HEALTH-PROMOTING DIET FOR ADULTS
© M. Read, 2008
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The normal diet for adults is based on the need to provide suffi cient nutrients to sustain life and an appropriate balance of nutrient intake to support optimal health. The first Surgeon General’s Report on Nutrition and Health in 1988 brought together a substantial body of research that documented that diet, aside from providing the essential nutrients for daily functioning, was a key factor with respect to chronic diseases such as coronary heart disease, cancer, diabetes, and obesity. The underlying premise of the various dietary guidelines/recommendations that have been developed has been to provide adequate nutrient intake while avoiding dietary patterns that might place an individual at greater risk for chronic disease. The following subsections describe the most commonly used dietary guidelines/recommendations, guidelines for counseling healthy adults, information on current food and nutrient consumption patterns of adults, and current research with respect to health implications of inappropriate macronutrient intake.
DIETARY RECOMMENDATIONS AND GUIDELINES
Dietary guidelines have undergone several revisions from the late 1970s to the recently released Dietary Guidelines for Americans 2005. The 1970s Dietary Goals provided recommendations with respect to energy intake, carbohydrate, fat, and sodium intakes. Specific percentage of calories from carbohydrate and fat were put forth, 48% and 30% respectively. Cholesterol intake was recommended at 300 mg/day and sodium intake was recommended not to exceed 5 g/day. The first set of the U.S. Dietary Guidelines was published in 1980. The most recent version is the 2005 Dietary Guidelines for Americans.
From the first edition of the guidelines to the current, the focus has been on a variety of foods to supply adequate nutrient
intake, increase complex carbohydrate consumption, moderate fat intake, and moderate alcohol consumption if one drinks. The
2005 guidelines add emphasis on "Weight Management," as well as a section on "Food Groups to Encourage." Another new
feature to the 2005 guidelines, in contrast to earlier versions, are recommendations for specific population groups under each
major guideline and a glossary of terms and appendices and tables for more detailed information. As with previous versions,
the guidelines continue to be based on current research. A review of all iterations, including the 2005 Dietary Guidelines, is
The Food Guide Pyramid
The 1992 Food Guide Pyramid set forth recommendations for a pattern of daily food choices based on servings from five major food groups — bread, cereal, rice, and pasta; fruit; vegetable; milk, yogurt, and cheese; and meat, poultry, fish, dry beans, eggs, and nuts. The visual presentation as a pyramid was meant to convey that, from the five food groups, emphasis should be placed on those shown in the lower three levels/sections of the pyramid. The Food Guide Pyramid was also meant to be used in concert with the dietary guidelines, that is, to eat a variety of foods and balance the foods eaten with physical activity and either maintain or improve weight. Each food group suggests a range of servings. Selecting the lower number of recommended servings is estimated to provide approximately 1600 kcal, with the midrange providing approximately 2200 kcal, and 2800 kcal at the upper range.
Cited advantages and disadvantages of the 1992 Food Guide Pyramid according to Kant et al.7 include:
The most recent version is titled "My Pyramid" (http://www.mypyramid.gov/). It is designed to
RECOMMENDED DIETARY ALLOWANCES, ESTIMATED SAFE AND ADEQUATE DAILY DIETARY INTAKES, DAILY REFERENCE INTAKE, AND DAILY VALUES
The most common reference standard for nutrient intake has been the RDA. This standard was first established by the Food and Nutrition Board in 1941, with the most recent edition in 1989. The original intent was to review and revise the RDAs every four to five years, taking into account current research. The constructs used in formulating a specific RDA were: (1) an estimation of how much of each essential nutrient the average healthy person requires to maintain health, and how those requirements vary among people; (2) an increase in the average requirement to cover the needs of almost all members of the population, based on a bell curve distribution; (3) an increase in the RDA again to cover cooking losses and ineffi cient body utilization, as well as provide for cases of greater nutrient need such as in pregnancy and infancy; and (4) use of scientific judgment in establishing the RDA. The following three central premises underlie the RDAs:
For nutrients that have scientific evidence providing support for their essentiality, but are insufficient to establish an RDA, there are Estimated Safe and Adequate Daily Dietary Intakes (ESADDIs). Most ESADDIs are shown as a range of intake values that represent the upper and lower limits of safe intake. ESADDIs are established for biotin, copper, manganese, and molybdenum.
