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Importance of Vitamin C

This well-known vitamin is important in the maintenance of collagen, the protein which holds most of the soft tissues of the body together. Along with B6, it is also vital to the utilization of amino acids. It enhances the absorption of iron from vegetable sources. It inhibits the synthesis of nitrosamines, compounds implicated in cancer. Fruit sources are citrus fruits, fresh strawberries, cantaloupe, pineapples and guava. Vegetable sources are broccoli, Brussel sprouts, tomatoes, spinach, kale, green peppers, cabbage and turnips. Regular intake of vitamin C insures health of the soft tissues of the body and perhaps an ounce of cancer protection. There is ample research evidence that substantial doses of vitamin C, taken regularly over the course of years, prolong a person's life expectancy by lowering the probability of vascular disease. (The same is true of vitamin E.)

Vitamin C contributes to healing wounds, maintenance of capillaries, bones and teeth, and absorption of iron. Citrus fruits, strawberries, and green vegetables such as broccoli are rich in vitamin C.

Vitamin C has been studied for many years. Vitamin C is important for every body process from bone formation to scar tissue repair. The only established role of the vitamin appears to be in curing or preventing scurvy. Vitamin C is the major water-soluble antioxidant within the body. A well-known function of Ascorbic acid is the role it plays in hydroxylation reactions that are essential for the formation of collagen. Vitamin C is important in collagen formation as it allows for a tight cross-linking of the triple helix, thereby resulting in stabilization of the peptide. Evidence also suggests that Ascorbic acid may be involved in collagen gene expression. Vitamin C is directly involved in the enzyme activity of two copper dependent mono-oxygenases, which are important in the formation of norepinephrine and serotonin. Furthermore, Ascorbic acid regulates the activity of some neurons within the brain. Some of these functions include neurotransmitter membrane receptor synthesis, and neurotransmitter dynamics. Indirectly, Ascorbic acid plays important regulatory roles throughout the entire body due to its involvement in the synthesis of hormones, hormone-releasing factors, and neurotransmitters. Animal models have also shown that Ascorbic acid is an important factor in development of the nervous system, specifically in the maturation of glial cells and myelin. Vitamin C is important to a host of numerous other functions within the body. The vitamin is an important aid in the absorption and conversion of iron to its storage form. Bile acid formation, and hence cholesterol degradation are highly dependent on Ascorbic acid. Some hypothesize that vitamin C may even have a hypocholesterolemic effect. This has been suggested because the enzyme needed for the first step in bile acid synthesis, cholesterol 7-alpha hydroxylase, is dependent upon the presence of vitamin C. Ascorbic acid may also has vasodilatory and anticlotting effects within the body by stimulating nitric oxide release. Physiological effects such as an antihistamine modified bronchial tone, and insulin responses have been linked to Ascorbic acid. The protection of neural and endothelial tissue, along with effects on cellular tone can also be attribute to vitamin C. Multiple other mechanisms of function for vitamin C have been proposed, but experimental results addressing these topics are variable. Possible other functions for vitamin C include regulation of cellular nucleotide concentrations, immune function, and the endocrine system. Vitamin C has been proposed by some to have pharmacological benefits in preventing cancer, infections, and the common cold. The role of vitamin C in preventing cancer is controversial, but has been studied for cancers of the oral cavity, uterus, esophagus, bladder, and pancreas. The research is at best equivocal and more studies are needed to further address the role of vitamin C in preventing cancer.

Vitamin C Deficiency

Between the 16th and 18th centuries numerous sea voyagers died mysterious deaths, but symptoms could be reversed with the consumption of citrus fruits. Dr. James Lind made this discovery in 1747 after the British Admiralty demanded that a cure for the disease be found. The disease was later termed scurvy and the cure ascorbic acid because of its antiscurvy properties (16). Today the disease still exists, but is rare in the United States. However, the symptoms and cure are well known. The disease is most commonly seen in people who have poor diets, cancers, are alcoholics, or have been institutionalized. The disease is more common in those who have cancer and those who are alcoholics due to the increased turnover rate of the vitamin.

Vitamin C daily recommended dosages

United States vitamin C daily recommendations

Recommended Dietary Allowance (adult male) 90 mg per day

Recommended Dietary Allowance (adult female) 75 mg per day

Tolerable Upper Intake Level (adult male) 2,000 mg per day

Tolerable Upper Intake Level (adult female) 2,000 mg per day

Recommendations for vitamin C intake have been set by various national agencies:

40 milligrams per day: the United Kingdom's Food Standards Agency

45 milligrams per day: the World Health Organization

60 mg/day: Health Canada 2007

60–95 milligrams per day: United States' National Academy of Sciences

Alternative recommendations on intakes

Some independent researchers have calculated the amount needed for an adult human to achieve similar blood serum levels as vitamin C synthesising mammals as follows:

400 milligrams per day: the Linus Pauling Institute.

500 milligrams per 12 hours: Professor Roc Ordman, from research into biological free radicals.

3,000 milligrams per day (or up to 300,000 mg during illness): the Vitamin C Foundation.

6,000–12,000 milligrams per day: Thomas E. Levy, Colorado Integrative Medical Centre.

6,000–18,000 milligrams per day: Linus Pauling's personal use.

