Download calculation and comparison of nutrient density/quality

Alim. Nutr., Araraquara
v. 23, n. 1, p. 7-14, jan./mar. 2012
ISSN 0103-4235
ISSN 2179-4448 on line
CALCULATION AND COMPARISON OF NUTRIENT
DENSITY/QUALITY SCORES FOR COMMONLY
CONSUMED FRESH FRUIT
Gail RAMPERSAUD*
Maria Filomena VALIM**
Sandy BARROS**
ABSTRACT: A number of methods have been developed
to quantitatively describe the nutrient density/quality
(ND/Q) of foods and beverages. Seventeen commonly
consumed fresh fruits were evaluated using six published
ND/Q methods. Nutrient data for each fruit were obtained
from the USDA National Nutrient Database for Standard
Reference, Release 23. Numerical scores were produced
and ranked for each fruit and method. The resulting ND/Q
scores varied in range and magnitude but there was good
to strong correlation among methods. The relative scores
indicated that cantaloupe, strawberries, oranges, and
grapefruit generally had the highest ND/Q scores across all
methods. Further analysis indicated that vitamins C and A,
nutrients common to all six methods, affected ND/Q scores
substantially for some but not all fruits, suggesting that high
values for specific nutrients may influence relative scoring
and higher scores may not necessarily reflect a greater
variety or balance of nutrients. Fresh fruits vary in their
ND/Q as defined by several quantitative scoring systems.
In this analysis, consistent results in how the fruits were
ranked were obtained when using six different methods to
quantify ND/Q for select fresh fruit.
KEYWORDS: Fruit; nutrients; nutrient density; nutrient
quality; nutrient profile.
INTRODUCTION
Recommendations in the 2010 Dietary Guidelines
for Americans (DGA) promote the consumption of nutrientdense foods and beverages.21 The 2005 DGA described
nutrient-dense foods as those that provide substantial
amounts of nutrients (i.e., vitamins and minerals) and
relatively fewer calories.22 The 2010 Dietary Guidelines
Advisory Committee expanded on the definition by
describing nutrient-dense foods as those that are naturally
rich in vitamins, minerals and phytochemicals and are lean
or low in solid fats and without added solid fats, sugars,
starches and sodium, and that retain naturally-occurring
components such as fiber.23 In the past, the US Food and
Drug Administration (FDA) expressed interest in depicting
a nutrient density indicator on food labels24 and this was
followed by the development and implementation of
a variety of point-of-purchase or other nutrient rating
systems designed to help consumers make healthy food
choices.3,4,7,11,17 More recently, the Institute of Medicine
convened a committee to examine front-of-pack nutrition
rating systems and symbols12 and the FDA is moving toward
establishing a voluntary program to convey the nutritional
value of food on front-of-pack although the nature and
design of a system is unknown at this time.27 Several food
industry and manufacturing groups, including the American
Beverage Association, Food Marketing Institute, and the
Grocery Manufacturer’s Association have developed and
approved front-of-pack systems that their members have
begun implementing.1,6
There have been several proposed methodologies
and algorithms to quantitatively describe the nutrient
density, quality or profile of foods as discussed by Zelman
& Kennedy29 and Rampersaud.13 Methodologies differ
primarily by how many and which nutrients are considered,
as well as the mathematical construct of the algorithm. Most
methods incorporate nutrients that should be encouraged in
the diet (for example, vitamins, minerals) as well as nutrients
to limit (for example, fat, sodium). To date, there has been
no consensus on a standard definition for nutrient-density
or quantitative approach to depict the nutrient density of
foods. In addition, there are few published sources that
compute and compare different ND/Q methods for various
foods or beverages.5,8,13,15
The purpose of this article is to compute and
compare nutrient density/quality (ND/Q) scores for the
most commonly consumed fruits in the U.S. using six
methods. The fruits were scored and ranked to examine the
consistency with which the various methodologies ranked
the fruit based on their scores as well as how individual
nutrients affect scores and rankings. The purpose of this
analysis was not to determine the most applicable or suitable
ND/Q method for fruit or other foods, but rather to provide
new data to the literature concerning scores specifically
* Food Science and Human Nutrition Department – Institute of Food and Agricultural Sciences – University of Florida – 32611-0720 –
Gainesville – FL – USA. E-mail: [email protected].
