Fundamentals of Human Nutrition/Vitamin C

Vitamin CEdit

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7.2.8.1 SourcesEdit

These are the colorful and raw fruits and vegetables that contain more vitamin C: red pepper, orange, lemon, grapefruit, cantaloupe, raspberries, strawberries, broccoli, tomatoes, etc..

Food Content (mg/100g)
Terminalia ferdinandiana
(Kakadu plum)
3000-5000
Goji berry 2500
Sea Buckthorn 750
Guava 243
Blackcurrants 200
Parsley 170
Dried Goji Berry 148
Sweet red pepper
tarragon
Leaf cabbage
120
Fennel
Pepper
100
Kiwi 80
Litch 75
Lemon 65
Strawberry
Orange
Cauliflower
60

Vitamin C is Very fragile, it is destroyed on contact with air (oxidation) or exposure to light (ultraviolet action) and heat accelerates the process. The heat of cooking destroys vitamin C. Vitamin C is destroyed between 60 and 75 ° C. Generally, consumption of at least 5 servings of fruits and vegetables allows filling largely recommended dietary in vitamin C.

7.2.8.2 FunctionsEdit

Vitamin C is an hydrosoluble vitamin. This vitamin is sensitive to heat and light, and play an important role in the human metabolism. Chemically, it is the L-ascorbic acid, one of the stereoisomers of ascorbic acid and its salts, ascorbate (the most common being sodium ascorbate and calcium ascorbate). Vitamin C is an enzyme cofactor involved in a number of physiological reactions (hydroxylation). It is required in the synthesis of collagen and red blood cells and helps the immune system. It also plays a role in iron metabolism as absorption promoter and its use is therefore not recommended in patients with iron overload and particularly hemochromatosis. Oxidized form (dehydroascorbic acid), it crosses the blood-brain barrier to reach the brain and multiple organs with high concentrations of vitamin C. It is an antioxidant molecule that can counteract the harmful effects of oxidants such as free radicals. For this purpose, we also used the D-(-) (levogyre) of ascorbic acid, which, unlike the L-form (+) (Dextrogyre) has no vitamin activity.

7.2.8.2 RequirementsEdit

European guidelines advise a daily intake of 75 mg for women and 90 mg for men. For example, an orange give an average of 53 mg of vitamin C (40 to 80 mg per 100 g). The North American Dietary Reference Intake recommends 90 milligrams per day and no more than 2 grams (2,000 mg) per day. The people who is exposing to the harmful effects of oxidants, such as smokers have an increased need for vitamin C. Some scientists like Linus Pauling (Nobel Prize in Chemistry in 1954), consider that the recommended dietary intake should be at least 6000mg, or 18 000mg [1].

7.2.8.2 DeficiencyEdit

A major deficiency of vitamin C, very rare, causes scurvy, when the supply is less than 10 mg per day. The more discreet hypovitaminosis are widespread and result in fatigue, weight loss, headache, bone pain, increased susceptibility to infections and sometimes bleeding problems [2].

7.2.8.2 ToxicityEdit

Vitamin C is not toxic at doses usually absorbed for a healthy individual. Since its synthesis in the 1930s, vitamin C is used at all doses throughout the world. The only side effects associated with its use and that are developed are mild diarrhea and diuretic action. These occur when consumed too quickly and too much. The body can not store it, it eliminates excess. Clinical studies show:

  • the consumption of vitamin C does not increase [3] ·[4] ·[5] and even reduces [6] the incidence of kidney stones.
  • that vitamin C has no mutagenic effect (study of doses up to 5000 mg per day) [7] ·[8].

In vivo studies show that vitamin C, even in the presence of transition metals has no mutagenic effect and instead it protects the cells of the mutagenic action of hydrogen peroxide [9].

Symptoms of an overdose of vitamin C may include: nausea, vomiting, headache, rash, and asthenia [10] . For doses greater than 500 mg/day , an increase of production of oxalic acid could induce a risk of kidney stones oxalate [11]. This side effect is controversial in some studies [12] . Indeed, plants that provide vitamin C also bring oxalate [13], hence the confusion.

References
  1. Pauling, Linus. My Love Affair with Vitamin C
  2. Pharamacorama - L'acide ascorbique ou vitamine C
  3. Intake of vitamins B6 and C and the risk of kidney stones in women. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. J Am Soc Nephrol. 1999 Apr;10(4):840-5.
  4. No contribution of ascorbic acid to renal calcium oxalate stones. Gerster H. Ann Nutr Metab. 1997;41(5):269-82.
  5. A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. J Urol. 1996 Jun;155(6):1847-51.
  6. Ascorbic acid and kidney stones. Hoffer A. Can Med Assoc J. 1985 Feb 15;132(4):320.
  7. New evidence for antioxidant properties of vitamin C. Vojdani A, Bazargan M, Vojdani E, Wright J. Cancer Detect Prev. 2000;24(6):508-23.
  8. The effects of iron and vitamin C co-supplementation on oxidative damage to DNA in healthy volunteers. Biochemical and Biophysical Research Communications 1998 May 8;246(1):293-8. Pubmed ID 9600109
  9. Suh J, Zhu BZ, Frei B (May 2003). "Ascorbate does not act as a pro-oxidant towards lipids and proteins in human plasma exposed to redox-active transition metal ions and hydrogen peroxide". Free Radic. Biol. Med. 34 (10): 1306–14. PMID 12726918. 
  10. http://www.inchem.org/documents/jecfa/jecmono/v05je20.htm
  11. Dossier Vitamine C sur doctissimo.fr
  12. Dossier Calculs rénaux sur passeportsante.net
  13. Les aliments les plus riches en oxalate, La Nutrition.fr
Last modified on 2 April 2013, at 22:22