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U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Food Surveys Research Group, Beltsville, Maryland (L.E.C., A.J.M., J.D.G.)
Bell Institute of Health and Nutrition, General Mills, Inc., Minneapolis, Minnesota (A.M.A.)
Address reprint requests to: Linda E. Cleveland, MS, RD, U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Food Surveys Research Group, 10300 Baltimore Ave, Bldg 005, Rm 102, BARC-West, Beltsville, MD 20705
| ABSTRACT |
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Methods: Data were collected from 9,323 individuals age 20 years and older in USDAs 199496 Continuing Survey of Food Intakes by Individuals through in-person interviews on two non-consecutive days using a multiple-pass 24-hour recall method. Foods reported by respondents were quantified in servings as defined by the Food Guide Pyramid using a new database developed by the USDA. Whole-grain and nonwhole-grain servings were determined based on the proportion, by weight, of the grain ingredients in each food that were whole grain and nonwhole grain. Sampling weights were applied to provide national probability estimates adjusted for differential rates of selection and nonresponse. Then, t tests were used to assess statistically significant differences in intakes of nutrients and food groups by whole-grain consumers and nonconsumers.
Results: According to the 199496 survey, U.S. adults consumed an average of 6.7 servings of grain products per day; 1.0 serving was whole grain. Thirty-six percent averaged less than one whole-grain serving per day based on two days of intake data, and only eight percent met the recommendation to eat at least three servings per day. Yeast breads and breakfast cereals each provided almost one-third of the whole-grain servings, grain-based snacks provided about one-fifth, and less than one-tenth came from quick breads, pasta, rice, cakes, cookies, pies, pastries and miscellaneous grains. Whole-grain consumers had significantly better nutrient profiles than nonconsumers, including higher intakes of vitamins and minerals as percentages of 1989 Recommended Dietary Allowances and as nutrients per 1000 kilocalories, and lower intakes of total fat, saturated fat and added sugars as percentages of food energy. Consumers were significantly more likely than nonconsumers to meet Pyramid recommendations for the grain, fruit and dairy food groups.
Conclusion: Consumption of whole-grain foods by U.S. adults falls well below the recommended level. A large proportion of the population could benefit from eating more whole grain, and efforts are needed to encourage consumption.
Key words: whole grain, food consumption, nutrient intake, United States, dietary survey, Food Guide Pyramid, database
| INTRODUCTION |
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Over the past 20 years, major governmental, scientific and nonprofit organizations have recommended whole grains as part of a healthful diet. Currently, increased whole-grain consumption is recommended by the U.S. Department of Agriculture (USDA) and U.S. Department of Health and Human Services (DHHS) in the publication Nutrition and Your Health: Dietary Guidelines for Americans [13], which provides the basis for Federal nutrition policy. Increased consumption is also recommended in The Surgeon Generals Report on Nutrition and Health [14] and the National Research Councils Recommended Dietary Allowances [15] and Diet and Health: Implications for Reducing Chronic Disease Risk [16]. In addition, the American Cancer Society [17] and the American Dietetic Association [18] support increased intake. Grain foods form the base of The Food Guide Pyramid, which recommends consuming six to eleven servings each day, including "several" whole-grain servings [19,20].
A number of recent initiatives indicate broad interest in promoting greater whole-grain consumption. At a 1993 conference entitled Narrowing the Whole Grain Gap: How Much and Why?, the USDA and the American Dietetic Association jointly proposed the message "3 Are Key" to specifically quantify guidance on the number of servings of whole grains to eat daily [21]. In July 1999, the Food and Drug Administration approved a health claim for use on food labels of products that contain at least 51 percent whole grain by weight and are low in total fat, saturated fat and cholesterol [22]. The claim reads, "Diets rich in whole-grain foods and other plant foods and low in total fat, saturated fat, and cholesterol may reduce the risk of heart disease and some cancers." It is intended to help consumers identify whole-grain foods and encourage consumption by describing relationships between whole grains and disease prevention. In January 2000, new national nutrition objectives for the Year 2010 were released by the DHHS. For the first time, an objective was included that targeted whole-grain intake. It states, "Increase the proportion of persons aged 2 and older who consume at least 6 daily servings of grain products, with at least 3 being whole grains" [23]. To track progress on this objective, data will be monitored on the percentage of selected populations consuming six or more grain servings daily, the percentage consuming three or more whole-grain servings daily and the percentage meeting the dual goals simultaneously.
Despite long standing and general agreement that the population would benefit significantly from increased consumption of whole-grain foods, little is known about how much people actually eat. The evidence that is available suggests that consumption is well below desired levels. Albertson and Tobelmann reported that the average number of eating occasions of whole-grain products by adults was 0.5 per day based on data collected in 1990 and 1992 [24]. Survey participants in their study recorded foods consumed, but not quantities, so an eating occasion was not necessarily synonymous with a serving as defined by the Food Guide Pyramid. However, less than two percent reported two or more daily eating occasions of whole-grain products, and 23 percent consumed no whole grain over the 14-day data collection period.