** Florida Department of Citrus – 33850 – Lake Alfred – FL – USA.
7
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
for fruit and to build on previously published data on the
nutrient density of 100 percent fruit juices 13
.
MATERIAL AND METHODS
Selection of Fresh Fruit for Evaluation
The most commonly consumed fresh fruits in the
U.S. were identified using the USDA/Economic Research
Service data that provides retail availability data, a proxy
for consumption, for a variety of fresh fruits on a pound
per capita basis.20 For this evaluation, only fruits that had
at least a one pound per capita consumption rate for 2009
(the most recent data available as of this analysis) were included. Fifteen fruit categories met this criterion: oranges
and temples, tangerines and tangelos, lemons, limes, grapefruit, apples, avocados, bananas, grapes, mangos, peaches
and nectarines, pears, pineapples, strawberries, and melons. Two fruits, lemons and limes, were excluded from the
analysis because they typically are not consumed in whole
or in part as a serving of fruit similar to other fruits.
Source of Nutrient Data
Nutrient data from the USDA National Nutrient
Database for Standard Reference, Release 2319 were used
for the analysis. This open access database provides nutrient
data for a variety of foods and beverages and is designed
for the collection and dissemination of food composition
data.18 Data for temples and tangelos are not included in
the database so the categories “oranges and temples”
and “tangerines and tangelos” included only oranges and
tangerines, respectively. Nectarines are included in the
database and are reported separately from peaches. The
“melon” category included summary data for three types
of melons: watermelon, cantaloupe, and honeydew. Each
has per capita consumption of at least one pound per year
and were therefore analyzed individually. For grapefruit,
the database included separate information for pink/red
and white grapefruit and these two varieties of grapefruit
were also analyzed separately. For six fruits (avocados,
grapefruit, grapes, oranges, pears, and pineapple), the
database included multiple entries with unique Nutrient
Databank (NDB) numbers. For these fruits, data from “all
commercial varieties” or “all areas” were used. For grapes,
data for the European variety was used since they are the
most typically consumed as a whole fresh fruit. The final
analysis included 17 unique fruits.
Methodologies Used to Calculate Nutrient Density/
Quality Scores
obtained from the USDA database were included in the
analysis. Any methods that required an assessment of
nutrient content by comparison to established criteria, other
food products, or that included a subjective assessment of
nutrient content or value were not included in the analysis.
Six methodologies that met the criteria were
identified. For each method, the “%DV” is the percent of
the Daily Value (DV)25 contributed by that nutrient. There is
no DV for sugar so the upper limit of the daily sugar intake
goal established by the World Health Organization/Food
and Agriculture Organization was used for this analysis.28
Some methods capped the %DV at 100% with the rationale
that levels above this are not likely to produce a health
benefit and may, in some cases, have negative effects
on health.8 Other methods capped nutrients to mitigate
excessively high scores as a result of nutrient fortification
or very high levels of single nutrients in foods.3,16 Each
method incorporates various combinations of nutrients
that should be encouraged in the diet (e.g., vitamins and
minerals) and those that should be limited in the diet (e.g.,
fats, sugar, sodium, cholesterol).
The following methodologies and algorithms were
used to assess ND/Q:
Nutrient-Rich Foods (NRF) Index3
This methodology incorporates nine nutrients to
encourage as well as three nutrients to limit. It is computed
based on the nutrient content of approximately 419kJ
(100kcal) of food or beverage:
NRF Index = %DV protein + %DV dietary fiber + %DV vitamin A +
%DV vitamin C + %DV vitamin E + %DV calcium + %DV iron +
%DV magnesium + %DV potassium - %DV saturated fat –
%DV sugar - %DV sodium
Values for added sugars are not included in the
USDA National Nutrient Database for Standard Reference
and were assumed to be zero for fresh fruit. This method
capped all DV percentages at 100%.
