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Auf die Merkliste Titel bewerten. E-Mail Facebook Twitter. Ihr eigenes Buch! Mehr erfahren. Vitamin C may save your life! A noted biochemist reveals for laymen the exciting research into ascorbic acid's powers against such deadly enemies as cancer, heart disease, strokes, mental illness, old age, diabetes, arthritis, kidney disease, hepatitis -- After 40 years research, Irwin Stone unfolds his startling conclusion that an ancient genetic mutation has left the primate virtually alone among animals in not producing ascorbic acid Vitamin C in his own body.
By treating it as a "minimum daily requirement" instead of the crucial enzyme it really is, we are living in a state of sub-clinical scurvy whose symptoms have been attributed to other ailments. The answer is to change our thinking about Vitamin C and consume enough to replenish this long-lost "healing factor. This range represents the lowest physiologic requirement. Note that during infection or physical trauma, an increase in the number of circulating leukocytes occurs and these take up vitamin C from the plasma 31, Therefore, both plasma and leukocyte levels may not be very precise indicators of body content or status at such times.
However, leukocyte ascorbate remains a better indicator of vitamin C status than plasma ascorbate most of the time and only in the period immediately after the onset of an infection are both values unreliable. Intestinal absorption of vitamin C is by an active, sodium-dependent, energy-requiring, carrier-mediated transport mechanism 33 and as intakes increase, the tissues progressively become more saturated.
Definition of population at risk The populations at risk of vitamin C deficiency are those for whom the fruit and vegetable supply is minimal. Epidemics of scurvy are associated with famine and war, when people are forced to become refugees and food supply is small and irregular.
The Healing Factor--Vitamin C Against Disease
Persons in whom the total body vitamin C content is saturated can subsist without vitamin C for approximately 2 months before the appearance of clinical signs, and as little as 6. In general, vitamin C status will reflect the regularity of fruit and vegetable consumption but also socio-economic conditions, because intake is determined not just by availability, but by cultural preferences and cost. In Europe and the United States an adequate intake of vitamin C is indicated by the results of various national surveys In all these studies there was a wide variation in vitamin C intake and percent of the US population consumed less than 2.
Likewise a survey of Latin American children in the United States suggested that less than 15 percent consumed the recommended intake of fruits and vegetables The WHO goal has been roughly translated into the recommendation of five portions per day In one study, low-income children consumed as little as 8. However, it is difficult to assess the extent to which sub-clinical infections are lowering the plasma vitamin C concentrations seen in such countries.
Data describing a positive association between vitamin C consumption and health status are frequently reported, but intervention studies do not support the observations. Low plasma concentrations are reported in patients with diabetes 47 and infections 48 and in smokers 49 , but the relative contribution of diet and stress to these situations is uncertain see Chapter Epidemiologic studies indicate that diets with a high vitamin C content have been associated with lower cancer risk, especially for cancers of the oral cavity, oesophagus, stomach, colon, and lung 39, However, there appears to be no effect of consumption of vitamin C supplements on the development of colorectal adenoma and stomach cancer , and data on the effect of vitamin C supplementation on coronary heart disease and cataract development are conflicting Currently there is no consistent evidence from population studies that heart disease, cancers, or cataract development are specifically associated with vitamin C status.
This of course does not preclude the possibility that other components in vitamin C - rich fruits and vegetables provide health benefits, but it is not yet possible to separate such an effect from other factors such as lifestyle patterns of people who have a high vitamin C intake. Dietary sources of vitamin C and limitations to vitamin C Ascorbate is found in many fruits and vegetables Citrus fruits and juices are particularly rich sources of vitamin C but other fruits including cantaloupe, honeydew melon, cherries, kiwi fruits, mangoes, papaya, strawberries, tangelo, watermelon, and tomatoes also contain variable amounts of vitamin C.
The Healing Factor: "Vitamin C" Against Disease
Vegetables such as cabbage, broccoli, Brussels sprouts, bean sprouts, cauliflower, kale, mustard greens, red and green peppers, peas, tomatoes, and potatoes may be more important sources of vitamin C than fruits. This is particularly true because the vegetable supply often extends for longer periods during the year than does the fruit supply. In many developing countries, limitations in the supply of vitamin C are often determined by seasonal factors i.
These fluctuations in dietary ascorbate intake were closely reflected by corresponding variations in plasma ascorbate Vitamin C is also very labile, and the loss of vitamin C on boiling milk provides one dramatic example of a cause of infantile scurvy. The vitamin C content of food is strongly influenced by season, transport to market, shelf life, time of storage, cooking practices, and chlorination of water. Cutting or bruising of produce releases ascorbate oxidase.
