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TABLE 1 Acceptable Macronutrient Distribution Ranges AMDR (as percent of energy)a Children Children Adults Macronutrient 1â3 y 4â18 y Fat 30â40 25â35 20â35 n-6 polyunsaturated fatty acidsb (linoleic acid) 5â10 5â10 5â10 n-3 polyunsaturated fatty acidsb (a-linolenic acid) 0.6â1.2 0.6â1.2 0.6â1.2 Carbohydrate 45â65 45â65 45â65 Protein 5â20 10â30 10â35 Additional Macronutrient Recommendations Macronutrient Recommendation Dietary cholesterol As low as possible while consuming a nutritionally adequate diet Trans fatty acids As low as possible while consuming a nutritionally adequate diet Saturated fatty acids As low as possible while consuming a nutritionally adequate diet Added sugars Limit to a maximal intake of no more than 25 percent total energyc a AMDR = Acceptable Macronutrient Distribution Range. This is the percent of energy intake that is associated with reduced risk of chronic disease, yet provides adequate amounts of essential nutrients. b Approximately 10 percent of the total can come from longer-chain n-3 or n-6 fatty acids. c Not a recommended intake. A daily intake of added sugars that individuals should aim for to achieve a healthful diet was not set.
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 71 MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY U nlike vitamins and minerals, fats, carbohydrates, and proteins can sub- stitute for one another to some extent in order to meet the bodyâs en- ergy needs. Thus, for a certain level of energy intake, increasing the proportion of one macronutrient necessitates decreasing the proportion of one or both of the other macronutrients. Acceptable ranges of intake for each of these energy sources were set based on a growing body of evidence that has shown that macronutrients play a role in the risk of chronic disease. These ranges, termed Acceptable Macronutrient Distribution Ranges (AMDRs), are defined as a range of intake for a particular energy source that is associated with reduced risk of chronic diseases (e.g., coronary heart disease [CHD], obesity, diabetes, and/or cancer) while providing adequate intakes of essential nutrients. These ranges are also based on adequate energy intake and physical activity to maintain energy balance. The AMDR of a macronutrient is expressed as a percentage of total energy intake because its requirement, in a classical sense, is not independent of other energy fuel sources or of the total energy requirement of the individual. Each must be expressed in terms relative to the other. A key feature of each AMDR is that it has a lower and upper boundary. If an individual consumes below or above this range, there is a po- tential for increasing risk of chronic diseases shown to affect long-term health, as well as increasing the risk of insufficient intakes of essential nutrients. For example, with regard to carbohydrate and fat, studies have shown a connection between low-fat and, therefore, high-carbohydrate diets and de- creased high density lipoprotein (HDL) cholesterol in the bloodstream, an indi- cator associated with increased risk of CHD. Conversely, diets too high in fat may result in increased energy and saturated fat intake, and therefore lead to increased risk of obesity and its complications, such as CHD. In this chapter, AMDRs for carbohydrate, fat, fatty acids (n-6 and n-3 poly- unsaturated), and protein are discussed. Recommendations for cholesterol, trans fatty acids, saturated fatty acids, and added sugars are also provided (see Table 1).
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 72 Finally, the chapter reviews the available data regarding the relationships between major chronic diseases that have been linked with consumption of dietary macronutrients (carbohydrate, fiber, fat, fatty acids, cholesterol, pro- tein, and amino acids) and physical activity. ACCEPTABLE MACRONUTRIENT DISTRIBUTION RANGES (AMDRs) Many causal relationships among over- or underconsumption of macronutri- ents, physical inactivity, and chronic disease have been proposed. When the diet is modified for one energy-yielding nutrient, it invariably changes the in- take of other nutrients, which makes it extremely difficult to have adequate substantiating evidence for providing clear and specific nutritional guidance. However, based on the evidence to suggest a role in chronic disease, as well as information to ensure sufficient intakes of other essential nutrients, Accept- able Macronutrient Distribution Ranges (AMDRs) have been established. An AMDR is defined as a range of intakes for a particular energy source that is associated with reduced risk of chronic disease while providing adequate in- takes of essential nutrients. The AMDR of a macronutrient is expressed as a percentage of total energy intake because its requirement is not independent of other energy fuel sources or of the total energy requirement of the individual. A key feature of each AMDR is that it has a lower and upper boundary. Intakes that fall above or below this range appear to increase the risk of chronic disease and may result in the inadequate consumption of essential nutrients. AMDRs have been set for carbohydrate, protein, fat, and n-6 and n-3 polyun- saturated fatty acids based on evidence from intervention trials, with support of epidemiological evidence. Recommendations have been made for limiting cho- lesterol, trans fatty acids, saturated fatty acids, and added sugars (see Table 1). An AMDR was not set for fiber or monounsaturated fatty acids. An AMDR was not set for fiber because it is an insignificant contributor to total energy intake; no known adverse effects associated with its consumption were avail- able. Monounsaturated fatty acids are not essential in the diet, and the evidence relating low and high intakes of monounsaturated fatty acids to chronic disease is limited. Practical limits on intakes of monounsaturated fatty acids will be imposed by AMDRs for total fat and other types of fatty acids. Total Fat and Carbohydrate BASIS FOR ADULT AMDRS FOR TOTAL FAT AND CARBOHYDRATE These AMDRs were estimated based on evidence indicating a risk for coronary heart disease (CHD) with diets high in carbohydrate and low in fat and on