Food Quality Score (FQS)8
This methodology incorporates eight nutrients to
encourage and five nutrients to limit. The authors evaluated
three nutrient density methodologies and found this method
to be preferable. The numerator of the equation is specific
for fruits and vegetables. This score is computed based on
the nutrient content of 100g of food or beverage:
(%DV dietary fiber + %DV vitamin A + %DV vitamin C + %DV vitamin E +
%DV folate + %DV calcium + %DV iron + %DV potassium) ÷ 8
FQS = -----------------------------------------------------------------------------(%DV energy [kcal] + %DV saturated fat + %DV cholesterol +
Published methodologies that evaluated nutrient
density or nutrient quality of foods were researched. Only
those methods that provided a quantitative assessment of
nutrient profile or quality and produced a single numerical
score based on absolute nutrient values that could be
8
%DV sodium + %DV trans fat) ÷ 5
Values for trans fat were not included in the nutrient
database and were assumed to be zero for fresh fruit. This
method capped all DV percentages at 100%.
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
Ratio of Recommended to Restricted (RRR) Nutrients16
This methodology produces a ratio based on six
recommended food components to five food components
that are suggested to be restricted in the diet. All values
are based on a serving of food or beverage (that is, the
Reference Amount Customarily Consumed [RACC]):26
(%DV protein + %DV dietary fiber + %DV calcium + %DV iron +
%DV vitamin A + %DV vitamin C) ÷ 6
RRR = -------------------------------------------------------------------------------(%DV energy [kcal] + %DV sugars + %DV cholesterol +
%DV saturated fat + %DV sodium) ÷ 5
For this method, DV percentages were not capped
at 100%.
Statistical Analysis
Nutrient density/quality scores were calculated and for
each fruit and method a simple rank order from one to 17 was
assigned with a rank of one representing the highest ND/Q
score. For each fruit, overall mean ranks were calculated
as an arithmetic mean of the individual ranks. Spearman
and Kendall correlation coefficients for ND/Q scores were
calculated using SAS statistical software (Version 9.2, SAS
Institute Inc., Cary, North Carolina, USA).
This method capped all DV percentages at 100%.
Nutrient for Calorie (NFC)29
RESULTS
This methodology is based on 12 nutrients to
encourage and two nutrients to limit. All values are based
on a serving of food or beverage (RACC):
Table 1 presents the ND/Q scores calculated for
each fruit. The magnitude and range of ND/Q scores varied
substantially depending on the method. There was a good
to very strong correlation among scores for the various
methods with absolute values of correlation coefficients
ranging from 0.63 to 0.93 (Spearman) and 0.54 to 0.83
(Kendall) (data not shown).
The fruits were ranked from one to 17 based on
the highest and lowest ND/Q scores, respectively (Table
2). For all methods except one (FQS), cantaloupe ranked
as the fruit with the highest ND/Q score. Strawberries
were ranked highest based on the FQS method and second
highest based on four other methods. In general, citrus
fruits, including oranges, pink/red grapefruit, and white
grapefruit, filled out the remaining top five positions with
mangos and pineapple also ranking in the top five for
several methods. In general, apples, avocados, bananas,
grapes, and pears had the lowest ND/Q scores. Overall
mean ranks were computed by averaging the individual
ranks (assigned from one to 17) for all fruits and methods,
and are presented in Table 3, column A, along with highest
and lowest ranks in parenthesis. Based on mean rank,
the fruits rank as follows from highest to lowest ND/Q:
cantaloupe > strawberries > pink/red grapefruit > oranges
> white grapefruit > pineapple > mangos > tangerines >
honeydew > watermelon > peaches > nectarines > bananas
> avocados > grapes > pears > apples.
(%DV protein + %DV vitamin B12 + %DV vitamin C + %DV vitamin A +
%DV vitamin E + %DV calcium + %DV iron + %DV zinc +
%DV potassium + %DV magnesium + %DV phosphorus + %DV dietary fiber –
%DV saturated fat – %DV sodium) ÷ 14
NFC = -----------------------------------------------------------------------------------------energy [kcal]
For this method, DV percentages were not capped
at 100%.
Calorie for Nutrient (CFN)9
The method is based on 13 food components,
expanded from the original nine.29 This methodology
characterizes the number of calories that would need to
be consumed to obtain a certain amount of nutrients and,
therefore, unlike the other methods in this analysis, lower
scores would be indicative of a food with higher ND/Q. All
values are based on 100g of food or beverage:
energy [kcal]
CFN = -----------------------------------------------------------------------------------------(%DV protein + %DV thiamin + %DV riboflavin + %DV niacin +
%DV folate + %DV vitamin B6 + %DV vitamin B12 + %DV vitamin C +
%DV vitamin A + %DV calcium + %DV magnesium + %DV iron + %DV zinc) ÷ 13
For this method, DV percentages were not capped
at 100%.
