RESUMEN
Only a few studies have explored relationships between thiamine intake and function, and a few studies have examined the effects of supplements on various clinical or biochemical outcomes. None of these studies, however, makes a useful contribution to understanding requirements in healthy populations. The requirement of thiamine relates to energy and carbohydrate intake. Clinical signs of deficiency have been observed at intakes below 0.5 mg/day, which corresponds to 0.05 mg/MJ. In other studies, thiamine excretion in the urine and normalisation of enzyme activity were normalised at intakes of 0.07-0.08 mg/MJ. The lower limit of intake thus estimates at 0.05 mg/MJ. It has not been possible to set a safe upper intake level for thiamine due to a lack of data. Studies on pregnant and lactating women indicate a higher requirement as assessed by biochemical parameters. A few studies indicate that thiamine utilisation is impaired among elderly subjects.
RESUMEN
Only a few studies have explored relationships between riboflavin intake and function and a few studies have examined the effects of supplements on various clinical or biochemical outcomes. None of these studies, however, make a useful contribution to understanding requirements in healthy populations. Thus, there is no strong evidence to change the recommendations. The requirement for riboflavin is estimated based on the relationship between intake and biochemical indices of riboflavin status, including urinary excretion and enzyme activities.
RESUMEN
Quantification of the specific folate vitamers to estimate total folate in foods is not standardized. A collaborative study, including eight European laboratories, was conducted in order to determine the repeatability and reproducibility of the method for folate quantification in foods using the plant-origin γ-glutamyl hydrolase as part of the extraction procedure. The seven food samples analyzed represent the food groups; fruits, vegetables, dairy products, legumes, offal, fish, and fortified infant formula. The homogenization step was included, and six folate vitamers were analyzed using LC-MS/MS. Total folate content, expressed as folic acid equivalent, was 17-490 µg/100 g in all samples. Horwitz ratio values were within the acceptable range (0.60-1.94), except for fish. The results for fortified infant formula, a certified reference material (NIST 1869), confirmed the trueness of the method. The collaborative study is part of a standardization project within the Nordic Committee on Food Analysis (NMKL).
Asunto(s)
Fraccionamiento Químico/métodos , Ácido Fólico/análisis , Análisis de los Alimentos/métodos , Espectrometría de Masas en Tándem/métodos , Animales , Cromatografía Liquida/métodos , Cromatografía Liquida/normas , Productos Lácteos/análisis , Grano Comestible/química , Productos Pesqueros/análisis , Análisis de los Alimentos/normas , Alimentos Fortificados/análisis , Frutas/química , Humanos , Lactante , Fórmulas Infantiles/análisis , Reproducibilidad de los Resultados , Espectrometría de Masas en Tándem/normas , Verduras/químicaRESUMEN
Tetrahydrofolate is the parent molecule of the folate coenzymes required for one carbon metabolism. Together with other unsubstituted folates such as dihydrofolate and folic acid, tetrahydrofolate represents the third pool of dietary folates following 5-methyltetrahydrofolate and formyl folates. Low intake of dietary folates and poor folate status are common problems in many countries. There is a critical need for reliable methods to determine folate in foods to accurately estimate folate intakes in populations. However, current values for folates in foods in databanks are often underestimated due to the high instability of several folate forms, especially tetrahydrofolate. The present review highlights the occurrence of unsubstituted folates in foods and their oxidation mechanisms and chemical behavior as well as interconversion reaction between tetrahydrofolate and 5,10-methylenetetrahydrofolate. The review shows also the important role of antioxidants in protecting folates during analysis and describes strategies to stabilize unsubstituted folates throughout all steps of the analytical procedure.