It has been hypothesised that increased asthma prevalence in westernised countries is associated with changes in lifestyle factors, including a poorer diet. However, little is known regarding the association between diet quality and asthma. In the diet–asthma association, the role of BMI as a potential mediator needs clarification; moreover, potential effect modification by non-diet sources of oxidants, such as smoking, merits investigation. We investigated the association between diet quality and change in asthma symptoms, as well as assessed effect modification by smoking, while accounting for BMI as a potential mediator. Using data from the French prospective Epidemiological study on the Genetics and Environment of Asthma study, we assessed diet quality using the Alternate Healthy Eating Index 2010 (AHEI-2010) at baseline and change in asthma symptoms (stable (reference), worsening, improved; mean follow-up time: 7 years). Mediation analysis was used to disentangle total and direct effects and the indirect effect mediated by BMI. The analyses included 969 adults (mean age 43 years; 49 % men; 42 % ever asthma). We observed a significant interaction between smoking and AHEI-2010 on change in asthma symptoms (P for interaction=0·04). Among never smokers (n 499), we observed a positive total effect (multivariable OR 1·39; 95 % CI 1·07, 1·80) and a positive direct effect (OR 1·41; 95 % CI 1·09, 1·80) of the AHEI-2010 (per ten-point increment) on improved symptoms. No indirect effect mediated through BMI was observed (OR 0·99; 95 % CI 0·91, 1·07). Among former and current smokers, all effects were statistically non-significant. Better diet quality was associated with improved asthma symptoms over time in never smokers, independently of BMI.

The alternate Mediterranean diet (aMED) score is an adaptation of the original Mediterranean diet score. Raw (aMED) and energy-standardised (aMED-e) versions have been used. How the diet scores and their association with health outcomes differ between the two versions is unclear. We examined differences in participants’ total and component scores and compared the association of aMED and aMED-e with all-cause, CVD and cancer mortality. As part of the Multiethnic Cohort, 193 527 men and women aged 45–75 years from Hawaii and Los Angeles completed a baseline FFQ and were followed up for 13–18 years. The association of aMED and aMED-e with mortality was examined using Cox’s regression, with adjustment for total energy intake. The correlation between aMED and aMED-e total scores was lower among people with higher BMI. Participants who were older, leaner, more educated and consumed less energy scored higher on aMED-e components compared with aMED, except for the red and processed meat and alcohol components. Men reporting more physical activity scored lower on most aMED-e components compared with aMED, whereas the opposite was observed for the meat component. Higher scores of both aMED and aMED-e were associated with lower risk of all-cause, CVD and cancer mortality. Although individuals may score differently with aMED and aMED-e, both scores show similar reductions in mortality risk for persons scoring high on the index scale. Either version can be used in studies of diet and mortality. Comparisons can be performed across studies using different versions of the score.

We assessed the association of four diet quality scores with multiple cardio-metabolic outcomes among Guatemalan young adults experiencing the nutrition transition. We obtained cross-sectional dietary, demographic, anthropometric and cardio-metabolic risk factor data from 1220 Guatemalan adults (mean age 32·7 (sd 5·8) years) in 2002–4, and computed a Recommended Food Score (RFS), Not Recommended Food Score (NRFS), Food Variety Score (FVS) and the Dietary Quality Index-International (DQI-I). All four scores were correlated with energy intake (r 0·23–0·49; all P < 0·01), but had varying associations with socio-demographic characteristics, lifestyle factors and nutrient intakes. None of the scores was inversely associated with the metabolic syndrome or its components; rather some were positively associated with risk factors. Among both men and women the DQI-I was positively associated with BMI (kg/m2; β = 0·10, 95 % CI 0·003, 0·21 (men); β = 0·07, 95 % CI 0·01, 0·14 (women)) and waist circumference (cm; β = 0·02, 95 % CI 0·01, 0·03 (men); β = 0·02, 95 % CI = 0·01, 0·02 (women)). Among men, the RFS was positively associated with TAG (mg/l; β = 0·11, 95 % CI 0·02, 0·21) and glucose (mg/l; β = 0·13: 95 % CI 0·03, 0·22). We conclude that indices of diet quality are not consistently associated with chronic disease risk factor prevalence in this population of Guatemalan young adults.