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Food Surveys Research Group, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Riverdale, MD 20737
2To whom correspondence and reprint requests should be addressed.
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ABSTRACT |
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 TOP ABSTRACT MATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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KEY WORDS: • inulin • oligofructose • humans • Continuing Survey of Food Intakes by Individuals • National Nutrition Monitoring and Related Research Program
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MATERIALS AND METHODS |
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TOPABSTRACTMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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The analyses presented here are based on data from the 1994–1996
Continuing Survey of Food Intakes by Individuals (CSFII). The CSFII is
conducted by the Agricultural Research Service of the USDA and forms an
integral part of the National Nutrition Monitoring and Related Research
Program (FASEB/LSRO 1995
). This survey is the 10th
nationwide food consumption survey conducted by the USDA since the
1930s. The objective of the survey was to measure the kinds and amounts
of food eaten by Americans. The survey comprised a nationally
representative sample of noninstitutionalized persons residing in the
United States. An independent sample was drawn for each year of data
collection and then combined for a 3-y sample of 16,103 individuals of
all ages. Data were weighted to make the estimates representative of
the U.S. population during the 3-y time period. National estimates were
produced by an estimation procedure that used sampling weights to
adjust the sample for variable probabilities of selection and
differential nonresponse. The procedure also calibrated the sample to
the national population along characteristics believed to be
determinants of food intake, including such factors as age, race,
ethnicity, income, employment status and day of the week.
Data were collected on all individuals by trained interviewers and included a variety of sociodemographic and household characteristic data in addition to an in-person, in the home, 24-h dietary recall for two nonconsecutive days for each individual. The two dietary recalls were spaced 3–10 d apart. The individual d 1 response rate was 80%, and 76% for d 2. The analytical sample for these analyses consisted of all respondents (excluding breast-fed infants) who provided 2 d of dietary data totaling 15,170 individuals of all ages.
Dietary data.
The dietary recall administered by interviewers in the Continuing
Survey included multiple passes to aid the respondent in remembering
everything they had eaten and drunk over the previous 24-h period. The
first pass was the quick list in which the respondent was asked to
report everything he or she ate or drank the previous day between
midnight and midnight in any way they wanted to recall. The second pass
comprised the detailed probes for descriptions and amounts. During this
pass, interviewers were required to use the USDA Food Instruction
Booklet, which provides standardized text to probe for details and
amounts of foods grouped into >100 food categories. The third and
final pass reviewed all foods eaten and probed for any additional foods
before the first eating occasion, after the last eating occasion and in
between all previously noted eating occasions. Further information
regarding the sampling, methodology, survey questionnaires and data
collection procedures are available in the CSFII Design and Operation
Report (Tippett and Cypel 1997
).
Three technical databases were used to code the food data collected in
the CSFII 1994–1996 and to calculate the nutritive values of those
foods. They are the Food Coding Database, the Recipe Database and the
Survey Nutrient Database. The Food Coding Database contains ~7300
unique food codes representing all of the foods reported in the survey.
The Recipe Database contains a recipe entry for each food code that
includes ingredient(s) and their amount(s), as well as information for
determining changes that may occur in nutrients during cooking. The
purpose of the Recipe Database is to provide information used to
generate the Survey Nutrient Database (Perloff et al. 1990
). The Survey Nutrient Database contains values for nearly
50 nutrients and dietary components for all foods reported in the
survey. However, values for the inulin and oligofructose content of
foods do not exist in the Survey Nutrient Database for the CSFII
1994–1996. Therefore, a special database was developed that contained
the content of inulin and oligofructose naturally occurring for each
food code in the CSFII 1994–1996.
Table 1 lists food sources of inulin and oligofructose eaten by Americans
that served as the basis for the specialized database. A range of upper
and lower concentration values of naturally occurring inulin and
oligofructose in grams per 100 g of each food are provided, based
on values reported by Van Loo et al. (1995)
. The average
of the range was calculated to determine the midpoint values. The food
sources include one fruit, eight vegetables and three cereal grains.
Bananas contain 0.5 g per 100 g each of inulin and
oligofructose. For vegetables, chicory root is the best source of these
components, providing 42 g of inulin and 23 g of
oligofructose per 100 g. Raw dandelion greens, dried garlic,
Jerusalem artichoke and dried onions have the next highest amounts
ranging from 13 to 28 g per 100 g of inulin and 11 to 13 g per 100 g of oligofructose. For cereal grains, wheat is the best
source, providing ~2.5 g/100 g of each component in raw bran and
baked flour.
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). Statistical analysis.
Estimates of inulin and oligofructose intake were calculated for all
individuals (excluding breast-fed infants) providing 2 d of
intake in CSFII 1994–1996 by using reported food intakes and the
special database for inulin and oligofructose. Analyses were performed
using SPSS-X (SPSS, Chicago, IL) and SUDAAN (Research Triangle
Institute, Research Triangle Park, NC) software, which are appropriate
for use with complex samples. ANOVA was used to test differences in
means between groups. The groups analyzed were defined by gender and
age, poverty category, origin and race, geographic region and month of
the first day of intake. The contribution of inulin and oligofructose
from food sources consumed was also calculated. Food sources were
categorized by 71 ARS-defined food groups used in the 1994–9696
CSFII (USDA 1998
).
Poverty category for each respondent was calculated as a ratio of a household's annual income to the poverty threshold appropriate for the household size and expressed as a percentage. The poverty thresholds are issued by the Bureau of the Census. Origin and race were used together to define each respondent's ethnic group. A respondent whose national origin was Mexican, Mexican American, Chicano, Puerto Rican, Cuban, or other Spanish/Hispanic was assigned to the "Hispanic" ethnic group. Race was used to assign the remaining respondents to the "white," "black" or "other" ethnic group. Due to the diverse composition of the "other" group, analyses were performed only on the Hispanic, white and black ethnic groups.
