Global cities and cultural diversity: challenges and opportunities for young people's nutrition

Ethnic differences in beta cell function occur independently of insulin sensitivity and pancreatic fat in black and white men

INTRODUCTION

It is increasingly recognized that type 2 diabetes (T2D) is a heterogenous disease with ethnic variations. Differences in insulin secretion, insulin resistance and ectopic fat are thought to contribute to these variations. Therefore, we aimed to compare postprandial insulin secretion and the relationships between insulin secretion, insulin sensitivity and pancreatic fat in men of black West African (BA) and white European (WE) ancestry.

RESEARCH DESIGN AND METHODS

A cross-sectional, observational study in which 23 WE and 23 BA men with normal glucose tolerance, matched for body mass index, underwent a mixed meal tolerance test with C peptide modeling to measure beta cell insulin secretion, an MRI to quantify intrapancreatic lipid (IPL), and a hyperinsulinemic-euglycemic clamp to measure whole-body insulin sensitivity.

RESULTS

Postprandial insulin secretion was lower in BA versus WE men following adjustment for insulin sensitivity (estimated marginal means, BA vs WE: 40.5 (95% CI 31.8 to 49.2) × 10³ vs 56.4 (95% CI 48.9 to 63.8) × 10³ pmol/m² body surface area × 180 min, p=0.008). There was a significantly different relationship by ethnicity between IPL and insulin secretion, with a stronger relationship in WE than in BA (r=0.59 vs r=0.39, interaction p=0.036); however, IPL was not a predictor of insulin secretion in either ethnic group following adjustment for insulin sensitivity.

CONCLUSIONS

Ethnicity is an independent determinant of beta cell function in black and white men. In response to a meal, healthy BA men exhibit lower insulin secretion compared with their WE counterparts for their given insulin sensitivity. Ethnic differences in beta cell function may contribute to the greater risk of T2D in populations of African ancestry.

Fruit and vegetable consumption and mental health across adolescence: evidence from a diverse urban British cohort study

BACKGROUND

Evidence on the relationship between fruit and vegetable consumption (FV) and mental health in adolescence is sparse and inconsistent. Social determinants of FV include ethnicity, family environments and economic disadvantage. We investigated the relationship between FV and mental health in the British multi-ethnic Determinants of Adolescents (now young Adult) Social well-being and Health (DASH) longitudinal study.

METHODS

A longitudinal study of 4683 adolescents living in London at age 11-13 years and followed up at 14-16 years. FV was measured using validated questions on the number of portions consumed daily. Mental health was measured by the Strengths and Difficulties Questionnaire as mean Total Difficulties Score (TDS) and by classification as a 'probable clinical case' (TDS > 17). Social measures included ethnicity, parenting and socioeconomic circumstances. Multilevel modelling was used to investigate the association between FV and mental health throughout adolescence.

RESULTS

Low FV was common among adolescents, with approximately 60-70% of adolescents reporting < 5 portions/day and 20-30% reporting < 1 portion/day. In late adolescence, most ethnic minority groups reported lower FV than their White peers. In fully adjusted models, < 1 portion/day remained a significant correlate with mean TDS (Coef: 0.55, 0.29-0.81, P < 0.001) and TDS > 17 (Odds Ratio: 1.43, 1.11-1.85, P = 0.007). Gender- or ethnic-specific effects were not observed. Low parental care partly attenuated the association between FV and mental health.

CONCLUSIONS

Low FV is a longitudinal correlate of poor mental health across adolescence. A focus on FV in parenting interventions could yield interrelated benefits across developmental outcomes given its importance to both physical and socioemotional health.