact that
smoking depletes vitamin C levels in the body & is a catalyst for biological processes which damage cells. As little as
5-7 mg a day will prevent scurvy & the average American gets about 72 mg a day.
It is interesting to note that Vitamin C is used as an inexpensive
preservative in many processed foods, making deficiencies even more rare.
How to Prepare
Foods to Retain Vitamin C
Vitamin C can be lost from foods during preparation, cooking, or storage.
To retain vitamin C:
- Serve fruits & vegetables raw whenever possible.
- Steam, boil, or simmer foods in a minimal amount of water, or microwave
them for the shortest time possible.
- Cook potatoes in their skins.
- Refrigerate prepared juices & store them for no more than 2 to 3 days.
- Store cut raw fruits & vegetables in an airtight container & refrigerate,
don't soak or store in water. Vitamin C will be dissolved in the water.
What about fortified foods?
Some juices not normally a source of vitamin C, such as grape & apple, have vitamin C added.
A 3/4-cup (juice glass) serving of these fortified juices may provide 40% or more of the U.S. RDA for
vitamin C. Check the label for the exact amount. Vitamin C (ascorbic acid) is added to frozen peaches to prevent discoloration.
Most ready-to-eat cereals are fortified w/vitamin C. Fortified ready-to-eat cereals usually contain at
least 25% of the U.S. RDA for vitamin C. Because cereals vary, check the label on the package for the percentage of the U.S.
RDA for a specific cereal.
What is a serving?
The serving sizes used on the list of good sources are only estimates of the amounts of food you might
eat. The amount of a nutrient in a serving depends on the weight of the serving.
For example, 1/2 cup of a cooked vegetable contains more vitamin C than 1/2 cup of the same vegetable
served raw, because a serving of the cooked vegetable weighs more.
Therefore, the cooked vegetable may appear on the list, while the raw form does not. The raw vegetable
provides the nutrient, just not enough in a 1/2-cup serving to be considered a good source.
Can Vitamin C cure a cold or cancer?
Nobel laureate Linus Pauling, Ph.D., in his last interview
months before his death (April 1994), continued to advocate high doses (megadoses) of vitamin
C to cure & prevent colds, prolong the lives of terminal cancer patients & prevent other ailments.
The basic premise
of his avocation of vitamin C in these doses was that because man was one of the few animals that don't produce its own vitamin
C, it's somehow a design flaw in our genetic make-up. He calculated that an average adult should need about 10-12 grams of
vitamin C daily to prevent a wide range of ailments.
Recent research has indicated that the intake
of of antioxidants like vitamin C can prevent or counteract cell damage due to aging & exposure to antioxidants. However,
studies have yet to prove that vitamin C's effectiveness at the cell level translates to the prevention of or cure for chronic
diseases. High doses of vitamin C at the beginning of a cold has only been shown in some cases to reduce the severity of the
symptoms to a modest degree, due to a mild antihistaminic effect.
Vitamin C has not been shown to prevent the
common cold. Similar high doses of vitamin C used for the treatment of cancer patients have not been found to be beneficial.
e.g., research done at the Mayo clinic in a
double blind trial (neither the doctors or the patients knew who was given the high doses of vitamin C) revealed
that those who received the vitamin C in the high doses actually did worse than those who got a placebo.
What's wrong w/taking high doses of vitamin C?
Some people believe that because vitamin C is
water-soluble, it's safe to take in high doses. While it's best to not exceed the recommended upper intake level of 2,000
mg a day, the most serious possible consequence of an intake above this dosage is diarrhea.
One myth about vitamin C is that it is an antioxidant,
but that isn't completely true. Vitamin C is a redox agent, meaning that it acts as an antioxidant in some cases & an
oxidant in others.
Antioxidants are important because they inhibit
chemical reactions w/oxygen or highly reactive free radicals. These reactions (oxidation reactions), cause damage to cells.
Vitamin C only acts as an antioxidant in some circumstances.
Vitamin C is an important part of a healthy
diet. It isn't a miracle drug & may cause harm if taken in extreme excess. A well-balanced, varied diet will ensure that
you receive more than enough vitamin C to prevent scurvy & other potential health problems.
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