Nutrient Density Score (NDS)2
This method is based on 16 nutrients to encourage
and was developed for fruits and vegetables. All values are
based on 100 g of food or beverage:
(%DV protein + %DV dietary fiber + %DV vitamin A + %DV thiamin +
%DV riboflavin + %DV niacin + %DV pantothenic acid + %DV vitamin B6 +
%DV folate + %DV vitamin B12 + %DV vitamin C + %DV vitamin E +
%DV vitamin D + %DV calcium + %DV iron + %DV magnesium) ÷ 16
NDS = -----------------------------------------------------------------------------------------energy [kcal]
DISCUSSION
The methodologies used in the analysis differed in
several ways. The NRF Index was the only method to base
nutrient data on energy content (100kcal). The FQS, CFN,
and NDS methods used food weight (100g) and the RRR
and NFC methods used serving size (RACC). The methods
differed based on the numbers and types of nutrients
included. All methods included nutrients to encourage,
with the number of nutrients ranging from six to 16. Four
methods (NRF Index, FQS, RRR, and NFC) incorporated
data for nutrients to limit in the diet, for instance saturated
9
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
Table 1 – Nutrient density/quality (ND/Q) scores for select fresh fruit.
Method
Fruit
NDB
Numbera
NRF Indexb
FQSb
RRRb
NFCb
CFNc
NDSb
Apples
Avocados
Bananas
Cantaloupe
Pink/red grapefruit
White grapefruit
Grapes
Honeydew
Mangos
Nectarines
Oranges
Peaches
Pears
Pineapple
Strawberries
Tangerines
Watermelon
09003
09037
09040
09181
09112
09116
09132
09184
09176
09191
09200
09236
09252
09266
09316
09218
09326
48
47
53
250
196
145
51
126
172
87
162
99
49
134
170
150
119
5
3
5
35
26
25
5
11
20
9
31
11
6
24
45
17
13
0.7
2.3
0.9
6.2
4.5
3.2
0.7
1.6
2.2
1.2
3.4
1.2
0.8
3.4
5.9
2.5
1.8
0.036
0.038
0.041
0.31
0.16
0.155
0.039
0.093
0.126
0.068
0.183
0.077
0.037
0.140
0.276
0.111
0.089
37.7
22.3
19
2.9
5.9
6.0
22.1
9.1
6.9
16.3
5.0
14.6
39.9
6.0
3.4
8.3
10.1
3.5
5.5
5.2
28.5
15.2
14.9
4.1
9.7
13.1
6.6
18.1
7.2
3.4
14.4
25.5
11.0
8.7
Abbreviations: NRF=Nutrient Rich Foods; FQS=Food Quality Score; RRR=Ratio of Recommended to Restricted Nutrients; NFC=Nutrient
for Calorie; CFN=Calorie for Nutrient; NDS=Nutrient Density Score.
a
NDB=Nutrient Databank.
b
Higher values indicate higher ND/Q.
c
Lower values indicate higher ND/Q.
Table 2 – Ranking of select fruits based on nutrient density/quality (ND/Q) scores.
Method
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
a
NRF Index
cantaloupe
pink/red grapefruit
mangos
strawberries
oranges
tangerines
white grapefruit
pineapple
honeydew
watermelon
peach
nectarines
bananas
grapes
pears
apples
avocados
FQS
strawberries
cantaloupe
oranges
pink/red grapefruit
white grapefruit
pineapple
mangos
tangerines
watermelon
peach
honeydew
nectarines
pears
apples
bananas
grapes
avocados
RRR
cantaloupe
strawberries
pink/red grapefruit
pineapple
oranges
white grapefruit
tangerines
avocados
mangos
watermelon
honeydew
nectarines
peaches
bananas
pears
apples
grapes
NFC
cantaloupe
strawberries
oranges
pink/red grapefruit
white grapefruit
pineapple
mangos
tangerines
honeydew
watermelon
peach
nectarines
bananas
grapes
avocados
pears
apples
CFN
cantaloupe
strawberries
oranges
pink/red grapefruit
pineapple
white grapefruit
mangos
tangerines
honeydew
watermelon
peach
nectarines
bananas
grapes
avocados
apples
pears
NDS
cantaloupe
strawberries
oranges
pink/red grapefruit
white grapefruit
pineapple
mangos
tangerines
honeydew
watermelon
peach
nectarines
avocados
bananas
grapes
apples
pears
Abbreviations: NRF=Nutrient Rich Foods; FQS=Food Quality Score; RRR=Ratio of Recommended to Restricted Nutrients; NFC=Nutrient
for Calorie; CFN=Calorie for Nutrient; NDS=Nutrient Density Score.