More recently the USDA developed a database for use in converting food intake data from its 199496 Continuing Survey of Food Intakes by Individuals into Pyramid servings. This database represents a significant advance in providing the ability to estimate whole-grain intake and compare intake to recommendations. The purpose of this study is to present national estimates of whole-grain intake, identify major dietary sources of whole grains and compare food and nutrient intakes of whole-grain consumers and nonconsumers using the new USDA Pyramid Servings Data Set [25].
| MATERIALS AND METHODS |
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Data Collection
Dietary intakes were collected by trained interviewers in respondents homes on two non-consecutive days using a 24-hour multiple-pass recall method. The survey design called for separating the day 1 and day 2 interviews by three to ten days and conducting each on a different day of the week. Interviewers used standardized probes to obtain complete descriptions of types and amounts of foods eaten by respondents. For example, for bread, respondents were asked, "Was it white, rye, whole wheat, pumpernickel, multigrain, garlic, or something else?" Respondents who said the bread was whole wheat were asked to check the food label and answer the question, "Was that 100% whole wheat?" For ready-to-eat cereals, pancakes, breakfast bars, granola bars, corn chips, crackers, and pretzels, respondents were asked, "What was the brand?" Interviewers also probed for information on ingredients in foods such as soups, mixed dishes, casseroles, tacos, enchiladas, fajitas, sandwiches and salads. These standardized probes made it possible to assign each reported food to a food code and associated recipe that represented the proportion of whole-grain ingredients it contained. When a food contained some whole grain and some nonwhole grain ingredients, the recipe could be used to determine the fraction of the grain servings from each. The food coding database for CSFII 199496 contains 7,352 food codes. It links foods to their nutritive values via a recipe database intended to be representative of foods eaten in the United States.
Method for Determining Grain Servings
For this study, foods reported in the survey were quantified in servings as defined by the Food Guide Pyramid using the Pyramid Servings Database that was first released by USDA for public use in 1997 [27,28]. To develop the database, food mixtures were separated into ingredients when necessary before categorizing foods into groups, and foods were categorized strictly according to Pyramid criteria. The database contains reference data for each food reported in the CSFII 199496 on servings per 100 grams from 30 Pyramid food groups and subgroups. Of the 30 groups, three are grain groups: total grain, whole grain, and nonwhole grain. For this study, grain servings were further identified according to the type of grain product from which they were derived: yeast bread; quick bread; breakfast cereal; pasta, rice; grain desserts such as cookies, cakes, pies; grain snacks such as crackers, chips, popcorn; and miscellaneous grains such as flour in gravies.
Definitions of grain serving sizes were derived from The Food Guide Pyramid and publications that describe its application. Operational definitions were developed based on the Pyramids consumer-oriented descriptions to determine gram weights for servings by using standardized procedures. A grain serving was defined as one slice of bread; 1/2 of an English muffin, bagel or croissant; one small roll, biscuit or muffin; and 1/2 cup of cooked cereal, rice or pasta. For these foods, the CSFII 199496 food coding database was the source for gram weights of servings. For ready-to-eat breakfast cereals, a serving was defined as one ounce as specified by the Pyramid, but the weight of ingredients such as dried fruits, nuts, seeds, sugar and fat that the Pyramid categorizes in food groups other than the grain group were excluded from the determination of grain servings.
For foods for which the Pyramid does not list serving sizes, serving weights were determined based on the grain content of the food. This method was used to derive serving weights for many snack-type grain products, grain-based desserts, some quick breads and miscellaneous grains used in batters, breading and thickeners. A grain serving was defined as the grams of grain product containing 16 grams of flourthe amount in a standard slice of commercial white bread.
Tabulating Servings of Whole Grains from Grain Products
USDA food specialists classified all grain ingredients used in the CSFII 199496 recipe database as whole grain or nonwhole grain. Table 1 presents a list of ingredients that were classified as whole grain. Some grain ingredients, including oat bran and wheat bran, which are not strictly whole grain, were classified as such if they had a high fiber content because a major objective of whole-grain recommendations has focused on promoting adequate fiber consumption.
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For the Pyramid Servings Database, whole-grain servings from grain foods were calculated using the following method. First, for each such food reported in CSFII 199496, the total number of grain servings per 100 grams was determined. Then, this total was divided into whole-grain and nonwhole-grain servings based on the proportion of the grain ingredients by weight that were whole grain and nonwhole grain. For example, 100 grams of cracked wheat bread provides four grain servings. The bread contains three grain ingredients: white-wheat flour which was classified as a nonwhole grain, and whole-wheat flour and wheat bran which were classified as whole grains. White-wheat flour contributes 67 percent of the total grain ingredient weight and whole-wheat flour and wheat bran together contribute 33 percent. Thus, 100 grams of cracked wheat bread provides 2.7 nonwhole-grain servings (4 x .67), and 1.3 whole-grain servings (4 x .33).
