Dietary exposure to 5-hydroxymethylfurfural from Norwegian food and correlations with urine metabolites of short-term exposure.

5-Hydroxymethylfurfural (HMF) is formed in carbohydrate-rich food during acid-catalysed dehydration and in the Maillard reaction from reducing sugars. HMF is found in mg quantities per kg in various foods. HMF is mainly metabolised to 5-hydroxymethyl-2-furoic acid (HMFA), but unknown quantities of the mutagenic 5-sulphoxymethylfurfural (SMF) may also be formed, making HMF potentially hazardous to humans. We determined the HMF content in Norwegian food items and estimated the dietary intake of HMF in 53 volunteers by means of 24h dietary recall. The estimated intakes of HMF were correlated with urinary excretion of HMFA. Coffee, prunes, dark beer, canned peaches and raisins had the highest levels of HMF. The 95th percentile of the estimated daily dietary intake of HMF and the 24h urinary excretion of HMFA were 27.6 and 28.6mg, respectively. Coffee, dried fruit, honey and alcohol were identified as independent determinants of urinary HMFA excretion. Most participants had lower estimated HMF intake than the amount of HMFA excreted in urine. In spite of this there was a significant correlation (r=0.57, P<0.001) between the estimated HMF intake and urinary HMFA. Further studies are needed to reveal alternative sources for HMF exposure.

Determination and quantification of urinary metabolites after dietary exposure to acrylamide.

It is known that heat-treated carbohydrate-rich foods may contain high levels of acrylamide (AA) and up to 4000 microg kg-1 in potato crisps and 2000 microg kg-1 in French fries have been reported. In order to obtain more information on the human exposure to and metabolism of AA, a method for the determination of known urinary metabolites from the dietary exposure of AA using solid-phase extraction and liquid chromatography with positive electrospray MS/MS detection was developed. The validated assay range was from 8.6 to 342.9 microg l-1. The urinary metabolites were synthesized and their structures determined by NMR and MS. To test the method, a pilot study was conducted in which all urine during 48 h starting with 24 h fasting was collected. The two urinary metabolites, N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine (MA-GA3) and N-acetyl-S-(3-amino-3-oxopropyl)cysteine (MA-AA), were found to be above the detection limit. Fasting during 1 day caused about a 50% decrease in the total level of the metabolites, but after 1 day of a normal diet, the metabolite levels increased back to pre-fasting levels. The total amount of AA in the form of urinary metabolites excreted over the period was estimated to be about 40 microg AA day-1 for the average non-smoker.