As part of the 1988-94 National Health and Nutrition

Examination Survey (NHANES-III), respondents completed a

physical examination, blood tests, and body measurements in a

Mobile Exam Center. Several measures of nutritional biochemistries, bone density, and lead poisoning provide a baseline

to monitor the nutrition and health status of the U.S. population.

Four subgroups of low-income Americans are the focus of this

study: participants in the Food Stamp Program (FSP), participants in the Special Supplemental Nutrition Program for

Women, Infants, and Children (WIC), school-age children, and

older adults ages 60 and above. FSP and WIC participants are

identified in NHANES. Nonparticipants are separated into

income-eligible and higher income groups using the income eligibility cutoff of 130-percent and 185-percent poverty level for

FSP and WIC, respectively.

School-age children and older adults ages 60 and above are

grouped into three income classes—lowest income (130 percent of

poverty level or less), low income (greater than 130 and no more

than 185 percent), and higher income (above 185 percent).

Additional population groups are created using gender and age.

Because of data limitations, the WIC portion of this summary

presents findings only for children ages 1-4. This summary focuses on the nutritional biochemistry blood tests and bone density

measures that showed differences between income groups. 

Iron Deficiency, Anemia, and

Iron Deficiency Anemia

The terms “iron deficiency,” “iron deficiency anemia,” and “anemia” are often used interchangeably, but they are not equivalent.

Iron deficiency can contribute to anemia, but anemia also can be

caused by other factors, including infection, inflammation, deficiencies of other nutrients, and hereditary anemia. When the

prevalence of iron deficiency is high, anemia is a good predictor

of iron deficiency. When the prevalence of iron deficiency is low,

the majority of anemia cases are due to other causes (U.S.

Department of Health and Human Services (HHS), 2000). 

Iron deficiency is the most common form of nutritional deficiency in the United States (Centers for Disease Control and

Prevention (CDC, 1997). Iron deficiency can lead to developmental delays, behavioral problems, and decreases in verbal

learning and memory. It can also affect immune function, energy

metabolism, and work performance (HHS, 2000; CDC, 1998;

and Looker et al., 1997). The prevalence of iron deficiency has

decreased dramatically over the past 3 decades, in part because of

the influence of WIC on increased iron intake among infants and

young children (Yip et al., 1987). Nonetheless, iron deficiency

remains a problem for young children, particularly low-income

children. The prevalence of iron deficiency for the U.S. population

was about 6 percent. Prevalence was greatest among 1-year-olds

(13 percent), females of childbearing age, ages 12-49 (8-15 percent), and females ages 80 and older (9 percent). 

Anemia is defined based on low hemoglobin or hematocrit. The

prevalence of anemia was 8 percent for the U.S. population, 8

percent for children ages 1-4, 6 percent among school-age children, and 14 percent among older adults. Iron-deficiency anemia

is defined as being iron-deficient and having low hemoglobin.

Iron deficiency anemia was observed in about 2 percent of all

Americans and 1- to 4-year-old children, in less than 1 percent of

school-age children, and in 3 percent of all older adults. The

prevalence of iron-deficiency anemia was substantially smaller

than the prevalence of the less narrow diagnosis of anemia. 

Food Stamp Participants. FSP participants were twice as likely as

higher income nonparticipants to be iron deficient (10 percent vs. 5

percent), to have anemia (14 percent vs. 7 percent), and to have

iron-deficiency anemia (4 percent vs. 2 percent). Much of these differences were among females of childbearing age (fig. 1).

WIC Children. The overall prevalence of iron deficiency among 1-

to 4-year-old children was about 6 percent. Prevalence was greatest

among 1-year-olds and was lower for older children. Overall, WIC

children were less likely than income-eligible children to be iron

deficient (5 percent vs. 10 percent), but more likely than higher

United States

Department of

Agriculture

Economic 

Research

Service

Agriculture Information Bulletin 796-5 February 2005

Nutrition and Health Characteristics of

Low-Income Populations

Clinic Measures of Iron, Folate,

Vitamin B12, Cholesterol, Bone

Density, and Lead Poisoning

Elizabeth Frazao, (202) 694-5455, efrazao@ers.usda.gov
income nonparticipants to have anemia (9 percent vs. 6 percent).

WIC children were also more likely than higher income children to

have iron-deficiency anemia, although this was a relatively uncommon finding for all children, particularly those older than 2. 

