WASHINGTON--The National Academy of Sciences' (NAS) Institute of Medicine (IOM) released new recommendations Sept. 5 for macronutrients such as carbohydrates, proteins and fats, in addition to increasing the amount of daily exercise, to reduce chronic disease risk. The report, "Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients)," was commissioned by the Health and Human Services' Office of Disease Prevention and Health Promotion, in collaboration with Health Canada. This report serves to expand and replace the Recommended Dietary Allowances published in 1989. These new recommendations were created to help promote good health and prevent the possible ill effects of over-consuming these nutrients.
IOM reported that in order to meet the body's daily energy and nutrition needs while minimizing the incidence of disease, adults should aim at getting 45 percent to 65 percent of their calories from carbohydrates, 10 percent to 35 percent from protein, and 20 percent to 35 percent from fat. For young infants and children, the fat requirements are slightly higher, at 25 percent to 40 percent of total caloric intake. Earlier guidelines had suggested diets should contain 50 percent or more of carbohydrates and 30 percent or less of fat; protein intake remained the same for each set of recommendations.
"Studies show that when people eat very low levels of fat combined with very high levels of carbohydrates, high-density lipoprotein [HDL] concentration, or `good' cholesterol, decreases," said Joanne R. Lupton, Ph.D., the panel chair who is also a professor of nutrition at Texas A&M University, College Station. "Conversely, high-fat diets can lead to obesity and its complications if caloric intake is increased as well, which is often the case."
The food industry was quick to respond to the new recommendations. "The National Food Processors Association [NFPA] applauds . this report for its focus on providing sound, actionable nutrition recommendations for the foods industry, health professionals and policymakers," stated Robert Earl, MPH, R.D., senior director of nutrition policy at NFPA. "The report provides important information that can be used to develop food and nutrition policy to educate consumers on how to create healthful diets. Especially useful are the report's specific dietary intake recommendations for fatty acids, dietary fiber and essential fatty acids."
The recommendations for carbohydrates, protein, fat and future study are as follows:
Children and adults should consume at least 130 g/d of carbohydrates (175 g/d for pregnant women) in order to produce enough glucose for the brain to function properly. Carbs such as added sugars should comprise no more than 25 percent of total caloric intake; they are found in products such as candy, soft drinks and pastries. "The suggested maximum level stems from the evidence that people whose diets are high in added sugars have lower intakes of essential nutrients," according to a statement from the NAS press office.
Also, the report contains the first recommended intake levels for fiber. Studies IOM reviewed indicated an increased risk for heart disease for a person eating a low-fiber diet; fiber intake may also prevent colon cancer and even promote weight control.
However, IOM has fiber divided into two categories: "dietary" and "functional." According to IOM, dietary fiber is the edible, indigestible component of carbohydrates and lignin; functional fiber has similar benefits as dietary fiber, but has been isolated or extracted from natural sources, such as pectin from citrus peel, or are synthetic. The recommended daily intake (RDI) for fiber is 38 g/d for men and 25 g/d for women under age 50 for the greatest level of protection against coronary heart disease.
Protein and Amino Acids
Protein continues to stay at an RDI of 0.8 g/kg of body weight for adults. Recommended intake for amino acids includes leucine (55 mg/g of protein), leucine (55 mg/g of protein) and lysine (51 mg/g of protein).
Fat is necessary for aiding in the absorption of essential vitamins. However, diets high in saturated fat can raise low-density lipoprotein (LDL, or "bad") cholesterol levels. "Because saturated fat and cholesterol provide no known beneficial role in preventing chronic diseases, they are not required at any level in the diet," the NAS said in its statement, which also noted that the only AI for fat has been set at around 30 g/d for children younger than one who feed on breast milk and/or formula.
However, the report does set recommended intakes for certain essential fatty acids (EFAs). Because neither the omega-3 alpha-linoleic acid (ALA) or omega-6 linoleic acid (LA) is synthesized by the body, IOM established an adequate intake (AI) level for each. The AI for ALA is 1.6 g/d for men and 1.1 g/d for women, while the AI for LA is 17 g/d for men and 12 g/d for women.
For optimum cardiovascular health, IOM recommended one hour daily of moderately intense exercise for adults and children, regardless of weight. This was increased from the 1996 suggestion by the Surgeon General's office requiring 30 minutes per day. The new exercise recommendation is based on studies showing energy expenditure--whether as vacuuming or running--helps a person maintain a healthy weight.
Areas for Further Study
IOM recognized information gaps existed when putting the report together. For example, long-term, dose-response studies need to be conducted to identify the requirement of individual macronutrients for all life stages and gender groups. Also, researchers need to further understand the beneficial roles both dietary and functional fibers play in human health, as well as how the glycemic response factors into preventing chronic disease.
For a copy of the report, click here.