The U.S. Department of Agriculture implements an array of

domestic Food Assistance and Nutrition Programs as a “food

safety net” to provide low-income households with access to a

healthy diet. Assessment of nutrient intakes helps determine

which nutrients are deficient in the diets of target populations.

The Nutrition and Health Characteristics of Low-Income

Populations study examined longrun average, or “usual” intakes

of 10 key nutrients and dietary components: energy intake, vitamin C, iron, zinc, calcium, total fat, saturated fat, cholesterol,

sodium, and fiber. Results were estimated for participants in the

Special Supplemental Nutrition Program for Women, Infants and

Children (WIC), Food Stamp Program (FSP) participants,

school-age children, and older adults. In addition to assessing

intake adequacy, the study also estimated usual intake distributions for the population subgroups. Because the recommendations for nutrient intake have been under revision, intake distributions are useful for estimating the prevalence of adequate

intake under different standards. The study provides a baseline

from which to monitor the nutrition and health characteristics of

each group over time and to identify priorities for further

research.

Methodology

The study used data from the 1988-94 National Health and

Nutrition Examination Survey (NHANES-III), applying assessment methodology and Dietary Reference Intakes (DRIs) published by the Institute of Medicine (IOM). The IOM methodology corrects several sources of bias in previous estimates of nutrient adequacy. The study estimated distributions of usual nutrient

intakes for all nutrients. Usual intake has a lower variance than

1-day intakes or averages over a small number of days because

the usual intake measure excludes the day-to-day variation within individuals’ daily intakes and includes only variation among

individuals. Thus, the percentage of individuals falling below a

cutoff point (for cutoffs below the mean) is generally lower for

usual intakes than for observed intakes or for 2-day averages as

used in previous studies.

The estimation of usual intake requires multiple intake days in

order to calculate the day-to-day variance for each individual.

Because NHANES collected 2 days of data from only a small

nonrandom subsample, the day-to-day variances were obtained

using the 2-day recall data from USDA’s 1994-96 Continuing

Survey of Food Intakes by Individuals.

The study assessed nutrient adequacy using the Dietary

Reference Intakes (DRIs) released starting in 1997 by the

Institute of Medicine (IOM, various issues). The DRIs are a set

of standards, including the Recommended Daily Allowances

(RDAs), Estimated Average Requirements (EARs), Adequate

Intakes (AIs), and Tolerable Upper Levels (ULs) of intakes.

RDAs represent levels expected to be adequate for 97-98 percent

of the population and are for assessing individual intakes. EARs

are the levels considered adequate for half the population and for

assessing intakes of population groups. For some nutrients with

insufficient data, IOM published AIs, which are based on experimental data or observed intake of an apparently healthy population. Finally, the DRIs include ULs, the highest level of continuing daily nutrient intake that is likely to pose no risk of adverse

health effects in almost all individuals in the specified life stage

group. 

The prevalences of adequate intake for vitamin C, zinc, and iron

were calculated by the percentage of the population with usual

intakes above the EARs. For females ages 9-50, the study used

more detailed tables by IOM on the risk of inadequacy at each

level of intake to account for the asymmetrical distribution of iron

requirements due to menstruation. Because the IOM could not

establish an EAR for calcium, the study compared mean calcium

intake with the AI. Mean intake above the AI is interpreted as a

high prevalence of adequate intake, but the prevalence of inadequate intake cannot be quantified when mean intake is below the AI. 

When the study was conducted, DRIs for energy, total fat,

saturated fat, cholesterol, sodium, and fiber had not been issued.

Earlier dietary recommendations were used to assess the intake

of total fat, saturated fat, cholesterol, fiber, and sodium. For

energy, the study compared mean intake with the 1989 Recommended Energy Allowance (REA). Since the completion of the

study, the IOM has also issued new recommendations for energy,

fat, fiber, and sodium.

