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Is adherence to dietary guidelines or specific dietary patterns, assessed by a predetermined score, related to the likelihood of developing cardiovascular disease?  

In the past, researchers looked at the relationship between individual foods and nutrients and health. Today, there is interest in looking at how combinations of foods and beverages, or dietary patterns, impact health. Many researchers use a score to measure how well individuals follow specific dietary guidance or a healthy diet. These are numeric scores of foods, food components, and nutrients and the individual components are summed to derive a total score for a dietary pattern. This summary of a NEL review presents what we know about dietary patterns, assessed using a score, and the likelihood of developing cardiovascular disease (CVD).
 
Conclusion

There is strong and consistent evidence that, in healthy adults, increased adherence to dietary patterns scoring high in fruits, vegetables, whole grains, nuts, legumes, unsaturated oils, low-fat dairy, poultry and fish; low in red and processed meat, high-fat dairy and added sugars; and moderate in alcohol is associated with decreased risk of fatal and non-fatal cardiovascular diseases, including coronary heart disease (CHD) and stroke.
 
What the Research Says
  • Results from this review tell us that consuming a Mediterranean-style dietary pattern or dietary guidelines-related pattern may prevent people from getting CVD
  • These studies show that consuming a diet that scores high in fruits, vegetables, whole grains, nuts, legumes, unsaturated oils, low-fat dairy, poultry and fish; low in red and processed meat, high-fat dairy and added sugars; and moderate in alcohol may decrease risk of fatal and non-fatal cardiovascular diseases, including CHD and stroke.

Technical Abstract

What is the relationship between adherence to dietary guidelines/recommendations or specific dietary patterns, assessed using an index or score, and risk of cardiovascular disease?

Background

The goal of this systematic review project was to identify dietary patterns of food and beverage intake that promote health and prevent disease. Historically, most dietary guidance has been based on research conducted on individual food components or nutrients. Dietary patterns are defined as the quantities, proportions, variety or combination of different foods, drinks and nutrients in diets, and the frequency with which they are habitually consumed. The objective of this systematic review was to assess the relationship between adherence to an a priori score and risk of CVD. An a priori score measures the degree of adherence to specific dietary guidelines or adherence to a healthy diet defined by scientific evidence on diet and disease. A priori scores are composite numeric scores of foods, food components and nutrients that are assessed as dichotomous variables (with predefined cut-points), ordinal variables such as quintiles or as continuous variables. The individual components are summed to derive a total score. 
 
Conclusion Statement

There is strong and consistent evidence that in healthy adults increased adherence to dietary patterns scoring high in fruits, vegetables, whole grains, nuts, legumes, unsaturated oils, low-fat dairy, poultry and fish; low in red and processed meat, high-fat dairy and added sugars; and moderate in alcohol is associated with decreased risk of fatal and non-fatal cardiovascular diseases, including coronary heart disease and stroke. (DGAC Grade: I-Strong)
 
Methods

Literature searches were conducted using PubMed, Embase, (BIOSIS, CAB Abstracts and Food Science and Technology Abstracts) and Cochrane databases to identify studies that evaluated the association between dietary patterns (using an a priori index or score) and risk of CVD. Studies that met the following criteria were included in the review:
  • Randomized controlled trials, non-randomized controlled trials or prospective cohort studies
  • Subjects aged two years to 18 years
  • Subjects who were healthy or at elevated chronic disease risk
  • Subjects from countries with high or very high human development (2011 Human Development Index)
  • Published in English in peer-reviewed journals
  • Unlimited date range
  • Diet exposure was assessed by adherence to a hypothesis-based dietary pattern, defined using a numerical scoring system.
A group of technical experts were involved in a qualitative synthesis of the body of evidence, development of a conclusion statement and assessment of the strength of the evidence (grade) using pre-established criteria including evaluation of the quality, quantity, consistency, magnitude of effect and generalizability of available evidence.
 
Findings
  • A total of 55 studies met the inclusion criteria for this systematic review and the body of evidence consisted primarily of large prospective cohort studies. These studies had large, relatively homogeneous populations of generally healthy adults, with long follow-up times.
  • The majority of studies that assessed CVD incidence or mortality reported a favorable association between increased adherence to a dietary pattern and risk of CVD. The decrease in risk of CVD ranged from 22% to 59% for increased adherence to a Mediterranean dietary pattern and from 20% to 44% for increased adherence to a dietary guidelines-related pattern.
  • In studies that examined CVD mortality secondary to total mortality, there were mixed results for favorable and null associations
  • The majority of studies that assessed CHD incidence or mortality reported a favorable association between adherence to a dietary pattern and CHD risk. The decreased risk of CHD ranged from 29% to 61% for increased adherence to a Mediterranean dietary pattern, from 24% to 31% for increased adherence to a dietary guidelines-related pattern, and from 14% to 27% for adherence to DASH.
  • The majority of studies that assessed stroke incidence or mortality reported a favorable association between adherence to a dietary pattern and stroke risk. The decreased risk of stroke ranged from 13% to 53% for increased adherence to a Mediterranean dietary pattern and from 14% to 60% for increased adherence to a dietary guidelines-related pattern.
  • A smaller number of studies examined intermediate, secondary outcomes and other individual clinical endpoint outcomes with mixed results.
Discussion

The preponderance of evidence from studies carried out in large, well-characterized prospective cohorts from the United States, Europe, Japan and Australia showed that an increase in a Mediterranean diet score or dietary guidelines-related score was associated with decreased risk of fatal and non-fatal CVD, defined as coronary heart disease (CHD) and stroke, as well as decreased risk of CHD and stroke as individual clinical outcomes. Scores that were most frequently associated with decreased risk of CVD, CHD or stroke were the original Mediterranean Diet Score (MDS), the Alternate Mediterranean Diet Score (aMed), the Healthy Eating Index (HEI)-2005, the Alternate HEI (AHEI) and updated AHEI-2010, the Recommended Food Score (RFS) and a DASH score. Positive food components of scores that were associated with decreased CVD risk were fruits, vegetables, whole grains, nuts, legumes, unsaturated fats and fish. Alcohol was included as a positive component when consumed in moderation, but not in all scores. Red and processed meats were negative components in the Mediterranean scores, AHEI scores and DASH; whereas poultry was included as a positive component in the original AHEI and RFS scores. Total high-fat dairy was a negative component in the MDS, but dairy was a positive component when meeting recommended intakes for the HEI-2005 or as low-fat dairy in the RFS and DASH scores. Certain scores also included sugars or sugar-sweetened beverages as negative components.
 
Limitations in this body of evidence were the use of different scores and differences between scores based on median population intakes vs. recommended intakes. However, in this relatively large body of evidence, a limited number of scores were predictive of risk, oftentimes less complicated versions of these scores, and in some studies different scores were tested in the same cohorts, making comparisons across these scores feasible.