Which of the following is a key recommendation by the Dietary Guidelines for Americans?

The Food Guidance System

The Dietary Guidelines for Americans and the Food Guidance System replaced the Food Guide Pyramid, which was first introduced in 1992.5,7 Key recommendations of the Dietary Guidelines are presented in an easy to use format that can be customized for the consumer. Depending on individual energy needs, specific quantities of foods from each food group are used to define potential optimal health. Furthermore, the current Food Guidance System includes physical activity assessment and recommendations for activity for the first time in the history of the Pyramid graphics.

The Center for Nutrition Policy and Promotion (CNPP), a branch of the USDA, is ultimately responsible for the promotion of the Dietary Guidelines for Americans. The “MyPyramid” (Figure 14-2), a tool designed to translate the Food Guidance System to a graphic and interactive representation, allows each person to monitor his or her food and physical activity to achieve optimum health. “MyPyramid” illustrates six recommendations including personalization, gradual improvement, physical activity, variety, moderation, and proportionality. The interactive technology afforded by the government website allows each consumer to enter his or her own age, gender, and physical activity for personal recommendations and to compare individual food intakes to the Dietary Guidelines for Americans.5

Federal Government

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Dietary Guidelines for Americans, 2005. The Dietary Guidelines for Americans is published jointly every 5 years by the Department of Health and Human Services and the USDA. The guidelines provide authoritative advice for people 2 years and older about how good dietary habits can promote health and reduce risk for major chronic diseases. They serve as the basis for federal food and nutrition education programs. Visit http://www.health.gov/DietaryGuidelines/dga2005/document/default.htm.

Dietary Guidelines for Americans, 2010. Provides the most recent dietary guidelines for Americans. Visit http://www.cnpp.usda.gov/dietaryguidelines.htm

MyPyramid.gov. MyPyramid offers personalized eating plans and interactive tools that help plan and assess healthy food choices based on the Dietary Guidelines for Americans. Visit http://www.mypyramid.gov/.

Health and Human Services Small Step Adult and Teen program. Information is presented about steps to take to improve health and well-being. Visit http://www.smallstep.gov/.

National Heart, Lung, and Blood Institute (NHLBI)

National Cholesterol Education Program. The goal of the NCEP is to reduce illness and death from CHD in the United States by reducing the percentage of Americans with high blood cholesterol. Through educational efforts directed at health professionals and the public, the NCEP aims to raise awareness and understanding about high blood cholesterol as a risk factor for CHD and the benefits of lowering cholesterol levels as a means of preventing CHD. Visit http://www.nhlbi.nih.gov/about/ncep/.

Hearts N’ Parks program is a national, community-based program supported by the NHLBI and the National Recreation and Park Association that is designed to encourage heart-healthy lifestyles in communities. Visit http://www.nhlbi.nih.gov/health/prof/heart/obesity/hrt_n_pk/index.htm.

Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Updated guidelines for hypertension for the health care professional. The report provides new evidence for treating high blood pressure. Visit http://www.nhlbi.nih.gov/guidelines/hypertension/jnc7full.htm.

Centers for Disease Control and Prevention

Healthy weight program is designed to help individuals achieve and maintain a healthy weight. Visit http://www.cdc.gov/healthyweight/index.html.

Nutrition program helps individuals follow a healthy diet. Visit http://www.cdc.gov/nutrition/index.html.

Physical activity program helps individuals learn about recommendations for active living. Visit http://www.cdc.gov/physicalactivity/index.html.

Cholesterol website provides information about blood cholesterol levels and risk of heart disease. Visit http://www.cdc.gov/cholesterol/.

Food and Drug Administration, food labeling and nutrition programs. Information is presented about labeling requirements for foods under the Federal Food Drug and Cosmetic Act and its amendments. Included in this is information about the nutrition facts panel, health claims/qualified health claims, and nutrient content claims. Visit http://www.fda.gov/Food/LabelingNutrition/default.htm.