United States

Department of

Agriculture

Economic 

Research

Service

Agriculture Information Bulletin 796-2 February 2005

Nutrition and Health Characteristics of

Low-Income Populations

Usual Nutrient Intakes

Katherine Ralston, (202) 694-5463, kralston@ers.usda.gov
Vitamin C, Iron, Zinc, and Calcium

Food Stamp Participants. The U.S. population was separated for

study purposes into FSP participants and nonparticipants. The

FSP income eligibility cutoff (130 percent of poverty level) was

used to separate nonparticipants into income-eligible and higher

income nonparticipants. By incorporating gender and age, a total

of 72 population subgroups were created in the study.

The prevalence of adequate intake of vitamin C was 95 percent

or higher for almost all population subgroups through age 13,

but was lower for older children and adults (fig. 1). Male Food

Stamp Program (FSP) participants were more likely than

income-eligible nonparticipants to have adequate vitamin C

intake, but for females, the reverse was true. Food stamp participants were less likely than income-eligible nonparticipants to

consume adequate zinc, largely due to differences among 9- to

13-year olds and 31- to 50-year-olds.

Over 95 percent of males in all age groups consumed adequate

iron, regardless of food stamp status. Among 14- to 18-year-olds,

FSP females were more likely than higher income females to

have an adequate iron intake, but the reverse was true among

females 19-50 years of age. The prevalence of adequate calcium

intake was high through age 8 but could not be quantified for

older children. Mean calcium intake was significantly lower for

food stamp participants than for either income-eligible nonparticipants or higher income nonparticipants (fig. 2).

WIC Children. Children under age 4 were separated by their

participation in WIC, and nonparticipants were classified into

income-eligible and higher income using the WIC’s income cutoff of 185 percent of poverty. Virtually all children ages 1-4

received adequate intakes of vitamin C (fig. 1). The patterns for

zinc and iron were similar. There were statistically significant but

negligible differences between participants and nonparticipants.

School-Age Children. School-age children and older adults

(ages 60 and over) were grouped into three income classes—

lowest income (below 130 percent of poverty), low income

(greater than 130 and no more than 185 percent of poverty), and

higher income (over 185 percent of poverty). The report gives

results for these income groups separated by age and gender. 

Over 95 percent of all children ages 5-8 and 9-13 consumed adequate vitamin C, while about 8 out of 10 children ages 14-18 did

so (fig. 1). For some age subgroups, prevalence of adequate

intake was lower among higher income children than lowest

2 Economic Research Service / USDA

Agriculture Information Bulletin 796-2

WIC participants

WIC ineligible

Ages 1-4

WIC income-eligible

nonparticipants

≤ 130% poverty

131-185% poverty

> 185% poverty

Ages 5-18

≤ 130% poverty

U.S. population

FSP participants

FSP income-eligible

nonparticipants

FSP ineligible

131-185% poverty

> 185% poverty

Ages 60+

0 20 40 60 80 100 120

*Significantly different from program participants or lowest income group 

at 0.05 level.

**Significantly different from program participants or lowest income group 

at 0.01 level.

***Significantly different from program participants or lowest income group 

at 0.001 level

Source: National Health and Nutrition Examination Survey, 1988-94.

Older Americans at highest risk of inadequate 

vitamin C intake

Prevalence of adequate vitamin C intake, 

percent

77.4

75

74.6

78*

99.9

100

99.9***

99.8***

91.5

93.3

92.4

91.2*

72.4

66.2

65.8

76.2***

Figure 1

Ages 1-4

WIC participants

WIC ineligible

WIC income-eligible

nonparticipants

≤ 130% poverty

131-185% poverty

> 185% poverty

Ages 5-18

≤ 130% poverty

U.S. population

FSP participants

FSP income-eligible

nonparticipants

FSP ineligible

131-185% poverty

> 185% poverty

Ages 60+

Calcium intake below Adequate Intake levels for 

school-age children, older adults

0 20 40 60 80 100 120 140 160 180

Calcium intake, percent of

Adequate Intake level

81.1

73.3

78.6**

82.7***

146.7

157.5

139.9***

148.5*

83.3

81.2

82.9

84.5*

61.1

52.5

57.6**

64***

*Significantly different from program participants or lowest income group 

at 0.05 level.