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 73 evidence for increased risk for obesity and its complications (including CHD) at high intakes of fat. Intakes of low-fat, high-carbohydrate diets, compared with higher fat in- takes, can induce a lipoprotein pattern called the atherogenic lipoprotein phe- notype (characterized by high triglycerides, low HDL cholesterol, and small low density lipoprotein [LDL] cholesterol particles), which is associated with high risk of CHD, particularly in sedentary people who tend to be overweight. On the other hand, when fat intake is high, many individuals consume addi- tional energy, and therefore gain additional weight. Weight gain on high-fat diets can be detrimental to individuals already susceptible to obesity and can worsen the metabolic consequences of obesity, particularly the risk of CHD. Moreover, high-fat diets are usually accompanied by increased intakes of satu- rated fatty acids, which can raise LDL cholesterol levels, further increasing risk of CHD. Diets containing energy from fat and carbohydrate in the recommended ranges minimize the risks of diabetes, obesity, and CHD. In addition, these ranges allow adequate consumption of essential nutrients and moderate satu- rated fat intake. Diets containing less than the minimum AMDR for carbohy- drate are highly unlikely to meet the AI for fiber. BASIS FOR AMDRS FOR CHILDREN FOR TOTAL FAT AND CARBOHYDRATE The AMDR for carbohydrate for children is the same as for adults. Children have a higher fat oxidation rate than adults, and low-fat diets can lead to re- duced intake of certain micronutrients, including fat-soluble vitamins. Con- versely, high-fat intakes during childhood may set the stage for CHD and obe- sity, although the evidence for this is tenuous. Because the evidence is less clear on whether low- or high-fat intakes dur- ing childhood can lead to increased risk of chronic diseases later in life, the estimated AMDRs for children are primarily based on a transition from high-fat intakes during infancy to the lower adult AMDR. During childhood, the amount of saturated fat in the diet should be as low as possible without compromising nutritional adequacy. Protein BASIS FOR AMDR FOR CHILDREN AND ADULTS There is no evidence suggesting that the AMDR for protein should be at levels below the adult Recommended Dietary Allowance (RDA) for protein (see Part II, âProteinâ), which is about 10 percent of energy for adults. In addition, there were insufficient data to suggest a UL for protein (see Part II, âProteinâ) and insufficient data to suggest an upper range or boundary for an AMDR for pro-
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 74 tein. All of the AMDRs were set, in part, to complement the AMDRs for fat and carbohydrate. n-6 Polyunsaturated Fatty Acids BASIS FOR AMDR FOR CHILDREN AND ADULTS Based on usual median intakes of energy reported in the U.S. Continuing Sur- vey of Food Intakes by Individuals (CSFII 1994â1996, 1998), it is estimated that a lower boundary level of 5 percent of energy from linoleic acid would be needed to meet the Adequate Intake (AI) (see Part II, âDietary Fat: Total Fat and Fatty Acidsâ). The upper boundary for linoleic acid of 10 percent of energy intake is based on the following information: â¢ In North America, individual dietary intakes rarely exceed 10 percent of energy from linoleic acid. â¢ Epidemiological evidence for the safety of intakes greater than 10 per- cent of energy are generally lacking. â¢ High intakes of linoleic acid create a pro-oxidant state that may predis- pose to several chronic diseases, such as CHD and cancer. Human stud- ies demonstrate that enrichment of lipoproteins and cell membranes with n-6 polyunsaturated fatty acids contributes to a pro-oxidant state. n-3 Polyunsaturated Fatty Acids BASIS FOR AMDR FOR CHILDREN AND ADULTS Based on usual median intakes of energy report in CSFII (1994â1996, 1998), it is estimated that a lower boundary level of 0.6 percent of energy from a-linolenic acid would be needed to meet the AI (see Part II, âDietary Fat: Total Fat and Fatty Acidsâ). The upper boundary corresponds to the highest a-linolenic acid intakes from foods consumed by individuals in the United States and Canada. Data supporting the benefit of even higher intakes of a-linolenic acid were not considered strong enough to warrant an upper boundary greater than 1.2 percent of energy. A growing body of evidence suggests that higher intakes of a-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) may af- ford some degree of protection against CHD. However, it is impossible to esti- mate an AMDR for all n-3 fatty acids because the physiological potency of EPA and DHA is much greater than that of a-linolenic acid. Up to 10 percent of the AMDR for n-3 fatty acids can be consumed as EPA and/or DHA.