Blanching techniques inactivate the oxidase enzyme and help to preserve ascorbate as also will low pH, as in the preparation of sauerkraut pickled cabbage. In contrast, heating and exposure to copper or iron or to mildly alkaline conditions destroys the vitamin, and too much water can leach it from the tissues during cooking.
Such data can indicate the important contribution the potato can make to human vitamin C requirements even though the potato vitamin C concentration is low. An extensive study has been made of losses of vitamin C during the packaging, storage, and cooking of blended foods maize and soya-based relief foods. Data from a US Agency for Internation Development programme show that vitamin C losses from packaging and storage in polythene bags of such relief foods are much less significant than the percent losses attributable to conventional cooking procedures Clinical signs of scurvy appear when the whole body content falls below mg, and the last signs disappear when the body content reaches about mg 28, There is a sigmoidal relationship between intake and plasma concentrations of vitamin C Figure 8.
Relationship between intake and plasma concentrations of vitamin C A body content of mg falls half way between tissue saturation and the point at which clinical signs of scurvy appear. Assuming an absorption efficiency of 85 percent, and a catabolic rate of 2. The recommended nutrient intake RNI would therefore be: x 2.
An RNI of 45 mg would achieve 50 percent saturation in the tissues in An intake of 45 mg vitamin C will produce a plasma ascorbate concentrations near the base of the steep slope of the diet-plasma dose response curve Figure 8.
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No turnover studies have been done in women, but from the smaller body size and whole body content of women, requirements might be expected to be lower. However, in depletion studies plasma concentrations fell more rapidly in women than in men It would seem prudent, therefore, to make the same recommendation for non-pregnant, non-lactating women as for men.
Wounds, bone fractures, and shock
This level however, is not sufficient to provide measurable amounts of ascorbate in plasma and leukocyte cells, which will remain low. As indicated above, no studies have been done on women and minimum requirements to protect non-pregnant and non-lactating women against scurvy might be slightly lower than in men. Therefore, the additional needs during pregnancy are unlikely to be more, particularly during the last trimester. For an assumed absorption efficiency of 85 percent, an extra 25 mg will be needed by the mother.
It is therefore recommended that the RNI should be set at 70 mg to fulfil the needs of both the mother and infant during lactation. Elderly Elderly people frequently have low plasma ascorbate values and intakes lower than those in younger people, often because of problems of poor dentition or mobility Elderly people are also more likely to have underlying sub-clinical diseases, which can also influence plasma ascorbate concentrations see Chapter It has been suggested, however, that the requirements of elderly people do not differ substantially from those of younger people in the absence of pathology, which may influence absorption or renal functioning Smokers Kallner et al.
However, there is no evidence that the health of smokers would be influenced in any way by increasing their RNI. The panel therefore found no justification in making a separate RNI for smokers. Recommended nutrient intakes for vitamin C Table 15 presents a summary of the above discussed RNIs for vitamin C by age groups.
Larger amounts may often be required to ensure an adequate absorption of non-haem iron. Vitamin C toxicity The potential toxicity of excessive doses of supplemental vitamin C relates to intra-intestinal events and to the effects of metabolites in the urinary system. Gastrointestinal disturbances can occur after ingestion of as little as 1 g because approximately half of the amount would not be absorbed at this dose Oxalate is an end product of ascorbate catabolism and plays an important role in kidney stone formation.
Excessive daily amounts of vitamin C produce hyperoxaluria. Vitamin C may precipitate haemolysis in some people, including those with glucosephosphate dehydrogenase deficiency 91 , paroxysmal nocturnal haemaglobinuria 92 , or other conditions where increased risk of red cell haemolysis may occur or where protection against the removal of the products of iron metabolism may be impaired, as in people with the haptoglobin Hp phenotype Of these conditions, only the haptoglobin Hp condition was associated with abnormal vitamin C metabolism lower plasma ascorbate than expected under conditions where intake of vitamin C was provided mainly from dietary sources.
Therefore, 1 g vitamin C appears to be the advisable upper limit of dietary intake. Future research Research is needed to gain a better understanding of the following: functions of endogenous gastric ascorbate and its effect on iron absorption; functional measurements of vitamin C status which reflect the whole body content of vitamin C and are not influenced by infection; and reasons for the vitamin C uptake by granulocytes, which is associated with infection.
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References 1. Stewart, C. Edinburgh, University Press. Nishikimi, M. Cloning and chromosomal mapping of the Human nonfunctional gene for L-gulono-gamma-lactone oxidase, the enzyme for L-ascorbic acid biosynthesis missing in man. Levine, M. New concepts in the biology and biochemistry of ascorbic acid. Englard, S.
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The biochemical functions of ascorbic acid. Wondrack, L.
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