Intake recommendations for vitamin B6 and other nutrients are provided in
Vitamin B6 is a water-soluble vitamin that’s naturally present in many foods, put into others, and available like a dietary supplement. It is the generic name for six compounds (vitamers) with vitamin B6 activity: pyridoxine, an alcohol; pyridoxal, an aldehyde; and pyridoxamine, containing an amino group; and their respective 5′-phosphate esters. Pyridoxal 5′ phosphate (PLP) and pyridoxamine 5′ phosphate (PMP) would be the active coenzyme forms of vitamin B6. Substantial proportions from the naturally occurring pyridoxine in fruits, vegetables, and grains appear in glycosylated forms that exhibit reduced bioavailability.
Vitamin B6 in coenzyme forms performs a multitude of functions in the body and is very versatile, with involvement in additional than 100 enzyme reactions, mostly worried about protein metabolism. Both PLP and PMP take part in amino acid metabolism, and PLP can also be involved in the metabolism of one-carbon units, carbohydrates, and lipids. Vitamin B6 also plays a part in cognitive development with the biosynthesis of neurotransmitters and to maintain normal levels of homocysteine, an protein in the blood.
Vitamin B6 is involved with gluconeogenesis and glycogenolysis, immune function (for example, it promotes lymphocyte and interleukin-2 production), and hemoglobin formation.
A persons body absorbs vitamin B6 within the jejunum. Phosphorylated forms of the vitamin are dephosphorylated, and the pool of free vitamin B6 is absorbed by passive diffusion.
Vitamin B6 concentrations could be measured directly by assessing concentrations of PLP; other vitamers; or total vitamin B6 in plasma, erythrocytes, or urine. Vitamin B6 concentrations may also be measured indirectly by assessing either erythrocyte aminotransferase saturation by PLP or tryptophan metabolites. Plasma PLP is easily the most common measure of vitamin B6 status.
PLP concentrations in excess of 30 nmol/L have been traditional indicators of adequate vitamin B6 status in grown-ups. However, the Food and Nutrition Board (FNB) in the Institute of Medicine from the National Academies (formerly Nas) used a plasma PLP degree of 20 nmol/L as the major indicator of adequacy to calculate the Recommended Dietary Allowances (RDAs) for adults.
Intake recommendations for vitamin B6 and other nutrients are supplied in the Dietary Reference Intakes (DRIs) produced by the FNB. DRI is the general term for some reference values used for planning and assessing protein and nutrient intakes of healthy people. These values, which vary by age and gender, include:
Recommended Dietary Allowance (RDA):
average daily degree of intake sufficient to satisfy the nutrient requirements of almost all (97%-98%) healthy individuals.
Adequate Intake (AI):
established when evidence is insufficient to build up an RDA and is set in a level assumed to make sure nutritional adequacy.
Tolerable Upper Intake Level (UL):
maximum daily intake unlikely to result in adverse health effects.
Table 1 lists the present RDAs for vitamin B6. For infants from birth to Twelve months, the FNB established an AI for vitamin B6 that’s equivalent to the mean intake of vitamin B6 in healthy, breastfed infants.
Causes of Vitamin B6
Vitamin B6 can be found in a wide variety of foods. The richest causes of vitamin B6 include fish, beef liver and other organ meats, potatoes and other starchy vegetables, and fruit (apart from citrus). In the United States, adults obtain the majority of their dietary vitamin B6 from fortified cereals, beef, poultry, starchy vegetables, and some non-citrus fruits. About 75% of vitamin B6 from the mixed diet is bioavailable.
Vitamin B6 Intakes and Status
Most children, adolescents, and adults in the usa consume the recommended levels of vitamin B6, according to an analysis of information from the 2003-2004 National Health and Nutrition Examination Survey (NHANES). The typical vitamin B6 intake is all about 1.5 mg/day in females and 2 mg/day in men.
However, 11% of vitamin B6 supplement users and 24% of individuals in the United States who do not take supplements containing vitamin B6 have low plasma PLP concentrations (under 20 nmol/L). In the 2003-2004 NHANES analysis, plasma PLP concentrations were low even just in some groups that took 2.0-2.9 mg/day, that is higher than the current RDA. Among supplement users and nonusers, plasma PLP levels were reduced in women than men, non-Hispanic blacks than non-Hispanic whites, current smokers than never smokers, and individuals who were underweight compared to those of normal weight. Teenagers had the cheapest vitamin B6 concentrations, then adults aged 21-44 years. However, plasma PLP levels within the elderly were not particularly low, even just in those who did not use supplements. According to these data, the authors of the analysis concluded that the present RDAs might not guarantee adequate vitamin B6 status in lots of population groups.
PLP concentrations are usually low in people with alcohol dependence; those people who are obese; and pregnant women, particularly those with preeclampsia or eclampsia. They’re also low in people with malabsorption syndromes for example celiac disease, Crohn’s disease, and ulcerative colitis.