a
Ranked from highest ND/Q score (1) to lowest ND/Q score (17).
10
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
Table 3 – Overall average rank and highest/lowest ranks based on six methods used to calculate nutrient density/quality
(ND/Q) for select fresh fruit.a
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
(A)
Fruit,
(highest, lowest rank)
cantaloupe (1, 2)
strawberries (1, 4)
pink/red grapefruit (2, 4)
oranges (3, 5)
white grapefruit (5, 7)
pineapple (4, 8)
mangos (3, 9)
tangerines (6, 8)
honeydew (9, 11)
watermelon (9, 10)
peaches (10, 13)
nectarines (12, 12)
bananas (13, 15)
avocados (8, 17)
grapes (14, 17)
pears (13, 17)
apples (14, 17)
(B)
Fruit, (highest, lowest rank)
minus Vitamin Cb
cantaloupe (1, 1)
pink/red grapefruit (2, 2)
mangos (3,7))
strawberries (3, 7)
watermelon (3, 8)
tangerines (5, 8)
peaches (5, 10)
oranges (5, 9)
nectarines (7, 9)
avocados (3, 16)
white grapefruit (10, 15)
honeydew (10, 16)
pineapple (11, 15)
bananas (12, 15)
pears (11, 16)
apples (13, 17)
grapes (15, 17)
(C)
Fruit, (highest, lowest rank)
minus Vitamin C, Vitamin Ac
strawberries (1, 3)
oranges (2, 9)
cantaloupe (1, 13)
peaches (2, 14)
nectarines (4, 12)
pink/red grapefruit (2, 13)
mangos (5, 15)
tangerines (7, 11)
white grapefruit (6, 11)
avocados (1, 16)
honeydew (4, 16)
pineapple (5, 16)
bananas (7, 14)
watermelon (4, 15)
pears (5, 16)
apple (10, 17)
grapes (15, 17)
a
Rankings were based on the arithmetic mean of the rankings (one to 17) for all six methods. Highest, lowest represents the highest and
lowest rank attained among methods.
b
ND/Q scores were calculated removing vitamin C from the equations.
c
ND/Q scores were calculated removing vitamin C and vitamin A from the equations.
fat, added sugar, sodium, and cholesterol. Since fresh fruit
are generally very low in or devoid of these nutrients, the
inclusion of them had little impact on the scores presented
here. Methods also differed in the comparative variable(s),
that is, the denominator of the equation. Two methods used
nutrients to limit in the denominator (FQS, RRR), two
methods used energy (NFC, NDS), and one method used
nutrients to encourage in the denominator (CFN). Higher
scores were indicative of higher ND/Q for all methods
except the CFN method for which lower scores were
indicative of a higher ND/Q.
Despite various differences, there was a substantial
consistency among methods with regard to the relative
ranking of the ND/Q of the fruits (Table 2), and this
consistency was confirmed by the fairly strong correlation
coefficients among methods. This consistency has also
been observed in other studies that compared ND/Q scores
for similar foods or beverages using various methods.8,13
The percent differences between the highest and lowest
scores for any method were somewhat similar, representing
a range from 81% to 93%. The consistency in the findings
also suggests that methods that included fewer nutrients in
the calculation (for example, NRF Index, FQS, and RRR)
may be as reliable at predicting relative ND/Q scores for
fresh fruit as methodologies that included more nutrients,
at least for the specific methods included in this analysis.