**Significantly different from program participants or lowest income group 

at 0.01 level.

***Significantly different from program participants or lowest income group 

at 0.001 level

Source: National Health and Nutrition Examination Survey, 1988-94.

Figure 2
income children. The pattern was similar for zinc. Only 6 out of

10 girls ages 14-18 in the higher income group consumed adequate zinc, compared with 81 percent for the lowest income and

100 percent for the low income.

While prevalence of adequate iron intake was above 95 percent

for most school-age children, only 8 out of 10 higher income

girls ages 14-18 consumed adequate iron, significantly less than

lowest income girls ages 14-18 (92 percent).

Mean calcium intake was above the AI for children ages 1-4 but

below the AI for most groups of older children (fig. 2). Mean

intake of lowest income boys was significantly lower than for

low- and higher income boys, whereas mean intake was actually

higher for lowest income girls ages 14-18 than for their lowincome counterparts. 

Older Adults. About 7 out of 10 adults over age 60 consumed

adequate vitamin C, but older adults with incomes at or below

130 percent of poverty were significantly less likely to have adequate intakes than those with higher income (fig. 1). The pattern

was similar for zinc. Nearly 99 percent of older adults had adequate usual intake of iron, with small differences among income

groups or age-sex groups. Prevalence of adequate calcium intake

could not be quantified for older adults (fig. 2). Lowest income

older adults had significantly lower mean calcium intake than

their low-income counterparts. 

Energy, Fat, Saturated Fat, Sodium, Fiber,

and Cholesterol

There was no difference in energy intake as a percentage of the

1989 REA between FSP males and their income-eligible nonparticipat-ing counterparts. However, FSP girls ages 9 and older and

women ages 19-30 had higher energy intake than their income-eligible nonparticipating counterparts. The pattern reversed among

women ages 31-50. For older adults, lowest income men and

women had lower energy intake than those with higher income.

WIC children consumed more energy as a percentage of the

1989 REA than income-eligible and higher income nonparticipating children. Among school-age children, energy intake was

significantly higher for lowest income girls than other girls but

the opposite was observed for boys.

Twenty-three percent of Americans ages 2 and above met the

Dietary Guideline limiting total fat to no more than 30 percent of

caloric intake, and 25 percent of Americans met the Guideline

limiting saturated fat to less than 10 percent of food energy.

Twenty-two percent of Americans ages 2 and above met the

dietary recommendation for dietary fiber (“age plus 5” up to 25

grams per day) (fig. 3), and 20 percent met the recommendation

for sodium (2,400 milligrams per day). Sixty-eight percent of

Americans met the Dietary Guideline for cholesterol intake (300

mg per day or less).

The recently issued DRIs include the Acceptable Macronutrient

Distribution Range (AMDR) of 25-35 percent for total fat, AIs

of 19 grams of total fiber for children and up to 38 grams for

teen boys and adult men, and UL of 2,300 mg per day for sodium. These DRIs specify stricter standards for fiber and sodium,

so future analysis is likely to show a lower percentage of

Americans meeting the new DRIs than those meeting the earlier

recommendations. The AMDR for fat is more lenient than the

Dietary Guideline, however, so a higher proportion is likely to

meet this DRI than met the Guideline. 

