Powell et al.

Journal of Ethnobiology and Ethnomedicine (2017) 13:23

DOI 10.1186/s13002-017-0150-2

RESEARCH Open Access

The determinants of dietary diversity and

nutrition: ethnonutrition knowledge of local
people in the East Usambara Mountains,
Tanzania
Bronwen Powell1,2* , Rachel Bezner Kerr3, Sera L. Young4 and Timothy Johns5

Abstract
Background: Diet and nutrition-related behaviours are embedded in cultural and environmental contexts: adoption
of new knowledge depends on how easily it can be integrated into existing knowledge systems. As dietary
diversity promotion becomes an increasingly common component of nutrition education, understanding local
nutrition knowledge systems and local concepts about dietary diversity is essential to formulate efficient messages.
Methods: This paper draws on in-depth qualitative ethnographic research conducted in small-scale agricultural
communities in Tanzania. Data were collected using interviews, focus group discussions and participant observation
in the East Usambara Mountains, an area that is home primarily to the Shambaa and Bondei ethnic groups, but has a
long history of ethnic diversity and ethnic intermixing.
Results: The data showed a high degree of consensus among participants who reported that dietary diversity is
important because it maintains and enhances appetite across days, months and seasons. Local people reported that
sufficient cash resources, agrobiodiversity, heterogeneity within the landscape, and livelihood diversity all supported
their ability to consume a varied diet and achieve good nutritional status. Other variables affecting diet and dietary
diversity included seasonality, household size, and gender.
Conclusions: The results suggest that dietary diversity was perceived as something all people, both rich and poor,
could achieve. There was significant overlap between local and scientific understandings of dietary diversity,
suggesting that novel information on the importance of dietary diversity promoted through education will likely
be easily integrated into the existing knowledge systems.
Keywords: Agrobiodiversity, Local knowledge, Dietary behaviour, Dietary diversity, Landscape diversity

Background Malnutrition, including undernutrition, micronutrient

deficiency and overnutrition, remains one of the biggest
“My grandfather used to advise me that if you want to challenges to global development [1–3]. Ensuring healthy
have a good life, a good life is not to have money, it is diets, along with reducing infectious disease, is the
about food which ensures that you will not be foundation of long-term and sustainable strategies for
troubled… If you want a good diet you must have overcoming global malnutrition [4–6]. However, dietary
foods for changing your diet.” Ramadhani Juma, practices are determined by a complicated mix of biology,
Tongwe village knowledge, skills, social-cultural factors (such as identity
and beliefs), psychological factors (emotion, motivation,
goals, memory, and attention), environmental context,
* Correspondence: bronwen.powell@psu.edu
1
Department of Geography and African Studies Program, Pennsylvania State
and resources [7–9]. There is growing recognition of the
University, State College, PA, USA important role of structural, environmental, cultural,
2
Center for International Forestry Research, Bogor, Indonesia social and psychological factors in dietary behaviour [10].
Full list of author information is available at the end of the article

© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 2 of 12

Krumeich et al. [11] note that health decisions are often if they see them as meeting their own needs and aspira-
shaped by factors such as social and cultural context, that tions [35]. Examining variations in local knowledge allows
are beyond the control of the individual, and that healthful for an understanding of the degree of consensus between
behaviour change is not simply a matter of convincing people from the same cultural group [28], and facilitates
people to act in a more rational manner. the examination of which forms of existing local
While traditional diets are often quite healthy [12], so- knowledge are better aligned with scientific ideas of
cial, cultural and economic change in many places has health-positive behaviour. In anthropological literature,
led to dietary transitions associated with decreasing knowledge of a culture or society is often referred to as
quality of diets [13]. In most contexts, intervention helps emic and outside or scientific knowledge as etic. Herein
to reverse, mitigate or prevent the negative impact of local knowledge is defined as that held by local people (this
nutrition transitions and the impact of outside drivers of term is synonymous with traditional knowledge, which we
dietary quality. The capacity of a nutrition education have chosen not to use because of the implied dichotomy
program is dependent on the quality of the education between traditional and modern) [36].
program, the acceptability of the message, and local To our knowledge there have been very few efforts
understandings of a particular issue [14]. Important anywhere to examine local knowledge of dietary diversity
innovation and progress in nutrition education has and nutrition [37]. This research therefore examines
drawn on psychology and behaviour change theories local (ethno-) nutrition knowledge in the East Usambara
[15], as well as social marketing and innovative ap- Mountains, Tanzania. The material presented focuses on
proaches such as inter-generational education [16–21]; dietary diversity, including local perceptions about its
however, there is still much room for improvement. role in health and nutrition as well as factors that
In the face of the underperformance of nutrition mediate local people’s ability to achieve and maintain a
education programs, anthropological and ethnomedical diverse diet. This research represents an important first
perspectives on knowledge systems and learning (also effort to understand if and how nutrition education
called knowledge exchange or knowledge transmission) messages promoting dietary diversity are aligned with
may offer novel insight to achieve more efficient exchange existing knowledge schemes. The results have important
and transmission of health and nutrition-related know- implications for understanding if, why, and how
ledge. This is likely to be particularly true in developing efficiently, dietary diversification messages promoted
countries and other settings where the knowledge systems through nutrition education can support good dietary
of local peoples may be significantly different from behaviour.
scientific knowledge systems.
Anthropological studies of local knowledge systems Methods
emphasize the dynamic nature of knowledge and focus on Study site: the East Usambara Mountains, Tanzania
syncretic combinations of local knowledge and other types The East Usambara Mountains lie 40 km inland from the
of knowledge, as well as acknowledging areas of conten- port city of Tanga. Human population density in the
tion [22, 23]. Anthropologists insist that knowledge is region is now 61.3 people per square kilometre, with an
fluid; they seek to understand how knowledge changes annual growth rate of 2.4% [38]. The mountains are the
and what factors mediate that process [24, 25]. When cul- home of the Shambaa and Bondei, and the surrounding
ture is defined as ‘shared knowledge’ [26–30], knowledge, lowlands are home to the Zigua ethnic group. The area
like culture, can be viewed as adaptive: “It seems likely was historically culturally diverse, even before immigra-
that the range of diversity in individual versions of the tion to the area for wage labour opportunities in the tea
‘common’ culture is not simply a social imperfection, but and timber industries [39, 40]. The political history of
an adaptive necessity: a crucial resource that can be drawn Tanzania has ensured that more than 90% of Tanzanians
on and selected from in cultural change” [31], p.88). These speak Swahili, the national language. In addition to being
approaches to knowledge would suggest that local know- the lingua franca, Swahili is increasingly used in the home,
ledge is often highly functional, ensuring individual and especially in culturally diverse areas such as this site.
community well-being [32, 33]. In his review ‘An Anthro- Local livelihoods are based on small-scale farming,
pology of Knowledge,’ Barth [29] noted: “We all live lives supplemented with cash crops, wage labour, small busi-
full of raw and unexpected events, and we can grasp them ness and animal husbandry. Local diets in the East
only if we can interpret them—cast them in terms of our Usambaras are based mainly on maize (Zea mays L.)
knowledge”. (most commonly prepared as ugali, maize flour cooked
Worsley [34] noted the need to pay careful attention to into a hard porridge), banana (Musa spp.), cassava
how knowledge frameworks are built and the ways nutri- (Manihot esculenta Crantz.), beans (Phaseolus vulgaris
tion knowledge is learnt. People are more likely to main- L. and others) and dry fish (such as dagaa, small dried
tain healthy behaviours or adopt new ideas or behaviours fresh water fish, including Rastrineobola argentea).
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 3 of 12

