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Review Article
Fish nutrient composition: a review of global data from poorly
assessed inland and marine species
Kendra A Byrd1, Shakuntala H Thilsted1and Kathryn J Fiorella2
,
*
1WorldFish, Penang, Malaysia: 2Master of Public Health Program, Department of Population Medicine and
Diagnostic, Cornell University, S2-004 Shurman Hall, Ithaca, NY 14853, USA
Submitted 12 April 2019: Final revision received 28 August 2020: Accepted 21 September 2020: First published online 14 December 2020
Abstract
Objective: Our understanding of the nutrient contribution of fish and other aquatic
species to human diets relies on nutrient composition data for a limited number of
species. Yet particularly for nutritionally vulnerable aquatic food consumers, con-
sumption includes a wide diversity of species whose nutrient composition data are
disparate, poorly compiled or unknown.
Design: To address the gap in understanding fish and other aquatic species’
nutrient composition data, we reviewed the literature with an emphasis on species
of fish that are under-represented in global databases. We reviewed 164 articles
containing 1370 entries of all available nutrient composition data (e.g. macronu-
trients, micronutrients and fatty acids) and heavy metals (e.g. Pb and Hg) for
515 species, including both inland and marine species of fish, as well as other
aquatic species (e.g. crustaceans, molluscs, etc.) when those species were returned
by our searches.
Results: We highlight aquatic species that are particularly high in nutrients of global
importance, including Fe, Zn, Ca, vitamin A and docosahexaenoic acid (DHA), and
demonstrate that, in many cases, a serving can fill critical nutrient needs for preg-
nant and lactating women and young children.
Conclusions: By collating the available nutrient composition data on species of fish
and other aquatic species, we provide a resource for fisheries and nutrition
researchers, experts and practitioners to better understand these critical species
and include them in fishery management as well as food-based programmes
and policies.
Keywords
Food security
Nutrition security
Fish access
Small indigenous species
Aquatic food systems
Marine food systems
Globally, more than 1 billion people rely on fish for con-
sumption and livelihoods(1). In fish-dependent regions,
fisheries provide livelihoods, income and nutritious food.
Fish have long been recognised as particularly nutritious,
contributing essential fatty acids, micronutrients, such as
Fe, Zn, Ca and vitamin A, as well as animal protein(2,3).
However, understanding of the nutrient contribution of
the world’s wide diversity of fish and other aquatic species
remains starkly limited.
The United Nations FAO has catalogued a growing num-
ber of fish species, recently expanding data on their
nutrient composition. In 2014, a total of 2033 fish species
were listed, but nutrient composition is only available
for a quarter of these (25·7%, 526 species) in FAO
INFOODS, a database commonly used to calculate nutrient
consumption(1,4). The nutrient composition of large-sized,
marine species of commercial importance is relatively bet-
ter assessed. In some settings, regional databases provide
nutrient composition data; for example, India’s Central
Inland Fisheries Research Institute maintains a detailed
database(5). Yet in many settings, because of data limita-
tions, fish are often treated as a largely homogenous food
group in analysing diets. Innovative modelling approaches
have attempted to fill gaps in nutrient composition data,
though they too are restricted to ray-finned species by lim-
ited data availability(6–8).
Public Health Nutrition: 24(3), 476–486 doi:10.1017/S1368980020003857
*Corresponding author: Email kfiorella@cornell.edu
© The Author(s), 2020. Published by Cambridge University Press on behalf of The Nutrition Society
Downloaded from https://www.cambridge.org/core. 03 Feb 2021 at 08:09:55, subject to the Cambridge Core terms of use.
The limitation of fish nutrient composition data is par-
ticularly problematic because the species consumed by
those who are the most food insecure and nutritionally vul-
nerable are the most poorly accounted. The species caught
by small-scale fishers, harvested in inland fisheries and rep-
resented by small-sized species (i.e. fish <25 cm at matu-
rity) are largely absent from global databases. A recent
study predicting nutrient availability of fish landing sites
underscores this point: nutrient content was available for
only 17 % of the finfish caught(8). Similarly, a recent report
in Nigeria found that nutrient content was available for
high-value, large species, while smaller species were
largely missing from available nutrient databases(9). The
confluence of aquatic biodiversity, nutrition insecurity
and high fish dependence necessitates a better understand-
ing of the nutrient composition of species from diverse set-
tings (e.g. across geographies; across inland, marine and
aquaculture).
In the few fisheries where nutrient information has been
well assessed, findings suggest there are important
differences in nutrient composition of different fish species.