The current iteration of recommended intakes includes the DRI, which, in essence, replaces the RDA. DRI encompasses four types of nutrient recommendations for healthy individuals: Adequate Intake (AI), Estimated Average Intake (EAR), RDA, and tolerable Upper Intake Levels (UL). AI is a nutrient recommendation based on observed or experimentally determined approximation of nutrient intake by a group (or groups) of healthy people when sufficient scientific evidence is not available to calculate an RDA or an EAR. The EAR is the average requirement of a nutrient for healthy individuals in which a functional or clinical assessment has been conducted and measures of adequacy have been made at a specified level of dietary intake. The EAR is an amount of intake of a nutrient at which approximately 50% of subjects would have their needs met and 50% would not. The EAR is intended to be used for assessing nutrient adequacy of populations and not individuals. The new RDA is the amount of a nutrient needed to meet the requirements of nearly all (97% to 98%) of the healthy population of individuals for whom it was developed.
An RDA for a nutrient should serve as an intake goal for individuals and not as a standard of adequacy for diets of populations. This is different than the previous or old RDA. UL values are established in cases where there is adequate scientific evidence to suggest an upper level of intake that is consistent with adverse or toxic reactions. The UL represents the maximum level of intake for a nutrient that will not cause adverse effects in most of the population ingesting that amount. The DRI can be found at: http://www.nal.usda.gov.
One other indication of dietary quality is the Health Eating Index (HEI). The HEI is intended to take into consideration compliance with the Dietary Guidelines for Americans as well as intake data to create a "score" that reflects how well American dietary patterns conform to the recommendations. The HEI score of American diets was 63.8, and can be interpreted as "needing improvement."
WORLD HEALTH ORGANIZATION RECOMMENDATIONS
The World Health Organization (WHO) has also published diet recommendations with the goal of reducing risk for chronic disease. WHO recommendations are expressed as a range of average daily intakes from lower to upper limits (Table 1).
Food labeling became mandatory in 1993 with the enactment of the Nutrition Labeling and Education Act (NLEA). The legislation required food labeling on most foods with the exceptions of low-nutrient-dense foods such as coffee, spices, and ready-to-eat foods prepared on site. Nutrition information remains voluntary on many raw foods. The nutrition facts panel on food labels provides information to help the consumer make more informed choices, including information on calories per serving, calories from fat, saturated fat and cholesterol, and protein among other nutrients (Table 2).
Daily Values (DVs) are used as standards in food labeling. DVs provide reference intake standards for nutrients that have an RDA, in which case they are referred to as reference daily intakes (RDIs), and for nutrients for which no RDA exists, in this case referred to as daily reference values (DRVs). DRVs are established for fat, saturated fat, cholesterol, carbohydrate, dietary fi ber, sodium, and potassium. As a rule, the RDIs are greater than the RDA for specifi c nutrients and provide a large margin of safety. The term RDI replaces the term U.S. Recommended Daily Allowances (USRDAs), used earlier on food labels.
AMERICAN CANCER SOCIETY AND NATIONAL CANCER INSTITUTE GUIDELINES
In the 1980s the American Cancer Society issued the following dietary guidelines aimed at reducing cancer risk within the populace (http://www.cancer.org/):
The National Cancer Institute endorses the following guidelines, which reflect in large part the recommendations of the American Cancer Society:
There are also guidelines set forth by the National Cholesterol Education Program and the American Heart Association.
NUTRITION COUNSELING FOR ADULTS
Determining Energy Requirements
To plan a diet consistent with dietary guidelines, the nutrition professional should first determine the caloric requirements of a client. The total energy requirements will be the sum of the resting energy requirement, energy needs for physical activity, and the energy needed for the thermic effect of foods. To determine the total energy requirement:
Step 1: Estimating Appropriate Body Weight. The Hamwi method is a common tool to estimate appropriate body weight.