Intake Distributions

Usual intake distributions are reported for 5th, 10th, 15th, 25th,

50th, 75th, 85th, 90th, and 95th percentiles. The distributions

allow researchers to estimate the effect of a change in intake

standards on the prevalence of adequate intake. For example, the

IOM’s AMDR for fat was issued when the analysis was completed so that it was not used in the study. The usual intake distribution shows that about 5 percent of WIC children age 2-4 exceeded the 40 percent upper AMDR for children (fig. 4), and about

20 percent of them fell below the 30 percent lower bound of the

AMDR. Note that only those falling below the lower bound of

Economic Research Service / USDA 3

Agriculture Information Bulletin 796-2

WIC participants

WIC ineligible

Ages 1-4

WIC income-eligible

nonparticipants

≤ 130% poverty

131-185% poverty

> 185% poverty

Ages 5-18

≤ 130% poverty

U.S. population

FSP participants

FSP income-eligible

nonparticipants

FSP ineligible

131-185% poverty

> 185% poverty

Ages 60+

Most Americans do not meet “age-plus-five” 

recommendation for fiber

0 20 10 30 50 70 40 60 80 90

Percent meeting fiber recommendation

22

20.6

22.6

22

76.7

76

78.4

77.6

46.1

47.8

39.6**

46.5

11.1

5.4

7.8

13.3***

*Significantly different from program participants or lowest income group 

at 0.05 level.

**Significantly different from program participants or lowest income group 

at 0.01 level.

***Significantly different from program participants or lowest income group 

at 0.001 level

Source: National Health and Nutrition Examination Survey, 1988-94.

Figure 3
the AMDR meet the Dietary Guideline of fat intake of no more

than 30 percent of calories.

Conclusions

Younger children were more likely to have adequate intake of

vitamin C, zinc, and calcium than older children and adults. In

many cases lower income individuals and food assistance recipients were less likely to have adequate intake than higher income

individuals, but in some cases, the reverse was true. 

Further research is needed to reconcile the high prevalence of

adequate iron intake with biochemical indicators, which show a

somewhat lower prevalence of adequate iron status. 

Adherence to guidelines for fat, saturated fat, and sodium intake

was low. Future analysis is likely to show a higher percentage of

the population with fat intakes within the IOM’s less restrictive

Acceptable Macronutrient Distribution Ranges for fat, but lower

percentages meeting the AI for total fiber and the UL for sodium.

Information Sources

Institute of Medicine, Food and Nutrition Board (2004). Dietary

Reference Intakes for Water, Potassium, Sodium, Chloride, and

Sulfate. Washington, DC: National Academy Press.

Institute of Medicine, Food and Nutrition Board (2001). Dietary

Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron,

Chromium, Copper, Iodine, Iron, Manganese, Molybdenum,

Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National

Academy Press.

Institute of Medicine, Food and Nutrition Board (2000). Dietary

Reference Intakes: Application in Dietary Assessment.

Washington, DC: National Academy Press.

Institute of Medicine, Food and Nutrition Board (1998). Dietary

Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6,

Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.

Washington, DC: National Academy Press. 

Institute of Medicine, Food and Nutrition Board (2000). Dietary

Reference Intakes for Vitamin C, Vitamin E, Selenium, and

Carotenoids. Washington, DC: National Academy Press.

Institute of Medicine, Food and Nutrition Board (1997). Dietary

Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin

D, and Fluoride. Washington, DC: National Academy Press.

4 Economic Research Service / USDA

Agriculture Information Bulletin 796-2

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex,

religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET

Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue,

SW, Washington, DC 20250-9410, or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

Cumulative percentiles

Figure 4

One in four WIC children falls outside Acceptable Macronutrient Distribution Range

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40 45

Fat intake as a percent of calories

100 - 95 = 5 percent above AMDR

20 percent below AMDR <-------AMDR-------->

WIC = Special Supplemental Nutrition Program for Women, Infants, and Children

Source: National Health and Nutrition Examination Survey, 1988-94

For more information, see www.ers.usda.gov/publications/ 

efan04014-1, 04014-2, 04014-3, 04014-4

NOTE: These studies were not designed to assess program

impacts. Do not interpret any reported differences between 

program participants and nonparticipants as impacts of food

assistance programs.