Читать книгу Textbook of Lifestyle Medicine - Labros S. Sidossis - Страница 91

Humans consume complex combinations of foods in the context of their meals, rather than individual foods or food groups.

A dietary pattern is categorized as “healthy” by either (i) an a priori‐defined healthy diet quality score/index based on the existing dietary guidelines; or (ii) a posteriori‐derived healthy dietary pattern based on variations in food intake, developed using principal component analysis (PCA).

An example of a well‐known dietary quality score/index is the Healthy Eating Index (HEI), originally published in 1995 to evaluate the extent to which Americans are following the dietary recommendations. Since then, the HEI index has been revised several times. The index has a number of questions, each of which receives a specific score as a reflection of an important aspect of diet quality. Higher scores indicate higher consumption and better adherence to a healthy dietary pattern. The DASH score and several Mediterranean diet scores (MedDietScore) are also well‐established examples of such indexes, and they will be further discussed in later chapters of this book.

The second approach to define a healthy dietary pattern is to use PCA. PCA is a statistical method that is used to identify potential patterns from weighted food frequency questionnaires (FFQs) or 24‐hour dietary recalls within a specific population. In other words, the method clusters variables that “behave in a similar way,” forming new components instead of analyzing these variables independently. For example, someone eats a lot of vegetables but at the same time eats a lot of fruits and whole grains. Every new component can thereafter be associated with several characteristics of a study's sample.

Despite evidence of the efficacy of both approaches, major drawbacks exist. Scores are based on the current understanding of the relationship between diet and disease without taking into consideration possible unknown factors. Therefore, false‐positive associations might be generated. A classic example is the one of serum cholesterol and eggs. While there is not a true relationship between the consumption of eggs with CHD and stroke, positive associations persist as eggs are high in cholesterol and saturated fat. Furthermore, an a posteriori‐defined dietary pattern is derived from the population under consideration, but it is often not reproducible across populations.

According to the 2015–2020 Dietary Guidelines for Americans, a healthy dietary pattern should include consumption of a variety of vegetables, fruits, grains and especially whole grains, a variety of protein foods based on lean meats, poultry, eggs, low‐fat dairy products, legumes, nuts, seafood, and soy products, while avoiding saturated and trans fats, as well as added sugars and sodium. It has been shown that people who adopt a healthy dietary pattern are also more likely to adopt other healthy lifestyle behaviors. For example, people who are more adherent to a prudent diet might also refrain from smoking and be more active compared to less‐adherent individuals.

Scientific findings provide moderate‐to‐strong evidence that healthy dietary patterns are closely related to decreased prevalence of chronic diseases, such as CVDs, T2DM, and several types of cancer. Major dietary patterns that have been shown to have protective effects against diet‐related diseases are the healthy Nordic dietary pattern, the healthy Asian dietary pattern, the healthy vegetarian pattern, and the healthy Mediterranean‐style dietary pattern. These dietary patterns share some typical features – increased consumption of fruits and vegetables, whole‐grain cereals, legumes, and nuts, a modest alcohol intake, and moderate to low consumption of red and processed meats, refined grains, and sweets.