Principles of Ambulatory Medicine, 7th Edition

Chapter 15

Principles of Nutrition in Ambulatory Care

Eugene C. Corbett Jr.

As much as any behavior, eating reflects the complexities and variability of human life. What and how we eat derives in large measure from our psychological and cultural milieu, as much as it does from what happens to be on the table or at the grocery store. Yet fundamentally, food is nutrient. It serves the biologic need for the growth, development, and maintenance of tissue structure and function. When chosen wisely by the consumer and coupled with the wisdom of the gastrointestinal tract in selection and absorption, nutrient elements fulfill their varied purposes without causing harm to the individual. However, when nutrient consumption significantly varies below or beyond biologic need, pathologic consequences may ensue. Although historically, and in certain parts of the world even now, diseases of under-nutrition have been more common, in Western culture, diseases of nutrient excess have become epidemic. It has been estimated that diet—activity patterns account for at least 14% of the causes of death in the United States, particularly through their influence on the development of cancer, cardiovascular disease, and diabetes mellitus (1). By implication, the morbid effects are even greater. In clinical care, an understanding of and attention to the essential aspects of human nutrition is therefore important, so that when aberrations in health occur, appropriate efforts to modify nutritional influences can be undertaken.

Food to the consumer is more than nutrient. It is also the source of important and pleasurable experiences that motivate eating beyond that which biologic need dictates. Thus, excessive or, at times, deficient intake of nutrient on a day-to-day basis is more likely the rule than the exception. Fortunately, the body has the capacity in many instances to eliminate nutrients that are consumed in excess of need, as well as the ability to store others in physiologically neutral depots for use when intake may be insufficient. Vitamin B₁₂, for example, is used at a rate of about 1 µg per day, while the capacity for hepatic storage is approximately 1500 times that much. When B₁₂ intake exceeds these metabolic needs and storage capacities, the excess is eliminated by the kidney, a process made easy because of the water-soluble nature of this vitamin. Caloric nutrient, however, which is maximally absorbed and generally not excreted, increases disease risk when accumulation begins to exceed 120% ideal body weight (IBW). And vitamin A, because of its fat-soluble nature and the body's more limited storage and elimination capacity of it, causes a variety of pathologic consequences when consumed in sufficient excess. In the final analysis, and despite the many influences that motivate what and how people eat, the essential clinical concern is the health risk associated with either a sustained deficit or excess of nutrient in the diet.

This chapter emphasizes an approach to assessing nutrition and those situations when nutritional advice is appropriate in the care of the ambulatory patient. Special attention is given to selected nutrients, consensus dietary recommendations, and contemporary dietary patterns. For easy reference, much of the information is provided in table form.

Standard Nutritional Information and Recommendations

Generally speaking, nutritional information should be considered approximate when compared to more objective data that are often available for evaluating health status. For example, nutritional studies show that dietary intake reported by the patient often understates, and only occasionally overestimates actual nutrient intake (2). Similarly, nutrient intake values included in many of the tables and charts in this chapter are approximations of food values derived from standard references. Understanding of general amounts is given priority over focusing on smaller differences that might be attributed to variable food portion sizes, the chosen example of a certain food group, or the variability that is generally assigned to differences in gender. Variability in labeled and reported nutrition data is a

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result of many factors, including differences in food packaging, growing environments, and manufacturing. Nutrient intake also varies from individual to individual, depending on food preferences, genetic endowment, body size, gastrointestinal function, physical activity, and, most of all, eating habits and even bite size. For most clinical thinking about nutrition in day-to-day practice, average values suffice for general assessment and advising purposes.

Guidelines for Americans

The availability and standardization of nutritional information has increased in recent years because of both consumer demand and government influence on food consumption recommendations and food labeling. Since 1980, the United States Departments of Agriculture (USDA) and Health and Human Services (DHHS) have published Dietary Guidelines for Americans every 5 years, most recently in 2005 (3). These represent consensus recommendations for food consumption in the United States and provide the basis for federal nutrition policy. They are based on the work of a committee of nutrition experts who regularly review existing published literature. The guidelines include theFood Guide Pyramid (Fig. 15.1), which is widely used to educate the consumer about ideal food consumption choice. The pyramid depicts, in terms understandable to the average layperson, daily recommended proportions from each major food group. In the 2005 version, the food guide pyramid was turned on its side to allow for depicting more selected variation in amounts of recommended nutrients based on age and physical activity level. An interactive version of the food pyramid that provides more information is available athttp://www.mypyramid.gov/pyramid/index.html.

Nutrients are reorganized into six categories (grains, vegetables, fruits, oils, milk, and meat/beans) plus a seventh “discretionary calorie allowance” category (e.g., solid fat, added sugars). Table 15.1 lists these seven food groups and the recommended daily amounts of each based on an average intake of 2000 calories. Table 15.2 contains a breakdown of recommended intake by selected individual nutrients.Tables 15.1 and 15.2 also contain recommendations for the DASH (Dietary Approaches to Stop Hypertension) Eating Plan. This federally sponsored set of dietary recommendations was originally developed to study the effects of an eating pattern on the prevention and treatment of hypertension. It differs from the standard Food Guide in recommending lower amounts of fat and sugar, and higher amounts of calcium, magnesium, and potassium. Table 15.3 illustrates the estimated calorie requirements as a function of age and gender for three levels of physical activity. Table 15.4 provides a guide for estimating caloric expenditure for a variety of common physical activities.

