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You are watching: What is the largest group of water-soluble vitamins?

National study Council (US) Committee on Diet and Health. Diet and Health: implications for to reduce Chronic condition Risk. Washington (DC): national Academies press (US); 1989.


The water-soluble vitamins encompass ascorbic mountain (vitamin C), thiamin, riboflavin, niacin, vitamin B6 (pyridoxine, pyridoxal, and pyridoxamine), folacin, vitamin B12, biotin, and pantothenic acid.

Vitamin C

Vitamin C is energetic in the body either together L-ascorbic mountain or together dehydroascorbic acid. That best-known duty is together a cofactor for the enzyme compelled to hydroxylate prolyl and also lysyl residues for the synthesis of connective organization proteins. The 1980 recommended Dietary pin money (RDA) because that adults—60 mg/day—maintains a body pool of 1.5 g, whereas 10 mg/day is adequate to avoid or healing scurvy (NRC, 1980).

Since the beginning of the century, the lot of vitamin C in the food supply has increased, partly due to the fact that of the greater supplies of citrus fruits and also dark-green vegetables and also partly since of the fortification of part foods. According to the U.S. Department of Agriculture"s proceeding Survey that Food intakes of individuals (CSFII) in 1985 (USDA, 1987), the typical vitamin C intake for children 1 come 5 year of period was 187% that the RDA, and for women 19 to 50 year of age, it was 125% the the RDA, based upon 4 nonconsecutive days of intake. For males 19 come 50 year of age, the average intake to be 207% of the RDA (USDA, 1986), based upon a 1-day intake.

NHANES II—the national Health and Nutrition examination Survey, conducted from 1976 to 1980—indicated that 3% that the respondents 3 to 74 year of period had low serum vitamin C levels. Therefore, the share Nutrition Monitoring review Committee concluded that this vitamin must be accorded high-priority status for future surveillance (DHHS-USDA, 1986).

The Nationwide Food usage Survey (NFCS) that 1977-1978 shown that 73% that the vitamin C intake come from fruits and vegetables. Typical intakes the vegetables and fruits to be decidedly less for women and children under 131% the the poverty level ~ above the communication of 4 nonconsecutive job of intake in 1985 (USDA, 1987).

The greatest levels of vitamin C are found in environment-friendly peppers, broccoli, citrus fruits, strawberries, melons, tomatoes, raw cabbage, and also leafy greens such as spinach, turnip, and mustard greens. Casualty of vitamin C occur when foodstuffs are cooking in large amounts of water, exposed to substantial heating, or exposed to air.


Thiamin functions in the body in the kind of thiamin pyrophosphate (TPP), the coenzyme because that the move of energetic aldehyde in carbohydrate metabolism and decarboxylation the α-keto mountain such together pyruvate. The requirement for thiamin is directly associated with carbohydrate intake and also increases together the metabolic price increases because of pregnancy, lactation, or boosted physical exercise. The 1980 RDA the 0.5 mg/1,000 kcal was set to keep normal level of TPP-dependent erythrocyte transketolase activity and urinary excretion. For those whose complete caloric input is less than 2,000 kcal, at least 1.0 mg/day is recommended.

NFCS data for 1977-1978 suggest that 83% of all respondents consumed 70% or much more of the thiamin RDA (USDA, 1984). Men and also women 19 come 50 years of age in the 1985 inspection averaged 0.70 mg/1,000 kcal, whereas youngsters 1 come 5 year old averaged 0.79 mg/1,000 kcal (USDA, 1986, 1987).


In its coenzyme forms (flavin mononucleotide and also flavin adenin dinucleotide), riboflavin attributes in oxidation-reduction reaction in power production, in the respiratory tract chain, and in countless other metabolic pathways. Richest food sources of riboflavin incorporate liver, milk, dark-green leafy vegetables, and also enriched breads and also cereals.

The 1980 RDA because that riboflavin is 0.6 mg/1,000 kcal; a minimum the 1.2 mg/day is recommended because that those who caloric entry is less than 2,000 kcal/day. In 1985 the median intake for men and women 19 to 50 year of age was 0.82 mg/1,000 kcal and also 0.88 mg/1,000 kcal, dong (USDA, 1986, 1987); for kids 1 to 5 year of age, it was 1.12 mg/1,000 kcal (USDA, 1987). Food teams contributing the many riboflavin to diet of women and children in the 1985 and also 1986 surveys were enriched serial products, milk and also milk products, meat, poultry, and also fish.


In nutrition literature, the term niacin is provided generically to encompass the energetic forms of this vitamin, nicotine castle acid and nicotinamide; however, approximates of niacin requirements take into account preformed niacin and that acquired as identical (NE) in the human body from tryptophan metabolism. Because that this purpose, that is approximated that once 60 mg that tryptophan space consumed by an adult, sufficient is oxidized to produce 1 mg of niacin (NRC, 1980).