The nutrient composition of a subset of inland fish in
Bangladesh, a country with high fish reliance and diversity,
has been well documented(10–13). The study of Bangladeshi
inland fish demonstrates high variation within key nutrients
across species. For example, in common small indigenous
species, Fe per 100 mg of raw, edible parts ranged from
0·46 to 19·0 mg(13). In the same set of fish species, Zn
per 100 mg raw, edible parts ranged from 0·60 to 4·7 mg
and variations for other nutrients have been reported for
both large indigenous fish and introduced fish species(13).
The policy implications of our findings are far reaching
as realised and projected fish declines across global species
are causing alarm(1,14). Even as incomplete data on nutrient
composition hamper our ability to understand the extent
and consequences of these declines, fish declines have
been highlighted as a particular nutritional concern(15)
and for their potential role in meeting the SDG and reduc-
ing malnutrition(16). Moreover, evidence from global(17) and
national(18) studies shows that better child linear growth is
correlated with higher fish consumption. Highlighting fish
and other aquatic species that are particularly nutritious will
be integral to addressing malnutrition in fish-dependent
regions, planning for conservation and management,
developing new strategies to promote production of nutri-
tious species and reducing waste and loss of aquatic
species.
To address the gap in availability of nutrient composi-
tion data on diverse fish species, we reviewed the literature
and extracted data on nutrient compositions of species
around the world, with an emphasis on small indigenous
and other species that are under-represented in global data-
bases. While we focused our search terms on fish, when
other aquatic species (e.g. crustaceans, molluscs, animals,
etc.) were also analysed, we included these within our
review, but did not search for them explicitly. We highlight
five nutrients (Fe, Zn, Ca, vitamin A and docosahexaenoic
acid (DHA)) that are commonly lacking in the diets of
women and young children in low- and middle-income
countries and have been analysed in a relatively larger sub-
set of species within our review. Appendix Table A1 pro-
vides a review of the highlighted nutrients, their
importance and global patterns of their deficiency.
Methods
We used an iterative process to identify appropriate search
terms initially inclusive of a term regarding nutrient compo-
sition (food composition, macronutrient composition,
micronutrient composition, nutrient composition and nutri-
tion composition) and a term inclusive of fish (small fish,
small indigenous fish, micronutrient fish and micronutrient-
rich fish). We also piloted use of the term seafood but
retained the use of fish due to concerns regarding limiting
freshwater species inclusion. We ultimately used the most
inclusive terms (fish*, *nutri* composition) and searched
three databases (EBSCO Host Agricola, Web of Science
and Web of Science using cabicode Food Composition
and Quality) and one research journal (Journal of Food
Composition and Analysis, search for fish*). To minimise
the risk of missing relevant articles, we also searched
reference lists of key studies and examined ‘cited by’
references in Web of Science. Searches were conducted
through August 2019; no beginning date was applied,
and archiving was limited only by the availability of litera-
ture online.
We focused our search on fish and retain that terminol-
ogy throughout. However, when our searches returned
nutrient composition analyses of other aquatic animals
(e.g. snails and reptiles), molluscs, cephalopods and other
shellfish, we included these within the review. The delimi-
tation of ‘fish’is culturally specific in many instances, with
many molluscs, snails and other aquatic species consid-
ered fish in some settings, and fish limited to only large
body species in others. As we did not search for all types
of aquatic species, our representation of them is likely
limited.
Inclusion criteria were as follows: articles contained
original aquatic species’nutrient composition analyses of
at least one aquatic species for use as human food (as
opposed to uses as pet food, livestock feed or aquaculture
feed). We defined nutrient composition data as inclusive of
macronutrients or micronutrients.
We excluded articles that analysed only large-body
marine fish species (e.g. Haddock, Cod and Salmon) for
which nutrient composition data are well established; in
which nutrient composition values were not reported
and could not be obtained from the study author; that relied
solely on aquatic food purchased at Western-style super-
markets, rather than local markets, and were unlikely to
have been regionally sourced; that focused on how
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different aquaculture feed alterations affected nutrient
composition; or included only data on heavy metal concen-
trations (e.g. lead and mercury) without also including
nutrient data. Even within included studies, we did not
include composite products (e.g. complementary foods
made with aquatic species) in our review. Unfortunately,
reasons for exclusion were not enumerated in the review
process, and the number of articles excluded by reason
is not available.
Following from our formal inclusion criteria, we note
some dimensions of the included studies. As we did not
exclude articles based on study type or the laboratory
methods used to assess nutrient composition, we remind
readers that some analytical methods produce more consis-
tent results and better detect nutrient presence and sub-
types of nutrients (such as the multiple forms of vitamin
A). Included articles often analysed the same species,
and some made comparisons among nutrient composition
based on processing method, season and location, in addi-
tion to analyses focused on different species allowing for
increased understanding of how these differences contrib-
ute to nutrient differences.