For females, the estimation is 100 lb for the first 5 ft of height and 5 lb/in. over 5 ft; for example, a 5'6'' woman would be
calculated as: (100 lb for the fi rst 5 ft) + (5 lb/in. over 5 ft = 5 x 6 = 30) = 130 lb. For men the estimation is 106 lb for the first
5 ft of height and 6 lbs/in. over 5 ft; for example, a 6'0'' man’s desirable weight would be calculated as: (106 lb for the fi rst 5 ft)
+ (6 lb/in. over 5 ft = 6 x 12 = 72) = 178 lb.
Step 2: Estimating Energy Needs Based on Body Weight. To estimate energy needs, the first step is to determine resting energy requirements (REE). Although several methods exist to calculate energy requirements based on weight, the abbreviated or quick method is probably useful for normal adults. The abbreviated method is as follows:
Women weight in kg x 23
Men weight in kg x 24
Step 3: Estimating Energy Required for Physical Activity.
Step 4: Add REE (Step 2) and Physical Activity (Step 3).
Step 5: Calculate Thermic Effect of Food.
Nutrition monitoring has been going on since the early 1900s in the United States, when the USDA’s Food Supply Series was initiated. Currently, the National Nutrition Monitoring and Related Research Program (NNMRRP) is the umbrella for activities that provide regular information about the contribution that diet and nutritional status make to health.
With respect to total energy intake, caloric consumption of adult men consistently exceeds that of adult women by approximately 400 kcal. With one age group exception (ages >70 years), men consumed in excess of 2000 kcal on average, whereas women consistently averaged less than 2000 kcal/day. Fat was contributing slightly above the recommended 30% of kcal for both men and women. Adult men derive somewhat more kilocalories from alcohol compared with women, but women are considerably higher in their carbohydrate intake than men. Men consumed not quite a third of their total energy intake from foods consumed away from home. The contribution of energy from foods eaten away from home is one-fourth of the total energy intake of women.
Men were more likely than women to consume a diet that met 100% of the RDA. Table 3 provides energy intake data on age cohorts for adult men and women based on the 1994 to 1996 Continuing Survey of Food Intake for Individuals (CSFII). Foods eaten away from home are contributing approximately 30% to 40% of total kilocalories consumed by young adults. The percentage of kilocalories derived from foods eaten away from home decreases with age (Table 4).
Total Protein, Carbohydrate, and Fat Intakes
Protein intake is higher for adult men compared with adult women, yet the mean protein intake for both men and women exceeds the 1989 RDA (Table 5). With their higher mean protein intake, more men (80.2%) than women (69.2%) met 100% of the 1989 RDA for protein. As with total energy intake, foods consumed away from home contribute at least 25% of the overall protein intake. For men, 29% of the total protein intake was derived from foods eaten away from home. For women, this was 24.6%.
Total carbohydrate intake is higher for men than women, consistent with their higher total energy intake. The mean intake of carbohydrate for adult men was roughly 50 to 60 g/day higher than the adult female intake (Table 5).
The mean fiber intake per day for both men and women is below even the lower level of the recommended 24 to 70 g/day (Table 6).
Fat intake for adult men and women, as with protein and carbohydrate intakes, reflects the gender differences in total energy intake pattern, that is, men consume more than women. The majority of adult men and women exceed the recommended 30% of energy from fat. Only 29.4% of adult men and 36.8% of adult women maintained a diet within the 30% recommendation. Foods eaten away from home contributed 30.9% of the total fat intake for men and 26.2% for women (Table 7). Cholesterol intake is considerably lesser in women than men. Women of all age groups consumed under 300 mg/day, whereas adult men generally consumed slightly more than 300 mg/day on average (Table 8 and Table 9). More adults consumed a diet consistent with the recommended cholesterol intake (55.1% of men; 79.4% of women) than that for total fat, where only 29.4% of adult men and 36.8% of adult women maintained a diet within 30% of the total energy intake. The intake of the types of fat — saturated, polyunsaturated, monounsaturated, and cholesterol — is presented in Table 8.
