Jonathan Berz, MD, MSc

Disclosures

August 21, 2012

In This Article

Diet and Chronic Disease

Poor diet is a major contributor to the leading causes of chronic disease and death in the United States, including coronary heart disease, diabetes, hyperlipidemia, and stroke.[1] In addition, recent data from the National Health and Nutrition Examination Survey show that more than 30% of adults in the United States are obese and that the prevalence of overweight and obesity combined is approximately 70%.[2] Lifestyle factors, especially healthy dietary practices that influence these trends, have a low level of adherence. Although it is true that the obesity and chronic disease epidemics have complicated origins, the contribution of our current society's easy access to highly processed foods and low consumption of fresh and whole foods cannot be overemphasized. At the turn of the millennium, the Centers for Disease Control and Prevention's Behavioral Risk Factor Surveillance Survey showed that less than 25% of Americans consumed the recommended amount of fruits and vegetables and equally few were as physically active as was recommended. More recent studies have not shown much improvement in the low prevalence of healthy lifestyle practices.[3,4]

In spite of this low level of adherence, a survey of adults in the United States showed that only one third reported receiving dietary advice from a physician on increasing consumption of fruits and vegetables.[5] Moreover, studies have shown that clinicians' knowledge and counseling about healthy diets are lacking.[6,7] In the recent past, numerous diets have been developed to combat weight gain and other disease risk factors, with varying degrees of evidence to show benefit. This article highlights 2 diets, each of which has a robust body of supporting literature: the Dietary Approaches to Stop Hypertension (DASH) diet and the Mediterranean diet.[8] This article will help clinicians improve their knowledge of healthy diets by reviewing key diets and the dietary components that have been shown to prevent chronic disease.

The DASH Diet

The Dietary Guidelines for Americans were updated in 2010 and the DASH diet was highlighted as a guideline for healthy eating.[9] DASH has as its core the increased consumption of fresh fruits and vegetables and low-fat dairy products. Fruits and vegetables are important because of the low-caloric and high-nutrient density of such foods and the satiating effects of fiber. Low-fat dairy consumption provides calcium that is needed for bone health and other health outcomes. Other components of DASH include nuts, legumes (dried beans and peas), whole grains, and limiting salt and added sugar intake.

Nuts are rich in beneficial mono- and polyunsaturated fats and are high in fiber and protein. Legumes are a rich source of protein as well as fiber, and lean meats are important sources of protein. Grains provide an important source of energy and should be consumed mostly as whole grains, which will increase fiber consumption. The DASH diet also limits salt to 2300 milligrams per day and added sugar intake to 5 tablespoons per week for the average 2000-calories/day diet. Table 1 shows the recommended intakes of each of these food groups in servings per day for those who consume 2000 calories per day.

Table 1. DASH Diet Food Group Servings for a 2000-Calories-Per-Day Diet

Food Group Target Serving Examples of 1 Serving
Low-fat dairy 2-3/day 1 cup milk or yogurt
Grains (mostly whole) 6-8/day 1 slice bread
1 oz dry cereal
1/2 cup cooked rice, pasta, or cereal
Lean meats, poultry, fish ≤6/day 1 oz cooked lean meat, poultry, or fish
1 egg
Nuts/seeds/legumes 4-5/week 1/3 cup or 1 1/2 oz nuts
2 Tbsp peanut butter 2 Tbsp or 1/2 oz seeds 1/2 cup cooked legumes
Fruits 4-5/day 1 medium fruit 1/4 cup dried fruit 1/2 cup fresh, frozen, or canned fruit 1/2 cup fruit juice
Vegetables 4-5/day 1 cup raw leafy vegetables
1/2 cup cut-up raw or cooked vegetables

Adapted from the 2010 Dietary Guidelines for Americans.[9]

DASH was originally developed and studied as a diet to reduce high blood pressure in a randomized controlled trial published in TheNew England Journal of Medicine[10] in 1997. In this study, a diet rich in fruits, vegetables, and low-fat dairy products and low in saturated fat was compared with a control diet and shown to result in substantial reductions in blood pressure. All of the diets had the same 3 grams per day of sodium. After 8 weeks, the systolic blood pressure of the participants assigned to the DASH diet was, on average, 5.5 mm Hg lower and diastolic blood pressure was 3 mm Hg lower compared with participants on the control diet.

Subsequent prospective observational studies have shown the DASH diet to have a number of other beneficial health effects. An analysis of the Nurses' Health Study showed that women who were in the highest quintile of consumption of a DASH-style diet and also had low consumption of processed meats and sugar-sweetened beverages had lower risk for coronary heart disease over almost 25 years of follow-up.[11] Other studies have shown beneficial effects in colorectal adenoma, metabolic syndrome, congestive heart failure, and obesity.[12,13,14]

One easy way to counsel patients on the basic message of the DASH diet is to describe and encourage the use of the healthy plate method. In 2011, the US Department of Agriculture introduced this diet counseling tool that replaced the food pyramid to make healthy food messages easier to deliver (Figure). The tool shows an easy-to-understand message on consuming the 5 food groups in a healthy way by portion size in relation to a typical dinner plate. Fruit and nonstarchy vegetables should take up one half of the plate; whole grain carbohydrates and lean protein one quarter each. Drinks should be primarily water or low-fat dairy products.[15]

Figure. The Healthy Plate.

The Mediterranean Diet

The Mediterranean diet is a food plan that came from the olive-growing countries bordering the Mediterranean Sea (Greece, Spain, and Italy) in the 1960s. A landmark ecological study that began in the 1950s was important to the origins of this eating pattern's health benefits and showed that mortality rates in selected countries near the Mediterranean Sea were substantially lower compared with those in westernized countries, such as the United States and Great Britain.[16] In 1993, the dietary pattern was defined at the International Conference on the Diets of the Mediterranean as being characterized by high consumption of olive oil, legumes, unrefined grains, fruits, and vegetables; moderate consumption of dairy products; moderate-to-high consumption of fish; low consumption of meat; and moderate consumption of alcohol. In early studies, the cardiovascular benefits of this eating plan were thought to be primarily from its lower saturated fat content.[17] It was later understood that the health benefits with respect to fat intake were not only the result of the low saturated fat content but also from the high content of beneficial fats. Monounsaturated fats, found in high levels in olive oils, and polyunsaturated fats, found in both fatty fish and nuts, were key reasons for the beneficial health effects of the diet (Table 2).

Table 2. Mediterranean Diet

High in fresh fruits and vegetables, olive oil, legumes, unrefined grains
Moderate in low-fat dairy
Low in meat
Moderate to high in fish
Moderate alcohol intake


Protection from a number of disease outcomes has been correlated with the Mediterranean eating pattern. Prospective observational studies in both European and US populations have shown that higher adherence to a Mediterranean food plan is associated with lower all-cause mortality, coronary heart disease, and cancer mortality. Those who more closely adhered to a Mediterranean dietary pattern had a higher monounsaturated-to-saturated fat ratio; higher consumption of vegetables, fruits, whole grains, and fish; and lower intake of red and processed meats. Moreover, specific intake levels of alcohol currently considered low to moderate were part of the diet. For men, this was 1-4 drinks per day and for women, it was one third to 2 drinks per day. Of interest, it was the overall dietary pattern that was linked with lower mortality rather than the specific food groups that make up the eating plan. It is possible that the synergy between different healthy food groups partly accounts for the benefits.[18,19]

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