Toxicity

The saturable kinetics of vitamin C make toxicity more likely when multiple large doses (~1gram) are consumed throughout a day versus one single dose. A common symptom of unabsorbed vitamin C left in the gastrointestinal tract is osmotic diarrhea. Vitamin C can be transformed in the body to oxalate, which is a common constituent of kidney stones. Doses up to 10 grams have shown to be associated with a higher prevalence of oxalate excretion, but the level does not fall outside of the normal range. As a precaution, people who are prone to kidney stones may want to avoid large doses (10 times the DRI or greater) of the vitamin. People who lack the control to regulate iron uptake should also avoid large doses of the vitamin. Vitamin C enhances iron absorption which, can lead to toxicity of iron in some people. Furthermore, excess ascorbate in the urine and feces can falsify lab tests such as glucose in the urine and fecal occult blood test.

Food sources of Vitamin C

A wide variety of food exists that contains vitamin C. A well-balanced diet easily obtains the DRI for vitamin C. It is widely known by the general public today that the best sources of vitamin C are citrus fruits and their juices. Fruits with a high vitamin C content include, but are not limited to oranges, lemons, peaches, strawberries, bananas and grapefruit. A wide variety of other foods also contain sufficient quantities of vitamin C. Cabbage, broccoli, cauliflower, leaf lettuce, tomatoes, potatoes, and beans also have relatively high (7 mg/100 g to 163 mg/100g) vitamin C content.

Fruit	mg vitamin C / 100 grams	mg vitamin C per average  size fruit/slice*	Ranking
**Acerola	1,677	80	exceptional*
Apple	6	8	fairly good
Apricot	10	4	-
Apricot, canned	3	2	-
Asian pear	4	5	-
Avocado	8	16	fairly good
Banana	9	11	good
Babaco	21 to 32	21 to 32	very good
Barbados Cherry	1,678	112	exceptional
Bilberry	1	0.01*(estim)	-
**Baobab	150 to 499	100	exceptional
Breadfruit	29	28*	very good
Blackberry	6	0.6(estim)	-
Blackcurrant	155 to 215	1.5 to 2*(estim.)	excellent
Blueberry	1.3 to 16.4	no data*	-
**Camu Camu	2,700	no data	astounding
Carambola	21	19	very good
Casimiroa	30	15*	very good
Crabapple	8	2 (estim.)	-
Cherimoya	9	10*	fairly good
Custard apple	19	no data	very good
Feijoa	25	13	good
Feijoa	31	16	very good
Feijoa	27	14	good
Fig	2	1	-
Grape, slip skin	4	.01	-
Grape, european	11	.60	good*
Grapefruit	34	44*	excellent
**Guava, Cattley	37	2	very good*
Guava, tropical	183	165	exceptional
**Java plum	14	.42	-
Jujube	500	no data	exceptional*
**Kei apple	117	17	excellent*
Kiwano™	0.5	0.5	-
Kiwifruit, green	98	74	exceptional
Kiwifruit, yellow	120 to 180	108 to 162	exceptional
Lemon juice	46	3*	-
Lime juice	29	1*	-
Longan	84	3*	good
Loquat	1	.5	-
Lychee	72	7*	very good
Mango	28	57	excellent
**Marula	68	60(estim)	excellent
Medlar	0.3	0.15(estim)	-
Melon, cantaloupe	42	29*	very good
Melon, honeydew	25	20*	very good
**Muntingia	80	4*(estim)	excellent
**Natal plum	38	8	good
Orange	53	70	excellent
Opuntia cactus	23	no data	very good?
Papaya	62	47*	excellent
**Pawpaw/Asimina	14	28(estim)	good†
Passionfruit, purple	30	5	-
Peach	7	6	-
Peach, canned	3	3	-
Pear	4	7	-
**Persimmon, American	66	13*(estim.)	excellent
Persimmon, Oriental	40	40*(estim.)	excellent
Pineapple	15	13	good
Plum	10	6	fairly good
Quince	15	15	good
Raspberry	25	.5	-
Raspberry	23 to 32	0.7 to 1*	very good
Redcurrant	58 to 81	0.58 to 0.81*(estim)	good
Rosehip	1,500	45(estim.)	excellent
Rosehip	1,150	34(estim.)	very good
Rosehip	2,000 to 2,500	60 to 75(estim.)	excellent
**Surinam cherry	26	2	-
Sapodilla	15	25	very good
Strawberry	57	7*	very good
Tangerine/Mandarin	31	26	very good
Tamarillo, red	40	40	excellent
Tamarillo, red	31	22	very good
Tamarillo, yellow	33	30	very good
Tamarillo, yellow	31	22	very good
Tomato	19	23	very good
Watermelon	10	27	very good
* The values are for one whole fruit, but no one eats a whole medium sized watermelon at a sitting, so for these larger fruit the value is for a slice, a 'slice' being, very generally, about an eighth of a medium sized fruit, or a quarter of a 'smaller' fruit. In the particular case of lemon and lime, the 'slice' value is juice of one wedge. For a few small fruit, such as Kei apple, the ranking is adjusted upward where the fruit mg/100 gram analysis shows it has large amounts of vitamin C, but the small size of the fruit gives it a lower per fruit vitamin C content. You are likely to eat more than one at a serving. In the case of tiny fruit, like red or black currants, a lot more, but probably still only 20-30 raw fruit, especially if they are a bit acid.. ** You won't find these fruit in the shops. They are natural environment fruits that we have not domesticated for one reason or another. Most will never be domesticated. Some can be grown at home in the backyard. † Asimina fruits range in vitamin C content from about 7mg/100 grams edible to about 21mg/100 grams, depending on the variety. Therefore some varieties are a 'good' source of vitamin C, others are a 'very good' source.
Vitamin C content of fruits table source : Naturalhub.com

See also: Vitamin News