We examined the paper title and abstract to identify
studies that were in English, topically relevant, and may
include fish nutrient composition data. Studies were then
further screened to ensure they included original fish
nutrient composition data and a full text of the manuscript
was available. In cases of full texts not being accessible
or available for purchase, every effort was made to contact
the study author to request a full-text copy and we were
successful in obtaining relevant articles in all but three
cases.
We did not apply any geographic exclusions. While a
number of studies of Chinese species are included in our
review, our focus on studies in English did lead to the omis-
sion of Chinese references that appeared relevant from their
English abstract. Further, our exclusion of articles focused on
only large-bodied marine fish species incidentally focused
our findings within those regions where diverse species’
nutrient composition has been most analysed.
Nutrient composition data and units were extracted
from each study for all macronutrients, micronutrients
and heavy metals reported. The fatty acids extracted
included alpha-linolenic acid, eicosapentaenoic acid
(EPA), DHA, arachidonic acid and linoleic acid, and the
protein extraction included separate amino acids. Alpha-
linolenic acid, EPA and DHA are omega-3 fatty acids,
and are mainly found in fish and seafood. Arachidonic acid
and linoleic acid are omega-6 fatty acids, and are com-
monly found in nuts, seeds, and vegetable oils. We
included nutrient composition data for each unique analy-
sis conducted by fish species, processing method, fish
location or season when applicable. For the limited subset
of studies (n7) that measured replicates of individual
fish species harvested in the same conditions (site, season,
etc.), the average nutrient value was retained and
included as a single entry. Note, given the expense of
nutrient analyses, multiple individuals are often combined
prior to nutrient composition analysis to create an ‘aver-
age’value.
From within the review, we present a subset of key
nutrients and five or more selected species. Micronutrients
were selected based on data showing global deficien-
cies(19,20) and include Fe, Zn, Ca and vitamin A. While addi-
tional nutrients, such as vitamin B
12
or folate, are of global
importance, very limited data availability prevented their
inclusion. DHA was also selected given that it is an essential
fatty acid commonly found in fish and was the most
analysed polyunsaturated fatty acid in the collated literature.
Additionally, some studies have found low concentrations of
DHA in blood within certain regions of Africa(21).Species
high in these micronutrients and DHA were selected purpos-
ively to demonstrate understudied species that provide these
nutrients in settings where there is particular concern about
inadequate dietary consumption of these nutrients. In addi-
tion, we include nutrient composition data from Atlantic Cod
and Atlantic Salmon for comparison. Due to disparities in
both laboratory analytical methods and units of measure-
ment, calculating summary data of nutrient composition
(e.g. average mg of Fe of marine species) introduces several
forms of bias and was not appropriate.
Contribution of a serving of fish to the
recommended nutrient intake
For each of our key nutrients –Fe, Zn, Ca, vitamin A and
DHA –we present a calculation where we compare the
nutrient content of a given uncooked fish species to the
daily recommended nutrient intake (RNI) of women and
children at different life stages. These calculations were
performed to highlight the variation in fish nutrient compo-
sition and density (nutrients per gram). The nutrient com-
position will fluctuate in response to how the fish are
cooked or handled, and other components in the diet
(e.g. phytates) influence how much of certain nutrient
people absorb; thus, these calculations are not meant to
provide individual dietary advice. However, these calcula-
tions do allow us to provide an estimate of how certain fish
species make potential nutrient contributions to diets. We
calculate the percentage of the RNI for pregnant women,
lactating women and children aged 6–12 months and aged
12–24 months(22,23) that a serving of fish fulfils. Following
previously used methods, in our calculations, we assume
a 50 g serving for women and a 25 g serving per d for
children(13).
The estimated amounts of Fe, Zn, Ca and vitamin A
amounts of each fish are listed in Appendix A2-6. For Fe,
we assume 10 % bioavailability(22). The RNI for Fe for preg-
nant women is based on the WHO 2004 value for women
aged 19–50 years, as no specific value for pregnant women
is given. The value of 29·4 mg/d is in close alignment with
the Institute of Medicine recommendation of 27 mg/d for
478 K Byrd et al.
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pregnant women(21). For Zn, we assume moderate bioavail-
ability(22). We calculated Zn requirements by averaging the
requirement across the three trimesters of pregnancy and
first 12 months of lactation, using a value of 7·5 mg/d for
pregnancy and 8·5 mg/d for lactation. The Ca and vitamin
A requirements were taken directly from the FAO/WHO
2004 for the ages of children reported, and for pregnant
and lactating women.