An appropriate diet is one that maintains an appropriate body weight, provides sufficient daily nutrient intake so that deficiency and excess are avoided, and minimizes the risk of subsequent disease. The guidelines summarized in Figure 15.1 and Tables 15.1,15.2,15.3,15.4provide help to health care practitioners and the public in this regard.

Nutritional Labeling

Uniformity in nutrition labeling accelerated in the United States with the passage of the Nutrition Labeling and Education Act in 1990 (NLEA, Public Law 101–535). This federal mandate preempted all existing state and federal laws and regulations and stimulated a planned schedule to achieve uniformity in the way that food content is named and quantified on all food products, including water (4). Food labels contain standardized information on serving size, caloric content, and ingredients (Fig. 15.2). Reference is also made to the amount of certain ingredients in comparison to recommended daily values (5). There are 14 mandatory per-serving components of the nutrition label: total calories, total fat, saturated fat, trans fat, cholesterol, sodium, total carbohydrate, dietary fiber, sugars, protein, vitamin A, vitamin C, calcium, and iron.

Percent of recommended daily values for specific nutrients as recommended by the USDA/HHS is required in food labeling and is listed as a footnote at the bottom of the label (Fig. 15.2). The daily value indicated is based on an average caloric intake of both a 2,000 and 2,500 kcal per day diet for an adult who performs at a light-to-moderate activity level. Although exact definitions are not used, this designation generally refers to an individual who is not sedentary in lifestyle and who does not perform specific daily exercise. The actual daily value may be higher or lower depending on physical activity level.

Recommended Daily Allowance/Dietary Reference Intake

The recommended daily allowance (RDA) for specific nutrients was established by the Food and Nutrition Board of the National Academy of Sciences and was last revised in 1989. They represent a nutrient intake value that is 2 standard deviations above the mean necessary to prevent disease in a healthy population (6). More recently, the dietary reference intake (DRI) has replaced the RDA. It is based on nutrient intake recommendations of the Institute of Medicine (7). The DRI is intended to incorporate a set of nutrient reference values that encompass the RDA and various Canadian and European value systems.

Organic Food Standards

In recent years, increasing emphasis is being given to foods that have been grown in more naturalized environments that do not involve synthetic growth influences or processing methods. Beginning with the Organic Food Production

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Act of 1990, the U.S. Department of Agriculture has implemented a set of national standards that must be met before nationally or internationally produced foods can be labeled as “organic.” The standards do not officially recognize or endorse other descriptive terms, such as “natural” or “hormone-free.” The USDA defines an organic food as follows:

FIGURE 15.1. The U.S. Department of Agriculture Food Guide Pyramid.

Organic food is produced by farmers who emphasize the use of renewable resources and the conservation of soil and water to enhance environmental quality for future generations. Organic meat, poultry, eggs, and dairy products come from animals that are given no antibiotics or growth hormones. Organic food is produced without using most conventional pesticides, fertilizers

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made with synthetic ingredients or sewage sludge, bioengineering, or ionizing radiation. Before a product can be labeled “organic,” a government-approved certifier inspects the farm where the food is grown to make sure the farmer is following all the rules necessary to meet USDA organic standards. Companies that handle or process organic food before it gets to your local supermarket or restaurant must be certified, too (8).

TABLE 15.1 Sample USDA Food Guide and the DASH Eating Plan at the 2,000-Calorie Levela

Amounts of various food groups that are recommended each day or each week in the USDA Food Guide and in the DASH (Dietary Approaches to Stop Hypertension) Eating Plan (amounts are daily unless otherwise specified) at the 2,000-calorie level. Also identified are equivalent amounts for different food choices in each group. To follow either eating pattern, food choices over time should provide these amounts of food from each group on average. Food Groups and Subgroups USDA Food Guide Amountb DASH Eating Plan Amount Amounts Fruit Group 2 cups (4 servings) 2–2.5 cups (4–5 servings) ½ cup equivalent is: ½ cup fresh, frozen, or canned fruit; 1 med fruit; ¼ cup dried fruit USDA: ½ cup fruit juice DASH: ¾ cup fruit juice Vegetable Group Dark green vegetables Orange vegetables Legumes (dry beans) Starchy vegetables Other vegetables 2.5 cups (5 servings) 3 cups/wk 2 cups/wk 3 cups/wk 3 cups/wk 6.5 cups/wk 2–2.5 cups (4–5 servings) ½ cup equivalent is: ½ cup of cut-up raw or cooked vegetable; 1 cup raw leafy vegetable USDA: ½ cup vegetable juice DASH: ¾ cup vegetable juice Grain Group Whole grains Other grains 6 ounce-equivalents 3 ounce-equivalents 3 ounce-equivalents 7–8 ounce-equivalents (7–8 servings) 1 ounce-equivalent is: 1 slice bread; 1 cup dry cereal; ½ cup cooked rice, pasta, cereal DASH: 1 oz dry cereal (½–1¼ cup depending on cereal type—check label) Meat and Beans Group 5.5 ounce-equivalents 6 ounces or less meat, poultry, fish 1 ounce-equivalent is: 1 ounce of cooked lean meats, poultry, fish; 1 egg 4–5 servings per wk nuts, seeds, and dry beansc USDA: ¼ cup cooked dry beans or tofu; 1 Tbsp peanut butter; ½ oz nuts or seeds DASH: 1½ oz nuts; ½ oz seeds; ½ cup cooked dry beans Milk Group 3 cups 2–3 cups 1 cup equivalent is: 1 cup low-fat/fat-free milk, yogurt; 1.5 oz of low-fat or fat-free natural cheese; 2 oz of low-fat or fat-free processed cheese Oils 27 g (6 tsp) 8–12 g (2–3 tsp) 1 tsp equivalent is: DASH: 1 tsp soft margarine; 1 Tbsp low-fat mayonnaise; 2 Tbsp light salad dressing; 1 tsp vegetable oil Discretionary Calorie Allowance 267 calories ~2 tsp of added sugar (5 Tbsp per wk) 1 Tbsp added sugar equivalent is: DASH: 1 Tbsp jelly or jam; ½ oz jelly beans; 8 oz lemonade Example of distribution: Solid fatd 18 g Added sugars 8 tsp aAll servings are per day unless otherwise noted. USDA vegetable subgroup amounts and amounts of DASH nuts, seeds, and dry beans are per week. bThe 2,000-calorie USDA Food Guide is appropriate for many sedentary males 51 to 70 years of age, sedentary females 19 to 30 years of age, and for some other gender/age groups who are more physically active. See Table 15.3 for information about gender/age/activity levels and appropriate calorie intakes. See Appendices A-1, A-2 and A-3 athttp://www.health.gov/dietaryguidelines/dga2005/document for more information on the food groups, amounts, and food intake patterns at other calorie levels. cIn the DASH Eating Plan, nuts, seeds, and dry beans are a separate food group from meat, poultry, and fish. The DASH diet generally recommends less sugar and fat, and more calcium, magnesium and potassium than the standard Food Guide (see text). dThe oils listed in this table are not considered to be part of discretionary calories because they are a major source of the vitamin E and polyunsaturated fatty acids, including the essential fatty acids, in the food pattern. In contrast, solid fats (i.e., saturated and trans fats) are listed separately as a source of discretionary calories. From Dietary Guidelines for Americans 2005, available athttp://www.health.gov/dietaryguidelines/dga2005/document . Last accessed December 18, 2005.

