Abstract
Background: Knowledge about folate bioavailability from food is essential for the estimation of dietary requirements. Yet, there is a lack of data obtained from validated human studies performed with physiological folate doses. Objective: In this pilot study, a new model for the determination of folate absorption is developed and validated. Design: Under strictly standardized procedures, two healthy ileostomy volunteers consumed single portions of test foods or an oral dose of a pharmaceutical folate preparation of the natural folate diastereomer (6S)-5- methyltetrahydrofolate. Relative folate absorption from oral doses versus an intramuscular injection of the same pharmaceutical preparation was determined using postdose plasma folate concentration curves. Nonabsorbed folate was estimated by postdose folate excretion into stomal effluent. Results: Estimated by plasma areas under the curve, relative folate absorption ranged from 47 to 67% for oral doses from the te st foods strawberries and broccoli and the pharmaceutical (6S)-5-methyltetrahydrofolate preparation. During 10 h postdose, 19-44% of the dietary folate was excreted with the stomal effluent. Varying gut passage times were observed for different food matrices by determining ileostomal folate excretion in 2 h intervals. Around 90% of the folate from the oral doses was recovered in the collected body fluids, plasma and stomal effluent, by 10 h postdose, independent of the size of the administered folate doses of 200 or 400 mg (0.4 or 0.9 mmol). Conclusion: The results imply that this model provides a suitable tool to estimate folate bioavailability from foods. Keywords: Folate absorption; folate in ileostomal effluent; ileostomists; plasma folate kinetics; urinary folate excretion
Highlights
An optimal folate status is linked to a diminished risk for neural tube defects and spontaneous abor-Abbreviations: 5-HCO-H4folate, 5-formyl-tetrahydrofolate, 5CH3-H4folate, 5-methyl-tetrahydrofolate, area under the plasma response curve (AUC), area under the curve, AUC00600, superscript indicates time range, C, C20, Cmax, concentration, suffix defines time or at maximum, D, dose, GC, gas chromatography, HPLC, high-performance liquid chromatography, H4folate, tetrahydrofolate, k, k21, k22, elimination constants, MS, mass spectrometry, PteGlu, pteroylglutamic acid, SAX, strong anion exchange, SPE, solid-phase extraction, t, t20, tmax, time (-point), suffix defines time or at maximum, V, distribution volume in the body6 # 2003 Taylor & Francis ISSN 1102-6480 tions [1], low serum homocysteine levels, some forms of cancer [2] and improved cognitive or mental functions [3]
After application of 5-CH3H4folate from pharmaceutical preparations and from test foods, plasma concentrations increased at Cmax to 2.5Á/ 14.9 ng ml(1 (5.4Á/32.4 nmol l(1) above predose concentrations (Table 1)
Relative folate absorption was estimated by plasma AUCs after ingestion of a test food versus a reference dose
Summary
6 # 2003 Taylor & Francis ISSN 1102-6480 tions [1], low serum homocysteine levels (elevated concentrations are associated with an increased risk of occlusive vascular diseases), some forms of cancer [2] and improved cognitive or mental functions [3] This new concept of health-protective effects is reflected in recent recommendations of the US Food and Nutrition Board [4] and latest editions of several European and the Nordic Nutritional Recommendations [5]. Relative folate absorption from oral doses versus an intramuscular injection of the same pharmaceutical preparation was determined using postdose plasma folate concentration curves. Results: Estimated by plasma areas under the curve, relative folate absorption ranged from 47 to 67% for oral doses from the test foods strawberries and broccoli and the pharmaceutical (6S)-5-methyltetrahydrofolate preparation. Conclusion: The results imply that this model provides a suitable tool to estimate folate bioavailability from foods
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