For DHA, the FAO recommends an intake of 200 mg/d of
DHA for pregnant and lactating women and the adequate
intake for children 6–23 months is estimated to be 10–12
mg/kg body weight per d(25). Based on the work of
Bogard et al.(13), we used a figure of 110 mg DHA/d for young
children, which is the midpoint of the recommended range of
intakes based on the respective body weights of children at 7
months and children at 23 months at the 50th percentile(25).
The percentage of the nutrient requirement was based on a
50 g/d serving of fish for pregnant and lactating women, and
a 25 g/d serving of fish for children 6–24 months. Exact DHA
values and sources can be found in Table A6.
The literature review data are provided in Appendix
Table A7.
Results
Distribution of nutrient analyses
Our searches yielded 8425 articles, and we ultimately
included and reviewed 164 articles analysing the nutrient
composition of 1370 entries on fish and other aquatic spe-
cies (e.g. crustaceans, molluscs; Figure A1). The review
includes 515 unique species with multiple species entries
analysed across different studies, or across cooking meth-
ods, harvest locations or seasons. Fifty percent of species
were classified as freshwater and 45 % as marine; 5 % of fish
were farmed (65 % of which were freshwater species).
Additionally, 14 % of the 515 species were described as
small indigenous species (SIS), or a similar term, in at least
one study; however, other species might also fit within this
categorisation.
Studies were conducted in forty-eight countries, with the
greatest number of species assessed in South and Southeast
Asia (Fig. 1). Analyses of inland species, notably including
a wider representation of African species, were conducted
in twenty-nine countries, and analyses of marine species were
conducted in thirty-four countries (Fig. 1).
(a) Number of Studies
(c) Number of Inland Analyses (d) Number of Marine Analyses
(b) Number of Analyses
Fig. 1 Number of a) studies and b) analyses, as well as c) inland analyses and d) marine analyses. Numbers of analyses refers to the
total number of analyses done, which exceeds the number of species analyzed as multiple studies may have analyzed the nutritional
composition of the same species, or a study may have compared nutritional composition of the same species across different con-
ditions (e.g., habitats, populations, times of year) resulting in multiple analyses
A review of fish nutrient composition 479
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Composition of key nutrients
For each nutrient, we highlight five or more fish and other
aquatic species from our review that are high in the given
nutrient and provide comparative nutrient data for Atlantic
Cod and Atlantic Salmon.
Iron
Fe was reported for 535 of the 1370 entries analysed
(39·1 %), and the Fe content for the selected species is
listed in Table A2. Compared with Atlantic Cod and
Salmon, small indigenous fish species and other aquatic
species from Bangladesh, India, Laos, and the countries
around Lake Victoria (Kenya, Tanzania and Uganda) had
a substantially higher Fe content. For example, Jat Punti
(Puntius sophore), a common small indigenous species
in Bangladesh, contains 11·6 mg Fe/100 g of wet weight,
compared with 0·38 mg/100 g raw Atlantic Cod (Gadus
morhua L.) and 0·80 mg/100 g raw Atlantic Salmon
(Salmo salar L.).Further,thetypeofFe(haemv. non-
haem) found in a food influences bioavailability or the
extent to which Fe can be absorbed by the body. In
the few cases in which Fe type has been analysed in fish,
such as in Mola (Amblypharyngodon mola), high con-
centrations of haem Fe, the more bioavailable type of
Fe, have been identified(26).
High nutrient concentrations of Fe in fish can meet
demands for Fe at critical periods in the life cycle. For a lac-
tating woman, a daily serving of Jat Punti fulfils 38 % of her
daily Fe needs (Fig. 2). For infants aged 6–11 months, a
serving of Jat Punti fulfils 31 % of daily Fe needs (Fig. 2).
Other aquatic species also have high Fe composition; the
Golden Apple Snail (Pomacea canaliculata, de-shelled)
from Laos contained 48·0 mg/100 g of wet weight, and a
daily serving fully meets the dietary need of lactating
women and children 6–24 months of age (Fig. 2).
Zinc
Zn was quantified in 31·2 % of entries in our review, and
Table A3 lists the Zn content of the selected species.
Darkina (Flying barb, Esomus danricus) and Mola
(A. mola) from Bangladesh, Hichiri (Spotty-faced
Anchovy, Stolephorus waitei) in India and Mukene (Silver
Cyprinid, Rastrineobola argentea) from the countries
around Lake Victoria are four small indigenous species that
provide particularly highconcentrations of Zn (Table A3). In
particular, Hichiri contained 26·0 mg/100 g wet weight of Zn,
while our reference fish, Atlantic Salmon and Cod, provided
insignificant amounts at <1·0 mg/100 g of raw fish (Table
A2). Other aquatic species can also play a role in addressing
Zn deficiency, and the Big Apple Snail (Pila sp., de-shelled)
provides 12·0 mg/100 g of wet weight (Table A3).