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In a more recent promulgation, the USDA allows for four categories of food labeling, depending on the organic purity of the foods produced: “100% Organic,” “Organic” (at least 95% organic ingredients), “Made With Organic Ingredients” (at least 75% organic ingredients), and “Made With Some Organic Ingredients” (less than 70% but more than 30% organic ingredients). The USDA makes no claim that organically produced food is safer or more nutritious than conventionally produced food.

TABLE 15.2 Comparison of Selected Nutrients in the Dietary Approaches to Stop Hypertension (DASH) Eating Plana, the USDA Food Guideb, and Nutrient Intakes Recommended per Day by the Institute of Medicine (IOM)c

Estimated nutrient levels in the DASH Eating Plan and the USDA Food Guide at the 2,000-calorie level, as well as the nutrient intake levels recommended by the Institute of Medicine for females 19–30 years of age. Nutrient DASH Eating Plan (2,000 kcals) USDA Food Guide (2,000 kcals) IOM Recommendations for Females 19–30 Years of Age Protein, g 108 91 RDA: 46 Protein, % kcal 21 18 AMDR: 10–35 Carbohydrate, g 288 271 RDA: 130 Carbohydrate, % kcal 57 55 AMDR: 45–65 Total fat, g 48 65 — Total fat, % kcal 22 29 AMDR: 20–35 Saturated fat, g 10 17 — Saturated fat, % kcal 5 7.8 ALAPd Monounsaturated fat, g 21 24 — Monounsaturated fat, % kcal 10 11 — Polyunsaturated fat, g 12 20 — Polyunsaturated fat, % kcal 5.5 9.0 — Linoleic acid, g 11 18 AI: 12 Alpha-linolenic acid, g 1 1.7 AI: 1.1 Cholesterol, mg 136 230 ALAPd Total dietary fiber, g 30 31 AI: 28e Potassium, mg 4,706 4,044 AI: 4,700 Sodium, mg 2,329f 1,779 AI: 1,500; UL: <2,300 Calcium, mg 1,619 1,316 AI: 1,000 Magnesium, mg 500 380 RDA: 310 Copper, mg 2 1.5 RDA: 0.9 Iron, mg 21 18 RDA: 18 Phosphorus, mg 2,066 1,740 RDA: 700 Zinc, mg 14 14 RDA: 8 Thiamin, mg 2.0 2.0 RDA: 1.1 Riboflavin, mg 2.8 2.8 RDA: 1.1 Niacin equivalents, mg 31 22 RDA: 14 Vitamin B6, mg 3.4 2.4 RDA: 1.3 Vitamin B12, µg 7.1 8.3 RDA: 2.4 Vitamin C, mg 181 155 RDA: 75 Vitamin E (AT)g 16.5 9.5 RDA: 15.0 Vitamin A, µg (RAE)h 851 1,052 RDA: 700 aDASH nutrient values are based on a 1-week menu of the DASH Eating Plan. NIH publication No. 03–4082. Available at http://www.nhlbi.nih.gov . bUSDA nutrient values are based on population-weighted averages of typical food choices within each food group or subgroup. cRecommended intakes for adult females 19–30 years of age; AI, adequate intake; AMDR, acceptable macronutrient distribution range; RDA, recommended dietary allowance; UL, upper limit. dAs low as possible (ALAP) while consuming a nutritionally adequate diet. eAmount listed is based on 14 g dietary fiber/1,000 kcal. fThe DASH Eating Plan recommends <1,500 mg of sodium per day for individuals with hypertension, blacks, and middle-aged and older adults. gAT, mg D-α-tocopherol. hRAE, retinol activity equivalents. From Dietary Guidelines for Americans 2005. Available athttp://www.health.gov/dietaryguidelines/dga2005/document . Last accessed December 18, 2005.

