In Western countries, vegetarian diets are associated with lower intakes of energy, saturated fatty acids and animal protein and higher intakes of fibre and phytochemicals, compared to omnivorous diets. Whether the corresponding health benefits in vegetarians outweigh the risks of nutrient deficiencies has not been fully clarified. It should be noted that vegetarians often have a higher socioeconomic status, follow a more health-conscious lifestyle with higher physical activity, and refrain from smoking more often than non-vegetarians. The nutritional needs of growing children and adolescents can generally be met through a balanced, vegetable-based diet; however, due to their higher nutrient requirements per kilogramme of body weight, vegetarian children have a higher risk for developing nutrient deficiencies than adults. With a vegetarian diet, the mean intakes of some nutrients, such as the omega-3 fatty acid docosahexaenoic acid (DHA), are lower than in omnivores or those eating fish. For other nutrients, such as iron and zinc, the bioavailability from vegetable foodstuffs is reduced when the intake of phytates and fibre is high; thus, the prevalence of iron deficiency can be increased despite high vitamin C intake. In addition, vitamin B12 is only found in animal-source foods. Vitamin B12 should be supplemented in people of all age groups who follow a strict vegan diet without consuming animal products. A vegetarian diet in childhood and adolescence requires good information and supervision by a paediatrician, if necessary, in cooperation with an appropriately trained dietary specialist.

Biosynthesis and functions of human milk oligosaccharides (HMO) are not well known. A typical housekeeping enzyme, β1,4-galactosyltransferase, links galactose to glucose to form lactose which is then used as backbone for the assembly of HMO. We investigated whether milk lactose and HMO may be labeled in vivo by an orally given ¹³C-galactose bolus. Eleven exclusively breastfeeding mothers were given a ¹³C-galactose bolus at the end of their breakfast. Milk and urine samples from each nursing up to 36 h were analyzed for carbohydrate composition by high-performance thin-layer chromatography, high-pH anion-exchange chromatography, and fast atom bombardment mass spectrometry. ¹³C enrichment of milk fractions, urinary carbohydrates, lactose, and oligosaccharides as well as of breath CO₂ was determined by isotope ratio mass spectrometry. Up to 10% of the orally given galactose bolus was directly transported to the mammary gland and incorporated into milk components. Characteristic for most milk samples was the appearance of two ¹³C-peaks, the first immediately after the ¹³C-bolus was taken and the second on the next morning. The highest ¹³C enrichment was found in lactose followed by neutral and acidic oligosaccharides. In breath samples, the ¹³C-excretion followed the same pattern as in milk. ¹³C nuclear magnetic resonance of isolated lactose revealed ¹³C only at C₁-atom of galactose and C₁-atom of glucose. This label was without any exception at the same position as the ¹³C-label of the orally applied galactose. Neutral and acidic HMO can easily be ¹³C-labeled in vivo which facilitates investigations of their metabolic fate in infants.

The intestinal microbiota is known to influence local immune homeostasis in the gut and to shape the developing immune system towards elimination of pathogens and tolerance towards self-antigens. Even though the lung was considered sterile for a long time, recent evidence using next-generation sequencing techniques confirmed that the lower airways possess their own local microbiota. Since then, there has been growing evidence that the local respiratory and intestinal microbiota play a role in acute and chronic pediatric lung diseases. The concept of the so-called gut–lung axis describing the mutual influence of local microbiota on distal immune mechanisms was established. The mechanisms by which the intestinal microbiota modulates the systemic immune response include the production of short-chain fatty acids (SCFA) and signaling through pattern recognition receptors (PRR) and segmented filamentous bacteria. Those factors influence the secretion of pro- and anti-inflammatory cytokines by immune cells and further modulate differentiation and recruitment of T cells to the lung. This article does not only aim at reviewing recent mechanistic evidence from animal studies regarding the gut–lung axis, but also summarizes current knowledge from observational studies and human trials investigating the role of the respiratory and intestinal microbiota and their modulation by pre-, pro-, and synbiotics in pediatric lung diseases.

Pureed complementary feeding products packed in squeezable plastic pouches, usually with a spout and a screw cap, have been increasingly marketed. The Committee on Nutrition recommends that infants and young children should not suck pureed or liquid complementary foods from baby food pouches. Complementary foods should be offered with a spoon or should be fed as finger foods. Infants and young children should be given the opportunity to get to know a variety of foods and food textures including pieces of foods, supported by responsive feeding between the child and their parents or caregivers. Complementary foods marketed in baby food pouches often have a high energy density and are predominantly extremely high in sugar content, with up to almost 90% of the total energy content. Regular consumption bears the risks of imbalanced nutrient provision and increased risks for dental caries and overweight. Complementary foods for infants and young children should have a balanced composition following the recommendations of the German Society of Pediatrics and Adolescent Medicine (DGKJ) and should contain only limited amounts of sugar. We discourage the feeding of pureed complementary foods from baby food pouches.

Scope: 2´‐Fucosyllactose (2´FL) is an abundant oligosaccharide in human milk. It is hypothesized that its brain enrichment is associated with improved learning. Accumulation of 2´FL in organs, biological fluids, and feces is assessed in wild‐type and germ‐free mice.Methods and results: ¹³C‐labelled 2´FL is applied to NMRI wild‐type mice intravenously (0.2 g kg⁻¹) or orally (1 g kg⁻¹), while controls receive saline. Biological samples are collected (0.5–15 h) and ¹³C‐enrichment is measured by elemental analysis isotope ratio mass spectrometry (EA‐IRMS). After oral application, 2´FL is primarily eliminated in the feces. ¹³C‐enrichment in organs including the brain follows the same pattern as in plasma with a maximum peak after 5 h. However, ¹³C‐enrichment is only detected when the ¹³C‐2´FL bolus reaches the colon. In contrast, in germ‐free mice, the ¹³C‐bolus remains in the intestinal content and is expelled via the feces. Furthermore, intravenously applied ¹³C‐2´FL is eliminated via urine; no ¹³C‐enrichment of organs is observed, suggesting that intact 2´FL is not retained.Conclusions: ¹³C‐enrichment in brain and other organs after oral application of ¹³C‐2´FL in wild‐type mice indicates cleaved fucose or other gut microbial 2´FL metabolites may be incorporated, as opposed to intact 2´FL.