Three methods (NRF Index, FQS, and RRR) capped DV
percentage values at a maximum of 100%. Fruits with
ND/Q scores affected by the 100% DV cap were oranges,
pink/red grapefruit, white grapefruit, cantaloupe, pineapple,
strawberries and mangos (vitamin C) and cantaloupe
(vitamin A). These fruits still had the highest ND/Q scores
even when the cap was applied, suggesting that these fruits
provided a range of other nutrients in substantial amounts
that helped contribute to their high relative ND/Q scores.
Each of the methodologies took into account nutrient
and energy content. Four nutrients were common to all six
methods: vitamin A, vitamin C, calcium, and iron. Calories,
protein, and fiber were represented in five methods, and
vitamin E, magnesium, saturated fat, and sodium were
represented in four methods. Because vitamin C, vitamin
A, calcium, and iron were common to all methods, the
impact of these individual nutrients on ND/Q scores was
further investigated. Fruits are not generally good sources
of calcium or iron. Data used for this analysis showed
that oranges provided the highest amount of calcium per
100g (~4% of the DV) and avocados provided the highest
amount of iron (~3% of the DV). Because these low
amounts were not expected to greatly impact the ND/Q
scores they were not considered further in this analysis.
Many fruits are good or excellent sources of vitamin C
and the fruits ranked as follows with regard to vitamin C
11
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
content (per 100g): strawberries > oranges > pineapple
> cantaloupe > mangos > white grapefruit > pink/red
grapefruit > tangerines > honeydew > grapes > avocados
> bananas > watermelon > peaches > nectarines > apples >
pears. The amount of vitamin C provided per 100g ranged
from 7% DV (pears) to 98% DV (strawberries). Only three
fruits provided less than 10% DV for vitamin C (per 100g):
pears, apples, and nectarines. In general, the vitamin C
rankings are fairly representative of the overall rankings
based on ND/Q scores (Table 2). Vitamin A precursors are
less widely distributed in these fruits compared to vitamin
C. Cantaloupe provided the highest amount of vitamin A
and provided approximately three times the amount as the
next highest source (pink/red grapefruit). Only five fruits
provided more than 10% of the DV for vitamin A per 100
g: cantaloupe, pink/red grapefruit, mangos, tangerines and
watermelon.
It was considered whether vitamin C, and to a
lesser extent vitamin A, might have a substantial bearing
on the rankings for these fruits and whether successively
removing these nutrients from the ND/Q equations would
substantially change ND/Q rank. After removing vitamin
C from all equations, cantaloupe still ranked the highest
(Table 3, column B). Mean rankings for pineapple, white
grapefruit and oranges decreased the most after removing
vitamin C suggesting that the ND/Q scores for these fruits
are especially sensitive to this nutrient. Mean rankings
for several fruits improved after removing vitamin C,
including watermelon, peaches, and avocados, all of which
tended to have lower amounts of vitamin C compared to
the other fruits. After additionally removing vitamin A
from all equations, several fruits (strawberries, oranges,
and cantaloupe) continued to rank high (Table 3, column
C). Some fruits dropped in rank (mangos, watermelon)
because they contained higher amounts of vitamin A
and were more sensitive to the removal of that nutrient,
while others benefited from higher rankings (peaches,
nectarines). Rankings for cantaloupe, strawberries, and
pink/red grapefruit were consistently high despite removing
both vitamins, suggesting that these fruits provided a
range of other nutrients in substantial amounts that, taken
collectively, contributed to their higher ND/Q scores.
Removal of both vitamins A and C from the equations
resulted in less consistent rankings among methods. This is
noted by comparing the highest and lowest ranks for each
equation iteration (Table 3, columns A, B, and C, highest
and lowest ranks in parenthesis) and observing that the
range between low and high ranks generally widened as
nutrients were sequentially removed from the equations.
The observed substantial drop in scores for some fruits
after removal of vitamin C or vitamin A also illustrates how
higher ND/Q scores may not necessarily reflect a greater
variety or balance of nutrients.
The magnitude of ND/Q scores can be
disproportionally affected by energy content, particularly
when energy forms the basis for all nutrient values (NRF
Index) or when energy alone constitutes the numerator or
denominator of the algorithm (NFC, CFN, NDS). On a
12
100g basis, watermelon, strawberries, white grapefruit and
cantaloupe had the lowest energy content and except for
watermelon, these fruits were ranked consistently high with
regard to ND/Q. Watermelon had one of the lowest energy
values yet ranked in the mid range with respect to ND/Q.