Hundreds of enzyme in the body require niacin in its coenzyme forms nicotinamide adenine di nucleotide (NAD) and also nicotinamide adenine di nucleotide phosphate (NADP). Many reactions using these enzyme are affiliated in power metabolism. Hence, the 1980 RDA is collection at 6.6 niacin equivalents (NE) per 1,000 kcal, and also an entry of not less than 13 NE is recommended once the caloric intake is much less than 2,000 kcal. One NE is equal to one of two people 1 mg of niacin or 60 mg of tryptophan.

The 1985 CSFII indicated that the median intake that preformed niacin for ladies (USDA, 1987) and men (USDA, 1986) 19 to 50 years to be 10.8 NE/1,000 kcal, vice versa, for youngsters 1 to 5 year it was 9.6 (USDA, 1987). Median diets in the unified States have been approximated to furnish 500 to 1,000 mg or an ext of tryptophan per day, offering 8 to 17 NE (NRC, 1980). Serial products, meat, poultry, and fish were the most essential sources the preformed niacin reported in the 1985 and 1986 CSFII; nuts and also legumes were identified as great sources.

Vitamin B6

Vitamin B6 is the share term supplied for pyridoxine, pyridoxal, and pyridoxamine, the coenzyme develops of which room pyridoxal phosphate and also pyridoxamine phosphate. Vitamin B6-dependent enzymes are required in a wide variety of reactions, most of i m sorry involve amino mountain metabolism. The 1980 RDAs were based on a proportion of 0.02 mg that vitamin B6 every gram that protein consumed. The pin money for adult females to be therefore set at 2.0 mg/day, presume a protein input of 100 g/day; because that adult males, it was set at 2.2 mg/day, presume a protein input of 110 g/day. A lower allowance presumably would be ideal for those with lower protein intakes.

A major an obstacle in assessing vitamin B6 input is that values for the B6 contents of food space unreliable. In the 1977-1978 NFCS, top top the 3 job studied, 72% of the respondents consumed at the very least 80% that the desired ratio the vitamin B6 come protein, whereas only 39% had at least 80% of the vitamin B6 RDA. The 1985 CSFII indicated that on the 1 day surveyed, males 19 come 50 years of age on median consumed 85% that the B6 RDA, however that only 27% of females consumed 70% or an ext of their B6 RDA (USDA, 1986, 1987). However, the average ratio the vitamin B6 to protein to be 0.019 because that women, regardless of the reality that 43% of lock consumed much less than 50% the the RDA (USDA, 1987). Failure to accomplish the RDA does not denote a deficient diet because actual demands differ in a population (see thing 3). Ladies in lower income groups had reduced intakes of vitamin B6 보다 did those of greater income brackets. The major food resources of vitamin B6 in those surveys to be meats, poultry, fish, serial products, fruits, and also vegetables. Much more research is required on the adequacy the vitamin B6 intake and also the nutritional status of the populace for this vitamin (DHHS-USDA, 1986).

Vitamin B12

Vitamin B12 substances space physiologically energetic cobalamins. The coenzyme (5"-deoxyadenosyl) and also methyl develops of this vitamin are important for the recyling the the active folate coenzyme, for the methylation of homocysteine to type methionine, and also for line of propionate. Vitamin B12 is also essential in the management of fat acids and also aliphatic amino acids v its role in the isomerization the methylmalonyl-CoA come succinyl-CoA.

Vitamin B12 is synthesized through bacteria and also is found only in animal foods such as meats, milk and milk products, and also eggs. The 1980 RDA is 3 µg/day for individuals 7 year of age and also older. National surveys suggest that join are greater for males than for females and greater for those in higher economic groups. The 1985 CSFII shown that 60% of women 19 come 50 years of period consumed 100% that the RDA or more (USDA, 1987).

Folacin (Folic acid or Folate)

Folacin intakes have actually been studied very little, because values because that this vitamin in food ingredient tables room imputed. In addition, current analytical methods for this vitamin space not very reliable. Over there is likewise some problem that the 1980 RDA because that folacin is unrealistically high (DHHS-USDA, 1986).

Folacin coenzymes are important in the body because that the transport of solitary carbon units. Lock are necessary for the synthesis of purine, methionine, and also thymidylate, for the catabolism that histidine, and also for the counter of serine to glycine. The line of folacin and vitamin B12 is linked since normal activity of methyl vitamin B12 is required to keep the metabolically active type of folacin.

The 1980 RDA was collection at 400 µg/day because that persons 11 year of age and also older. The first national inspection to report folacin intakes to be CSFII in 1985. Women 19 to 50 years of period had typical intakes of 189 µg/day (USDA, 1987), whereas join for males 19 come 50 years of period averaged 305 µg/day (USDA, 1986). On the basis of restricted data, ladies 20 come 44 year of period were reported in NHANES II to be at best risk for folacin deficiency (Senti and Pilch, 1984).