Low-fat diets

The Dietary Guidelines for Americans and the MyPlate program provide examples of low-fat diets. Eating a diet that consists of 20%–35% fats helps manage weight, promote health, and reduce risks of chronic disease. Foods to reduce include saturated and trans fats, cholesterol, sodium, added sugar, refined grains, and alcohol. Foods to increase include fruits, vegetables, whole grains, low-fat dairy and protein foods, and oils. This helps maximize nutrient content and the health promotion potential of the diet. Additional low-fat diets include the DASH diet and the diets recommended by the American Diabetes Association, American Heart Association, and American Cancer Society. The commercial Weight Watchers program is also a low-fat diet.

Focus on the Dietary Guidelines for Americans

The Dietary Guidelines for Americans is now in its eighth edition and consists of five suggestions that should be followed. They are as follows:

Follow a healthy eating pattern across the life span. Maintain a healthy weight, support nutrient adequacy, and reduce risks of chronic disease.

Focus on variety, nutrient density, and amount. Meet nutrient needs, but stay within calorie limits.

Limit calories from added sugars and saturated fats, and reduce sodium intake. These include sodas, snacks, desserts, sandwiches, and pizza.

Shift to healthier food and beverage choices. For example, instead of fried chicken, eat chicken baked with herbs. Instead of canned peaches in syrup, eat fresh or frozen peaches without added sugars.

Support healthy eating patterns for all. Work with others to encourage better diet at home, at school, or in the workplace.

Focus on MyPlate

The US government’s MyPlate program suggests that each meal should consist of the following:

50%—approximately 20% fruits and 30% vegetables—vary your vegetables, and focus on whole fruits. Whole fruits can be fresh, frozen, dried, or canned in 100% juice. Eat colorful fruits and vegetables because they provide more vitamins and minerals and are usually lower in calories. Fruits can be eaten with meals, as snacks, or as desserts. Fresh, frozen, or canned vegetables are acceptable, and they can be steamed, sautéed, roasted, or raw.

50%—approximately 20% proteins and 30% grains—mix up protein foods to include seafood, beans, peas, unsalted nuts and seeds, soy products, lean meats, and poultry. Make half your grains whole grains, which should be listed first or second on the ingredients list—such as oatmeal, whole-grain bread, and brown rice. Limit grain-based desserts and snacks, such as cakes, cookies, and pastries.

Drink low-fat or fat-free milk, or eat similar types of yogurt. Soymilk is also great. Replace sour cream, cream, and regular cheese with low-fat yogurt, milk, and cheese. Drink beverages that have less sodium, saturated fat, and added sugars. For oils, use vegetable oils instead of butter, and oil-based sauces and dips instead of those with butter, cream, or cheese. Drink water as much as possible, and avoid nondiet soda, energy or sports drinks, and other sugar-sweetened drinks.

There has been more in-depth study of low-fat diets than on any other type of diet. In many studies, low-fat diets have shown significantly greater weight loss than people who did not follow these diet plans. Low-fat diets also provided improvements in hemoglobin A1c (HbA1c), blood pressure (BP), high-density lipoprotein (HDL), and triacylglycerides (TAG). The Women’s Health Initiative Dietary Modification Trial revealed that a low-fat diet without any instructions for calorie restriction helped maintain weight loss slightly better than following a diet that was higher in fat. Therefore it can be stated that a low-fat diet is an effective weight control strategy over any length of time, as long as it is followed correctly.

USDA/My Pyramid

The Dietary Guidelines for Americans56 are written to “promote good dietary habits, reserve health and reduce risk for major chronic diseases” (Table 19-3). Like all low-fat diets, the emphasis in the USDA food guide diet is on fruits, vegetables, and whole grains. The Dietary Guidelines are explained in visual form as the USDA My Pyramid, an evolution from the previous USDA Food Guide Pyramid. In 2005, the USDA food guide pyramid was rebuilt with the food groups being represented by a rainbow of colored, vertical stripes and an illustration of a person climbing steps to emphasize the importance of exercise (Figure 19-2). It was also individualized for age, gender, and activity level and simplified to make serving sizes and food choices easier to comprehend by the public. A Web site highlighting this diet (http://www.mypyramid.gov) allows individuals to receive a personal, tailored diet regimen plan. This in turn creates an individualized approach to balancing nutrition and exercise, which is promoted to lead to a better lifestyle. Unfortunately, the basic pyramid contains no text and has an abstract illustration that limits its usefulness to individuals with access to it—persons with access to the Web site or a full copy.

