Cristina Delgado-Andrade

Maillard reaction products modulate gut microbiota composition in adolescents

SCOPE Scarce data are available concerning effects of certain bioactive substances such as Maillard reaction products (MRP) on the gut microbiota composition, and the question of how a diet rich in MRP affects gut microbiota in humans is still open. METHODS AND RESULTS Two experiments were conducted. In expt. 1, adolescents consumed diets either high or low in MRP in a two-period crossover trial; in expt. 2, rats were fed diets supplemented or not with MRP model-systems. Intestinal microbiota composition in fecal (adolescents) or cecal (rat) samples was assessed by qPCR analysis. Negative correlations were found in the human assay between lactobacilli numbers and dietary advanced MRP (r = -0.418 and -0.387, for hydroxymethylfurfural and carboxymethyl-lysine respectively, p < 0.05), whereas bifidobacteria counts were negatively correlated with Amadori compounds intake. In the rat assay, total bacteria and lactobacilli were negatively correlated with MRP intake (r = -0.674,-0.675 and -0.676, for Amadori compounds, hydroxymethylfurfural and carboxymethyl-lysine respectively, p < 0.05), but no correlations were found with bifidobacteria. CONCLUSIONS Dietary MRP are able to modulate in vivo the intestinal microbiota composition both in humans and in rats, and the specific effects are likely to be linked to the chemical structure and dietary amounts of the different browning compounds.

Intake of Maillard reaction products reduces iron bioavailability in male adolescents.

The effects of diets with different Maillard reaction products (MRPs) content on biological iron utilization were compared using in vitro/in vivo assays. Diets were rich (brown diet, BD) or poor (white diet) in MRP. In vitro studies included iron solubility after in vitro digestion of diets and iron transport across Caco-2 cells. In the human assay 18 healthy adolescent males (11-14 years) participated in a 2-wk randomized two-period crossover trial. Subjects collected urine and faeces on the last 3 days of each dietary period, and fasting blood samples were obtained after periods. In vitro dietary iron availability was significantly lower with the BD than the white diet (9.52 and 12.92%, respectively), as a consequence of the lower iron solubility after the in vitro digestion, but not as a result of decreased transport of the remaining soluble iron. The BD consumption increased iron fecal excretion ( approximately 1.4-fold) and significantly decreased its bioavailability ( approximately 2.7-fold), mainly due to the effects found at digestive level. Serum biochemical parameters related to iron metabolism remained unaltered. It is concluded the presence of MRP in the diet negatively affects iron bioavailability. As iron deficiency may be related to learning impairment and to reductions of cognitive and physical functions, possible long-term effects of excessive MRP intake during adolescence warrant attention.

Maillard reaction products: some considerations on their health effects.

Abstract For several decades, researchers have been investigating the relations between the consumption of Maillard reaction products (MRPs) and biological activities, whether harmful or beneficial. Interest in this area is growing because the intake of these compounds has increased in parallel with the consumption of thermally processed foods. MRPs are bioavailable to some degree and, although there is little consensus about possible harmful effects or pathways of action, there are pathological implications regarding the progress and development of various degenerative disorders. Besides these considerations, it has been reported that some MRPs, particularly melanoidins, have beneficial effects as antioxidant, anti-inflammatory or anti-aging factors, among others. Some interesting aspects of this dual nature of MRPs are addressed in the present review. In this context, it is difficult to draw firm conclusions about the physiological consequences resulting from MRPs intake, due to the diversity of compounds formed in the different food matrixes. Maintaining a balanced and varied diet, not only in the food consumed but also in how it is processed, is increasingly viewed as the best strategy to limit the negative effects and to preserve the positive actions of dietary MRPs. Much remains to be done to elucidate the chemical structures of these compounds and to relate it to specific physiologic actions. For that purpose, setting the chromatographic determinations as the most reliable analytical tools to measure them in foods and biological tissues/fluids seems essential. Moreover,designing more realistic and better controlled clinical studies, based on the real diet of the population, will be the only method to perform an effective health-risk assessment of MRPs consumption.

Increased intake of Maillard reaction products reduces phosphorous digestibility in male adolescents

OBJECTIVE To examine the effects of consuming diets rich in Maillard reaction products (MRPs) on phosphorus bioavailability in male adolescents. METHODS A 2-wk randomized two-period crossover trial was performed among healthy male adolescents aged 11-14 y (n = 20), with a 40-d washout period. The diets consumed were rich (brown diet) or poor (white diet) in MRPs. Three-day balances were performed on the last of each dietary period, and fasting blood samples were obtained. Dietary phosphorus utilization was examined by phosphorus intake in diet and phosphorus output in feces and urine, as measured colorimetrically by the vanadomolibdate procedure. Serum phosphorus, parathyroid hormone, and total alkaline phosphatase were determined. RESULTS A tendency to increase daily phosphorus fecal excretion was observed subsequent to the brown diet consumption compared with the white diet (P = 0.10), which led to significant reductions in phosphorus apparent absorption (P = 0.03) and fractional absorption (P = 0.04). Values of apparent phosphorus retention and bioavailability tended to decrease after the high-MRP diet. Serum parameters analyzed remained unchanged between diets and were within normal values. CONCLUSION The consumption of a rich-MRP diet in male adolescents had a negative influence on dietary phosphorus absorption, tending to decrease the phosphorus balance. Given the actual dietary habits of adolescents, possible long-term repercussions of this kind of diet should be studied.