TABLE 15.3 Estimated Calorie Requirements (in Kilocalories) for Each Gender and Age Group at Three Levels of Physical Activitya

Estimated amounts of calories needed to maintain energy balance for various gender and age groups at three different levels of physical activity. The estimates are rounded to the nearest 200 calories and were determined using the Institute of Medicine (IOM) equation. Activity Levelb,c,d Gender Age (Years) Sedentaryb Moderately Activec Actived Child 2–3 1,000 1,000–1,400e 1,000–1,400e Female 4–8 9–13 14–18 19–30 31–50 51+ 1,200 1,600 1,800 2,000 1,800 1,600 1,400–1,600 1,600–2,000 2,000 2,000–2,200 2,000 1,800 1,400–1,800 1,800–2,200 2,400 2,400 2,200 2,000–2,200 Male 4–8 9–13 14–18 19–30 31–50 51+ 1,400 1,800 2,200 2,400 2,200 2,000 1,400–1,600 1,800–2,200 2,400–2,800 2,600–2,800 2,400–2,600 2,200–2,400 1,600–2,000 2,000–2,600 2,800–3,200 3,000 2,800–3,000 2,400–2,800 aThese levels are based on estimated energy requirements (EER) from the Institute of Medicine Dietary Reference Intakes Macronutrients Report (2002), calculated by gender, age, and activity level for reference-sized individuals. “Reference size,” as determined by IOM, is based on median height and weight for ages up to age 18 years of age and median height and weight for that height to give a body mass index (BMI) of 21.5 for adult females and 22.5 for adult males. bSedentary means a lifestyle that includes only the light physical activity associated with typical day-to-day life. cModerately active means a lifestyle that includes physical activity equivalent to walking about 1.5 to 3 miles per day at 3 to 4 miles per hour, in addition to the light physical activity associated with typical day-to-day life. dActive means a lifestyle that includes physical activity equivalent to walking more than 3 miles per day at 3 to 4 miles per hour, in addition to the light physical activity associated with typical day-to-day life. eThe calorie ranges shown are to accommodate needs of different ages within the group. For children and adolescents, more calories are needed at older ages. For adults, fewer calories are needed at older ages. From Dietary Guidelines for Americans 2005. Available athttp://www.health.gov/dietaryguidelines/dga2005/document . Last accessed December 18, 2005.

TABLE 15.4 Physical Activity and Caloric Expenditurea

Physical Activity Calories Expended (Kcal/Houra) Rest 90 Sitting 120 Stand and move 252 Walk 2 mph 198 Walk 4 mph 396 Cycle 5 mph 180 Cycle 10 mph 396 Swim 20 yds/min 294 Swim 40 yds/min 594 Run 5 mph 564 Run 10 mph 1128 Hike with pack 420 Tennis, singles 468 Basketball 462 Racquetball 606 aCalculated from Appendix C tables in Williams MH. Nutrition for health, fitness and sport. 5th ed. Boston: McGraw-Hill, 1999:425–431.5

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Survey Data on Nutritional Patterns

Because the study of nutrition and its relationship to health status has become increasingly important, national nutritional surveillance surveys were begun in the United States in 1970 (9). National Health and Nutrition Examination Surveys (NHANES) have been conducted three times—1971, 1976, and 1988—by the National Center for Health Statistics of the Centers for Disease Control and Prevention (NCHI/CDC). These population-based surveys use a probability sample of 25,000 to 35,000 individuals, using 24-hour dietary recall and food frequency questionnaires. Physical examination and a battery of clinical measurements and tests are also performed on all individuals in the sample. The NHANES data are used to establish food consumption patterns and nutritional status by both demographic and nutrient-specific criteria.

In 1995, the USDA initiated the Healthy Eating Index to measure how well American diets conform to recommended healthful eating patterns such as those included

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in the Food Guide Pyramid. The 10 components of this index include grains, vegetables, fruits, milk, meat, total fat, saturated fat, cholesterol, sodium, and food variety. For two studies done in 1989 and 1990, a 3-day dietary intake was obtained using a sample size of approximately 4,000 individuals 2 years of age and older. The maximum score for the 10-component index is 100 points. Average overall scores for the 1989 and 1990 data were 63.8 and 63.9, respectively. Approximately 12% of persons had an index score above 80, and 15% were at 50 or below. The majority of individuals studied had diets that were rated as “Needs Improvement” (10).

FIGURE 15.2. How to read a nutrition facts label. (From the U.S. Food and Drug Administration/Center for Food Safety & Applied Nutrition. How to Understand and Use the Nutrition Facts Label. June 2000; updated July 2003, and November 2004. Reproduced with permission from http://www.cfsan.fda.gov/~dms/foodlab.html. Last accessed December 15, 2005.)

Nutritional Assessment

Although primary care practitioners may refer patients to nutritionists for detailed assessments of dietary habits and for assistance in managing patients with nutritionally related disease such as obesity, atherosclerosis, diabetes, and renal failure, much general dietary counseling can be and is done by primary care practitioners. Useful dietary counseling requires a practical approach to nutritional assessment that helps to identify dietary deficiencies and excesses. The two steps of a practical approach to assessment include (a) taking a nutritional history and assessing nutrient intake and (b) recognizing manifestations of nutritional deficiency or excess.

Table 15.2 shows the important human macronutrients and micronutrients. Macronutrients are consumed in readily observed forms. Micronutrients, on the other hand, are less visible constituents of the major food groups. They include vitamins (organic compounds that are required in small amounts) and minerals.

The portion sizes used in this chapter, which may vary considerably from individual to individual, are based on a standard reference that is widely used by nutrition professionals (11).

