Skip to main content

Currently Skimming:

7 Vitamin B6
Pages 150-195

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 150...
... intake from both food and supplements has been estimated to be 6 to 10 ma/ day. The critical adverse effect from high intake of the vitamin is sensory neuropathy.
From page 151...
... . Function PLPis a coenzyme for more than 100 enzymes involved in amino acid metabolism, including aminotransferases, clecarboxylases, racemases, and clehyciratases.
From page 152...
... Microbial synthesis of B6 in the lower gut makes it difficult to evaluate the extent of this excretion. Body Stores Pharmacokinetic analyses of urinary excretion of a tracer close of labeled PN and its metabolites have suggested a two-compartment model for body B6 stores Johansson et al., 1966~.
From page 153...
... In one depletionrepletion study (Kretsch et al., 1991) 2 of 11 young women placed on a diet containing less than 0.05 mg of B6 exhibited abnormal EEG patterns within 12 clays.
From page 154...
... . 1 1 Plasma Pyridoxal Sl-Phosphate The plasma PLP concentration reflects liver PLP (Lumen" and Li, 1974)
From page 155...
... Results from a large number of studies involving various population groups (Brown et al., 1975; Driskell and Moak, 1986; Linciberg et al., 1983; Lumeng et al., 1974; Miller et al., 1975, 1985; Rose et al., 1976; Tarr et al., 1981) have shown that a substantial proportion of inclivicluals in these populations, in some cases half, have plasma PLP concentrations below 30 nmol/L, but there are no confirming clinical or other data to suggest B6 deficiency.
From page 156...
... Erythrocyte PLP concentrations are similar to those for plasma PLP in inclivicluals on normal flints, but they increase to much higher values than floes plasma PLP in subjects taking large closes of the vitamin (Bhagavan et al., 1975~. This reflects the high binding capacity of hemoglobin for PLP.
From page 157...
... of erythrocyte aspartate aminotransferase (oc-EAST) and erythrocyte alanine Aminotransferase (oc-EALT)
From page 158...
... Racial and gentler differences in homocysteine values and response to vitamin intervention have been found in some studies (Ubbink et al., 1995~. In a South African comparison of black and white subjects with similar lifestyles and folate and vitamin BE status, plasma PLP concentrations were significantly lower in the black subjects; fasting plasma homocysteine concentration was similar.
From page 159...
... Results from population-baseci studies using ciata acljusteci for folate and BE status and for age indicate that B6 status as measured by PLP is inversely correlated with nonfasting plasma homocysteine concentration (Selhub et al., 1993~. At least part of the increase in plasma homocysteine concentration that occurs with aging may be clue to clecreaseci renal function (Hultberg et al., 1993)
From page 160...
... Cognitive Function The relationship of vitamin status to cognitive function was recently evaluated in the elderly (Riggs et al., 1996~. B6 status, as evaluated by plasma PLP concentrations, was related to 2 out of a battery of about 20 tests.
From page 161...
... Nutrient-Nutrient Interactions Because of PLP's role as a coenzyme for many enzymes involved in amino acid metabolism, it has been proposed that B6 requirements are influenced by protein intake. Many studies have clemonstrateci that increased protein intake causes a relative decrease in B6 status as jucigeci by a variety of B6 status indicators (Baker et al., 1964; Hansen et al., 1996b; Linkswiler, 1978; Miller et al., 1985; Sauberlich, 1964~.
From page 162...
... Increased excretion of tryptophan metabolites seen may also partly be clue to the increased clietary tryptophan content. The relationship between plasma PLP concentrations and the amount of B6 per kilogram of protein intake (cleriveci from a number of studies and compiled by I
From page 163...
... Plasma PLP concentrations are clecreasecT but the decrease is quite small. Normalization of the tryptophan load test in subjects receiving oral contraceptives requires very high levels of PN, up to 25 mg (Rose, 1978~.
From page 164...
... have clemonstrateci the usefulness of B6 status indicators for tracking relative vitamin status. However, many of the studies are flawoci in that requirements have usually been assessed by identifying the B6 intakes that return status indicators to the prestucly baseline values.
From page 165...
... for some adult age groups. Various indicators of B6 status are used, but when possible, a plasma pyridoxal phosphate (PLP)
From page 166...
