M. Pilar Navarro

Calcium Nutrition in Adolescence

Adolescence is an important period of nutritional vulnerability due to increased dietary requirements for growth and development and special dietary habits. Calcium needs are elevated as a result of the intensive bone and muscular development and thus adequate calcium intake during growth is extremely important to reach the optimum peak bone mass and to protect against osteoporosis in the adult age, a major public health threat whose incidence is increasing in Western countries. However, most children and adolescents worldwide fail to achieve the recommended calcium intake. The hormonal changes associated with the pubertal period promote greater mineral utilization, which needs to be satisfied with suitable calcium consumption. Diet, therefore, must contribute nutrients in sufficient quality and quantity to allow maximum bone mass development. Consequently, adolescents should be educated and encouraged to consume adjusted and balanced diets that, together with healthy lifestyles, enable optimal calcium utilization.

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.

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.

Iron Nutrition in Adolescence

Adolescence is an important period of nutritional vulnerability due to increased dietary requirements for growth and development. Iron needs are elevated as a result of intensive growth and muscular development, which implies an increase in blood volume; thus, it is extremely important for the adolescents iron requirements to be met. Diet, therefore, must provide enough iron and, moreover, nutrients producing adequate iron bioavailability to favor element utilization and thus be sufficient for needs at this stage of life. Currently, many adolescents consume monotonous and unbalanced diets which may limit mineral intake and/or bioavailability, leading to iron deficiency and, consequently, to ferropenic anemia, a nutritional deficit of worldwide prevalence. Iron deficiency, apart from provoking important physiological repercussions, can adversely affect adolescents’ cognitive ability and behavior. Accordingly, promoting the consumption of a varied, adjusted, and balanced diet by adolescents will facilitate iron utilization, benefiting their health both at present and in adulthood. This review discusses how physiological changes during adolescence can cause iron requirements to increase. Consequently, it is important that diet should contribute an appropriate amount of this mineral and, moreover, with an adequate bioavailability to satisfy needs during this special period of life.

The beneficial effect of Mediterranean dietary patterns on dietary iron utilization in male adolescents aged 11–14 years

The effects of a diet based on Mediterranean patterns on iron bioavailability and iron status in adolescents were studied. The study was divided into two periods: basal period, in which 21 male adolescents consumed their habitual diet (basal diet); and nutritional intervention period, during which an experimental diet based on the Mediterranean model was consumed. Dietary iron utilization was studied by means of iron intake and iron output in faeces and urine, and iron status was analysed in fasting blood samples collected at the end of each period. No differences in total iron intake were found between diets, but consumption of the experimental diet increased iron absorption and retention compared with the basal diet. Biochemical parameters related to iron metabolism did not vary after the intervention period, although serum ferritin tended to increase. Therefore, a diet based on Mediterranean dietary patterns may improve dietary iron utilization during adolescence and may prevent iron deficiency.

Effects of diets containing oils from repeated frying on magnesium absorption

Olive oil, sunflower oil and palm olein were used in repeated potato fryings until the oils reached the limit of 25% of polar compounds allowed by law. Six groups of rats, over 28 days, were fed diets containing 8% of: olive oil; olive oil from 69 fryings; sunflower oil; sunflower oil from 48 frying; palm olein, and palm olein from 80 fryings. Body weight and food intake were monitored weekly, during days 21–28 faeces and urine were collected and finally blood and carcasses were also collected and stored. No significant differences were observed in food intake and body weight among the six groups of animals. The type of oil did not modify magnesium intake, the urinary and faecal excretion of this mineral nor its apparent absorption or retention. The consumption of oils from frying, however, induced an increase in apparent magnesium absorption due to a decrease in faecal magnesium excretion, but magnesium retention did not vary owing to the increase in urinary losses. Serum magnesium and magnesium contents and concentrations in carcasses were unaffected. Therefore, it was concluded that the consumption of used frying oils enhances magnesium absorption, independently from the type of oil, although magnesium retention is not affected due to a an elevation of urinary excretion. © 1999 Society of Chemical Industry

Modifications in bacterial groups and short chain fatty acid production in the gut of healthy adult rats after long-term consumption of dietary Maillard reaction products