TABLE 15.5 Disease–Nutrient Associations

Disease Associated Nutrients Atherosclerosis Saturated fat, cholesterol Diarrheal disease Water, electrolytes, most nutrients Liver disease Alcohol Cancer Fat, antioxidants (A, C, E) Diabetes mellitus Fat, sugar, total energy, alcohol Renal disease Water, electrolytes, protein Osteoporosis Calcium, vitamin D Hypertension Sodium, potassium, calcium Malnutrition Many nutrients Congestive heart failure Sodium, water, potassium Anemia Iron, folate, vitamin B12 Obesity Fat, carbohydrate, total energy Breast Disease Vitamin E, caffeine

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Obtaining Information about a Patient's Nutrition

Importance of Nutritional History Taking

The initial step in identifying dietary influence in the routine care of the patient is to collect information that provides a database for each individual with respect to important nutrients. From this, a judgment can then be made about whether these nutrients are deficient or excessive in the patient's diet. The nutrient history can be obtained by the health care practitioner directly or by another staff member. A practitioner-directed history has the advantage that the practitioner can simultaneously assess the patient's willingness to discuss his or her eating habits and make a judgment as to the veracity of the information. Additionally, the patient is more likely to conclude that personal nutrition has value comparable with other data that one seeks in the clinical interview. Given the major impact that diet has upon the etiology, pathogenesis, and course of many diseases, such a dialogue is important in current prevention and treatment strategies. Table 15.5 lists the nutrients associated with the most common contemporary diseases of people (12,13).

Practical Assessment of Nutrient Intake

Formal nutritional intake information is usually obtained with the use of either food frequency (FFQ) or daily food intake questionnaire. The latter may be done on the basis of a 24-hour dietary recall (past 24 hours) or by having the patient complete a daily food diary over a specified period of time.

Table 15.6 contains a list of questions that represent a suggested narrative for nutritional assessment. It combines elements of specific 24-hour dietary recall with that of general questioning about a patient's eating habits. It has the advantage of validating an individual's self-perception of personal nutrition with 24-hour eating recall information and includes specific inquiry about between-meal intake. When inconsistency in responses occur, discussion of them may lead to a better understanding of a patient's pattern of food consumption and of the type of exceptions that the patient makes in the day-to-day personal rules for eating. Although a single 24-hour hour dietary recall may be atypical, repeated 24-hour recalls can provide a fairly reliable assessment of average dietary intake.

TABLE 15.6 Sample Clinical Nutrition History That Combines Specific Dietary Recall and General Information

Meal-Oriented Questioning: 1. How many meals do you generally eat on a daily basis? How many yesterday or today? 2. What do you generally eat for breakfast? What did you eat this morning? 3. What do you generally eat for lunch? What did you actually eat for lunch today or yesterday? 4. Do you ever eat or drink anything between breakfast and lunch? What might you have had between breakfast and lunch today or yesterday? 5. What do you generally have for dinner/supper? What did you have today or yesterday? 6. Do you normally eat or drink between lunch and dinner/supper? If so, what do you have? Did you do so today or yesterday? 7. What do you generally eat or drink between dinner/supper and bedtime? What did you have then either today or yesterday? 8. Do you generally snack? If so, what are your preferred snacks? How often do you snack? Selected Nutrient Questioning: 1. What liquids do you generally consume? What and how much did you drink in the past 24 hours? Do you drink water by itself? How often/how much? 2. Do you add salt to your food at the table? Do you cook with salt? 3. What fats do you generally cook with? What did you use yesterday? 4. Do you ever eat sweets? Daily? How often? What do you usually reach for in a snack? Do you add sugar to coffee or tea? 5. Do you consume foods with caffeine? Coffee? Tea? Soda? Chocolate? Quantities? 6. Do you know what fiber-containing foods you eat on a daily basis? Fresh vegetables? Fresh fruits? Salad? Fiber supplements? 7. Do you know how much cholesterol-related foods you eat on a daily basis? Red Meat? Saturated fats? 8. What and how much dairy products do you eat daily? Dark greens? Calcium supplements?

An alternative, more time-efficient way to assess 24-hour intake is to give the patient a readable table of information about food groups such as Table 15.1, and have the patient fill in the number of servings of each food group consumed in the prior day. Because food intake reporting methods have been shown to collect information that often underestimates actual food consumption (2), it is wise to interpret any food intake report as representing minimal food consumption at best. Nevertheless, such information

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is essential in developing a starting point for discussion of an individual's food consumption behavior.

TABLE 15.7 Micronutrient Laboratory Tests

Nutrient Test Normal Rangea Calcium Serum calcium 8.2–10.0 mg/dL radiologic Bone mineral density reference Folate Serum folate 2.6–17.0 ng/mL Red cell folate 150–450 ng/mL Iron Serum iron 40–160 µg/dL % Saturation 20–55% Transferrin 213–360 mg/dL Ferritin 18–311 ng/mL Magnesium Serum Mg 1.9–2.7 mg/dL Potassium Serum K+ 3.6–5.0 mEq/L 24-hr urinary excretion 25–125 mEq/d (varies with diet) Sodium Serum sodium 135–145 mEq/L 24-hr urinary excretion 20–250 mEq/d (varies with diet) Vitamin A Serum retinol 35–70 µg/dL Vitamin B12 Serum B12 251–911 pg/mL Vitamin C Serum ascorbic acid 0.6–2.0 mg/dL Vitamin D 25-OH vitamin D 15–80 ng/mL 1,25(OH)2 vitamin D 18–62 pg/mL Vitamin E Serum tocopherol 0.5–1.2 mg/dL aReference values vary with laboratories.