Region of the country was defined by the four census regions of the United States for the 1990 Census of the Population. The month of the first day of intake was used to define the season in which the intake occurred. Intakes reported during the months of January, February and March were classified as winter; April, May and June as spring; July, August and September as summer; and October, November and December as fall.
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RESULTS AND DISCUSSION |
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TOPABSTRACTMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Mean daily intakes of inulin and oligofructose by Americans are
provided in Table 2. Inulin and oligofructose intakes were estimated using the upper
and lower range values and the midpoint value of the inulin and
oligofructose content of foods. Results of analyses are discussed for
inulin and for oligofructose according to midpoint values for each
component. Mean intakes of inulin were almost identical to those of
oligofructose. American diets provided on average 2.6 g of inulin
and 2.5 g of oligofructose per individual per day. Mean intakes of
inulin and oligofructose differed across gender and age groups.
Children <6 y of age had the lowest intakes, and males 20–49 y of age
had the highest intakes, 1.3 and 3.4 g, respectively. For children
12 y of age, mean intake of inulin ranged from 1.3 to 2.2 g.
Mean intakes for males beginning in the teen years and adults 20–49 y
of age was ~3.4 g and decreased to 3.0 g for males 
50 y of
age. For females, mean intake for teens and adults 20–49 y old was
~2.3 g. Mean intake decreased to 2.1 g for females 50 y.
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Intakes by demographic categories.
The effects of various demographic variables on intakes of inulin and
oligofructose by Americans were determined. Table 3 provides the percentage of the population by demographic
categories during the period 1994 through 1996 when the Continuing
Survey of Food Intakes by Individuals was conducted. Whites, who make
up 73% of the U.S. population, consumed significantly more inulin and
oligofructose than blacks or Hispanics. Mean intakes by whites was
2.7 g of each component compared with 2.3 g for Hispanics and
~2.2 g for blacks as shown in Table 4.
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shows the effect of income as defined by poverty categories on
intakes of inulin and oligofructose. Mean intakes of both components
increased as income increased. Americans in the highest income category
consumed significantly more inulin and oligofructose that those in the
middle and lowest income categories, i.e., 2.8 g compared with 2.5
and 2.3 g, respectively.
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). The West was significantly lower than the Midwest. In the
1994–1996 CSFII, data were collected throughout the entire year; thus
season of the year is equally represented in reported food intakes.
Season did affect intakes of inulin and oligofructose. The lowest
intakes of these components was reported in summer, defined by the
months of July through September. For summer, mean intake of inulin and
oligofructose was 2.5 and 2.4 g, respectively (Table 7). Although intakes differed within categories of each of the
demographic variables analyzed, the actual differences were relatively
small.
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Figure 1
illustrates the contribution of food sources to inulin and
oligofructose in American diets. In terms of amounts of inulin and
oligofructose in foods, chicory root provided the most concentrated
source of these components. However, when consumption of food was
accounted for, wheat was the most important source of both components
in American diets followed by onions. Wheat and onions were consumed by
>90% of Americans on any given day in 1994–1996. Wheat contributed
69% of the inulin and 71% of the oligofructose. Onions contributed
~25% of each of these components.
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illustrates the types of foods Americans consumed that provided
wheat and onions. Food items were categorized by 71 ARS-defined
food groups used in the 1994–1996 CSFII. It is not surprising that
grain products contributed most of the wheat in American diets. Grain
products are a food group defined as items in which the grain portion
is the major ingredient but could also include other ingredients. For
example, items such as pizza or spaghetti with sauce were categorized
as grain products in addition to items such as breads and cereals. Meat
dishes, defined as items in which meat is the major ingredient,
contributed 12% of the wheat. These would include items such as a
hamburger on a bun and breaded and fried chicken. Onions were consumed
in American diets somewhat equally in vegetable dishes, meat dishes and
grain products.
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FOOTNOTES |
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REFERENCES |
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TOPABSTRACTMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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1. Federation of American Societies for Experimental Biology, Life Sciences Research Office (1995) Third Report on Nutrition Monitoring in the United States: Volume 1. U.S. Government Printing Office, Washington, DC.
2. Perloff B. P., Rizek R. L., Haytowitz D. B., Reid P. R. Dietary intake methodology II: USDA's nutrient database for nationwide dietary intake surveys. J. Nutr. 1990;120:1530-1534
3. Powers P. M., Hoover L.W. Calculating the nutrient composition of recipes with computers. J. Am. Diet. Assoc. 1989;89:224-232[Medline]
4. Tippett, K. S. & Cypel, Y. S. (1997) Design and Operation: The Continuing Survey of Food Intakes by Individuals and the Diet and Health Knowledge Survey, 1994–96: Nationwide Food Surveys Report No. 96–1. Agricultural Research Service, U.S. Department of Agriculture, Riverdale, MD.
5. U.S. Department of Agriculture, Agricultural Research Service. (1998) 1994–96 Continuing Survey of Food Intakes by Individuals and 1994–96 Diet and Health Knowledge Survey [CD-ROM, Accession No. PB98–500457]. National Technical Information Service, Springfield, VA.
6. Van Loo J., Coussement P., De Leenheer L., Hoebregs H., Smits G. On the presence of inulin and oligofructose as natural ingredients in the Western diet. Crit. Rev. Food Sci. Nutr. 1995;35:525-552[Medline]
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