IOM Issues Recommendations To Reduce Chronic Disease Risk

WASHINGTON--The National Academy of Sciences' (NAS) Instituteof Medicine (IOM) released new recommendations Sept. 5 for macronutrients suchas carbohydrates, proteins and fats, in addition to increasing the amount ofdaily exercise, to reduce chronic disease risk. The report, "DietaryReference 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 HealthCanada. This report serves to expand and replace the Recommended DietaryAllowances published in 1989. These new recommendations were created to helppromote good health and prevent the possible ill effects of over-consuming thesenutrients.

IOM reported that in order to meet the body's daily energy and nutritionneeds while minimizing the incidence of disease, adults should aim at getting 45percent to 65 percent of their calories from carbohydrates, 10 percent to 35percent from protein, and 20 percent to 35 percent from fat. For young infantsand children, the fat requirements are slightly higher, at 25 percent to 40percent of total caloric intake. Earlier guidelines had suggested diets shouldcontain 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 withvery high levels of carbohydrates, high-density lipoprotein [HDL] concentration,or `good' cholesterol, decreases," said Joanne R. Lupton, Ph.D., the panelchair who is also a professor of nutrition at Texas A&M University, CollegeStation. "Conversely, high-fat diets can lead to obesity and itscomplications if caloric intake is increased as well, which is often thecase."

The food industry was quick to respond to the new recommendations. "TheNational Food Processors Association [NFPA] applauds . this report for its focuson 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 importantinformation that can be used to develop food and nutrition policy to educateconsumers on how to create healthful diets. Especially useful are the report'sspecific dietary intake recommendations for fatty acids, dietary fiber andessential fatty acids."

The recommendations for carbohydrates, protein, fat and future study are asfollows:

Carbohydrates

Children and adults should consume at least 130 g/d of carbohydrates (175 g/dfor pregnant women) in order to produce enough glucose for the brain to functionproperly. Carbs such as added sugars should comprise no more than 25 percent oftotal caloric intake; they are found in products such as candy, soft drinks andpastries. "The suggested maximum level stems from the evidence that peoplewhose diets are high in added sugars have lower intakes of essentialnutrients," 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 personeating a low-fiber diet; fiber intake may also prevent colon cancer and evenpromote 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 similarbenefits as dietary fiber, but has been isolated or extracted from naturalsources, such as pectin from citrus peel, or are synthetic. The recommendeddaily intake (RDI) for fiber is 38 g/d for men and 25 g/d for women under age 50for 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

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 cholesterolprovide no known beneficial role in preventing chronic diseases, they are notrequired at any level in the diet," the NAS said in its statement, whichalso noted that the only AI for fat has been set at around 30 g/d for childrenyounger than one who feed on breast milk and/or formula.

However, the report does set recommended intakes for certain essential fattyacids (EFAs). Because neither the omega-3 alpha-linoleic acid (ALA) or omega-6linoleic acid (LA) is synthesized by the body, IOM established an adequateintake (AI) level for each. The AI for ALA is 1.6 g/d for men and 1.1 g/d forwomen, while the AI for LA is 17 g/d for men and 12 g/d for women.

Exercise

For optimum cardiovascular health, IOM recommended one hour daily ofmoderately intense exercise for adults and children, regardless of weight. Thiswas increased from the 1996 suggestion by the Surgeon General's office requiring30 minutes per day. The new exercise recommendation is based on studies showingenergy expenditure--whether as vacuuming or running--helps a person maintain ahealthy weight.

Areas for Further Study

IOM recognized information gaps existed when putting the report together. Forexample, long-term, dose-response studies need to be conducted to identify therequirement of individual macronutrients for all life stages and gender groups.Also, researchers need to further understand the beneficial roles both dietaryand functional fibers play in human health, as well as how the glycemic responsefactors into preventing chronic disease.