School-Age Children. School-age children in the lowest income

group were more likely to be iron deficient than school-age children in the higher income group (6 percent vs. 4 percent). This difference was attributable to a difference among females (10 percent

vs. 5 percent). Overall, there were no significant differences in the

prevalence of anemia or iron deficiency anemia between the three

income groups for school-age children. 

Older Americans. Among older adults, 6 percent had iron deficiency, 14 percent had anemia, and 3 percent had iron-deficiency anemia. The relatively low prevalence of iron deficiency and iron-deficiency anemia observed in this population suggests that much of

the anemia observed in older adults is likely due to causes other

than iron deficiency, such as chronic disease, deficiencies of folate

and/or vitamin B12, gastrointestinal bleeding, and cancer. Although

there were no differences between income groups in the prevalence

of iron deficiency or iron deficiency anemia, the prevalence of anemia was greater in the lowest income group than in either of the

other income groups (18 percent vs. 12-13 percent).

Low Red Blood Cell (RBC) Folate

Overall, 7 percent of the U.S. population, 6 percent of school-age

children, and 5 percent of older adults had low levels of RBC

folate, an indicator of long-term folate status. Adequate RBC

folate levels are particularly important for women of childbearing

age, because inadequate maternal folate has been associated with

birth defects. RBC folate was not measured for children younger

than 3. FSP participants were more likely than higher income nonparticipants to have low RBC folate (11 percent vs. 6 percent).

School-age children in the lowest income group were more likely

than children in either the low-income or higher income groups to

have low levels of RBC folate (9 percent vs. 4 and 6 percent). The

prevalence was greatest among 14- to 18-year-olds, especially

females. Similarly, older adults in the lowest income group were

more likely to have low levels of RBC folate than their higher

income counterpart (9 percent vs. 3 percent). 

Low Serum Vitamin B12

Overall, 3 percent of the U.S. population, 1 percent of schoolage children, and 5 percent of older adults had low serum vitamin B12 (not measured for children younger than 3). Vitamin B12

deficiency is observed more often among older adults than

among other population groups, due to age-related gastrointestinal changes, including decreased levels of hydrochloric acid,

which impede absorption of the vitamin. Low levels of vitamin

B12 may contribute to anemia.

FSP participants were less likely than higher income nonparticipants to have low levels of serum vitamin B12 (2 percent vs. 3 percent). Overall, there were no differences among older adults

between income groups in the prevalence of this condition.

However, among the two oldest cohorts (ages 80-84 and 85 and

above), the problem of low serum vitamin B12 was less common

in the lowest income group than in the higher income group.

These differences were concentrated among females.

Cholesterol 

Elevated serum cholesterol levels have been associated with

increased risk of coronary heart disease in adults. Further, there

is evidence that the process of atherosclerosis, or the buildup of

fatty deposits in the arteries, begins early in childhood. For children up to age 19, the National Cholesterol Education Program

(NCEP) considers a serum cholesterol level of 200 milligrams

per deciliter (mg/dL) or more to be high and levels between 170

mg/dL and 199 mg/dL to be borderline high (National Institutes

of Health (NIH), 1991). For adults, serum cholesterol of 240

mg/dL or more is considered high, and levels of 200-239 mg/dL

are considered borderline high (NIH, 2001). 

Overall, 18 percent of the U.S. population, 10 percent of schoolage children, and 33 percent of older adults had high cholesterol

levels; 31 percent of the U.S. population, 28 percent of schoolage children, and 36 percent of older adults had borderline-high

levels of cholesterol.

FSP participants were less likely than income-eligible nonparticipants to have high serum cholesterol (16 percent vs. 19 percent).

2 Economic Research Service / USDA

Agriculture Information Bulletin 796-5

12-19 20-29 30-39 40-49

8

10

20

17

21

6*

9*

18

14 14 14 14

Percent

Figure 1

Females of childbearing age with iron deficiency

Age in years

*Statistically significant difference from FSP participants at the 0.05 level 

or better.

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

Higher income 

nonparticipants

FSP 

participants

Income-eligible 

nonparticants
Among females, FSP participants were less likely than either

group of nonparticipants to have high cholesterol (16 percent vs.

20 percent and 19 percent). There were no differences between

FSP participants and either group of nonparticipants in the

prevalence of borderline-high cholesterol levels. There were few

differences among children by income on blood cholesterol levels. Among older adults, neither the prevalence of high or borderline-high serum cholesterol varied by income. 

