Examining changes in school vending machine beverage availability and sugar-sweetened beverage intake among Canadian adolescents participating in the COMPASS study: a longitudinal assessment of provincial school nutrition policy compliance and effectiveness

Background

School nutrition policies can encourage restrictions in sugar-sweetened beverage (SSB) availability in school food outlets in order to discourage students’ SSB intake. The main objective was to examine how beverage availability in school vending machines changes over three school years across schools in distinct school nutrition policy contexts. Secondary objectives were to examine how students’ weekday SSB intake varies with time and identify longitudinal associations between beverage availability and SSB intake.

Methods

This longitudinal study used data from the COMPASS study (2013/14–2015/16), representing 7679 students from 78 Canadian secondary schools and three provincial school nutrition policy contexts (Alberta – voluntary guidelines, Ontario public – mandatory guidelines, and Ontario private schools – no guidelines). We assessed availability of 10 beverage categories in schools’ vending machines via the COMPASS School Environment Application and participants’ intake of three SSB varieties (soft drinks, sweetened coffees/teas, and energy drinks) via a questionnaire. Hierarchical regression models were used to examine whether: i) progression of time and policy group were associated with beverage availability; and, ii) beverage availability was associated with students’ SSB intake.

Results

Ontario public schools were significantly less likely than the other policy groups to serve SSBs in their vending machines, with the exception of flavoured milks. Vending machine beverage availability was consistent over time. Participants’ overall SSB intake remained relatively stable; reductions in soft drink intake were partially offset by increased sweetened coffee/tea consumption. Relative to Ontario public schools, attending school in Alberta was associated with more frequent energy drink intake and overall SSB intake whereas attending an Ontario private school was associated with less frequent soft drink intake, with no differences in overall SSB intake. Few beverage availability variables were significantly associated with participants’ SSB intake.

Conclusions

Mandatory provincial school nutrition policies were predictive of more limited SSB availability in school vending machines. SSB intake was significantly lower in Ontario public and private schools, although we did not detect a direct association between SSB consumption and availability. The findings provide support for mandatory school nutrition policies, as well as the need for comprehensive school- and broader population-level efforts to reduce SSB intake.

     

Maternal administration of granulocyte colony-stimulating factor improves neonatal rat survival after a lethal group B streptococcal infection

Maternally administered recombinant human granulocyte colony- stimulating factor (rhG-CSF) has been shown to cross the placenta and induce a peripheral neutrophilia and increases in the marrow and spleen neutrophil storage pools in fetal and newborn rats. In the present study, we have used this model system to investigate the efficacy of prenatally administered rhG-CSF on neonatal defense to a lethal challenge with Group B-beta hemolytic Streptococcus (GBS). Pregnant rats were injected with rhG-CSF twice daily beginning 6 days before parturition. At birth, all pups were infected with a dose of GBS that is lethal for 90% of infected pups (LD90). Survival was monitored daily for 5 days. Survival of infected pups from saline-treated mothers beyond 60 hours after infection was 10%. No difference in survival was observed among pups from mothers treated 2 and 4 days before parturition. In contrast, we determined that survival was 82.5% among infected pups from mothers treated for 6 days before parturition with rhG-CSF. Our results demonstrate that maternal administration of rhG- CSF augments neonatal defenses against a lethal bacterial challenge.     

Granulocyte-macrophage colony-stimulating factor augmentation of T-cell receptor-dependent and T-cell receptor-independent thymocyte proliferation

The effects of granulocyte-macrophage colony-stimulating factor (GM- CSF) are not confined to cells of the myeloid lineage. GM-CSF has been shown to have effects on mature T cells and both mature and immature T- cell lines. We therefore examined the GM-CSF responsiveness of murine thymocytes to investigate whether GM-CSF also affected normal immature T lymphocytes. The studies presented here indicate that GM-CSF augments accessory cell (AC)-dependent T-cell receptor (TCR)-mediated proliferation of unseparated thymocyte populations. To identify the GM- CSF responsive cell type, thymic AC and T cells were examined for GM- CSF responsiveness. We found that GM-CSF augmentation of TCR-induced thymocyte proliferation appears to be mediated via augmentation of AC function, and not via direct effects on mature single-positive (SP) thymocytes. Enriched double-negative (DN) thymocytes were also tested for GM-CSF responsiveness. GM-CSF induced the proliferation of adult and fetal DN thymocytes in an AC-independent and TCR-independent single- cell assay. Thus, in contrast to the SP thymocytes, a DN thymocyte population was directly responsive to GM-CSF. GM-CSF therefore may play a direct role in the expansion of DN thymocytes and an indirect role in the expansion of SP thymocytes.