ENERGY AND OBESITY ISSUES
Overweight is associated with several chronic diseases — coronary heart disease, hypertension, non-insulin-dependent diabetes mellitus, and some forms of cancer.19,20 WHO declared overweight as one of the current top ten health risks. An estimated 300,000 Americans die every year from obesity-related conditions. Obesity is also an associated risk factor for joint disease, gallstones, and obstructive sleep apnea. In 1995, the economic cost associated with obesity was estimated at $62.3 billion. The seriousness of obesity was further emphasized by the Surgeon General’s "Call to Action".
From 1976–1980 and 1988–1994, the Centers for Disease Control and Prevention (CDC) reported an increase of 10% in the incidence of overweight in the American population. Data from the CSFII, 1994, indicate that among adults, both men and women, the incidence of overweight is approximately 30% (Table 10). If the incidence of obesity continues to rise at current rates, it is predicted that, by 2230, every adult in the United States will be overweight. Recent Behavioral Risk Factor Surveillance System (BRFSS) data indicate an increase in overweight in all demographic and geographic segments of the U.S. population.
The prevalence of overweight/obesity among Americans is at odds with the perceptions of the importance of maintaining an appropriate body weight. When Americans were surveyed as part of the 1994 to 1996 USDA Diet and Health Knowledge survey, 68.1% of adult males over 20 years of age reported that "maintaining a healthy weight" was very important. For that same survey, 77% of the adult women over 20 years of age reported maintenance of a healthy body weight as very important. Given the importance Americans place on maintaining healthy body weight and given the high incidence of overweight/obesity, it is little wonder that Americans are forecast to spend some $54 billion on weight-loss products in 2009. In addition, there are the myriad of weight-loss diets that appear on the market every year. In 1992, 33% to 40% of American women and 20% to 24% of American men reported being on a diet.
FAD DIETS USED FOR WEIGHT-LOSS PROMOTION
While numerous fad diets come and go, several categories tend to remain fairly common. These include high-protein/low-carbohydrate diet regimens, low-fat diets, and very-low-calorie diets.
These diets generally restrict the carbohydrate intake to 100 g/day or less. Restriction of carbohydrate leads to an initial mobilization of glycogen and then to gluconeogenesis and ketosis, all of which promote water loss and some lean tissue loss, which constitute a significant portion of the weight loss. Some of the low-carbohydrate diets promote high protein and consequently a higher animal fat intake, which is inconsistent with the dietary guidelines for fat intake. Examples of high-protein/lowcarbohydrate diets are Atkins’ Diet Revolution, Calories Don’t Count, and The Doctor’s Quick Weight Loss Diet (Stillman’s).
Generally these diets restrict fat intake to 20% or less of the total energy intake. Examples of these types of diets include the T-factor Diet, the Pasta Diet, the Pritikin Diet, and Fit or Fat. The average weight loss on these types of diets is 0.1 to 0.2 kg/week. With the limited fat intake, one drawback is the low-satiety factor, which may prompt noncompliant diet behavior.
These diets arose during the 1970s and were known as protein-sparing modified fasts or liquid protein diets. These diet plans generally rely on liquid supplements to substitute for food intake and restrict the overall caloric level to less than 800 kcal/day. These diets may be indicated for moderately to highly obese patients (body mass index > 30). The severe caloric restriction does lead to weight loss, but generally this level of caloric intake cannot be sustained, and weight regain is a potential problem. These diets may also lead to weight loss from lean tissue mass.
The Zone Diet
The Zone Diet is a modified approach to the low-carbohydrate/high-protein type of diet. The diet promotes a macronutrient intake of 30% protein, 30% fat, and 40% carbohydrate. At this ratio of protein, fat, and carbohydrate, the author contends that insulin levels will remain stable, and this, in turn, dampens insulin’s potential to promote the conversion of carbohydrates into fat and thereby to promote weight gain. The Zone Diet claims go beyond the promise of weight loss via insulin regulation into the realms of disease prevention. The Zone Diet author argues that a high-carbohydrate/low-fat diet promotes an imbalance in "bad" eicosanoid production, which can lead to the development of such diseases as arthritis and coronary heart disease. However, there is no signifi cant body of evidence to support the author’s claims.