Once information about the average daily food intake is collected, an estimate of actual macronutrient and micronutrient element consumption can be made using the basic information in Tables 15.1 and 15.2.

Micronutrient intake is generally assessed by an analysis of food type consumption. It can also be inferred from serum biochemical testing (Table 15.7). Table 15.8 contains additional information about selected micronutrients that is pertinent to assessment regarding sufficient intake. It includes the recommended daily DRI, the type of food that generally provides each nutrient (vegetal, meat, dairy), and the food servings that would provide all of the RDA. The amount of each micronutrient which is contained in a standard over-the-counter multivitamin or pill supplement is also shown. Finally, when considering micronutrient dietary adequacy, it is helpful to know the amount that is stored in the body, the estimated duration of use of the body's storage amount, and amount lost daily (Table 15.9) (6).

TABLE 15.8 Micronutrient Dietary Sources (Recommended Amounts May Vary with Age and Gender)

Nutrient Dietary Reference Intake Food Source Food Servings Standard Over-the-Counter Preparation Calcium 1,200 mg Dairy, vegetal 1 qt milk 200–1000 mg Folate 400 µg Vegetal 5 400 µg Iron 15 mg Meat, vegetal 6 15 mg Magnesium 400 mg Vegetal > meat 6 100 mg Potassium 4,700 mg Most foods 8 80 mg Sodium < 2,300 mg Most foods 8 None Vitamin A 800 µg Vegetal, dairy, 4 800 µg liver <1 Vitamin B12 2.4 µg Meat, fish 1 6 µg Vitamin C 80 mg Vegetal 2 80 mg Vitamin D 400 IU Dairy 1 qt milk 400 IU Vitamin E 15 mg Vegetal oil 3 tbsp 15 mg Most foods 6 From Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals. Food and Nutrition Board, Institute of Medicine, National Academies. Available athttp://www.iom.edu/Object.File/Master/21/372/0.pdf .

Recognizing Clinical Manifestations of Nutritional Deficiency and Excess

In addition to the nutrition history, physical examination offers important clues to both macro- and micronutrient-related abnormalities.Tables 15.10 and 15.11 summarize some of the more important signs of nutrient deficiency and excess.

Considerations Related to Selected Nutrients

Certain nutrients are particularly important in their relationship to health and disease; some because they constitute the basic components of a selective diet (e.g., a vegetarian diet), some because of their influence upon caloric intake, some because of refinement in the processing of foods in the past century, and others because they contribute to commonly experienced symptoms.

TABLE 15.9 Micronutrient Storage Capacity and Daily Losses

Nutrient Storage Capacity Supply Duration Average Daily Loss Calcium 1,200 g (1% extraskeletal) Years 200 mg Folate 4,000 µg 60 days 60 µg Iron 500 mg >1 year male: 1 mg; female: 1.5 mg Magnesium* 2,500 mg 100 days 150 mg Potassium* 180,000 mg (4,500 mEq) ~1 wk 800 mg (20 mEq) Sodiuma >100,000 mg (>4,400 mEq) Years <230 mg (10 mEq) Vitamin A 500,000 µg >1 year 1,000 µg Vitamin B12 >2,000 µg >3 years 2 µg Vitamin C 1,500 mg 30+ days >30 mg Vitamin Db ? Unknown 100 IU (2.5 µg) Vitamin Ec ? ? ? aElectrolytes in storage serve active biologic functions. bVitamin D is one of the nonessential vitamins. cVitamin E deficiency is rare. Modified from Food and Nutrition Board, National Research Council. Recommended Daily Allowances, 10th ed. Washington, DC: National Academy Press, 1989.

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Vegetarian Diets

Vegetarian diets are increasingly popular. One of the more obvious reasons is the current epidemic of hypercholesterolemia and atherosclerosis related to the intake of saturated fats and the cholesterol content in animal protein foods. Secondly, evidence that vegetal sources of protein contain sufficient amounts of the ten essential amino acids is debunking the long-held myth that vegetarian eating does not provide as complete a protein source as animal meats (14). An important example is the demonstration that soybeans contain an amino acid content equivalent to that of egg albumin, the long-held standard referent for an ideal protein source (15).

Finally, it is increasingly appreciated that vegetarian eating not only can sustain health, but it can lead to improved health status. For example, studies show that vegetarian diets are consistently associated with lower rates of ischemic heart disease (16, 17, 18, 19, 20, 21). In addition, studies of Seventh-Day Adventists reveal that their vegetarian-oriented lifestyle is also associated with decreased rates of cancer and all-cause mortality (22). Vegetarian diets contain higher amounts of fiber, antioxidants, folic acid, and phytochemicals, all of which are receiving increasing attention in modern dietary recommendations.

The vegetarian tradition is Asian in origin, particularly among Hindu populations. It currently includes a number of variations along a continuum of vegetarian purity. A vegan diet is considered the strictest diet. It excludes all forms of animal products including dairy and honey. A lactovegetarian diet includes dairy products, and ovolactovegetarian allows for the inclusion of both eggs and dairy. Many individuals use the term partial-vegetarian to indicate that they occasionally use animal products. A macrobiotic diet derives from East Asian traditions and in its most traditional form, involves the practice of a gradual change from a balanced vegetarian diet to one that primarily consists of grain, all in the interest of progressive nutritional and spiritual purity. Generally it emphasizes brown rice, fruits, and vegetables. Cooking is preferred over raw foods. Processed foods are avoided, as are tomatoes and potatoes. Fish is permitted.

