Objective: To grade the evidence from published meta-analyses of prospective observational studies that assessed the association of dietary patterns, specific foods, food groups, beverages (including alcohol), macronutrients, and micronutrients with the incidence of CRC.
Data Sources: MEDLINE, Embase, and the Cochrane Library were searched from database inception to September 2019.
Evidence Review: Only meta-analyses of prospective observational studies with a cohort study design were eligible. Evidence of association was graded according to established criteria as follows: convincing, highly suggestive, suggestive, weak, or not significant.
Results: From 9954 publications, 222 full-text articles (2.2%) were evaluated for eligibility, and 45 meta-analyses (20.3%) that described 109 associations between dietary factors and CRC incidence were selected. Overall, 35 of the 109 associations (32.1%) were nominally statistically significant using random-effects meta-analysis models; 17 associations (15.6%) demonstrated large heterogeneity between studies (I2 > 50%), whereas small-study effects were found for 11 associations (10.1%). Excess significance bias was not detected for any association between diet and CRC. The primary analysis identified 5 (4.6%) convincing, 2 (1.8%) highly suggestive, 10 (9.2%) suggestive, and 18 (16.5%) weak associations between diet and CRC, while there was no evidence for 74 (67.9%) associations. There was convincing evidence of an association of intake of red meat (high vs low) and alcohol (≥4 drinks/d vs 0 or occasional drinks) with the incidence of CRC and an inverse association of higher vs lower intakes of dietary fiber, calcium, and yogurt with CRC risk. The evidence for convincing associations remained robust following sensitivity analyses.
Conclusions and Relevance: This umbrella review found convincing evidence of an association between lower CRC risk and higher intakes of dietary fiber, dietary calcium, and yogurt and lower intakes of alcohol and red meat. More research is needed on specific foods for which evidence remains suggestive, including other dairy products, whole grains, processed meat, and specific dietary patterns.
METHODS: The Prospective Urban Rural Epidemiology (PURE) study is a large multinational cohort study of individuals aged 35-70 years enrolled from 21 countries in five continents. Dietary intakes of dairy products for 136 384 individuals were recorded using country-specific validated food frequency questionnaires. Dairy products comprised milk, yoghurt, and cheese. We further grouped these foods into whole-fat and low-fat dairy. The primary outcome was the composite of mortality or major cardiovascular events (defined as death from cardiovascular causes, non-fatal myocardial infarction, stroke, or heart failure). Hazard ratios (HRs) were calculated using multivariable Cox frailty models with random intercepts to account for clustering of participants by centre.
FINDINGS: Between Jan 1, 2003, and July 14, 2018, we recorded 10 567 composite events (deaths [n=6796] or major cardiovascular events [n=5855]) during the 9·1 years of follow-up. Higher intake of total dairy (>2 servings per day compared with no intake) was associated with a lower risk of the composite outcome (HR 0·84, 95% CI 0·75-0·94; ptrend=0·0004), total mortality (0·83, 0·72-0·96; ptrend=0·0052), non-cardiovascular mortality (0·86, 0·72-1·02; ptrend=0·046), cardiovascular mortality (0·77, 0·58-1·01; ptrend=0·029), major cardiovascular disease (0·78, 0·67-0·90; ptrend=0·0001), and stroke (0·66, 0·53-0·82; ptrend=0·0003). No significant association with myocardial infarction was observed (HR 0·89, 95% CI 0·71-1·11; ptrend=0·163). Higher intake (>1 serving vs no intake) of milk (HR 0·90, 95% CI 0·82-0·99; ptrend=0·0529) and yogurt (0·86, 0·75-0·99; ptrend=0·0051) was associated with lower risk of the composite outcome, whereas cheese intake was not significantly associated with the composite outcome (0·88, 0·76-1·02; ptrend=0·1399). Butter intake was low and was not significantly associated with clinical outcomes (HR 1·09, 95% CI 0·90-1·33; ptrend=0·4113).
INTERPRETATION: Dairy consumption was associated with lower risk of mortality and major cardiovascular disease events in a diverse multinational cohort.
FUNDING: Full funding sources are listed at the end of the paper (see Acknowledgments).
METHODS AND STUDY DESIGN: A case-control study was conducted involving 57 acne vulgaris patients and 57 age-, gender- and ethnicity-matched controls. All participants were aged 14 and above. The Comprehensive Acne Severity Scale (CASS) was used to categorise patients (grades 2 to 5) and controls (grades 0 to 1). Information such as the demographics, family history, smoking habits and dietary intake were collected using a self-administered questionnaire.
RESULTS: In the patient arm, the gender ratio of male to female was 1.5:1. 43 patients (75.4%) had a family history of acne vulgaris. No significant association was found for acne in patients with a history of smoking. Milk consumption was significantly higher in patients (63.2%, n=36) versus controls (43.9%, n=25), (OR=2.19, p<0.05). In addition, chocolate consumption was also significantly higher in patients (43.9%, n=25) versus controls (24.6%, n=14), (OR=2.4, p<0.05). No significant association was found with the intakes of sweets, potatoes, chips, nuts, yoghurt, ice-cream or carbonated drinks.
CONCLUSIONS: Dietary intake of milk and chocolate may play a role in acne vulgaris. Prospective cohort and intervention studies are recommended to explore whether a causal relationship might obtain.