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Department of Nutrition, Arizona State University East, Mesa, Arizona 85212
1To whom correspondence should be addressed. E-mail: >carol.johnston@asu.edu" locator-type="email">locator-type="email">carol.johnston@asu.edu locator="" locator-type="email">
| ABSTRACT |
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KEY WORDS: "5 a day" fruits vegetables phytochemicals
| INTRODUCTION |
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At the national level, surveys conducted since the implementation of
the "5 A Day" program show that Americans as a group are consuming
more servings of fruits and vegetables daily (Table 1
). A recent report indicated that per capita consumption of fruits and
vegetables increased by 3 and 8%, respectively, between 1991 and 1994
(Putnam and Allshouse 1996
). Actual daily intakes of
fruits and vegetables combined increased from 4.1 to 4.6 mean servings
during this time period, a 12% change (Department of Health and Human Services 1999
). We analyzed the 19941996 Continuing
Survey of Food Intakes by Individuals (CSFII) and demonstrated that
Americans aged 2575 y consumed an average of 5.2 servings of fruits
and vegetables daily (Taylor et al. 2000
). Furthermore,
45% of Americans consumed five or more servings of fruits and
vegetables daily in 19941996, compared with only 32% several years
earlier (Table 1)
.
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The "5 A Day" message in its current form does not promote the consumption of specific fruits and vegetables. Although Americans may be increasing their intake of fruits and vegetables, little is known regarding the identity of commonly consumed fruits and vegetables in the American diet; nor do we know whether Americans are regularly eating the specific fruits and vegetables associated with reduced risk for cancer. We used data from a large national probability sample of U.S. adults to specifically examine the types of fruits and vegetables consumed by Americans.
| METHODS |
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2 mo, from rural, urban, and suburban areas.
Low-income households were purposely oversampled to increase the
precision of the survey. The d 1 recalls and nearly all (93%) of the d
2 recalls were collected in person; d 2 recalls were conducted 310 d
after the first recall and represented a different day of the week.
Measurement guides, such as cups and spoons, were used to assist with
estimation of food amounts. The overall response rate for individuals
providing two dietary recalls was 76.1%. The specific methods used to
conduct these random-sample, multistage, stratified area surveys
are available (Agricultural Research Service 1997Our analytic sample included data from men and women of ages of 2575 y. Subjects were excluded from analyses if they were pregnant and/or lactating at the time of data collection or if they failed to complete two nonconsecutive 24-h recalls and the Diet and Health Knowledge Survey, which accompanied the CSFII. In the original survey, the U.S.D.A. assigned each food and beverage item a seven-digit code number and provided food groups to categorize all foods and beverages. Items such as iceberg lettuce, apples and bananas represented a large proportion of all fruits and vegetables consumed; however, these items were classified as "other vegetables" and "other fruits," and their relevance to the diet was not emphasized. We recoded and recategorized all fruits and vegetables to effectively demonstrate food intake patterns of Americans. The CSFII calculated serving sizes as defined by the U.S.D.A. Food Guide Pyramid. For example, a serving of vegetables was defined as 1 c raw leafy, 1/2 c cooked or chopped raw or 3/4 cup juice. A serving of fruit was defined as a medium-size whole fruit, a grapefruit half, a melon wedge, 3/4 c fruit juice, 1/2 c berries, 1/4 cup dried fruit or 1/2 c chopped, cooked or canned fruit.
Data were analyzed using SPSS 9.0 (1999; SPSS, Chicago, IL) and SUDAAN, version 7.5 (Research Triangle Institute, Research Triangle Park, NC), a software program that adjusts for the complex CSFII sample design. The analyses incorporated sampling weights that adjusted for unequal sampling probabilities. SUDAAN was used to calculate weighted means, percentages and SDs.
| RESULTS |
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With the use of sampling weights, the data indicated that Americans
consumed 5.2 ± 3.2 servings of fruits and vegetables daily
(Table 2
). Vegetable consumption averaged 3.6 ± 2.3 servings daily, and on
average, 1.6 ± 2.0 servings of fruit were ingested daily. White
potatoes accounted for 30% of all vegetables consumed, equaling nearly
1.1 servings daily; French fried potatoes represented more than one
third of potatoes consumed, averaging 0.4 serving daily. Men consumed
24% more fruits and vegetables than women, and this difference was
explained by an added serving of vegetables. Nearly 45% of Americans
consumed at least five servings of fruits and vegetables daily, but
only 18% met the recommendation of two servings of fruit and three
servings of vegetables per day. Americans were more likely to consume
the recommended number of servings of vegetables than of fruit: 37.2%
of Americans consumed three or more servings of vegetables, whereas
only 10.5% consumed two or more servings of fruit.