... These ciata also suggest that the infant fed human milk does not have a large reservoir of B6. Other studies, however, have reported higher plasma PLP concentrations in infants of unsupplemented mothers.
From page 167...
... B6 Al Summary, Ages O through I2 Months AI for Infants 0-6 months 0.1 mg/day of vitamin B6 ~0.014 mg/kg 7-12 months 0.3 mg/day of vitamin B6 ~0~033 mg/kg Special Considerations Infant formula typically provides much higher levels of B6 to the infant than floes human milk (Borschel et al., 1986) , and formulafeci infants have higher PLP concentrations and lower erythrocyte aspartate aminotransferase (oc-EAST)
From page 168...
... The average plasma PLP concentrations .
From page 169...
... The results of applying that method to ciata on protein intake from the Third National Health and Nutrition Examination Survey for children were jucigeci to be unreasonably high. (See also the previous discussion about the protein-B6 relationship.)
From page 170...
... Linkswiler (1978) summarized a large number of early studies of men receiving various protein intakes.
From page 171...
... During the clepletion period, plasma PLP concentrations fell from about 50 to about 14 nmol/L. On the two repletion regimens they increased to
From page 172...
... No hematological or EEG abnormalities were observed cluring clepletion, and the plasma PLP concentration was above 20 nmol/L at the end of the clepletion period. With longer depletion, PLP values might have dropped more.
From page 173...
... For women on the highest protein intake, PLP concentrations ciroppeci below 30 nmol/L but remained above 20 nmol/L. There was a slight elevation in tryptophan catabolites after a loaci, which may have been clue to the increased clietary tryptophan intake.
From page 174...
... Plasma PLP concentrations averageci 60 nmol/L in the obese group and 63 nmol/L in the control group, inclicating no apparent effect of obesity on B6 status. These ciata clo, however, suggest an EAR of considerably less than 1.2 mg for adult women.
From page 175...
... The ciata were acljusteci for age, gentler, and folate and BE intakes. No clear cutoff for homocysteine has been established, but about half the subjects whose B6 intakes were 1.4 mg (anci who haci plasma PLP concentrations of 25 nmol/L)
From page 176...
... Pregnancy Evidence Considered in Estimating the Average Requirement Concentrations of indicators of B6 status in plasma and blood decrease throughout pregnancy, especially in the third trimester (Cleary et al., 1975; Hamfelt and Tuvemo, 1972; Shane and Contractor, 1980~. Many studies have clemonstrateci a drop in plasma PLP to about 10 nmol/L; this is substantially more than can be accounted for by increased blood volume.
From page 177...
... In the pregnant rat about 15 percent of an intraperitoneal close of PN is initially taken up by the uterus, placenta, and fetus. Maintenance of plasma PLP concentrations at nonpregnant values requires about 2 mg/ciay of supplemental PN in the first trimester and between 4 and 10 mg/ciay in the third trimester (Cleary et al., 1975; Hamfelt and Tuvemo, 1972; Lumeng et al., 1976~.
From page 178...
... RI) A for Pregnancy 14-18 years 19-30 years 31-50 years Lactation 1.9 mg/day of vitamin B6 1.9 mg/day of vitamin B6 1.9 mg/day of vitamin B6 Evidence Considered in Estimating the Average Requirement As clescribeci above, the B6 concentration in human milk varies clepencling on the mother's B6 intake, and some women consuming less than 2.5 mg/day of B6 produce milk with a B6 content that is not much higher than that associated with consuming formula that resulted in convulsions in infants because of low levels of B6.
From page 179...
... , it would be prudent to acici 0.6 mg of B6 to the EAR of 1.1 mg for nonpregnant women, giving an EAR for lactation of 1.7 mg/ciay of B6. Because this is an approximation baseci on a number of assumptions, no adjustment is macle for adolescent females who are lactating.
From page 180...