Putting fad diets aside, an approach to weight management that recognizes overweight or obesity as a chronic condition and incorporates the elements of a healthy diet, exercise, and behavior modification is more likely to be successful over time, particularly in the maintenance of weight loss.
The Weight Control Information Network (WIN) provides research-based educational resources to Americans on weightloss strategies, etc.
PROTEIN INTAKE — HEALTH ISSUES
The average American diet is very liberal with respect to protein intake. The RDA for protein for women aged 19 to 24 years is 46 g, and for men of the same age the RDA is 58 g. In contrast, the average protein intake in grams for adults over 20 years in the United States is 63.8 g for women and 94.9 g for men. Some concern has been expressed over the long-term health consequences of excessive protein intake. There is some evidence in humans that a lifetime on a high-animal-protein diet (typical American diet pattern) can aggravate existing renal problems, may increase the risk for cancer of the kidney, and can accelerate adult bone loss. Lastly, higher animal protein intake is associated with higher-than-desirable levels of total fat and saturated fat intake.
A primary, although not exclusive, source of protein in the American diet is meat. The U.S. Food Guide Pyramid recommends between 5 and 7 oz of cooked lean meat or equivalent in meat alternatives per day. To be consistent with the Dietary Guidelines to reduce total fat and saturated fat in the diet, it would be helpful to consume lower-fat types of meat and perhaps a greater amount of some forms of meat alternatives such as soybean products. However, Americans derive the majority of their protein from meat. The 1994 to 1996 CSFII indicated that, for adult males over 20 years of age, the average daily intake of meat and meat alternatives was 6.4 oz, and for women the total was 3.9 oz. With respect to total intake, men were consuming sufficient amounts of meat and meat alternatives when compared with the recommended 5 to 7 oz. Women, on the other hand, fell below the minimum 5 oz recommended in the U.S. Food Guide Pyramid. With that in mind, data from the CSFII indicate that, regardless of meat servings, protein intake is meeting RDA requirements. Consequently, the source of protein may be an important consideration. The ratio of meat to meat alternatives is skewed heavily in favor of meat (beef, pork, lamb, and veal). In men, of the average 6.4 oz of lean meat and meat alternatives consumed daily, 2.7 oz are derived from lean meat and another 1.0 oz from the higher fat-sources of frankfurter and lunch meat. Consequently, 3.7 of the 6.4 oz, or 58%, were from meat. Only 1.5 and 0.5 oz, respectively, were contributed by poultry and fish. Among women, 1.4 oz of meat and 0.5 oz of frankfurter and lunch meat were consumed on a daily average. This accounts for 49% of the total meat or meat-alternative consumption. In women, poultry contributed 1.1 oz and fi sh 0.4 oz toward the total meat and meat-alternative intake. Some data suggest that an increase in fish and consequently in omega-3 fatty acid intake may be warranted from a cancer prevention perspective.
Protein supplements are quite common among athletes and physically active adults as part of their strength training regimens. Bucci argues that, although there is very little research that documents the benefits of protein supplementation, high-protein diets are safe. However, the amount recommended for endurance athletes is 70 g/day, and for strength athletes 112 to 178 g. The lower range of these recommendations is clearly within the normal intake of American men. This argues against the need for further protein supplementation.
Amino Acid Supplements
Individual amino acid supplements have periodically been promoted on the market periodically. Again, a target audience has often been the athlete or physically active adult, with promises of enhanced performance. There is a dearth of research that can support such claims. In addition, in 1992 a scientific panel convened to address the safety of amino acid supplements concluded that there is little research on which to support making amino acid supplement recommendations, and some amino acid supplementation (serine and proline) can have adverse health effects. Consequently, the panel concluded that no level of amino acid supplementation may be considered safe at this time.