Metabolic transit of Nε-carboxymethyl-lysine after consumption of AGEs from bread crust

Our aim was to investigate carboxymethyl-lysine (CML) intake and excretion after feeding rats with diets containing advanced glycation end-products (AGEs) from bread crust (BC) or its soluble or insoluble fractions, and to identify the factors responsible for the effects observed. CML in serum and different tissues was measured to detect possible accumulations. For 88 days, weanling rats were fed with either a control diet or one containing BC, or its soluble low molecular weight (LMW), soluble high molecular weight (HMW) or insoluble fractions. In the last week of the assay, faeces and urine were collected daily and stored as a 1 week pool. After sacrifice, blood was drawn to obtain serum and some organs were removed. CML analysis was performed by HPLC/MS/MS in diets, faeces, urines, serum and tissues. Faecal excretion of CML was strongly influenced by dietary CML levels and represents the major route of excretion (i.e. 33.2%). However, the urinary elimination of CML was probably limited or saturated, especially when more complex compounds were present in the diet. BC consumption increased CML in the cardiac tissue (170 ± 18 vs. 97 ± 3 μmol per mol lysine for BC and control groups), which correlated with the CML intake. The levels of this AGE in bone were unaffected by the dietary treatment, but in tail tendons CML was greatly increased in the animals that consumed the BC diet (102 ± 13 vs. 51 ± 8 μmol per mol lysine for BC and control groups, P = 0.006), which was associated with the intake of soluble LMW compounds present in BC. Despite the CML accumulation detected in different tissues, serum levels of protein-bound CML were unchanged, indicating the importance of measuring the free CML in this fluid as a real index of dietary CML.

Estimation of hydroxymethylfurfural availability in breakfast cereals. Studies in Caco-2 cells

The transport and availability of hydroxymethylfurfural (HMF), an intermediary product of the Maillard reaction, was investigated in the Caco-2 cell line after in vitro gastrointestinal digestion. The study was carried out at two levels; (a) an HMF-spiked culture medium, and (b) digested commercial breakfast cereals (BC). In both assays, the higher the amount of HMF offered to the cells, the higher the absolute value of transported HMF. However, HMF availability and transport are not directly proportional to the initial HMF content since HMF is partly retained in the non-soluble fraction after digestion. In addition, HMF is degraded to some extent during the gastrointestinal digestion of both HMF-spiked cell medium and BC. Average HMF availability from three commercial breakfast cereals was 9.1% (4.98-12.99%). Variations in HMF availability may be related to the particular composition of each BC, where fibre could play an important role. On the other hand, possible metabolization into the cell should also be considered.

Assessing the effects of severe heat treatment of milk on calcium bioavailability: In vitro and in vivo studies

Thermal processing of milk is a common practice. As milk is the main source of dietary calcium, this study aimed to assess the effects of overheating milk on calcium availability. Thus, thermally damaged milk (overheated, OH, milk; 3 cycles of sterilization at 116 °C, 16 min) was compared with UHT milk (150 °C, 6s) in 2 types of assays: in vitro and in vivo (rats). In addition, the greater Maillard reaction rate associated with thermal treatment in OH milk was confirmed by determining specific (furosine) and unspecific markers (CieLab color). A negative effect on calcium solubility was observed after in vitro digestion of OH milk compared with UHT milk. Feeding rats the diet containing OH milk as the protein source led to significantly lower values of apparent calcium absorption and retention than those found among animals fed the UHT milk diet. Whereas reducing the absorption appears to result mainly from the decreased food intake, the negative effect on retention seems to be due to factors derived from milk thermal damage, such as the formation of Maillard reaction products. It was concluded that milk-processing conditions warrant special attention to prevent impaired dietary calcium utilization. This may be especially important in situations where milk and dairy products are the main dietary components, such as in early infancy.

Antioxidant capacity, total phenols and color profile during the storage of selected plants used for infusion.