The joint Nutrition Monitoring evaluation Committee accorded high priority to surveillance the standing of vitamin C, because of part low serum values reported in NHANES II and also concluded the thiamin, riboflavin, and niacin warrant ongoing monitoring. The committee additionally recommended further investigation the the relationship between dietary intakes and also nutritional status for both vitamin B6 and folacin (DHHS-USDA, 1986).

Following is the proof relating water-soluble vitamin to chronic diseases.

Human Studies

In epidemiologic studies, the association of vitamin C with cancer is greatly indirect, since it is based upon the usage of foods known to contain high or low concentrations that the vitamin rather than on measure up ingestion of ascorbic acid.

Meinsma (1964) listed that the intake of citrus fruit by persons with gastric cancer was lower than the by controls. Comparable inverse associations in between fresh fruit usage or vitamin C intake and gastric cancer to be reported by Bjelke (1978), Higginson (1966), Haenszel and also Correa (1975), and also Kolonel et al. (1981). In a case-control study of stomach cancer performed in Canada, Risch et al. (1985) discovered that citrus fruit intake was somewhat protective (odds ratio 0.75 per 100 g daily average intake). In a univariate analysis, vitamin C input was substantially (p = .0056) protective against stomach cancer. Risch and also colleagues analyzed vitamin C intake native 21 usual vegetables in addition to the entry of nitrate and found that vitamin C usage had a solid and highly protective effect. In a multiple logistic regression model, however, vitamin C input did no make a far-reaching contribution to hazard reduction beyond a security effect found for diet fiber. This can partly be explained by the correlation in between the sources of vitamin C and also dietary fiber.

Mettlin et al. (1981) uncovered inverse associations of indices of vitamin A and also vitamin C intake with esophageal cancer based on frequency of usage of selected food item by male cases and also controls. The relationship was stronger for vitamin C than for vitamin A, and only the association with vitamin C to be statistically far-reaching after controlling for smoking and also alcohol use.

In research studies of esophageal cancer in the Caspian Littoral that Iran, inverse associations to be found between esophageal cancer and also consumption of fresh fruits and also estimated vitamin C intake based on correlational and also case-control data (Cook-Mozaffari, 1979; Cook-Mozaffari et al., 1979; Hormozdiari et al., 1975; joint Iran-International company for research study on Cancer research Group, 1977). In a research of diet and also esophageal cancer performed in the Calvados an ar of France, Tuyns et al. (1987b) discovered further proof for a protective result of vitamin C consumption as estimated from food data banks. The calculation of family member risk for moderate consumer of vitamin C was 0.7 and also for heavy consumers, 0.4. Similar protective impacts were likewise found for vitamin E, carotene, and also some other micronutrients. That is no clear even if it is the results of this research reflect basic nutritional deficiency, particularly in people with high alcohol consumption, or a an ext specific result of vitamin C.

Jain et al. (1980) discovered no association between vitamin C consumption, also estimated native food data banks, and also colon cancer in a case-control research in Canada. In a case-control study on colorectal cancer in Marseilles, Macquart-Moulin et al. (1986) found a far-ranging protective impact of vitamin C after ~ adjustment because that age, caloric intake, and weight. The risk in the highest consumption category relative come the lowest was 0.16. In a multivariate evaluation including various other macro-and micronutrients, however, vitamin C to be no longer considerably protective. The effect of vitamin C was also evaluated in two case-control researches of colorectal cancer in Australia. In one (Potter and also McMichael, 1986), vitamin C intake was connected with a diminished relative threat for rectal cancer in males and also females (ages 30-74 years), specifically for younger males; the effect disappeared by 70 year of age. No protective result was found for colon cancer. In one more case-control study, conducted in Belgium through Tuyns et al. (1987a), there was no point out of a protective impact of vitamin C.

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The result of vitamin C has also been assessed in number of studies of various other cancer sites. In a case-control study of laryngeal cancer, Graham et al. (1981) discovered an station relationship between risk and also indices of both vitamin C and vitamin A usage after regulating for tobacco smoking and also alcohol consumption. There was a similar relationship for vegetable consumption in general. Wassertheil-Smoller et al. (1981) report an association in between vitamin C consumption and uterine cervical dysplasia in a case-control examine in new York. The findings persisted after the investigators managed for sex-related activity. Stähelin et al. (1984) evaluated plasma vitamin C in a cohort of much more than 4,000 men primarily studied for the risk of cardiovascular disease. Plasma vitamin C was uncovered to it is in consistently reduced in cancer situations than in controls. The largest differences were for cancers that the lung and stomach. Böing et al. (1985) analyzed local nutritional data native a national survey ~ above income and also food intake in the commonwealth Republic the Germany and also correlated mortality prices with the food intake data for 15 nutrients. Far-ranging positive correlations to be found in between vitamin C and also cancers that the breast, prostate, liver, and colon. In a case-control research of lung cancer in Hawaii, however, Hinds et al. (1984) uncovered no association between dietary vitamin C intake and also lung cancer risk.