Effect of probiotics on thymus size and markers of infection in late infancy: a randomized controlled trial.

BACKGROUND: Probiotics are known to stimulate the immune system but the effect on thymus size in late infancy is unknown. We examined the effect of probiotics on thymus size and C-reactive protein (CRP) in healthy Danish infants starting daycare. We further examined associations between thymus size, CRP and recent infections. METHODS: The study included 186 children randomized to a combination of Lactobacillus rhamnosus, LGG® and Bifidobacterium animalis spp. lactis, BB-12® or placebo for 6 months. Thymus size, assessed as thymus index (TI) and thymus weight index (TWI), was measured by ultrasound at baseline and at endpoint. Blood samples were drawn to measure CRP. Infections were parent-reported. RESULTS: There was no significant difference in thymus size between the probiotic group and placebo (p ≥ 0.248) but TWI tended to be higher in the probiotic group corresponding to 5% higher than placebo (p = 0.068) in an adjusted model. There was no effect of probiotics on CRP (p = 0.331). At the endpoint, thymus size was inversely associated with CRP (p ≤ 0.040), diarrhea (p ≤ 0.050), and TI was also associated with the absence from daycare due to respiratory or gastrointestinal infections (p = 0.010). CONCLUSION: The probiotic intervention had no effect on thymus size or CRP in Danish children at the age of starting daycare. IMPACT: Overall there was no effect on thymus size of a combination of Lactobacillus rhamnosus, LGG® and Bifidobacterium animalis spp. lactis, BB-12® administered to Danish children starting daycare. This study examines the effect of probiotics on thymus size in healthy children when they start daycare thus exposed for infections while their immune system is still developing. This has to our knowledge not been described before. We found no significant difference in thymus size between the probiotic and placebo groups, but for thymus weight index, there was a trend. This should be investigated further in studies designed for this as primary outcome.

Thymus size is associated with breastfeeding and having pets in a sex-specific manner.

AIM: The aim was to examine associations between thymus size and anthropometric measurements, sex, age, breastfeeding status, presence of siblings, household pets, and infections and allergies since birth in 8- to 13-month-old healthy Danish infants. METHODS: Data collected from 256 healthy infants enrolled in the ProbiComp study were used. Thymus size was assessed using sonographic measures, and thymic index (TI) and thymus weight index (TWI) was used as an absolute and a relative volume estimate, respectively. RESULTS: In terms of TI and TWI, boys had approximately 15% and 5% larger thymus than girls (P < .001 and P < .02, respectively). TWI was larger in girls who were still breastfed than girls who were no longer breastfed (ß: 0.16 cm3 /kg; 95% CI: 0.004, 0.29; P = .01), but no difference was observed for boys. Having household pets was associated with a larger TI (P = .02), which seemed to be driven by associations for boys (ß: 1.38 cm3 ; 95% CI: 0.02, 2.74). No other factors associated with thymus size were identified. CONCLUSION: Thymus size was associated with current breastfeeding in girls and with having household pets in boys. Sex-specific associations should be further explored in future studies on factors associated with thymus size.

Provision of healthy school meals does not affect the metabolic syndrome score in 8-11-year-old children, but reduces cardiometabolic risk markers despite increasing waist circumference.

An increasing number of children are exhibiting features of the metabolic syndrome (MetS) including abdominal fatness, hypertension, adverse lipid profile and insulin resistance. Healthy eating practices during school hours may improve the cardiometabolic profile, but there is a lack of evidence. In the present study, the effect of provision of school meals rich in fish, vegetables and fibre on a MetS score (primary outcome) and on individual cardiometabolic markers and body composition (secondary outcomes) was investigated in 834 Danish school children. The study was carried out as a cluster-randomised, controlled, non-blinded, cross-over trial at nine schools. Children aged 8-11 years received freshly prepared school lunch and snacks or usual packed lunch from home (control) each for 3 months. Dietary intake, physical activity, cardiometabolic markers and body composition were measured at baseline and after each dietary period. The school meals did not affect the MetS score (P= 1.00). However, it was found that mean arterial pressure was reduced by 0.4 (95% CI 0.0, 0.8) mmHg (P= 0.04), fasting total cholesterol concentrations by 0.05 (95% CI 0.02, 0.08) mmol/l (P= 0.001), HDL-cholesterol concentrations by 0.02 (95% CI 0.00, 0.03) mmol/l, TAG concentrations by 0.02 (95% CI 0.00, 0.04) mmol/l (both P< 0.05), and homeostasis model of assessment-insulin resistance by 0.10 (95% CI 0.04, 0.16) points (P= 0.001) compared with the control diet in the intention-to-treat analyses. Waist circumference increased 0.5 (95% CI 0.3, 0.7) cm (P< 0.001), but BMI z-score remained unaffected. Complete-case analyses and analyses adjusted for household educational level, pubertal status and physical activity confirmed the results. In conclusion, the school meals did not affect the MetS score in 8-11-year-olds, as small improvements in blood pressure, TAG concentrations and insulin resistance were counterbalanced by slight undesired effects on waist circumference and HDL-cholesterol concentrations.