Relative to the other fruits in the analysis, watermelon
ranked fairly low in key nutrients such as fiber, potassium,
folate, and vitamin C. When nutrient content is high, energy
content is expected to make less of an impact on scores and
vice versa.
A limitation of current ND/Q approaches is that
phytochemicals were not included in any methodology
used in this analysis. Fruits contain a wide range of
phytochemicals, ranging from anthocyanins and resveratrol
in dark-colored grapes, quercetin in apples, to flavanones
such as hesperidin and naringin in citrus. Phytochemicals
in foods have been associated with beneficial effects
toward health.10,14 In order to incorporate phytochemicals
into a ND/Q methodology, intake reference standards and
more comprehensive and complete food phytochemical
databases need to be established. Another limitation is that
the practice of assigning a rank based on ND/Q score fails
to discriminate for relative differences between any two
scores. For one method, the difference between the highest
and second highest scores may be small while for another
method the difference may be large. Therefore, the rankings
are not reflective of whether small or large differences exist
among the scores for any given method.
CONCLUSION
Fresh fruits vary in their ND/Q as determined by
several quantitative scoring systems. These results indicate
that cantaloupe, strawberries, oranges, and grapefruit
consistently have a higher ND/Q compared to other
commonly consumed fresh fruit. This analysis demonstrated
that using six different methods to quantify ND/Q for select
fresh fruit produced consistent results. However, for some
fresh fruit ND/Q scores may be sensitive to key nutrients
such as vitamin C and vitamin A, suggesting that high
values for specific nutrients may influence relative scoring
and higher scores may not necessarily reflect a greater
variety or balance of nutrients. This analysis was not
designed to determine the most applicable ND/Q method,
but contributes to the limited body of data that quantifies
and compares ND/Q methods for various foods.
ACKNOWLEDGMENTS
The authors thank Mark Brown, PhD, for consultation
and assistance with statistical evaluation.
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S.
Estimativa e comparação de vários índices utilizados para
cálculo de densidade nutricional/qualidade de frutas. Alim.
Nutr., Araraquara, v. 23, n. 1, p. 7-14, jan./mar. 2012.
RAMPERSAUD, G.; VALIM, M. F.; BARROS, S. Comparison of nutrient density/ quality scores for fresh fruit. Alim. Nutr., Araraquara, v. 23,
n. 1, p. 7-14, jan./mar. 2012.
RESUMO: Vários métodos foram desenvolvidos e publicados com o objetivo de quantificar por meio de um índice a densidade nutricional e ou a qualidade de alimentos
e bebidas. Neste trabalho foram estimados os índices de
densidade nutricional de dezessete frutas mais consumidas
nos Estados Unidos utilizando seis métodos diferentes.
Os dados nutricionais utilizados no cálculo dos índices
de cada fruta foram obtidos na USDA National Nutrient
Database for Standard Reference, Release 23 e os índices
estimados foram classificados em ordem decrescente de
acordo com o método utilizado. Os resultados mostraram
uma ampla faixa de variação na magnitude dos índices
de densidade nutricional, mas com alta correlação entre
as metodologias utilizadas. As frutas melão (cantaloupe),
morango, laranja e grapefruit apresentaram, de maneira
consistente, os mais altos índices de densidade nutricional
entre os vários métodos utilizados. Foi observado que os
teores de vitaminas A e C, dois nutrientes computados na
maioria dos métodos, podem influenciar os resultados e
alterar a ordem de classificação de algumas frutas. Assim
sendo, frutas que apresentam altos índices de densidade
nutricional não necessariamente apresentam maior variedade ou equilíbrio entre os nutrientes, mas uma elevada
concentração de nutrientes específicos. Em conclusão, o
índice de densidade nutricional variou de acordo com o
método utilizado para cálculo, porém, os seis métodos
utilizados neste trabalho apresentaram resultados consistentes na ordem de classificação das frutas.
PALAVRAS-CHAVE: Frutas; nutrientes; densidade nutricional; qualidade nutricional; perfil nutricional.
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