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 75 ADDITIONAL MACRONUTRIENT RECOMMENDATIONS Saturated Fatty Acids, Trans Fatty Acids, and Cholesterol BASIS FOR RECOMMENDATIONS There are no known risks of chronic disease associated with consuming diets very low in saturated fatty acids, trans fatty acids, or cholesterol. Since certain micronutrients are found mainly in animal foods (which are typically high in saturated fats and cholesterol), it is possible that diets low in saturated fat and cholesterol may contain low levels of micronutrients, such as iron and zinc. Furthermore, analysis of nutritionally adequate menus indicates that there is a minimum amount of saturated fat that can be consumed so that adequate levels of linoleic and a-linolenic acids are provided. A substantial body of evidence suggests that saturated fatty acids, trans fatty acids, and cholesterol raise blood total and LDL cholesterol levels, which in turn increases risk of CHD. Because there is a positive linear trend between intake of each of these fats and risk of CHD, even very low intakes of each may increase risk. It is thus recommended that intakes of saturated fatty acids, trans fatty acids, and cholesterol remain as low as possible while a nutritionally ad- equate diet is consumed. Added Sugars BASIS FOR RECOMMENDATIONS It has been shown the increasing intakes of added sugars can result in decreased intakes of certain micronutrients in United States subpopulations. This can oc- cur because of the abundance of added sugars in energy-dense, nutrient-poor foods in a diet. As such, it is suggested that adults and children consume no more than 25 percent of energy from added sugars to ensure sufficient con- sumption of essential micronutrients. Note that a daily intake of added sugars that individuals should aim for to achieve a healthy diet was not set. Foods containing added sugars and few micronutrients include soft drinks, fruit drinks, cakes, cookies, and candies. The impact of total sugar intake on the intake of micronutrients does not appear to be as great as for added sugars. Total sugars include both the added sugars and the naturally occurring sugars found in fruits, milk, and dairy products.
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 76 TABLE 2 Relationship of Macronutrients and Physical Activity to Chronic Disease Energy Fat Protein Cancer â¢ Animal studies â¢ High fat intakes have â¢ No clear role for total suggest that been implicated in protein has yet energy restriction development of certain emerged. may inhibit cell cancers, although proliferation and evidence is mixed. tumor growth. â¢ Epidemiological studies â¢ Increased childhood have shown an inverse energy intakes have relationship between fish been associated with consumption and risk of increased cancer breast and colorectal mortality. cancer, possibly due â¢ Excess energy to protective effects of contributes to n-3 fatty acids. obesity, which may increase risk of certain cancers. Heart Disease â¢ Excess energy â¢ Increased saturated fat â¢ Independent effects contributes to intake can increase total of protein on heart obesity, which and LDL blood disease mortality increases risk of cholesterol levels. have not been shown. heart disease. â¢ Increasing intakes of â¢ Soy-based protein trans fatty acids and may reduce blood cholesterol increase total cholesterol, but the and LDL blood cholesterol evidence is mixed. levels, although there is wide interindividual variation in serum cholesterol response to dietary cholesterol. â¢ Monounsaturated and polyunsaturated fatty acids decrease total and LDL blood cholesterol levels. â¢ High intakes of n-6 and n-3 polyunsaturated fats are associated with decreased risk of heart disease.