Zn is commonly lacking in many diets of low- and middle-
income countries(27), and fish high in Zn can address this gap.
For example, a serving of Mukene fulfils 27 % of daily recom-
mended Zn intake for a pregnant woman and 24 % for an
infant (Fig. 3). A serving of Hichiri from India fulfils over
100 % of the Zn requirement for pregnant and lactating
women and children 6–24 months of age, taking into account
moderate bioavailability.
Calcium
Ca was analysed in 35·0 % of entries in our review, and
Table A4 highlights the content from selected species
from Bangladesh, India, Laos, Malawi and Uganda. Two
small indigenous species from Bangladesh contain high
concentrations of Ca, with Jat Punti (Pool barb, P. sophore)
providing 1711·0 mg/100 g and Kata Phasa (Spined
anchovy, Stolephorus tri) 1500·0 mg/100 g of raw, edible
parts (Table A4). In Malawi, Utaka (Copadichromis
inornatus) provides 1883·8 mg/100 g of wet weight
(Table A4). Notably, again an indigenous snail, the Small
0
%20
%40
%60
%80
% 100
%
Chapila (Bangladesh)
Mola (Bangladesh)
Jat Punti (India)
Mukene (Uganda)
Golden Apple Snail (Laos)
Atlantic Cod (USA)
Atlantic Salmon (USA)
Iron
Fig. 2 Contribution (%) of recommended nutrient intake (RNI)(22) of iron by fish and other aquatic species. Percentages are estimated
based on a 50 g/d serving of fish for pregnant and lactating women, a 25 g/d serving for children 6–24 months, and assuming 10 %
bioavailability of iron. The RNI for iron for pregnant women is based on the value of 29·4 mg/d for women aged 19–50 years, as no
specific value for pregnant women is given. This is in alignment with the Institute of Medicine (IOM) RDA of 27 mg/d for pregnant
women(24). Iron values and sources are given in Table A2. , Pregnant women; , lactating women; , children 6-11 months; ,
children 12-24 months
480 K Byrd et al.
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Apple Snail (Cipangopaludina chinensis, de-shelled)
from Laos is also a very good source of Ca, providing
1200·0 mg/100 g wet weight. By comparison, Ca in
Atlantic Cod (16·0 mg/100 g raw) and Atlantic Salmon
(12·0 mg/100 g raw) is relatively low.
Four of the small indigenous species highlighted in
Fig. 4 fulfil 50 % or more of the recommended Ca intake
for all age categories listed. For example, a serving of Jat
Punti fulfils 71 % of the Ca requirement for pregnant
woman and 86 % for a lactating woman. For a child aged
6–11 months, a single serving of either Jat Punti or Utaka
provides over 100 % of recommended daily Ca intake.
Fish consumed whole, including bones, or as fish
powder have high Ca concentrations. These include spe-
cies that were noted as consumed whole(28) as well as
fish by-products that have a low market value and are
locally consumed and leftoverwhenfishareprocessed
for an export industry(29). The highest levels of Ca were
contributed by species for which ‘plate waste’,leftover
after eating, was particularly low, as is typical for
small indigenous species compared with moderate-
and large-sized fish(10).
Vitamin A
Vitamin A was quantified in 18·6 % of the entries analysed
in our review, and Table A5 lists the vitamin A content for
selected species from Bangladesh, Cambodia and India. In
stark contrast to Atlantic Cod and Atlantic Salmon, which
both contain 12·0 μgRAE/100 g raw fish, Darkina
(Esomus danricus), Chanda (Parambassis baculis) and
Mola (A. mola) from Bangladesh all contain over 800
μgRAE/100 g raw, edible parts, with Chanda and Mola
containing over 2500 μgRAE/100 g raw, edible parts.