... Foods Within the Group that Provide at Least 0.4 mg of Vitamin B6C per Serving Food Group Men Women 0.4-0.8 mg > 0.8 mg Food groups providing at least 5% of total vitamin B6 intake Ready-to-eat cereals 10.8 13.7 Moderately fortified Highly fortified Mixed foodsd 10.1 8.6 NAe NA White potatoes and 9.7 9.2 White potato with other starchy peel and plantain vegetablesf Non-citrus fruits" 7.0 9.5 Bananas and watermelon Poultryh 6.9 7.1 Chicken breast, turkey light meat, and Cornish game hen Beef 6.4 4.2 Mixed foods, main 5.4 4.8 NA NA ingredient is grain Other vegetables" 4.1 4.6 Vitamin B6 from other food groups Organ meats 0.2 0.2 Calf, chicken, or Beef liver pork liver and kidney Soy-based 0.7 0.2 Some soy- Some soy supplements and based meat based meat meal replacements substitutes substitutes Pasta, rice, and 3.2 3.3 Fortified instant cooked cereals oatmeal Finfish 1.2 1.7 Fresh tuna and trout Deep yellow 0.8 1.2 Sweet potatoes vegetables with peel a CSFII = Continuing Survey of Food Intakes by Individuals. b Contribution to total intake reflects both the concentration of the nutrient in the food and the amount of the food consumed.
From page 181...
... indicates that this relatively advantaged group of people over age 60 reported a median B6 intake of 1.2 mg/day for men and 1.0 mg/ciay for women. TABLE 7-2 Life Stage and Gentler Groups in the United States with Reported Vitamin B6 Intake Less than the Estimated Average Requirement (EAR)
From page 182...
... This review focuses on pyricloxine, the form of B6 that was consumed in the reports cited below. Large oral supplemental closes of pyricloxine used to treat many conditions, including carpal tunnel syndrome and premenstrual syndrome, have been associated with the development of sensory neuropathy and clermatological lesions (Cohen and Benclich, 1986; Schaumourg and Berger, 1988~.
From page 183...
... Summary On the basis of considerations of causality, relevance, and the quality and completeness of the database, sensory neuropathy was selected as the critical endpoint on which to base a Tolerable Upper Intake Level (UL)
From page 184...
... treated 70 patients with diabetic neuropathy or carpal tunnel syndrome with 100 to 150 mg/ciay of pyricloxine some for up to ~ years. Despite rigorous neurological examination and testing, sensory neuropathy was not cletecteci in any of these patients.
From page 185...
... A local television report publicizing this syndrome before the study may have biased the selection of patients and reporting of neurological symptoms. Two aciclitional studies that report sensory neuropathy at closes of less than 200 mg/day (Dalton, 1985; Dalton and Dalton, 1987)
From page 186...
... Scientifically baseci, controlled studies clesigneci to assess the potential adverse effects of pyricloxine intake by pregnant and lactating women are lacking. As noted above, the weight of the evidence from controlled studies in animals cluring pregnancy reveals no adverse effects related to teratogenicity, and the evidence from humans reveals no adverse effects from intakes up to 200 mg/ciay.
From page 187...
... Risk Charactenzation The risk of adverse effects resulting from excess intake of B6 from food and supplements appears to be very low at the highest intakes noted above. Increased risks are likely to result from large intakes of PN used to treat conditions such as carpal tunnel syndrome, painful neuropathies, seizures, premenstrual syndrome, asthma, and sickle cell disease.
From page 188...
... Am ~ Clin Nutr 43:7-15. Brattstrom LE, Israelsson B
From page 189...
... Am J Clin Nutr 60:552-558. Dakshinamurti K, ed.
From page 190...
... Am ~ Clin Nutr 43:816-824. Driskell JA, Moak SW.
From page 191...
... Am J Clin Nutr 60:907-910. Heiskanen K, Kallio M, Salmenpera L, Siimes MA, Ruokonen I, Perheentupa l.
From page 192...
... Am ~ Clin Nutr 27:326-333. Lumeng L, Cleary RE, Wagner R
From page 193...
... Am ~ Clin Nutr 15:67-72. Ribaya-Mercado ~D, Russell RM, Sahyoun N
From page 194...
... Am ~ Clin Nutr 34:1731-1735. Selhub l, ~acques PF, Wilson PWF, Rush D, Rosenberg IH.
From page 195...
... Am ~ Clin Nutr 62:802-808. Ubbink JOB, van der Merwe A, Delport R


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.