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 77 Carbohydrate Fiber Physical Activity â¢ Several case-control â¢ High fiber diets may â¢ Regular exercise has been studies have shown protect against colorectal negatively correlated with risk of increased risk of cancer, though the colon cancer. colorectal cancer in evidence is conflicting. â¢ Numerous epidemiological studies people with high intakes â¢ Fiber may protect suggest that regular physical of sugar-rich foods. against hormone-related activity decreases risk of breast â¢ High vegetable and fruit cancers including cancer. intake and avoidance of prostate, endometrial, â¢ Exercise may help compensate for foods with highly refined and ovarian cancer. potential cancer-promoting effects sugars have been â¢ Certain cereal foods may of excess energy intake. negatively correlated to protect against some â¢ Exercise may bolster the immune risk of colon cancer. types and stages of system. breast cancer. â¢ High carbohydrate (low â¢ Dietary fiber, particularly â¢ Numerous studies have shown fat) intakes tend to naturally occurring an inverse relationship between increase plasma viscous fiber, reduces exercise and heart disease triacylglycerol and decrease total and LDL cholesterol mortality. plasma HDL cholesterol levels. â¢ Regular exercise increases HDL levels. These effects are â¢ Reduced rates of heart cholesterol; decreases more extreme if the source disease have been triacylglycerol, blood pressure, is monosaccharides, observed in individuals and risk of cardiac arrhythmias; especially fructose. consuming high fiber enhances fibrinolysis, glucose diets. effectiveness, and insulin â¢ Dietary fiber intake has sensitivity; and lessens been shown to be platelet adherence. negatively associated with hypertension in men. continued
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 78 TABLE 2 Continued Energy Fat Protein Dental Caries Type II â¢ Excess energy â¢ Some studies show a Diabetes contributes to obesity, correlation between high Mellitus which may increase fat intakes and insulin risk of Type II diabetes. resistance, but it is not â¢ Obesity, particularly clear whether the abdominal obesity, is association is due to fat a risk factor for Type or to obesity. II diabetes. Obesity â¢ Excess energy intake â¢ Available data on whether â¢ Available data on causes obesity. diets high in total fat whether diets high in increase the risk for protein are associated obesity are conflicting; this with obesity are may be partly due to mixed: some have underreporting of food shown a positive intake, notably fat intake. association with protein intake and body fatness, others have demonstrated weight loss. Bone Health â¢ The relationship between protein intake and bone health is very controversial with some studies showing bone loss and osteoporosis in relationship to high intakes and others showing no association in the presence of adequate calcium intakes.
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 79 Carbohydrate Fiber Physical Activity â¢ Sugars play a role in development of dental caries (as do fluoride, oral hygiene and frequency of food intake). â¢ While there is little evidence â¢ Viscous soluble fibers â¢ Increased physical activity levels that total carbohydrate is may attenuate the insulin improve insulin sensitivity in associated with Type II response and thus protect people with Type II diabetes. diabetes, there may be against Type II diabetes. â¢ Physical activity can reduce increased risk when the risk of Type II diabetes and can glycemic index of a meal, reduce total and abdominal rather than total obesity, which are risk factors carbohydrate, is considered. for Type II diabetes. â¢ Published reports have â¢ Intervention studies â¢ Physical inactivity is a produced conflicting suggest that high fiber major risk factor for results about the existence diets may assist in weight development of of a direct link between loss, although evidence obesity. high sugar intakes and overall is mixed. obesity; this may be partly due to underreporting of food intake. â¢ Physical activity increases bone mass in children and adolescents and maintains bone mass in adults. â¢ Physical activity enhances muscle strength, coordination, and flexibility, which may prevent falls and fractures in elderly adults.
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 80 RELATIONSHIP TO CHRONIC DISEASE During the past 40 years, a growing body of evidence has accumulated regard- ing the risk of chronic disease and consumption of energy and the macronutri- ents, specifically dietary fats, carbohydrate, protein, and fiber. Because most diets are composed of a variety of foods that provide varying amounts of macro- nutrients, research to determine causal relationships is somewhat limited. Re- search linking chronic diseases with dietary macronutrients and physical activ- ity is summarized in Table 2.
MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY 81 KEY POINTS FOR MACRONUTRIENTS, HEALTHFUL DIETS, AND PHYSICAL ACTIVITY Fats, carbohydrates, and proteins can substitute for one 3 another to some extent to meet the bodyâs energy needs. Acceptable Macronutrient Distribution Ranges (AMDRs) were 3 set for some macronutrients based on evidence that consumption above or below these ranges may be associated with nutrient inadequacy and increased risk of developing chronic diseases, including coronary heart disease, obesity, diabetes, and/or cancer. An AMDR is defined as a range of intakes for a particular 3 energy source that is associated with reduced risk of chronic disease while providing adequate intakes of essential nutrients. The AMDR for a macronutrient is expressed as a percentage of 3 total energy intake because its requirement is not independent of other energy fuel sources or of the total energy requirement of the individual. To meet the bodyâs daily nutritional needs while minimizing risk 3 for chronic disease, adults should consume 45â65 percent of their total calories from carbohydrates, 20â35 percent from fat, and 10â35 percent from protein. The acceptable ranges for children are similar to those for adults, except that infants and younger children need a somewhat higher proportion of fat in their diets. These ranges may be more useful and flexible for dietary 3 planning than single values recommended in the past. AMDRs were not set for fiber or monounsaturated fatty acids. 3 Over- and underconsumption of macronutrients as well as 3 physical inactivity and energy imbalance have been linked to major chronic diseases such as cancer, obesity, coronary heart disease, dental caries, and Type II diabetes, and to skeletal health.