The Mediterranean diet (MedDiet), one of the most studied and well‐known dietary patterns worldwide, has been associated with a wide range of benefits for health. In the present narrative review, we aimed to provide a comprehensive overview of the current knowledge on the relation of the MedDiet to important health outcomes, considering both observational and intervention studies with both risk factors and clinical diseases as outcomes. In addition, we considered the clinical and public health impacts of the MedDiet on both human and planetary health. Earlier research confirmed by recent studies has provided strong evidence for the benefits of the MedDiet on cardiovascular health, including reduction in the incidence of cardiovascular outcomes as well as risk factors including obesity, hypertension, metabolic syndrome, and dyslipidaemia. There is also evidence that MedDiet is associated with lower rates of incident diabetes, and better glycaemic control in diabetic patients compared to control diets. In prospective studies, adherence to the MedDiet reduced mortality, especially cardiovascular mortality, hence increased longevity. In addition, it has been associated with less age‐related cognitive dysfunction and lower incidence of neurodegenerative disorders, particularly Alzheimer’s disease. Furthermore, the relatively low environmental impacts (water, nitrogen and carbon footprint) of the MedDiet is an additional positive aspect of the Mediterranean dietary model. It is likely that the combination of a healthy diet with social behaviours and the way of life of Mediterranean regions makes the MedDiet a sustainable lifestyle model that could likely be followed in other regions with country‐specific and culturally appropriate variations.

The authors evaluated the validity of a 152-item semiquantitative food frequency questionnaire (SFFQ) by comparing it with two 7-day dietary records (7DDRs) or up to 4 automated self-administered 24-hour recalls (ASA24s) over a 1-year period in the women's Lifestyle Validation Study (2010–2012), conducted among subgroups of the Nurses’ Health Studies. Intakes of energy and 44 nutrients were assessed using the 3 methods among 632 US women. Compared with the 7DDRs, SFFQ responses tended to underestimate sodium intake but overestimate intakes of energy, macronutrients, and several nutrients in fruits and vegetables, such as carotenoids. Spearman correlation coefficients between energy-adjusted intakes from 7DDRs and the SFFQ completed at the end of the data-collection period ranged from 0.36 for lauric acid to 0.77 for alcohol (mean r = 0.53). Correlations of the end-period SFFQ were weaker when ASA24s were used as the comparison method (mean r = 0.43). After adjustment for within-person variation in the comparison method, the correlations of the final SFFQ were similar with 7DDRs (mean r = 0.63) and ASA24s (mean r = 0.62). These data indicate that this SFFQ provided reasonably valid estimates for intakes of a wide variety of dietary variables and that use of multiple 24-hour recalls or 7DDRs as a comparison method provided similar conclusions if day-to-day variation was taken into account.

Unhealthful diet is an important cause of many major noncommunicable diseases, including cardiovascular disease, type 2 diabetes mellitus, and certain types of cancer, and ranks among the top contributors to the burden of disease and death in the United States.¹ Therefore, adopting a healthful diet is an important strategy to prevent adverse health outcomes and optimize long-term health.² Evaluation of population trends in dietary quality is essential because this provides feedback and guidance for public health policy. One approach to assess overall dietary quality is to calculate a score or index on the basis of aspects of diet related to health outcomes.³ For example, in 1996, Popkin et al⁴ used the Diet Quality Index to evaluate trends in a nationally representative US population and found significant improvements from 1965 to 1991. Since the late 1990s, many changes have occurred in the food supply, national economy, and policy environment, and scientific evidence and dietary recommendations have been continuously evolving. We therefore applied the Alternate Healthy Eating Index 2010 (AHEI-2010), an 11-dimension dietary quality index, to investigate recent trends in dietary quality in the US adult population. The AHEI-2010 is based on a combination of food and nutrient variables that have established relationships with important health outcomes and has strongly predicted major chronic disease.⁵ We also performed a sensitivity analysis by applying the recently updated Healthy Eating Index 2010 (HEI-2010), a measure of conformity to the 2010 Dietary Guidelines for Americans,⁶ in the same study population.

The authors examined the associations of dietary fat and specific types of fat with risk of coronary heart disease (CHD) among 78,778 US women initially free of cardiovascular disease and diabetes in 1980. They documented 1,766 incident CHD cases (including 1,241 nonfatal myocardial infarctions and 525 CHD deaths) during 20 years of follow-up. Polyunsaturated fat intake was inversely associated with CHD risk (multivariate relative risk (RR) for the highest vs. the lowest quintile = 0.75, 95% confidence interval (CI): 0.60, 0.92; p_trend = 0.004), whereas trans-fat intake was associated with an elevated risk of CHD (RR = 1.33, 95% CI: 1.07, 1.66; p_trend = 0.01). The associations between intakes of polyunsaturated fat and trans-fat with CHD risk were most evident among women younger than age 65 years (for polyunsaturated fat, RR = 0.66, 95% CI: 0.50, 0.85; p_trend = 0.002 and for trans-fat, RR = 1.50, 95% CI: 1.13, 2.00; p_trend = 0.01). The inverse association between polyunsaturated fat intake and CHD risk was strongest among women whose body mass index was ≥25 kg/m². Findings continue to support an inverse relation between polyunsaturated fat intake and CHD risk, particularly among younger or overweight women. In addition, trans-fat intake was associated with increased risk of CHD, particularly for younger women.

The relation between consumption of different types of dairy and risk of type 2 diabetes (T2D) remains uncertain. Therefore, we aimed to evaluate the association between total dairy and individual types of dairy consumptions and incident T2D in US adults. We followed 41,436 men in the Health Professionals Follow-Up Study (1986 to 2010), 67,138 women in the Nurses’ Health Study (1980 to 2010), and 85,884 women in the Nurses’ Health Study II (1991 to 2009). Diet was assessed by validated food-frequency questionnaires, and data were updated every four years. Incident T2D was confirmed by a validated supplementary questionnaire. During 3,984,203 person-years of follow-up, we documented 15,156 incident T2D cases. After adjustment for age, body mass index (BMI) and other lifestyle and dietary risk factors, total dairy consumption was not associated with T2D risk and the pooled hazard ratio (HR) (95% confidence interval (CI)) of T2D for one serving/day increase in total dairy was 0.99 (0.98, 1.01). Among different types of dairy products, neither low-fat nor high-fat dairy intake was appreciably associated with risk of T2D. However, yogurt intake was consistently and inversely associated with T2D risk across the three cohorts with the pooled HR of 0.83 (0.75, 0.92) for one serving/day increment (P for trend <0.001). We conducted a meta-analysis of 14 prospective cohorts with 459,790 participants and 35,863 incident T2D cases; the pooled relative risks (RRs) (95% CIs) were 0.98 (0.96, 1.01) and 0.82 (0.70, 0.96) for one serving total dairy/day and one serving yogurt/day, respectively. Higher intake of yogurt is associated with a reduced risk of T2D, whereas other dairy foods and consumption of total dairy are not appreciably associated with incidence of T2D.