Figure 5 shows that vitamin A concentrations in several
small indigenous species exceed the recommended intake
for vitamin A; thus, a small quantity of these species can
make a meaningful impact in meeting vitamin A need. A
serving of mola fulfils 157 % and 147 % of the vitamin A
0
%20
%40
%60
%80
% 100
%
Darkina (Bangladesh)
Mola (Bangladesh)
Hichiri (India)
Mukene (Uganda)
Big Apple Snail (Laos)
Atlantic Cod (USA)
A
tlantic Salmon (USA)
Zinc
Fig. 3 Contribution (%) of recommended nutrient intake (RNI)(22) of zinc by fish and other aquatic species. Percentages are estimated
based on a 50 g/d serving of fish for pregnant and lactating women, a 25 g/d serving for children 6–24 months, and assuming moderate
bioavailability. For pregnant and lactating women, zinc contributions were calculated by averaging the requirements throughout the
three trimesters of pregnancy, and first 12 months of lactation, given that they vary slightly depending on trimester and month of
lactation. Zinc values and sources are given in Table A3. , Pregnant women; , lactating women; , children 6-24 months
0
%20
%40
%60
%80
% 100
%
Jat Punti (Bangladesh)
Calcium
Kata Phasa (Bangladesh)
Katli (India)
Utaka (Malawi)
Mukene (Uganda)
Small Apple Snail (Laos)
Atlantic Cod (USA)
Atlantic Salmon (USA)
Fig. 4 Contribution (%) of mean recommended intake(22) of calcium by fish and other aquatic species. Percentages are estimated
based on a 50 g/d serving of fish for pregnant and lactating women, and a 25 g/d serving for children 6–24 months. Calcium values and
sources are given in Table A4. , Pregnant women; , lactating women; , children 6-11 months; , children 12-24 months
A review of fish nutrient composition 481
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recommended intake for pregnant and lactating women,
respectively, and fulfils 167 % of the recommended intake
for a child 6–24 months of age (Fig. 5). Put another way, to
fulfil 100 % of the recommended intake of vitamin A, a
pregnant woman would need to consume 29 g, a lactating
women 32 g and a child 6–24 months of age 15 g of whole
mola. The concentration of vitamin A in mola is particularly
high in the eyes and therefore nutritionally advantageous
that the fish are consumed whole(30).
DHA
DHA was analysed in 33·4 % of the entries in our review,
and Table A6 highlights the content from selected species
from Bangladesh, Laos, Malawi, and the countries border-
ing Lake Victoria. Several fish species provide high quan-
tities of DHA. For example, Usipa from Malawi and Nile
Perch from Uganda contain 444 mg/100 g wet weight
and 970 mg/100 g wet weight. A serving of Atlantic
Salmon contains 1115 mg DHA/100 g raw; however, it is
not an accessible food to many populations (Table A6).
A serving of Usipa, Marbled Lungfish and Nile Perch fulfils
over 100 % of the recommended DHA intake for both
women and children within the first 1000 d of life, com-
pared with the Atlantic Cod, which provides 30 % or
less (Fig. 6).
Notably, freshwater species provide high amounts of
DHA in settings where DHA access is of concern. While
cold water marine species are often assumed to contribute
relatively high levels of essential fatty acids, inland species
such as Dagaa or Nile Perch may also make important con-
tributions to dietary DHA, especially where fish are widely
and frequently consumed(31–33).
Discussion
By collating the available nutrient composition data, we
provide a resource for fisheries and nutrition researchers,
experts and practitioners to better understand the diversity
of fish species and include them in programmes and poli-
cies. Our findings regarding fish nutrient composition sug-
gest that poorly assessed fish species are high in nutrients of
global importance. Such species may be of particular value
for meeting the nutritional needs of vulnerable people
around the world. Yet, our findings also reveal the geo-
graphic limitations in fish nutrient composition data avail-
ability, with a subset of fisheries being relatively well
assessed, compared with others where data are highly
limited.
Many of the fish included within our review offer prom-
ising but under-utilised opportunities to increase access to
key nutrients and address nutrient deficiencies that cause
widespread morbidity and mortality. We present the RNI
in our analyses(22). The RNI provide an estimated require-
ment that ensures the needs of nearly all of a group (97·5 %
of the needs of a given age group or life stage) are met and
are thus a more conservative estimate than the estimated
average requirement (EAR), which provide a nutrient value
that meets the needs of 50 % of a group.
Policy implications
Small indigenous fish species and food and nutrition
security
Fish are typically treated as a homogenous category in ana-
lysing diets. Although ‘fish’are normally placed on par with
poultry, beef or pork, the categorisation of fish refers to
thousands of different species which offer unique nutrient
profiles to the consumer. While the large marine fish spe-
cies with better established nutrient composition are
unquestionably nutritious, there are relevant distinctions
between them and other types of fish, particularly small
indigenous species and species that are supplied by global
small-scale fisheries.