The Diabetes Prevention Program57 examined the USDA diet in a 27-center, randomized, clinical trial that evaluated the effects of lifestyle intervention and pharmacotherapy on the incidence of type 2 diabetes in persons with impaired glucose tolerance. In this study, 3234 overweight participants (32% men) were randomly assigned to one of three groups: (1) placebo plus standard lifestyle recommendations, (2) metformin plus standard lifestyle recommendations, and (3) intensive lifestyle intervention. Participants in the medication and placebo groups were provided written information on the food guide pyramid and were seen annually in individual sessions. Patients in the intensive lifestyle group also followed the food guide pyramid but received closer follow-up. Participants in the intensive lifestyle group lost significantly more weight than those in the metformin and placebo groups. The intensive lifestyle group also had a significantly lower incidence of type 2 diabetes than the placebo or metformin group at 1 year.

Potential Benefits of Dietary Supplements

The 2000 Dietary Guidelines for Americans (new release due 2005) emphasizes choosing foods sensibly, maintaining a healthy weight, and exercising regularly. It acknowledges that some people may need a vitamin–mineral supplement to meet specific needs. Similarly, the Food and Nutrition Board and the American Dietetic Association also recognize that dietary supplements may be desirable for some nutrients and for some individuals. The following is a compilation of recommendations by these groups:

Folic acid supplements for women of childbearing age due to the risk of neural tube defects

Vitamin B12 supplements for people older than age 50 years due to inefficient absorption

Vitamin B12 supplements for vegans who eat no animal products

Calcium for people who seldom eat dairy products

Vitamin D for elderly people who do not consume fortified dairy products and for others with little exposure to sunlight

Iron supplementation for pregnant women

Multivitamin-mineral supplement for people who are following a severely restricted weight-loss diet.

Specifically for athletes, the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine is that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. In sports, athletes who are at greatest risk of micronutrient deficiencies are those who restrict energy intake or use severe weight-loss practices, eliminate one or more food groups from their diet, are sick or recovering from injury, or consume high-carbohydrate diets with low micronutrient density. In practice, athletes should consume diets that provide at least the Recommeded Dietary Allowances/Direct References Intakes for all micronutrients from food. It follows that, in general, no vitamin and mineral supplements are required if an athlete is consuming adequate energy from a variety of foods to maintain body weight. Supplementation may be necessary under conditions of inadequate food intake. Athletes, as for the general population, should follow supplementation recommendations unrelated to exercise, such as folic acid in women who may become pregnant.

d. WHOLE GRAIN.

Although current dietary guidelines for Americans recommend increased intake of grain products to prevent CHD, epidemiologic data relating whole-grain intake to the risk of CHD are sparse. The investigators of the Nurses’ Health Study evaluated whether high whole-grain intake reduces risk of CHD in women. [53]. After adjustment for age and smoking, increased whole-grain intake was associated with decreased risk of CHD. For increasing quintiles of intake, the corresponding RRs were 1.0 (reference), 0.86, 0.82, 0.72, and 0.67 (95% CI comparing 2 extreme quintiles: 0.54, 0.84; P for trend <0.001). After additional adjustment for body mass index (BMI), postmenopausal hormone use, alcohol intake, multivitamin use, vitamin E supplement use, aspirin use, physical activity, and types of fat intake, these RRs were 1.0, 0.92, 0.93, 0.83, and 0.75 (95% CI: 0.59, 0.95; P for trend = 0.01). The inverse relation between whole-grain intake and CHD risk was even stronger in the subgroup of never smokers (RR=0.49 for extreme quintiles; 95% CI: 0.30, 0.79; P for trend = 0.003). The lower risk associated with higher whole-grain intake was not fully explained by its contribution to intakes of dietary fiber, folate, vitamin B-6, and vitamin E. Therefore, increased intake of whole grains may protect against CHD in women. Moreover, this group has also shown a protective effect of whole grains in relation to ischemic stroke [54]. These findings are consistent with those from the Iowa Women's Health Study demonstrating a beneficial effect of whole grain [55] and fiber intakes on risk for IHD [56].