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Iceberg lettuce, tomatoes, French fried potatoes, bananas and orange
juice were the most commonly consumed fruits and vegetables in the
American diet, accounting for nearly 30% of all fruit and vegetables
consumed (Table 3
). About 40% of Americans consumed iceberg lettuce during the reporting
period, and nearly 40% of Americans ate tomatoes on 1 of the 2 d
surveyed. However, more than three fourths of the lettuce and tomatoes
consumed by Americans were consumed at levels of less than a full
U.S.D.A. serving; hence, these items were typically ingested as
condiments or as ingredients in mixed dishes. In contrast, French fried
potatoes, bananas or orange juice, which were present in the diets of
1624% of Americans, tended to be consumed as full servings (Table 3)
.
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| DISCUSSION |
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Differing methodologies preclude a comparison of diet surveys conducted
during the past 25 y. However, the CSFII surveys from the past
10 y had similar methodologies, permitting an examination of
recent trends in fruit and vegetable intake. The 19891991 CSFII data
indicated that U.S. adults consumed on average 4.3 servings of fruits
and vegetables, 1.2 servings of fruit and 3.1 servings of vegetables
(Krebs-Smith et al. 1995
). Men generally consumed more
fruits and vegetables than women (+0.8 serving/d). White potatoes
represented 32% of vegetable consumption (1 serving), with French
fried potatoes accounting for a majority of white potato servings (0.4
serving). Only 0.3 serving of deep yellow or dark green vegetables was
consumed daily.
Our analyses of the 19941996 CSFII data showed that Americans consumed 20% more fruits and vegetables than in the earlier survey: 1.6 servings of fruit and 3.6 servings of vegetables. Men continue to consume more fruits and vegetables than women (5.7 versus 4.6 servings/d). White potato consumption, including the consumption of French fries, remained similar to the earlier survey, and the consumption of dark green or deep yellow vegetables was <0.4 serving/d. The Dietary Guidelines, as well as the Healthy People 2010 campaign, encourage the consumption of dark green and deep yellow vegetables because they are particularly rich sources of vitamin C and folic acid and of ß-carotene, respectively. Intake from these categories combined continues to be <1/2 serving/d.
Aside from these micronutrients, other substances in dark green
vegetables, the phytochemicals, are biologically active in humans and
may mitigate disease and promote health (Hasler 1998
).
The biological activities of the phytochemicals are diverse, but the
major functional effects may be grouped as antioxidant, carcinogen
detoxifier or cell regulator (Hasler and Blumberg 1999
).
Procedures have been developed to measure the antioxidant and
detoxification properties of whole fruits and vegetables. These tests,
the oxygen radical absorbance capacity (ORAC) assay (Cao et al. 1996
, Wang et al. 1996
) and the quinone
reductase (QR) inducer activity assay (Prochaska et al. 1992
), demonstrate that the biological activity of specific
fruits and vegetables varies greatly (Table 3)
. Interestingly, the
items with the highest ORAC or QR induction score, dark green and
cruciferous vegetables, onions and citrus fruits, are the fruits and
vegetables most commonly related to reduced cancer risk in
epidemiological investigations (Ferguson 1999
). Indeed,
recent clinical trials have shown physiological benefits associated
specifically with the regular ingestion of citrus fruits
(Brouwer et al. 1999
, Harats et al. 1998
)
and Brussels sprouts (Verhagen et al. 1995
).
Americans do not commonly consume foods with high ORAC and QR induction
scores (Table 3)
. Low consumption of these foods may reduce serum
antioxidant capacity, as some research suggests (Cao et al. 1998a and 1998b
, Comstock et al. 1997
), as well
as affect nutritional status, because these foods are also rich sources
of micronutrients, particularly vitamin C. Interestingly, our analyses
indicated that the vitamin C content of fruits and vegetables is
correlated to the ORAC score (r = 0.47, P
< 0.001). Individual nutrient or phytochemical supplementation
may raise serum antioxidant capacity and specific nutritional status,
yet the benefit afforded by whole food consumption is greater than that
afforded by supplementation alone (Cao et al. 1998a and 1998b
). Although many epidemiological studies have consistently
related a reduced risk of cancer with a specific nutrient or
phytochemical in fruits and vegetables, large, prospective trials have
not convincingly supported a role for supplementation in reduced cancer
risk (Shibata et al. 1992
, Yong et al. 1997
). In fact, it has become clear that oral supplementation
with the phytochemical ß-carotene may raise the risk of lung cancer
among smokers (Omenn 1998
). Phytochemicals and plant
micronutrients are likely most beneficial when consumed as a
"cocktail," that is, in their natural array in intact fruits and
vegetables. Hence, high profile campaigns to specifically promote the
consumption of dark green and cruciferous vegetables and citrus fruits
by Americans seems prudent.
Americans are consuming more fruits and vegetables, but they are not regularly consuming the particular fruits and vegetables that are likely to impart robust health effects. Both epidemiological studies and experimental research indicate that regular consumption of dark green and cruciferous vegetables and citrus fruits reduces risk for chronic disease. Health professionals need to continue to promote the consumption of fruits and vegetables in general, but specific recommendations regarding daily fruit and vegetable consumption may better serve the public.
| FOOTNOTES |
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Manuscript received June 30, 2000. Initial review completed July 24, 2000. Revision accepted September 5, 2000.
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