Many plants, like tea, are widely used for preparing herbal infusions. These plants have an interesting antioxidant capacity that may change after harvesting depending on the technological processing and the storage conditions. We determined the antioxidant capacity (ABTS, DPPH and FRAP methods), total phenolic content and color analysis (reflectance) of 36 plants traditionally consumed in Spain as infusion. Green tea was the most antioxidant herb, although oregano and lemon balm showed also a very high antioxidant capacity, as well as phenolic content. The antioxidant study after 3-month storage at different temperatures showed that up to a 50% of the total antioxidant capacity could be lost. Color analysis correlated with antioxidant capacity evolution, being a quick tool to control the storage conditions. Finally, our data confirm that the intake of one serving of plant infusion could release the equivalent of up to 1,500 μmol trolox, being a good source of antioxidants for the human diet.

An Advanced Glycation End Product (AGE)-Rich Diet Promotes Nε-Carboxymethyl-lysine Accumulation in the Cardiac Tissue and Tendons of Rats

The purpose of this study was to investigate the intake, excretion, and tissue accumulation of carboxymethyl-lysine (CML), after feeding rats a diet containing advanced glycation end products (AGEs) from a glucose-lysine (GL) model system. Rats were distributed into two groups and assigned to a control diet or a diet including 3% heated GL (GL diet) for three months. Feces and urine were collected over the last week. After sacrifice, serum was obtained and some organs were removed for CML analysis. The percentage of fecal CML was 2.5-fold higher in the animals fed the GL diet (33.2 vs 76.5% for control and GL group), whereby total recovery was 91.8% compared with a level of 54.6% in the animals fed the control chow, evidencing the importance of the chemical form and the net quantity of dietary CML on its elimination. We suggest that dietary dicarbonyl compounds from GL diet or dietary CML itself are responsible for CML accumulation in hearts and tendons. The most significant result of the present study is that the regular consumption of dietary AGEs in healthy individuals promotes CML accumulation in some organs.

Dietary calcium utilization among a group of spanish boys aged 11–14 years on their usual diets

Adolescence constitutes a period of nutritional vulnerability due to increased dietary requirements for growth and development and special dietary habits. A pilot trial was performed to evaluate the dietary calcium utilization among a sample of Spanish boys on their usual diets, in which the calcium intake and consumption of dairy products were as well examined. Nutrient and food intake was recorded using a 24-h dietary recall and a 2-d food consumption record for 21 subjects aged 11–14 years. Dietary calcium utilization was assessed by means of calcium intake in food and calcium output in faeces and urine as measured by flame atomic absorption spectrophotometry. Overall intake of dairy products was 399.3±22.1 g/d, and the single most consumed item was milk (72% of the total). An inverse relationship was found between dairy product consumption at breakfast (55% of the total) and BMI (p=0.016, r=−0.5168). Dairy products contributed the majority of dietary calcium (66.9%). Mean calcium intake was 881.7±39.9 mg/d, 88% of the recommended value for Spanish adolescents. Net calcium absorption (271.7±51.7 mg/d) and retention (170.6±50.9 mg/d) seemed not to be sufficient to meet growth demands during puberty. The results shown that adolescents of the study absorbed 31% of dietary calcium and retained nearly 20% of the total intake, but dietary calcium intake and consumption of dairy products failed to meet recommended values. Optimizing calcium intake is of crucial importance among adolescents, to maximize calcium retention and to help prevent osteoporosis in later life.ResumenLa adolescencia constituye una etapa vulnerable desde el punto de vista nutricional, tanto por sus elevadas necesidades para el crecimiento y la maduración como por sus especiales hábitos alimentarios. Este trabajo supone un estudio piloto diseñado para evaluar la utilización del calcio dietético en un grupo de 21 chicos de 11–14 años que consumen su dieta habitual, examinando la ingesta de calcio y el consumo de productos lácteos. La ingesta alimentaria fue evaluada mediante un recordatorio de 24-h y un registro estimado de alimentos de 2 días. Para evaluar la utilización del calcio de la dieta se analizó la excreción en orina y heces mediante espectrofotometría de absorción atómica. La ingesta media de productos lácteos fue de 399,3±22,1 g/día, aportando el 66,9% del calcio total de la dieta y siendo la leche el producto más consumido (72% del total). Se encontró una correlación inversa entra el consumo de lácteos en el desayuno (55% del total) y el IMC (p=0,016, r=−5,168). La ingesta media de calcio fue de 881,7±39,9 mg/d, lo cual supone el 88% del valor recomendado para adolescentes españoles. Las cifras de absorción (271,7±51,7 mg/d) y retención (170,6±50,9 mg/d) de calcio parecieron insuficientes para satisfacer las demandas para el crecimiento durante la pubertad. Los resultados mostraron que los adolescentes del estudio absorbieron el 31% del calcio dietético y retuvieron casi el 20%, aunque ni la ingesta de calcio ni el consumo de productos lácteos alcanzaron las recomendaciones. Una ingesta adecuada de calcio y ayudar a prevenir la osteoporosis en la edad adulta.