Balancing Macronutrients

July 2001

Finding a sound balance between carbohydrates, protein and fat in the diet seems to be the topic of many books on the market today. Consumers are wondering whether to eat based on protein, blood-sugar levels or the volume of food. And while some recommendations shun fat altogether, others encourage its intake. Consumer confusion at the bookstore continues into the grocery store.

The skinny on diets
According to a recent USDA report on popular diets, many diets may help people shed pounds initially, but only traditional moderate-fat, high-carbohydrate programs seem to help maintain long-term weight loss. The report found that diet plans backed by science, such as the American Heart Association (AHA) diet, encourage consumption of no more than 30% of the calories from fat, protein intake averaging 20% of the diet, and more complex carbohydrate consumption with foods such as whole grains and grain products, legumes, and some vegetables and fruits. The study uncovered that plans following the USDA Food Guide Pyramid are the most nutritionally adequate and boast some of the best improvements in blood-cholesterol and glucose levels. They found less evidence to back low-carbohydrate or very low-fat plans.

The researchers compared various diets to the healthy eating index (HEI) based on the Continuing Survey of Food Intake by Individuals (CSFII) 1994-1996. The overall diet quality, as measured by the HEI, was highest for the high-carbohydrate (greater than 55% of energy) pyramid group — individuals consuming 30% or less of their energy from fat and eating at least one serving from each of the five groups from the USDA Food Guide Pyramid (Journal of the American Dietetic Association, April 2001). Body Mass Index (BMI) levels were significantly lower for men and women on the high-carbohydrate diet, while the highest BMIs were found for those on a low-carbohydrate diet.

Carbohydrate commotion
Carbohydrates seem to be taking the most heat in the ongoing diet frenzy. While some suggest a ban on anything white (white flour, white sugar, white rice and pasta), other authors maintain eating too much carbohydrate may lead to fat gain. Although, for some, consuming a high-carbohydrate diet (55% or more of calories from carbohydrates) consistently for many years may promote high blood-triglyceride levels and possibly high blood-sugar levels, this appears to be based on each individual. Those predisposed to these conditions may benefit from slightly decreasing carbohydrate intake while incorporating more monounsaturated fats into the diet — patterned after the Mediterranean diet, which is high in monounsaturated fats.

The type of carbohydrate also greatly affects overall diet quality. The AHA’s updated 2000 Dietary Guidelines for Americans recommends choosing a variety of grains daily, especially whole grains; choosing a variety of fruits and vegetables daily; and choosing beverages and foods to moderate sugar intake. Eating primarily whole grains and whole-grain products, legumes, vegetables, fruits and nonfat/lowfat milk products improves nutrient intake and enhances satiety.

Protein percentage
The Recommended Dietary Allowance (RDA) of protein is 0.8 grams of protein per kilogram body weight. This generally accounts for 10% to 20% of the total intake. Athletes may require up to two times that amount, but the average person’s needs are more in line with the RDA.

Although many Americans consume more protein than they need, many older adults may not be taking in enough due to chewing problems, ill-fitting dentures, anorexia or the inability to prepare meals. In addition, protein needs increase for adults over age 50, as people may utilize protein less efficiently as they age. They may benefit from 1.00 to 1.25 grams of protein per kilogram body weight. Easy-to-chew and -prepare protein sources, such as eggs and egg substitutes, soft meats cut into small pieces, nut butters, fish, legumes, dairy products, and protein-enriched drinks and mixes are possible areas for future development.

But going overboard on protein is not warranted. According to a statement made by the AHA, “There is, at present, no scientific evidence to support the concepts that high-protein diets result in sustained weight loss, significant changes in metabolism or improved health. Most Americans consume protein in excess of their needs.”

Fear of fat
The AHA’s 2000 revision of its Dietary Guidelines recommends a fat intake of less than 30% of total energy to assist in limiting consumption of total energy as well as saturated fat. In addition, AHA population-wide recommendations include limiting saturated fat to less than 10% of energy and cholesterol to less than 300 mg per day. Polyunsaturated fats should be limited to less than 10% of calories, with monounsaturated fats making up 10% to 15% of energy intake.

The AHA does not recommend very low-fat diets for the general population, stating weight loss may not be sustained and these diets may lead to nutritional deficiencies of essential fatty acids. In addition, the AHA notes that low-fat foods are often very calorie-dense, and that a low-fat diet might amplify low HDL cholesterol, high triglycerides and high insulin levels.

Consumers are searching for ways to replace saturated fats with monounsaturated fats in their diet. Helping consumers find practical ways to consume more flax, nuts and nut oils; olive and canola oil; seeds; and fatty fish, such as tuna, salmon, mackerel and sardines may present areas for new food products.

Finding a balance
Current research teamed with national recommendations for health point to a macronutrient mix of 50% to 60% carbohydrate (focusing on complex carbohydrates), 10% to 20% protein and 20% to 30% fat intake. Although personal medical conditions, age and activity levels may require modification to these recommendations, they are prudent for the general population.

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