The Food Guide Pyramid (Fig. 15.1) includes vegetarian eating in its general design and recommended food selections. The U.S. Department of Agriculture website

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contains more detailed information on vegetal choice (see http://www.hopkinsbayview.org/PAM). Complete sources of amino acids are obtained in diets that include a combination of legumes (beans, peas, lentils, soybeans) and grain. Tofu is a particularly versatile soybean-based product used in the preparation of many vegetarian dishes.

TABLE 15.10 Clinical Manifestations Related to Macronutrients

Macronutrient Signs of Deficiency Signs of Excess Carbohydrate, total Weight loss, asthenia, urinary ketosis Obesity, weight gain Carbohydrate, fiber Constipation Frequent stooling, abdominal bloating Carbohydrate, starch Weight loss, asthenia Obesity, weight gain, insulin resistance, glucose intolerance Carbohydrate, sugar None Obesity, weight gain, insulin resistance, glucose intolerance, halitosis, dental caries Carbohydrate–alcohol None Facial plethora, alcoholic breath, large parotid glands, hepatitis, cirrhosis, cerebellar abnormalities Total fat Weight loss, asthenia, vitamin D deficiency (see Table 15.10) Obesity, weight gain, xanthelasma, atherosclerosis Saturated fat Unknown Hypercholesterolemia, atherosclerosis, corneal arcus Cholesterol Unknown Hypercholesterolemia, atherosclerosis, corneal arcus Protein Weight loss, edema, infection, lethargy, hypoalbuminemia (kwashiorkor) None Water Dehydration, high urine specific gravity, many organ system abnormalities Hyponatremia (unusual)

TABLE 15.11 Clinical Manifestations Related to Micronutrients

Micronutrient Signs of Deficiency Signs of Excess Calcium Osteoporosis, kyphosis, hypocalcemia Constipation, hypercalcemia, hypercalciuria, urolithiasis Folate Macrocytic anemia, neurologic birth defects Unknown Iron Microcytic anemia Hemochromatosis Magnesium Muscle weakness, low serum Mg, hypokalemia, long QT interval Unknown Potassium Neuromuscular symptoms, ECG U-wave prominence Cardiac arrhythmia, ECG peaked T waves Salt Neuromuscular symptoms, hyponatremia, hypotension Hypertension, edema Vitamin A Impaired night vision, xerophthalmia, follicular hyperkeratosis, dry skin Headache, desquamation, alopecia, osteosclerosis, splenomegaly Vitamin B12 Macrocytic anemia, glossitis, peripheral neuropathy Unknown Vitamin C Scurvy, malaise Diarrhea Vitamin D Hypocalcemia, rickets, osteomalacia Hypercalcemia, hypercalciuria, calcinosis Vitamin E Reproductive failure, neuromuscular dysfunction (chronic malabsorption states) Excesses may contribute to cardiovascular morbidity ECG, electrocardiogram.

In addition to alternative protein sources, vegetarian diets differ from meat-based diets in that they contain lower fat content and little saturated fat. They also have less iron, little if any vitamin B₁₂, and less calcium and zinc. However, they contain more fiber and antioxidant vitamins, more magnesium, and more folate (23,24). In addition, they potentially limit vitamin D availability in wintry months when sun exposure is limited. Although years can pass before people who become vegans develop B₁₂ deficiency, breast-fed infants of strict vegetarian mothers have been reported to develop B₁₂ deficiency (25). As well, milk-free diets can lead to rickets in young children (26). Significant nutrient deficiency is unusual in nonvegan vegetarian individuals. When eggs and dairy are avoided, however, supplementation with vitamin B₁₂, calcium, and vitamin D is recommended.

Calories

Caloric nutrient excess has reached epidemic proportions in the United States today. Obesity rates approach 40% of the adult population in this country and are increasing in many other countries (see Chapter 83). The increasing availability of energy-dense foods coupled with more sedentary lifestyles together contribute to this phenomenon. Furthermore, the epidemic of type II diabetes is associated with chronic caloric excess, sedentary lifestyle, and obesity.

The word calorie is derived from the Latin word calor meaning warm. The term is used as a measure of heat energy in food. Specifically, it refers to the amount of heat required to raise the temperature of 1 kg of water 1°C. In common food-related usage, the word calorie is used, although technically the term kilocalorie is the more correct designation. Table 15.12 shows the caloric value of the four major energy-containing nutrients.

Once ingested, more than 99% of caloric foods are absorbed. Very little of ingested caloric content is excreted in urine or stool under normal conditions. An exception is alcohol, which can be excreted unmetabolized in the urine. Ketones, which represent the incompletely metabolized combustion products of fat breakdown, are the other exception to this rule. Thus, most caloric intake is destined for either immediate metabolic use or storage as either glycogen (liver, muscle) or triglyceride (adipose cells).

The absorption and metabolic processing of caloric nutrients require energy. The incremental amount of caloric energy required in providing for metabolic processing varies from nutrient to nutrient (27,28). Table 15.13 shows average estimates for the metabolic cost of caloric macronutrient processing and storage. The net amount of calories stored for an equivalent (100 calories) amount of ingested carbohydrate, fat, or protein is shown. The last column of the table gives an estimate of the comparative annual weight that might be gained if an extra 100 kcal per day were eaten for each nutrient.