Because of the beneficial effects of whole grains, the AHA recommends 3 or more servings per day from whole grain breads and cereals [22]. Although whole grains are a good source of dietary fiber, it is now evident that their cardioprotective effects extend beyond dietary fiber, and include folate, vitamin B6, and vitamin E and likely numerous phytochemicals [53]. Nonetheless, whole grain foods are a source of soluble (viscous) fiber, which reduces LDL-cholesterol levels [5–10 g soluble (viscous) fiber reduces LDL-cholesterol by approximately 5%.

Biological Plausibility of Whole Grain-Mediated Effects on Adiposity

The 2010 Dietary Guidelines for Americans and various international dietary guidelines recommend increasing whole-grain intake by replacing refined grains with whole grains [6,12,20–24]. If adopting this recommendation is to favorably affect abdominal adiposity, then replacing refined grains with whole grains must, in theory, deter weight gain, promote weight loss, and/or preferentially spare or build lean body mass. As will be discussed below, some of these effects are biologically plausible, and a number of feasible mechanisms have been proposed. These mechanisms include appetite suppression and weight loss, reduced dietary glycemic load, improved insulin sensitivity, and, more recently, modulation of the gut microbiota [2,3,19]. The capacity of whole grains to mediate these mechanisms is attributed to the independent and synergistic physiologic effects of nutrients within whole grains, many of which are lost during refining, and the physical properties of whole grains (e.g. structural intactness and integrity, as well as particle size) [2–4,19].

Fiber is the component of whole grains that is most likely to influence physiologic effects relevant to the regulation of body weight and adiposity. The relationship between fiber and adiposity is mediated by the physicochemical properties of different fibers, which include viscosity, water-binding capacity, and fermentability [25]. Viscous fibers (e.g. arabinoxylans and β-glucans) form gels when mixed with digesta. This slows gastric emptying and nutrient absorption, thereby promoting satiety, reducing energy intake, and attenuating postprandial glycemic responses [26]. The high water-binding capacity and low energy density (i.e. metabolizable energy per unit mass) of fiber also promotes satiety and reduces energy intake by adding bulk and volume without additional energy to the diet [27]. Fermentable fibers (e.g. wheat dextrin, fructans, resistant starches, and β-glucans) have less effect on energy density because they are fermented by bacteria in the colon. The fermentation process produces energy from an otherwise unavailable energy source in the form of short-chain fatty acids (SCFAs) [28]. Although SCFA production increases the metabolizable energy content of fiber, it also influences body weight and composition by directly mediating hepatic and peripheral glucose and lipid oxidation, and stimulating secretion of the gut hormones peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) [29]. The actions of these hormones include appetite suppression, slowed gastrointestinal transit rate, and modulation of glucose metabolism [30]. SCFAs also lower colonic pH and, in combination with the proliferation of bacteria stimulated by fermentable fiber, alter the composition of the microbiota in the colon. Altering gut microbiota composition may have relevant effects on adiposity, given the emerging recognition of gut microbes as important mediators of human metabolism, as well as associations between gut microbiota composition and human obesity [31].

The superior nutrient content of whole grains relative to refined grains may also mediate the effects of whole grains on adiposity. Relative to refined grains, whole grains are higher in magnesium and antioxidants, nutrients that have been associated with lower fasting glucose and insulin levels, and improved insulin sensitivity [32,33]. Moreover, whole grains are rich sources of polyphenols [4]. Polyphenols are metabolized by gut microbes, have antimicrobial properties, and may alter the composition of the gut microbiota [34].

Perhaps the primary determinant of the physiologic effects of whole grains is grain structure. Preserving the grain structure decreases the accessibility of nutrients within the grain to pancreatic amylases. Consequently, intact and less-processed whole grains produce lower postprandial glycemic responses compared to both processed whole grains and refined grains [35]. In support of this, Holt et al. [36] demonstrated progressive increases in postprandial glycemic and insulinemic responses as the particle size of the whole grains consumed progressively decreased from an intact to a finely ground form. Similar findings have been reported for other grains [37–40]. Appetite may also be affected by grain processing because higher satiety ratings following consumption of intact relative to ground grain have been reported [36,41], which may be attributable in part to greater stomach distension with increasing particle size [41]. When available for hydrolysis, the proportion of different starches within the grain also influences postprandial physiology because high-amylose grains attenuate postprandial glycemia and insulinemia owing to the slower rate of hydrolysis of amylose relative to amylopectin [35]. In less-processed whole grains, the decreased availability of starch to amylases results in higher amounts of starch reaching the colon in an undigested state [42]; it can then be readily fermented by gut microbes, resulting in increased SCFA production and possible alterations in gut microbiota composition.

