Ascorbic acid vitamin iron absorption

Ascorbic acid or vitamin C is found in fruits, especially citrus fruits, and in fresh vegetables. Man is one of the few mammals unable to manufacture vitamin C in the liver. It is essential for the formation of collagen as it is a cofactor for the conversion of proline and lysine residues to hydroxyproline and hydroxylysine. It is also a cofactor for carnitine synthesis, for the conversion of folic acid to folinic acid and for the hydroxylation of dopamine to form norepinephrine. Being a lactone with two hydroxyl groups which can be oxidized to two keto groups forming dehydroascorbic acid, ascorbic acid is also an anti-oxidant. By reducing ferric iron to the ferrous state in the stomach, ascorbic acid promotes iron absorption. 

Interactions. Antacids inhibit iron absorption. Combination with ascorbic acid (Vitamin C), for protecting Fe + from oxidation to Fe +, is theoretically sound, but practically is not needed. 

Q9 Treatment consists of correcting the underlying cause and replacing the deficient iron. Oral administration of ferrous sulphate (containing 120-200 mg of elemental iron daily) is the standard treatment. This should be taken on an empty stomach, if tolerated, with vitamin C (ascorbic acid), which aids absorption. When the normal haemoglobin concentration in blood has been achieved, the treatment should be continued for an extra three to six months to ensure that body iron stores are replenished. 

Ascorbic acid (Vitamin C) Vegetables and citrus fruits Sore gums, loose teeth, joint pain, edema, anaemia, fatigue, depression, impaired iron absorption, impaired wound healing. 

In the diet and at the tissue level, ascorbic acid can interact with mineral nutrients. In the intestine, ascorbic acid enhances the absorption of dietary iron and selenium reduces the absorption of copper, nickel, and manganese but apparently has little effect on zinc or cobalt. Ascorbic acid fails to affect the intestinal absorption of two toxic minerals studied, cadmium and mercury. At the tissue level, iron overload enhances the oxidative catabolism of ascorbic acid. Thus, the level of dietary vitamin C can have important nutritional consequences through a wide range of inhibitory and enhancing interactions with mineral nutrients. 

An extractive spectrophotometric procedure based on the complexation of reduced Iron(II) with 5-Chloro-7-iodo-8-hydroxyquinoline (CIHQ) for the estimation of micro amounts of vitamin C. The resulting brown colored complex was extracted into chloroform to give a reddish brown extract which shows an absorption band at 485 nm. This chelate was formed immediately and the apparent molar absorptivity and Sandell s sensitivity for vitamin C was found to be 8.5 x 105 dm3 mol"1 cm 1 and 2.072xl0 4g cm 2. Linear relationship between absorbance and concentration of ascorbic acid is observed up to 0.8 pg ml"1. Interference studies of different substances including sugars, vitamins and amino acids, metal ions and organic acids were carried out. The utility of the method was tested by analysing some of the marketed products of vitamin C... 

As noted, vitamin C is needed for the production of collagen in the body, but it is also essential in the production of certain hormones such as dopamine and adrenaline. Ascorbic acid is also essential in the metabolism of some amino acids. It helps protect cells from free radical damage, helps iron absorption, and is essential for many metabolic processes. The dietary need of vitamin C is not clearly established, but the U.S. National Academy of Science has established a recommended dietary allowance (RDA) of 60 mg per day. Some groups and individuals, notably Linus Pauling in the 1980s, recommend dosages as high as... 

Vitamin C [ascorbic acid) Men 90 mg/d Women 75 mg/d Cofactor for reactions requiring reduced copper or iron met-alloenzyme and as a protective antioxidant prevents scurvy Gastrointestinal disturbances, kidney stones, excess iron absorption... 

It is used in the treatment of scurvy, postoperative cases, and healing bedsores and chronic leg ulcers. Vitamin C increases the absorption of iron during anemia and is frequently combined with ferrous salts. It is used in urinary tract infections to acidify urine. Large doses of vitamin C have been tried to cure everything from the common cold to cancer, with not much success. The usefulness of vitamin C in asthma, cancer, atherosclerosis, psychologic symptoms, and fertility is doubtful. Ascorbic acid is well tolerated in large doses and may cause rebound scurvy on withdrawal. There is a possibility of forming urinary stones. 

Nonheme iron is absorbed as Fe +, and not as Fe + ascorbic acid in the intestinal lumen will both maintain iron in the reduced state and also chelate it, thus increasing absorption. A dose of 25 mg of vitamin C taken together with a semisynthetic meal increases the absorption of iron 65%, whereas a 1 -g dose gives a nine-fold increase (Hallberg, 1982). 

Three cases that demonstrate the value of additional research are the eflFects of smoking on the rate of ascorbic acid metabolism, as described in chapter 16 in this book the increase in the RDA for vitamin C in 1980 over that in 1974 on the basis of the significant improvement in iron absorption (40) and the blocking of nitrosamine production as described in chapter 24 in this book. 

The iron in meats is in the form of heme, which is readily absorbed. The non-heme iron in plants is not as readily absorbed, in part because plants often contain oxalates, phytates, tannins, and other phenolic compounds that chelate or form insoluble precipitates with iron, preventing its absorption. Conversely, vitamin C (ascorbic acid) increases the uptake of non-heme iron from the digestive tract. The uptake of iron is also increased in times of need by mechanisms that are not yet understood. Iron is absorbed in the ferrous (Fe ) state (Fig. 44.6), but is oxidized to the ferric state by a ferroxidase known as ceruloplasmin (a copper-containing enzyme) for transport through the body. 

There are numerous reports of interactions of dietary elements that cause variation in the absorption of chromium. Amino acids, which chelate chromium, prevent precipitation at the basic pH in the small intestine, which increases its absorption [13]. Other chelating agents have mixed effects. Phytates significantly decrease absorption whereas oxalates lead to increased absorption [15]. Certain vitamins such as nicotinic acid and ascorbic acid have been shown to increase absorption [16]. Starch has also been shown to increase absorption to a greater degree than glucose, fructose, and sucrose. Some metals can compete with chromium and decrease its absorption. Studies show that zinc, vanadium, and iron have a common intestinal transport mechanism with chromium and can decrease the absorption of chromium [9]. 

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