Because individual foods or nutrients are not typically consumed in isolation, it is important to understand health effects of overall dietary patterns, which can provide a more comprehensive view of overall diet, reflecting real-world eating habits [119]. Moreover, evaluating overall dietary patterns can help capture the synergistic or antagonistic effects of different food components consumed concurrently and reduce confounding from intercorrelated dietary components. Moreover, dietary patterns can take into account cultural and regional variations in diet, making dietary recommendations more adaptable and relevant for diverse global populations.

The Mediterranean diet (MedDiet)

The traditional MedDiet is widely considered a model for healthy eating. The main features of the MedDiet include an abundance of plant foods, such as fruits, vegetables, whole grains, nuts, and legumes; olive oil as the main source of dietary fat; fish and poultry consumed in low-to-moderate amounts; relatively low consumption of red meat; and moderate consumption of wine, typically in conjunction with meals [94]. A recent comprehensive review [120] conducted by Guasch-Ferre and Willett summarized the extensive body of evidence from both observational studies and clinical trials on the relationships between adherence to the Mediterranean dietary patterns and a wide spectrum of health outcomes. Overall, there is compelling evidence that greater adherence to the MedDiet is associated with reduced risk of obesity, type 2 diabetes, hypertension, dyslipidemia, CHD, stroke, and heart failure. In prospective cohort studies, adherence to the Mediterranean dietary pattern is associated with reduced mortality, especially cardiovascular mortality, thus contributing to increased longevity. In addition, the MedDiet has been associated with slower progression of age-related cognitive decline [121] and lower risk of neurodegenerative disorders such as dementia and Alzheimer’s disease [122]. The MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay)—a hybrid of the MedDiet and the DASH (Dietary Approaches to Stop Hypertension) diet—has been consistently associated with a decreased risk of cognitive decline and dementia in large cohort studies [123]. However, a recent RCT did not find significant effects of the MIND diet intervention on changes in cognition over three years [124]. The relatively short duration of the intervention and similar weight loss between the intervention and control groups might have contributed to the null findings.
The Nordic diet

Similar to the MedDiet, the Nordic diet focuses on plant-based and locally sourced foods that are typically found in the Nordic countries, such as Sweden, Denmark, Norway, Iceland, and Finland [125]. One notable difference between the MedDiet and the Nordic diet is the type of oil used. The MedDiet mainly uses EVOO, whereas in the Nordic diet rapeseed oil is commonly used. Although olive oil is high in oleic acid, rapeseed oil is rich in oleic acid, linoleic acid, and alpha-linolenic acid. The types of whole grains in the Nordic regions are mostly rye, barley, and oats. Among various fruits, berries are featured more prominently in the Nordic diet.

Compared to the MedDiet, the extent of research available regarding health benefits of the Nordic diet is more limited and more recent. A systematic review and meta-analysis summarized data on Nordic dietary patterns and cardiometabolic outcomes from 15 prospective cohort studies [126] and 6 RCTs. In cohort studies, adherence to the Nordic dietary pattern was associated with a small reduction in risk of CVD (7%) and type 2 diabetes (9%). Small RCTs showed that the Nordic dietary pattern led to a modest reduction in LDL-cholesterol, ApoB, body weight, insulin, and SBP, compared to a control diet. Several cohort studies suggested that adherence to the MedDiet was more strongly associated with total mortality than adherence to the Nordic diet [125]. While the landmark PREDIMED trial has demonstrated the benefits of the MedDiet supplemented with EVOO or mixed nuts on CVD and other clinical end points, no such trial has been conducted to investigate long-term effects of the Nordic diet.

The Okinawa diet

The traditional Okinawa diet has been linked to high concentrations of centenarians on the island of Okinawa [127, 128]. This dietary pattern resembles a vegetarian diet, characterized by its emphasis on root vegetables (mainly purple sweet potatoes), green and yellow vegetables, soybean-based foods, seaweeds and algae, tea, and a variety of medicinal plants (e.g. bitter melon) and spices such as turmeric. Animal food consumption is often limited except for marine fish in coastal regions of the island. In addition to its food composition, a unique feature of the Okinawan diet is the practice of stopping eating when one is 80% full, known as Hara Hachi Bu [129]. This practice is akin to a natural form of mild caloric restriction.

Okinawa is one of the five “Blue Zones,” a concept introduced by Buettner [130]. In addition to Okinawa, the other Blue Zones include Sardinia in Italy, Nicoya Peninsula in Costa Rica, Ikaria in Greece, and Loma Linda in California, USA. These regions were recognized for their residents’ longevity and high numbers of centenarians. The diets of the Blue Zones are believed to play a crucial role in the exceptional longevity observed in these regions. However, the lifestyles in the Blue Zones also encompass shared features, such as plant-based eating, moderation in consumption, being physically active, and strong familial and social connections. Therefore, it is not possible to attribute the longevity observed in these regions solely to their diets.

Although the traditional diets in the Blue Zones have garnered much attention for their potential influence on longevity and health, it is worth noting that not all these diets and their health effects have been rigorously studied. In particular, while the Seventh-day Adventists Study based in Loma Linda is a well-established cohort to examine long-term effects of diet on health outcomes and longevity spanning decades [131], the diets in other Blue Zone regions and their health implications have been less well described. Moreover, the diets in the Blue Zones have evolved over time and thus differ substantially from traditional practices due to shifts in social-economic and cultural factors. For instance, the Okinawa diet has undergone considerable Westernization in recent years, which might have contributed to the rise of chronic diseases and decreased life expectancy on the island [132].