FAT INTAKE ISSUES — AMOUNT AND TYPE OF FAT
The fat intake in the adult American diet is slightly over the recommended 30% of the total energy. Data from the 1994 to 1996 CSFII
reveals that approximately 25% of the total energy intake is contributed by discretionary fats such as cream, butter, margarine, cream
cheese, oil, lard, meat drippings, cocoa, and chocolate. Based on the average energy intake of adult males, discretionary fat contributes
614 kcal/day and, in females, 412 kcal/day. By cutting back on discretionary fat intake, American adults could conceivably lose
Biochemically, trans-fatty acids act similarly to saturated fatty acids, raising low-density lipoprotein (LDL) levels and decreasing high-density lipoprotein (HDL) levels. Although their effect is not as great as saturated fat, they may contribute to a lipid intake pattern that raises the risk for coronary heart disease. trans-Fatty acids are formed as a result of the hydrogenation process and are found in such food items as margarine, shortening, commercial frying fats, and many high-fat baked and snack foods. trans-Fatty acids also occur naturally in milk and butter because of the fatty acids synthesized by rumen flora in the rumen. Concern over trans-fatty acid intake has led some consumers to question whether they should forgo margarine and return to butter. Research suggests that saturated fat, as in butter, still exerts a greater negative effect on a person’s lipid profile than do trans-fatty acids. However, use of less-hydrogenated forms such as tub rather than stick margarine may be beneficial.
However, some controversy has recently arisen with respect to the efficacy of low-fat diets with respect to breast cancer, colorectal cancer, and cardiovascular disease. Data from the Women’s Health Initiative randomized, controlled dietary modifi cation trial failed to demonstrate that low-fat diets could significantly reduce the risk for these conditions.
CARBOHYDRATE INTAKE ISSUES
Two issues arise with respect to the carbohydrate intake of American adults — low-fiber intake and high-sugar intake. Low-fiber intake is associated with a higher incidence of such chronic diseases as heart disease, cancer, and diabetes. At least partial explanation for the low-fiber intake is related to the low fruit and vegetable intake associated with the typical American diet. Data from the 1994 to 1996 CSFII indicated that for adult males the average total servings (based on the Food Guide Pyramid serving recommendations) of vegetables per day was four. For females, the average was three servings. For both men and women, one-third of the vegetable servings were accounted for by white potatoes. Average serving of fruit per day for both men and women was 1.5. This is just under the minimum Food Guide Pyramid recommendation for two servings per day. Another contributing factor to the low-fiber intake is the lack of whole-grain foods in the diet. Adult men consumed on average 8 servings of grain products per day, which is approximately midrange of the 6 to 11 servings of grain products recommended by the Food Guide Pyramid. Women averaged 6 servings from grain products. However, for both men and women, only one of these servings was from wholegrain products. The health benefi ts of a higher-fiber diet are addressed in other relevant sections of this handbook.
The other carbohydrate intake issue is the consumption of refined sugar, which contributes calories but little other nutritive value to the diet. The 1994 to 1996 CSFII data revealed that approximately 14% of the average energy intake for adult males was from added sugars. For women, the caloric contribution from added sugars was slightly higher at approximately 15%. Foods such as breads, cakes, soft drinks, jam, and ice cream were contributing to the discretionary sugar intake. In 1994 to 1996, soft drink consumption outpaced milk and coffee, and approximately 75% of the soft drink consumption is of the sugar-sweetened variety.
During the last decade, consumption of snack foods such as cakes, cookies, pastries, and pies has increased 15%, likely contributing to the high intake of discretionary sugar. These data are in contrast to the importance consumer’s report they place on a diet moderate in sugar intake. A majority (slightly over 50%) of adults surveyed in the 1994 to 1996 CSFII indicated that it was very important to consume a diet moderate in sugar.
Counseling the normal healthy American adult should focus on dietary intake patterns that promote health and reduce risk for chronic disease, that is, diet recommendations should follow the U.S. Dietary Guidelines. Therefore, consistent with the 2005 version of the U.S. Dietary Guidelines, the focus on nutrition counseling should be:
Adequate nutrients within calorie needs:
For individuals whose body weight is inappropriate, initiate counseling to assist in weight reduction. This may include calculation of appropriate caloric intake, recommendations of sources of caloric intake from the macronutrients of protein, fat, and carbohydrate, appropriate portion sizes to control caloric intake, and increases in physical activity.
Be physically active each day (see following guideline):