Bread crust (BC) is one of the major sources of Maillard reaction products (MRPs) in the Western diet. This work was designed to analyze the impact of diets containing important levels of MRPs from BC on intestinal bacterial growth and short chain fatty acids (SCFAs) production in adult rats. Additionally, the pools of compounds excreted in feces attending to their molecular weights were analyzed. Rats were fed for 88days a control diet or diets containing BC or its soluble high molecular weight (HMW), soluble low molecular weight (LMW) or insoluble fractions, respectively. Intestinal (cecum) microbiota composition was determined by qPCR analysis. Consumption of the BC diet lowered (P<0.05) Lactobacillus spp. and Bifidobacterium spp. log10 counts (8 and 14%, respectively), an effect for which soluble LMW and HMW fractions of BC seemed to be responsible. In these same animals, Escherichia/Shigella counts increased by around 45% (P<0.05), a fact which correlated with a higher production of formic acid in feces (r=0.8197, P=0.0458), and likely caused by the combined consumption of all MRPs contained in the BC. A significant 5-fold increment (P<0.05) was detected in the fecal proportion of propionic acid in the BC group, one of the products that have largely been associated with anti-inflammatory actions. Regarding the distribution of MRPs in feces, only the LMW fed group exhibited a predominance of those ranging between 90,000-1000Da, whereas the rest of the groups presented higher amounts of products above 90,000Da. It is concluded that dietary Maillard reaction products are in vivo fermented by the gut microbiota, thereby changing both the pattern of SCFAs production and the microbiota composition.

Does the pelleting process affect the nutritive value of a pre-starter diet for suckling piglets? Ex vivo studies on mineral absorption†

BACKGROUND The effects of pelleting on the extent of the Maillard reaction (MR) and on calcium, magnesium and zinc solubility and absorption were analysed in a conventional pre-starter diet for suckling piglets. Development was tested measuring colour, absorbance (280/420 nm), fluorescence, residual free lysine, furosine, hydroxymethylfurfural (HMF) and furfural contents before and after pelleting. Fluorescence, absorbance and mineral solubility were also measured after in vitro digestion of diets. The effects on mineral absorption were tested using Caco-2 cells. RESULTS MR indexes confirmed the development of the reaction during the pelleting of this particular diet compared with the meal diet. The CIE-Lab colour parameters showed a decrease in luminosity (L*) and progress of the colour to the red zone (a*) in the pelleted diet. A 36% decrease in free lysine content was observed. Significant correlations were observed between fluorescence intensity and furosine levels, HMF and furfural. The pelleting process did not modify calcium and magnesium solubility after in vitro digestion, but soluble zinc increased. The efficiency of calcium and zinc transport across Caco-2 cell monolayers was greater in the pelleted diet. CONCLUSIONS Evidence of MR development is shown, resulting in various nutritional consequences. Optimisation of pelleting could result in a better formulation of diets for feedstuffs.

Is the Mediterranean diet adequate to satisfy zinc requirements during adolescence

OBJECTIVE To evaluate Zn utilization and status among a sample of Spanish boys consuming a diet based on Mediterranean patterns. DESIGN Dietary Zn balance was assessed by means of Zn intake in food and Zn output in faeces and urine as measured by flame atomic absorption spectrophotometry. In addition, biomarkers of Zn status were analysed. SETTING Province of Granada, Spain. SUBJECTS Twenty healthy male adolescents aged 11-14 years, selected based on medical questionnaire, physical examination and nutritional survey of food habits and lifestyle. RESULTS Mean Zn intake was 11·36 (se 0·31) mg/d, 76% of the recommended value for Spanish adolescents. Zn absorption (2·53 (se 0·55) mg/d) was close to the value of 3·0 mg/d required for the growth spurt. Zn status biomarkers and growth parameters were within the normal values for this age group. CONCLUSIONS Although a diet based on Mediterranean patterns is associated with factors which can affect Zn absorption, such as high consumption of phytate, its consumption in adequate amounts allows Zn status to be maintained during adolescence. Due to the importance of Zn in preventing growth and behavioural disorders among adolescents, long-term intervention trials to investigate the suitability of the Mediterranean diet with respect to Zn requirements at this time of life are needed.

Intake of unused palm olein and palm olein used in frying does not affect calcium and phosphorus bioavailability in rats

Palm oil is widely used as a cooking medium. This study was undertaken to examine whether extensive use leading to the formation of polar compounds has any effect on calcium and phosphorus balances. Three isocaloric diets containing 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying uses (PF) without turnover, and which nearly reached the limit of 25% polar compounds allowed by law, were prepared and given to three groups of growing rats during a study period of 28 days. Body weight and food intake were monitored and faeces and urine were collected to calculate calcium and phosphorus balances during the last week of the study. At the end of the experiment the animals were killed and their livers, serum and carcases stored. No differences were observed between food intake, body weight and food efficiency of rats which consumed palm olein, whether unused or used in frying, and the control group (O). The liver mass index was higher in PF than O rats. No significant differences were observed in apparent absorption and retention of calcium and phosphorus. Faecal calcium (p =0.065) and the percentage of phosphorus absorbed (p =0.084) showed a tendency to increase in rats fed diets with both unused and used palm olein and could be due to the known higher affinity of fat for Ca than P. No variations in serum calcium and carcase calcium and phosphorus levels were seen. The conclusion of this study was that consumption of palm olein, whether unused or used in frying, does not alter calcium and phosphorus bioavailability.