Whole Grains

The 2010 Dietary Guidelines for Americans recommend that at least half of the total grain intake be from whole grains. On average, Americans eat less than 1 ounce-equivalent of whole grains per day. The minimum recommended amount of whole grains is about 3 ounce-equivalents per day. The FDA definition of whole grains is “cereal grains that consist of the intact and unrefined, ground, cracked or flaked fruit of the grains whose principal components – the starchy endosperm, germ and bran – are present in the same relative proportions as they exist in the intact grain” (USFDA, 2006). In addition, the FDA acknowledged a health claim for whole grain, which includes the requirement that 51% or more of the product weight be a whole-grain ingredient. Examples of whole grains include barley, buckwheat, bulgur, corn, millet, rice, rye, oats, sorghum, wheat, and wild rice.

Each component of the grain provides unique nutritional attributes, the endosperm is composed largely of starch with some protein, while the bran contains most of the dietary fiber and many compounds thought to be highly bioactive, such as phenolic acids, flavonoids, and vitamin E. The germ is rich in vitamins, minerals, oil, and a variety of antioxidants. Oats and barely contain substantial amounts of β-glucans, a type of viscous fiber that increases fecal loss of bile acids with a concomitant decrease in LDL-C, whereas wheat, rice, and corn contain little β-glucans.

Evidence to support the benefits of whole grains on CVD risk continues to grow. A meta-analysis of 12 prospective cohort studies by Anderson et al (2000) reported a 26% reduction in CHD risk in individuals who consumed whole grains on a regular basis. Based on this analysis, whole grains, rather than cereal, fruits, or vegetables, had the most consistent and significant impact on CHD risk. In 2004, Jacobs and Gallaher conducted a review of 17 prospective cohort studies and estimated a 20–40% reduction in CHD risk with frequent whole-grain consumption. Flint et al. (2009) found an independent inverse association between intake of whole grains (grams per day) and incidence of hypertension in a large prospective cohort of men, which may explain the cardioprotective benefits of whole grains.

A Cochrane systematic review and meta-analysis evaluated nine intervention trials (eight oat, one rye) to assess the effect of whole grains on CVD risk factors. Oats significantly lowered total and LDL-C compared to the control diets. There was a similar, dose-dependent effect for barley (Shimizu et al., 2008). In contrast, diets containing whole grain low in viscous fiber typically do not have the same effect on lipids.

There is inconclusive evidence from two intervention studies that evaluated the CVD benefits of whole grains. Brownlee et al. (2010) examined markers of CVD risk in a large RCT (n = 266 completers) of overweight/obese participants. They found that an increase in whole-grain consumption for a 16-week period (8 weeks at 60 g day−1 followed by another 8 weeks at 120 g day−1) did not significantly affect any of the biomarkers of cardiovascular health. These results are consistent with the findings of Andersson et al. (2007), who also noted no benefit of consumption of a range of whole-grain foods (112 g day−1 from mixed grain sources) on any marker of CVD risk. The studies by Brownlee et al. (2010) and Andersson et al. (2007) are the only randomized, controlled whole-grain intervention studies that conducted robust power calculations to determine sample size. Based on the evaluation of these and other studies, the 2010 Dietary Guidelines Advisory Committee rated the evidence for the protective relationship between whole grains and CVD as ‘moderate’ (DGAC, 2010).