First, some small indigenous species and other aquatic
species caught within small-scale fisheries may be higher
in micronutrient content than large, high market value spe-
cies. For example, the Ca content of Kata Phasa is 93 times
higher than that of Atlantic Cod, the Zn content of the Big
Apple Snail is 20 times higher than Atlantic Salmon, and the
Fe content of Jat Punti is 209 times higher than Atlantic Cod
or Atlantic Salmon. Consumption patterns are a factor in
these differences. Small fish are commonly consumed
0
%20
%
Vitamin A
40
%60
%80
% 100
%
Chanda (Bangladesh)
Darkina (Bangladesh)
Mola (Bangladesh)
Chunteas Phlunk (Cambodia)
Jat Punti (India)
Atlantic Cod
Atlantic Salmon
Fig. 5 Contribution (%) of recommended nutrient intake (RNI)(22) of vitamin A by fish species. Percentage is estimated based on a 50
g/d serving of fish for pregnant and lactating women, and a 25 g/d serving of fish for children 6–24 months. Vitamin A values and
sources are given in Table A5. , Pregnant women; , lactating women; , children 6-24 months
482 K Byrd et al.
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whole, leading to a high density and wide variety of
nutrients when compared with fish for which only the
muscle is consumed(16). For example, Ca delivered by con-
sumption of whole fish is much higher than when fish
bones are relegated to plate waste for larger fish spe-
cies(30,34). Fish for which the head is consumed also deliver
higher quantities of micronutrients, particularly vitamin A,
often attributed to the consumption of the eyes(30). Further,
some fish are rich in Fe of high bioavailability and contain
little to no anti-nutrients, which inhibit the absorption of
nutrients by the body(35). More detailed accounting of the
nutrient contribution of small fish within dietary analyses
could better inform the importance of fisheries to nutrition
security.
Second, small-sized species are also typically low on the
food web, meaning that when heavy metals such as mer-
cury are present, small fish may have relatively lower levels
of these heavy metals. Fish body size and trophic level have
been associated with methyl mercury in a range of stud-
ies(36,37). Both across and within species, larger fish tend
to have higher levels of mercury(38,39). Still, fish mercury
concentrations are highly variable, and small fish may also
dwell in environments where conditions increase mercury
methylation(40).
Third, small species and harvests from small-scale fish-
ers are often more financially and physically accessible.
Small-scale fishers typically use relatively simple boats
and gears to access small indigenous species, compared
with the ocean-going vessels and associated gears required
to target large marine and pelagic fisheries. The harvest of
small indigenous species(16) and inland species(41,42) is also
more often directed to local consumption as they are less
often exported, typically sold for low prices, available in
small quantities, and, some theories suggest, underfished
relative to larger fish(43). Further, processing of small spe-
cies is often easier as they can be dried in the sun or with
a small amount of heat, meaning that refrigeration is not
required for storage for household use and facilitating
transport from rural to urban markets.
Importantly, recognising the nutritional importance of
small indigenous and other under-appreciated species is
more complex than equating their catch with food and
nutrition security. While some communities eat large pro-
portions of the fish they catch, fish remain one of the most
widely traded commodities and other communities eat little
of their catch or only particular fish types(44). High market
value fisheries can contribute substantially to local incomes
and thereby food and nutrition security, and a better under-
standing of local patterns and demographics of sale and
consumption are paramount to understanding how and
when fisheries can support food and nutrition security(45).
Finally, threats to the availability of small species are
looming. Small species are most often targeted for fishmeal
and fish oil for use in aquaculture and pet food industries,
which may impact their accessibility in the future(46). The
expansion of aquaculture has the potential to affect the
way small indigenous species are used, their prices and
their habitats. Thus, the current and future diversion of
these fish to feeds and the effect on food and nutrition secu-
rity of poor consumers that rely on them should be carefully
analysed.
Nutrient composition data opportunities and
challenges
Harmonising and comparing nutrient composition data in
fish remains challenging because of differences in units
and fish parts measured. The food composition literature
uses a range of units (e.g. whole fish, dry weight, muscle
and raw, edible parts), of which we suggest raw, edible
parts that account for plate waste (e.g. discarded bones)
are the most salient metric. Delimiting what is edible, how-
ever, must be done carefully. Analyses of muscle tissue may
miss substantial edible portions of fish that are widely con-
sumed in many settings, especially for small fish.
Conversely, analyses of whole fish may overestimate the
nutrients consumed if substantial parts of the fish are dis-
carded. Efforts to take into consideration differences in
nutrients as a function of cooking, drying and
0
%10
%20
%30
%40
%50
%60
%70
%80
%90
% 100
%
Ilish (Bangladesh)
DHA
Usipa (Malawi)
Marbled Lungfish (Uganda)
Atlantic Salmon (USA)
Atlantic Cod (USA)
Nile Perch (Uganda)
Fig. 6 Contribution (%) of daily recommendation of DHA by fish species. The FAO recommends an intake of 200 mg/d of DHA for
pregnant and lactating women, and the adequate intake for children 6–23 months is estimated to be 10–12 mg/kg per d(25). Based on
the work of Bogard et al.(13), we used a figure of 110 mg DHA/d for young children, which is the midpoint of the recommended range of
intakes based on the respective body weights of children at 7 months and children at 23 months at the 50th percentile(26). Percentages
are estimated based on a 50 g/d serving of fish for pregnant and lactating women, and a 25 g/d serving of fish for children 6–24 months.
