Rethinking the Acceptable Macronutrient Distribution Range for the 21st Century: A Letter Report (2024)
Chapter: 3 Description of the Acceptable Macronutrient Distribution Range
3
Description of the Acceptable Macronutrient Distribution Range
DEVELOPMENT OF THE DIETARY REFERENCE INTAKES
A Paradigm Shift from RDAs to DRIs
In 1993 the National Academies’ Food and Nutrition Board held a symposium and public hearing to explore how the Recommended Dietary Allowances (RDAs) should be revised. The symposium discussants considered expanding the RDA model in a way that would unite the concepts of a healthful diet to reduce risk of chronic disease with intakes that meet essential nutrient requirements (IOM, 1994). At that time, under the existing RDA paradigm, carbohydrate was determined to have no absolute dietary requirement (NRC, 1989). The expert panel for the 1989 RDAs recognized that amino acids and fatty acids could be used for energy, thus, intake recommendations were based on avoidance of ketosis. Because of its caloric contribution to the diet, albeit in the absence of data to support the supposition, fat intake was recommended at amounts not to exceed 30 percent of dietary energy. Additionally, due to an adequacy requirement for protein, an RDA was set for this macronutrient (NRC, 1989).
Beginning in 1995, the RDA nutrients were reviewed by nutrient groupings and developed into the Dietary Reference Intakes (DRIs). This new paradigm established a set of quantitative reference values for nutrient intakes that were bounded by an Estimated Average Requirement (EAR) and a Tolerable Upper Intake Level (UL). The paradigm introduced the concept of a safe and adequate intake range and included recommendations for a variety of applications beyond the single intake value represented by the RDAs (Figure 3-1).
NOTES: The Estimated Average Requirement (EAR) is the intake at which the risk of inadequacy is 0.5 (50 percent) for an individual. The Recommended Dietary Allowance (RDA) is the intake at which the risk of inadequacy is very small—only 0.02 to 0.03 (2 to 3 percent). The Adequate Intake (AI) (not shown) does not bear a consistent relationship to the EAR or the RDA because it is set without the estimate of the requirement. At intakes between the RDA and the Tolerable Upper Intake Level (UL), the risks of inadequacy and of excess are both close to zero. At intakes above the UL, the risk of adverse effects may increase.
SOURCE: IOM, 2006.
In the DRI paradigm, EARs and RDAs were set for carbohydrate, based on glucose use by the brain, and for protein, based on meta-analyses of nitrogen balance studies (IOM, 2002/2005). Based on a lack of evidence for a dietary requirement, no EARs or RDAs were set for fat, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), or cholesterol.
Introduction of the Acceptable Macronutrient Intake Range
To address the need for intake guidance for macronutrients, based on evidence that fat and carbohydrate play a role in chronic disease along with the recognized need for sufficient intake of essential amino acids, fatty acids, and micronutrients, the study committee on DRIs for macronutrients proposed an intake range for nutrients that are sources of energy: the Acceptable Macronutrient Distribution Range (AMDR) (IOM, 2002/2005). AMDR values were set for carbohydrate, fat, omega-6 and omega-3 polyunsaturated fatty acids, and protein. For these nutrients, recommended intakes were presented as a percentage of total energy intake by age group. Table 3-1 shows the AMDRs by age group, independent of sex. The supposition was that intakes above the AMDR increase the
TABLE 3-1 Acceptable Macronutrient Distribution Ranges (AMDRs) by Age Group
| Macronutrient | AMDR (as percent of energy) | ||
|---|---|---|---|
| Children 1–3 years | Children 4–18 years | Adults | |
| Fat | 30–40 | 25–35 | 20–35 |
| n-6 polyunsaturated fatty acids (linoleic acid)a | 5–10 | 5–10 | 5–10 |
| n-3 polyunsaturated fatty acids (α-linolenic acid)a | 0.6–1.2 | 0.6–1.2 | 0.6–1.2 |
| Carbohydrate | 45–65 | 45–65 | 45–65 |
| Protein | 5–20 | 10–30 | 10–35 |
a Approximately 10 percent of the total can come from longer-chain n-3 or n-6 fatty acids. The lower boundary of the AMDR for both linoleic and α-linolenic acid are based on the Adequate Intake (AI) values for these fatty acids.
SOURCE: IOM, 2002/2005.
risk of chronic disease while intakes outside the range increase the risk of nutrient insufficiency. The relationship between the AMDRs and nutrient intake was assessed by reviewing median intakes from population survey data at different macronutrient composition levels.
The evidence base for the AMDRs included intervention trials and observational data suggesting a role in either prevention of chronic disease risk or adequacy of essential micronutrients associated with intake amounts. This yielded estimates based on the committee’s interpretation of the published literature identified at the time.
APPLICATION OF THE AMDRs IN DIETARY PLANNING AND ASSESSMENT
Consistent with other DRI values, the report on DRIs for macronutrients included guidance for applying the AMDRs to help users in planning and assessing dietary intakes of individuals and groups (IOM, 2002/2005). To plan intakes for individuals, the report noted that diets should be designed so that intakes of carbohydrate, total fat, n-3 (α-linolenic acid) and n-6 polyunsaturated fatty acids, and protein are within their respective AMDRs, while, at the same time, intakes of macronutrients also meet the RDA or Adequate Intake (AI) and remain below the UL for these macronutrients (IOM, 2002/2005).
In dietary planning for groups, the report on DRIs for macronutrients proposed that one method to achieve a low prevalence of intake outside the AMDR is to develop menus and meal patterns that exemplify mean
intakes for the group at the midpoint of each of the AMDRs. Another method that could be applied is to plan a dietary pattern in which the mean intake from fat is set at 30 percent of total energy intake (i.e., higher than the midpoint of the AMDR). Post-implementation assessment may show a low prevalence of fat intakes outside the AMDR, even though mean fat intake is higher than the midpoint of the range. This suggests applying the AMDR as a general quantitative guideline for planning and assessing diets. Nevertheless, qualitative considerations (e.g., a menu low in saturated fats) remain an important consideration (IOM, 2002/2005).
The report The Essential Guide to Dietary Reference Intakes (IOM, 2006) summarized the guidance from the DRI report on macronutrients but added that when assessing intakes of individuals, observed mean intakes that fall between the lower and upper bounds of the AMDR may be within the acceptable range. However, observed mean intakes that fall below or above the AMDR may indicate concern for potential adverse consequences (IOM, 2006). Thus, an additional goal when planning for groups is to aim for a macronutrient distribution in which the intakes of most of the group fall within the AMDRs (IOM, 2006).
SUMMARY
The AMDR was established to provide health professionals with guidance on using a range of intakes for energy-containing macronutrients (i.e., carbohydrate, protein, and fat) associated with both micronutrient intake adequacy and decreased risk of chronic disease. To achieve this goal, an intake range based on the percent of total calories was established.