In 2012, Ye et al., did a systematic review and meta-analysis to evaluate the relationship between whole grains and the prevention of vascular disease. The authors evaluated longitudinal evidence that assessed whole-grain and fiber intake in relation to CVD risk, type 2 diabetes, weight gain, and metabolic risk factors. Of the 66 articles eligible for review, 16 prospective studies and 21 RCTs met the eligibility criteria. The findings indicated that individuals reporting an average consumption of 48–80 g day−1 of whole grains (three to five servings day−1) had a 21% reduction in CVD risk compared to those who rarely or never consumed whole grains.

In general, characterizing which types of carbohydrates, including whole grains and fiber, reduce the risk for CVD is challenging. The varying nutrient compositions of different whole grains each could potentially affect CVD risk via different mechanisms. Whole grains high in viscous fiber (oats, barley) decrease LDL-C and BP. Grains high in insoluble fiber (wheat) moderately lower BP. There is growing evidence that whole grains and dietary fiber benefit the gut flora. Understanding how different grains, both whole and refined, affect CVD risk, metabolic syndrome, and visceral adiposity is an area that requires further research.

1.6 The 2015 Dietary Guidelines for Americans and the Healthy Dietary Patterns Such as the Mediterranean Diet

According to the Dietary Guidelines for Americans “preventable, diet and lifestyle-related chronic diseases, including obesity, high blood pressure, type 2 diabetes, and cardiovascular disease, contribute to the high and rising costs of U.S. health care”. According to these guidelines: “the alarming current situation is that 65 percent of adult American females and 70 percent of adult American males are overweight or obese, and rates are highest in adults ages 40 years and older. Moreover, adults with overweight or obesity frequently have co-morbid conditions and higher chronic disease risk profiles that contribute substantially to higher health care costs. In fact, rates of elevated blood pressure, adverse blood lipid profiles…, and diabetes are highest in adults with elevated abdominal obesity (waist circumference greater than 102 cm in men, greater than 88 cm in women)”… Furthermore, many adults have personal health profiles in which multiple metabolic risk factors coexist and substantially increase risks for coronary heart disease, hypertension and stroke, diabetes, and other obesity-related co-morbidities [36].

The Dietary Guidelines for Americans were first released in 1980, and since that time, they have provided science-based advice on promoting health and reducing risk of major chronic diseases through a healthy diet and regular physical activity. The Dietary Guidelines for Americans is published by the Federal government every 5 years. The 2015 Dietary Guidelines Advisory Committee was established for the single, time-limited task of reviewing the 2010 edition of Dietary Guidelines for Americans and developing nutrition and related health recommendations to the Federal government for its subsequent development of the 2015 edition.

In this sense, the 2015 Dietary Guidelines Advisory Committee advocates “achieving healthy dietary patterns through healthy food and beverage choices rather than with nutrient or dietary supplements except as needed.” Healthy eating patterns can be achieved for a variety of eating styles, including the “Healthy U.S.-Style Pattern,” the “Healthy Vegetarian-Style Pattern,” and the “Healthy Mediterranean-Style Pattern.” According to this committee strong and consistent evidence demonstrates that dietary patterns associated with decreased risk of cardiovascular disease are characterized by higher consumption of vegetables, fruits, whole grains, low-fat dairy, and seafood, and lower consumption of red and processed meat, and lower intakes of refined grains, and sugar-sweetened foods and beverages relative to less healthy patterns. Regular consumption of nuts and legumes and moderate consumption of alcohol also are shown to be components of a beneficial dietary pattern in most studies. To reach this conclusion the Dietary Guidelines Advisory Committee examined research compiled in the NEL (USDA’s Nutrition Evidence Library) Dietary Patterns Systematic Review Project, which included 55 articles summarizing evidence from 52 prospective cohort studies and 7 randomized clinical trials, and other guidelines and reports. The Committee drew additional evidence and effect size estimates from six published systematic reviews/meta-analyses published since 2008 that included one or more studies not covered in the NEL or other reports. In total, 142 articles were considered in these reports. Some of these results are derived from systematic reviews and clinical trials designed to test the beneficial role of the Mediterranean Diet. Therefore, at this point it is important to describe the epidemiological evidences that have supported the beneficial role of the Mediterranean Diet and that have made to include it in the most recent American Dietary Guidelines as a healthy dietary pattern in the prevention of cardiovascular disease and other cardio-metabolic conditions such as obesity, diabetes, or hypertension.