DHA values and sources are given in Table A6. , Pregnant and lactating women; , children 6-24 months
A review of fish nutrient composition 483
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bioavailability(10) will provide more detailed and relevant
data. Some nutrients are also particularly sensitive to ana-
lytic discrepancies. For example, vitamin A estimates may
be low as vitamin A in fish is found as both 3,4 didehydror-
etinol (vitamin A
2
) and retinol (vitamin A
1
) with the biologi-
cal activity of didehydroretinol being 119–127 % higher
than retinol(47). Harmonising nutrition composition metrics
with a production literature that often uses other units is
also a challenge, and a more comparable set of nutrient
composition data from fish will provide for improved
understanding of the links between fish production and
nutrient availability.
In addition to differences reflected by processing and
cooking, environmental factors may have substantial
effects on nutrient levels in fish. The studies we review
highlight the role of harvest location(48) and season(49–52)
in affecting nutrient concentrations in fish. For example,
for Mytilus coruscus, a thick-shelled mussel in China, the
concentrations of macronutrients and minerals (e.g. Fe,
Mg, Mn and Zn) varied vastly across seasons. In addition,
several studies examined different size classes of the same
species to assess differences in nutrient composition across
fish life spans and found significant differences in amino
acids, fatty acids and vitamin A concentrations(11,53,54).
Differences across season, location and life stage may
reflect important seasonal patterns in temperature and food
availability, as well as potential differences across sub-
populations of fish and other aquatic species.
Finally, laboratory methods to analyse nutrient compo-
sition continue to evolve. The newest methods require
state-of-the-art laboratories that are often unavailable in
low- and middle-income countries. However, these new
techniques have highlighted unique components found
in fish. For example, new techniques have shown that
washing the fish sample with additional acetone yielded
greater haem Fe, and traditional techniques in the past
may have underestimated the amount of haem Fe in fish
species(26). Further, analyses have often looked only for
vitamin A
1
, whereas many small indigenous species are
rich in the more bioactive vitamin A
2
(55). While these
new methodologies are not part of common laboratory
methods to analyse fish nutrient composition, future ana-
lytical methods should aim to use these to better assess fish
nutrient composition, where possible. Modelling may also
prove useful in extending nutrient profiles to better under-
stand nutrient composition of additional species(6,8).
Conclusions
The cost and laboratory requirements necessary to conduct
nutrient composition analyses prohibit analysing the full
extent of fish diversity. Still, broader understanding of the
nutritional contributions of fish consumed locally and by
vulnerable populations, including in the first 1000 d of life,
is needed. The incorporation of these species into dietary
recommendations and nutrition programmes depends on
recognition of their nutrient contributions. So, too, does
appreciating the ecosystem services fish and other aquatic
species provide, conserving these species, and prioritising
local access to them.
Small indigenous species and small-scale fisheries are
likely to remain essential for meeting the micronutrient
and essential fatty acid needs of the poor. Nutrient-rich fish
and other aquatic species could also provide food-based
approaches to reducing nutrient deficiencies, with increas-
ing access and consumption offering many advantages
over nutrient supplementation, which faces safety and
access concerns(56,57). It is the hope of the authors that this
review provides as a useful tool for those working around
fisheries with poorly characterised nutrient data.
Our review also provides a starting point for future
research. Future analyses should examine nutrient patterns
across species’ecological niches, diets or other traits, or
how different conditions shape fish nutrient composition
as environments change. Future research should also seek
to expand modelling of nutrient composition for species
that have not been fully analysed and particularly so within
geographies where nutritional composition is poorly
assessed but fish dependence is high.
Acknowledgements
Acknowledgements: We gratefully acknowledge Asha
Plattner Belsan, Santana Silver, Dorai Raz, Bendula
Wisman and Sanjna Das for their contributions to the com-
pilation of the database. Financial support: It was provided
by Cornell University’s Atkinson Center for a Sustainable
Future (to K.J.F.) and by the European Commission under
the Putting Research into Use for Nutrition, Sustainable
Agriculture and Resilience programme (PRUNSAR) to
WorldFish through the International Fund for Agricultural
Development (IFAD) grant no. 2000001538 (to K.B. and
S.H.T.). Conflict of interest: There are no conflicts of inter-
est. Authorship: K.J.F. and S.H.T. designed the literature
review. K.J.F. lead the literature review. K.A.B. analysed
the review data. K.J.F. and K.A.B. wrote the manuscript.
All authors reviewed and edited the manuscript. Ethics of
human subject participation: Not applicable.
Supplementary material
For supplementary material accompanying this paper visit
https://doi.org/10.1017/S1368980020003857
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