TABLE 15.12 Energy Contained in Caloric Nutrients

Nutrient Energy (Kcal/g) Protein 4 Carbohydrate 4 Alcohol 7 Fat 9

TABLE 15.13 Caloric Processing and Storage

Caloric Nutrient % Calories Expended in Processing and Storage Net Calories Storedafrom 100 Ingested Weight Gain Per Yearb in Pounds Fat 3% 97 9.7 Carbohydrate 25% 75 7.5 Protein 25–50% 50–75 5–7 aAssuming that calories (kcal) eaten exceed those needed for metabolic use. bWeight gain if an extra 100 calories (kcal) per day is eaten of nutrient = net excess calories stored per day × 365 days/3,500 calories per pound as stored triglyceride.

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Salt

Sodium chloride is the major osmotic constituent of the extracellular vascular and interstitial spaces. It is also the major component of intravenous fluids. From a dietary perspective, it is also a nutrient that can be deficient or excessive in the diet. Excessive salt can contribute to expansion of the extracellular space and influence the development of hypertension and congestive heart failure. In an otherwise healthy individual, diet-related salt deficiency is rare.

The normal human is capable of adapting to a very wide range of salt intake. Under conditions of limited salt intake, the kidney will excrete less than 230 mg (10 mEq) of sodium per day. This represents about one-tenth of a teaspoon of salt. On the other hand, among certain Oriental cultures, an intake of more than 25 g per day has been documented. The renin–angiotensin–aldosterone system adjusts salt excretion to match salt intake.

In U.S. surveys, daily sodium intake ranges from 3.8 to 7.5 g (29). In a workplace study of urinary 24-hour sodium excretion, a large range (4 to 24 g) was observed (30). Approximately 50% of salt intake is that added by the consumer for seasoning. For example, 1 teaspoon of salt contains 1,800 mg of sodium. Because of its importance in common health problems, quantitative information about the amount of sodium is required for standard nutritional labeling (see Fig. 15.2). The maximum amount of sodium per day that is recommended is 2,400 mg (6 g of salt) (5). Table 15.14 lists the sodium and salt content of selected intake sources.

Sugar

The consumption of sugar in the American diet increased throughout the 20th century, continuing a trend that began in the 19th century when inexpensive methods of sugar production developed. The average annual per capita consumption was estimated to be 75 pounds in 1909, rising to approximately 130 pounds today. Sugar comprises approximately 25% of the total energy consumption in the U.S. diet. As an energy-dense nutrient that is easily consumed, it contributes to excess caloric intake and thus influences the development of obesity and diabetes. It also contributes to the development of dental caries.

TABLE 15.14 Sodium–Salt Equivalents

Intake Sodium (mg) Sodium (mEq) Salt (g) Milk, 1 pint 150 6.5 0.375 French fries 4 oz 220 10 0.550 Minimal intake 250 11 0.625 Low-sodium diet 500 22 1.5 Hamburger 530 23 1.3 Soup 8 oz 1,000 43 2.5 Big Mac 1,010 44 2.5 1 tsp salt 1,800 78 4.5 Recommended daily value 2,400 104 6.0 1 L lactated Ringer solution 3,100 134 7.75 1 L 0.9% normal saline 3,500 154 8.75 Average U.S. intake 5,000 217 12.0 125 mL/hr of normal saline ×24 hr 10,600 462 26.25 1 mEq Na = 23 mg; 2.5 mg NaCl contains 1 mg Na.

Three-fourths of dietary sugar is sucrose, the type found in refined sugars; the remaining dietary sugars (fructose, maltose, lactose) come from natural foods such as fruit, honey, and milk. Sugar is added to many manufactured foods, including products not thought of as “sweet,” such as salad dressings, mayonnaise, catsup, bread, crackers, and chips. Table 15.15 lists the sugar and caloric content of a variety of modern foodstuffs.

TABLE 15.15 Sugar Content of Selected Foods

Food Item Sugar Content (g) Total Sugar Calories Total Serving Caloriesa Teaspoon of sugar 4.5 18 18 Soda, 12 ozb 40 160 160 Ice cream, 1 cup 32 128 340 Yogurt, 4 oz 29 116 130 Juice, 8 oz 26 104 104 Chocolate bar, 1.6 oz 22 88 230 Cookie, 1 oz 21 84 120 Crackers, 5 16 64 70 aIncludes sugar and nonsugar calories. bDiet sodas contain less than 10 calories per 12 oz.

TABLE 15.16 Fiber Content of Selected Foods

Food Serving Fiber Content (g) Lettuce 0.5 White bread slice 0.6 Tomato 1.4 Wheat bread slice 2.0 Green beans 2.0 Oatmeal 2.6 Broccoli 2.7 Granola 3.0 Orange 3.1 Apple 3.7 Popcorn 4.0 Raisin Bran 6.0 Chili beans 6.0

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Fiber

Since the 1960s, the importance of fiber in the diet has become more appreciated. It had been considered an inert ingredient until clinical studies revealed an association between colonic disease and the lack of fiber in the diet, and a favorable effect of fiber on blood sugar control in diabetes.

There are six vegetal fiber constituents: gum, mucilage, pectin, hemicellulose, lignin, and cellulose. All but the latter two are at least partially digested by human colonic bacteria. The term bran generally refers to the form of fiber that passes unaltered through the digestive tract, usually consisting of cellulose, hemicellulose, and lignin. Dietary fiber has hydrophilic activity and increases the water content of small intestinal and colonic stool. These factors explain why fiber increases stool bulk and diminishes bowel transit time (31). Dietary fiber also slows gastric emptying time and moderates carbohydrate absorption rates (32). Fiber can increase the fecal loss of nutrients, but this effect has not been associated with overt nutritional deficiency. Table 15.16 shows the fiber content of common foods.

Specific References*

For annotated General References and resources related to this chapter, visit http://www.hopkinsbayview.org/PAMreferences.

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