Statistical Analysis
Sample weights were applied to the data to provide national probability estimates adjusted for differential rates of selection and nonresponse. The sampling weights calibrate the sample so that it matches the U.S. population for characteristics thought to be correlated with eating behavior, including age, race, ethnicity, income, household composition, region, urbanization, day of the week and season of the year. t tests were used to test for statistically significant differences in food and nutrient intakes of whole-grain consumers and nonconsumers, and to test the significance of differences in percentages of individuals consuming whole grains within categories of demographic and personal characteristics. In testing for differences in food and nutrient intakes, comparisons were made only between those who consumed no whole grain and those who consumed some whole grain. However, the findings should hold for comparisons between those who consumed no whole grain and those who consumed three or more whole-grain servings per day as well. All statistical analyses were done with SUDAAN software, which is appropriate for weighted data from complex samples [29].
| RESULTS |
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.01). Percentages meeting recommendations were about three-fold higher for those who consumed three or more whole-grain servings per day compared to those who consumed none.
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| DISCUSSION |
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Differences in nutrient intakes of those who meet versus those who do not meet the recommendation can be accounted for, at least in part, by the nutrient contribution of whole-grain foods themselves. Whole grains are higher than nonwhole grains in a number of micronutrients, including vitamin E, vitamin B6, folate, magnesium, zinc and copper, and some whole-grain foods, notably breakfast cereals, are fortified as well. However, differences in nutrient intakes may also result from a more health-conscious approach to dietary choices in general by whole-grain consumers. This conclusion is consistent with results showing that whole-grain consumers are more likely than nonconsumers to meet Pyramid recommendations for several food groups and to consume a lower percent of calories from fat and added sugars. They exhibit other health conscious behaviors as well. They are less likely to smoke or to be overweight and more likely to exercise and take dietary supplements. Although the research base for developing the Pyramid indicates that the nutrient profile of whole grains is superior to that of nonwhole grains [30], additional research is needed to determine the specific contributions of whole-grain foods to nutrient intake, including micronutrients and other compounds not included in the data set that are known to exist in whole-grain foods. Questions remain about how much of the improved nutrient profile relates to whole-grain food choices themselves and how much relates to other differences in food choices of whole-grain consumers compared to nonconsumers.
Nonetheless, it seems clear that a large proportion of the population could benefit from eating more whole grain, and efforts are needed to encourage consumption. Consumer awareness of health benefits of whole grains may be limited. Until recently, the only health messages on whole-grain products were fiber-content claims, so one might expect consumer understanding of their health benefits, beyond fiber content, to be limited. In a recent consumer market research study, approximately 25 percent of respondents said they were making a strong effort to eat whole grains [31]. Of these, over 66 percent were also making a strong effort to eat foods high in fiber. In the market research, demographic groups that reported the strongest effort to consume whole grains were generally the same as those with higher consumption levels in the present study. They were older, more likely to be white and had higher education and incomes than individuals less inclined to consume whole grains. New health messages, beyond those on fiber content, are likely to increase interest in whole-grain foods. Continued research on the positive effects of whole grain in the diet on various chronic disease conditions will also help strengthen and sustain the message.
Current efforts to encourage Americans to increase whole-grain consumption, such as the FDAs recently approved health claim for use on food packages, should help consumers identify whole-grain foods and recognize their health benefits. This along with advice from other governmental agencies should help solidify the message in the minds of consumers. Several manufacturers have already adopted the FDA health claim on their food packages. Past campaigns, such as those on fruit and vegetable intake and cancer [32], fiber intake and cancer [33], and fat reduction and blood cholesterol [34] have demonstrated that consumers are responsive to positive diet and health messages that are clear, actionable and sustained.
One of the major hurdles for some whole-grain foods is consumer perception of inferior taste and texture compared to those that are more highly refined. These present a challenge to the food industry to continue to explore new ways of making whole grain in the food supply more acceptable to consumers both as the dominant ingredient and as secondary ingredients. Additional hurdles to higher consumption include issues of availability, variety, price and preparation. With the majority of whole grain consumed as breads and breakfast cereals, there is clearly an opportunity for increased availability of good tasting, convenient whole-grain snack foods as well as main course offerings.
If appealing whole-grain products are made widely available and easily identifiable, and their health benefits are promoted, consumption by the U.S. population may begin to approach the goal of three servings per day. The next national survey of what Americans eat, scheduled for early in the new millennium, will provide the means of assessing progress towards this goal.
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