Bone Density

A reduction in bone mass or bone density can lead to deteriorated

or fragile bones (HHS, 2000). Reduced bone density, or osteopenia, has been defined as bone density that is 1 to 2.5 standard deviations below the mean for non-Hispanic White women between

ages 20-29, as measured in the 1988-94 NHANES (National

Center for Health Statistics (NCHS), 1999). Severely reduced bone

mass, or osteoporosis, is defined as bone density more than 2.5

standard deviations below this norm. In NHANES-III, bone density

was not measured for those younger than 20. 

Male FSP participants ages 20-29 and 40-49 were less likely

than their income-eligible or higher income counterparts to have

reduced or severely reduced bone density. However, among

those most at risk of osteoporosis—adults 80 and over—FSP

participants were more likely than higher income nonparticipants

to have severely reduced bone density (42 percent vs. 24 percent) (fig. 2). 

Overall, 50 percent of adults 60 years of age and older had

reduced or severely reduced bone density. Older adults in the

lowest income group were more likely than those in the other

income groups to have reduced or severely reduced bone density

(58 percent vs. 48-50 percent). Older adults in the lowest income

group were also more likely than other older adults to have

severely reduced bone density—osteoporosis (21 percent vs. 14

percent).

Lead Poisoning

The prevalence of lead poisoning has been declining sharply in

recent years, from 77.8 percent in 1976-80 to 4.4 percent in

1988-91 (CDC, 1997). Based on 1988-94 NHANES laboratory

tests and CDC-defined standards for elevated levels of blood

lead, 3 percent of children ages 1-16 were found to have high

levels of blood lead, indicative of lead poisoning. Prevalence was

highest among the youngest age groups. 

FSP children were more likely than children in either of the nonparticipant groups to have high levels of blood lead (fig. 3).

Seventeen percent of 1- to 2-year-old FSP participants and 13 percent of 3- to 5-year-old FSP participants had abnormally high levels of lead in their blood, compared with 6 percent and 4 percent,

respectively, for income-eligible nonparticipants, and 5 percent

and 2 percent, respectively, for higher income nonparticipants. 

Similarly, the prevalence of high blood lead levels was greater for

WIC children than for income-eligible or higher income nonparticipating children. Fourteen percent of WIC children had abnormally high blood lead levels, compared with 8 percent for incomeeligible children and 3 percent for higher income children. Lead

poisoning was being used as a nutritional risk criteria for WIC

when 1988-94 NHANES was conducted.

Economic Research Service / USDA 3

Agriculture Information Bulletin 796-5

42

39

24*

Percent

Figure 2

Adults 80 and older with severely reduced bone density

*Statistically significant difference from FSP participants at the 0.05 level 

or better.

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

Higher income 

nonparticipants

FSP 

participants

Income-eligible 

nonparticants

17

13

6*

5*

4*

2*

Percent

Figure 3

Children with high blood lead levels

*Statistically significant difference from FSP participants at the 0.05 level 

or better.

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

1-2 years 3-5 years

Higher income 

nonparticipants

FSP 

participants

Income-eligible 

nonparticants
Information Sources

Centers for Disease Control and Prevention (1998).

Recommendations to Prevent and Control Iron Deficiency in the

United States. MMWR, 47 (No. RR-3).

Centers for Disease Control and Prevention (1997). “Update:

Blood Lead Levels—United States, 1991-1994,” Morbidity and

Mortality Weekly Report 46(7): 141-46.

Looker, A., P. Dallman, M. Carroll, et al., (1997). “Prevalence of

iron deficiency in the United States,” J. American Medical

Assoc. 277: 973-76.

National Center for Health Statistics (1999). Health, United

States, 1999. With Health and Aging Chartbook. Hyattsville, MD:

U.S. Department of Health and Human Services, Centers for

Disease Control and Prevention.

National Institutes of Health, National Cholesterol Education

Campaign (2001). Third Report of the Expert Panel on

Detection, Evaluation, and Treatment of High Blood Cholesterol

in Adults (Adult Treatment Panel III) Executive Summary. NIH

Publication No. 01-3670. Washington, DC: National Cholesterol

Education Program. 

National Institutes of Health, National Cholesterol Education

Campaign (1991). Report of the Expert Panel on Blood

Cholesterol in Children and Adolescents. Bethesda, MD.

U.S. Department of Health and Human Services (2000). Healthy

People 2010: Understanding and Improving Health, 2nd Edition.

Yip, R., N.J. Binkin, L. Fleshood, and F. Trowbridge (1987).

“Declining prevalence of anemia among low-income children in

the United States,” J. American Medical Assoc. 258: 1619-23.

4 Economic Research Service / USDA

Agriculture Information Bulletin 796-5

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.

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.