Malnutrition, especially micronutrient deficiencies (e.g., Text analysis and coding were conducted manually by
vitamin A and iron), remains a problem in the East BP following methods laid out by Bernard [45]. The final
Usambaras and in Tanzania in general [41]. transcribed and translated text, including the English
The East Usambara Mountains were chosen as the field and Swahili, was just under 200,000 words. BP read the
site for this research because the area is known for its high text multiple times to identify and code descriptions of
dietary diversity, largely obtained through subsistence ac- why dietary diversity was “important” and “drivers (what
tivities [39, 42–44]. This area also provides an interesting a household needs to ensure/support)” of dietary diver-
setting for the study of local food and nutrition knowledge sity. An initial exhaustive list of codes for “importance”
because the high cultural diversity, combined with long and “drivers” was compiled so that all relevant material
history of a shared language use, create the possibility for was included under at least one code. Codes were then
both high and low cultural consensus. grouped into categories. Finally, the all of the text for
each category was collected into one place for final
analysis of the relative importance (how frequently a
Data collection and analysis given topic was discussed/percent of households in
Qualitative data collection took place between September which it was discussed) and identification of themes
2008 and November 2009 and included focus groups and (what Saldaña calls Pattern and Focused coding [50]).
one-on-one discussions with over 120 people in six villages The results from the quantitative research and a draft of
(Kiwanda, Tongwe, Bombani, Kwatango, Shambangeda and this paper have been returned to the communities and
Misalai) [45]. The majority of material herein comes from local government officials (two info briefs in Swahili,
15 case study households (N = 28 people) that were selected Additional files 1 and 2). Participants cited herein have
for in-depth qualitative work from a larger sample of 275 had a chance to review the paper (in English, with a trans-
households who participated in a household survey to as- lator present to answer questions) and their quotations (in
sess diet in relation to biodiversity [46–48]. These 15 case Swahili) and provide comments and corrections. None of
study households were purposefully selected to achieve a the informants requested changes.
range from those with poor diets to those with good diets
(including high and low dietary diversity), as well as house- Results
holds with varying livelihood strategies and socioeconomic Local knowledge on the importance of dietary diversity
status. In each household, ethnographic work was sup- Local people were very comfortable with the concept of
ported with participant observation, in-depth interviews dietary diversity: “eating different types of food” or
and life histories of adult members. Data collection was “changing the diet/foods” (described in Swahili as “kuba-
framed within an EcoHealth framework [49] aimed at un- dilisha mlo/vyakula” or “kukula aina aina ya vyakula
derstanding people’s perceptions of their diets, the environ- mbalimbali”, among others). Although dietary diversity
mental constraints on their diets, and the social and was one of the focus topics of the research, it frequently
cultural variables that mediate their ability to maintain their came up spontaneously, even before exposure to the re-
preferred diet. search questions. For example, in group discussions on
Research underwent ethics approval at McGill Univer- diet, nutrition and well-being in the communities, in
sity (IRB #916-0708) and the National Ethics Board in which village leaders were asked to rank the households
Tanzania (COSTECH) and research agreements were of the village in terms of diet quality, nutrition and
signed with village governments. Informed consent was health, dietary diversity was an important aspect of how
obtained verbally from adults and guardians of children, the diets and health of villagers was assessed. Arguments
was recorded by an enumerator, and, confirmed by the that a household belonged in a higher or lower group,
lead researcher (BP) prior to participation in the study. because they had higher or lower dietary diversity, were
No payment was offered to the 15 case study households presented in multiple villages.
for their participation in the qualitative work. During Virtually all participants reported that dietary diversity
consent, all participants requested that they be identified is important because it maintains and enhances appetite.
by name when their stories and words were published. In Tongwe village, Beatrice Akida, who is a single
Interviews were conducted in Swahili by BP, with sup- mother and a kindergarten teacher explained:
port from a translator (Shundi Ndoe). The life story and
history of the adults in each household were collected “The benefit [of changing your diet] is that food
and research topics discussed through in-depth inter- should not bore you so that you don’t lose your
views drawing on an interview schedule. Interviews were appetite for eating. Because with one food, many
transcribed and then translated from Swahili to English people lose their appetite. That’s why human beings
by a different research assistant (Ruth Adeka and need to change food. Children get an appetite if today
Sylvester Aura), after removal of in-text English. you have cooked cassava ugali, tomorrow let it be
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 4 of 12

cassava ugali with good mlenda (Corchorus spp.). So value..... Every food crop has got its own value. We eat
tomorrow if you change to ugali [of maize] and beans fruits because every fruit like pineapple (Ananas
it will be better than eating ugali and beans [for many comosus L) helps the blood (inasaida damu).”
days in a row]. [If you do not change] you will Mention of vitamins or nutrients as a benefit of dietary
discover the children saying that they are not going to diversity was uncommon and only occurred with more
eat, they go to play outside, yet they are hungry.” educated participants. In virtually all interviews, the
concept that vitamins are one of the benefits of dietary
Similarly, Saidi Kombo, a well-educated government diversity was mentioned only after their importance for
employee in Misalai village told us: appetite had been discussed. Indeed, many participants
did not report dietary diversity as having any benefit be-
“If you eat dagaa (small dried whitebait fish) today, yond its value for enhanced appetite, and those who did
tomorrow dagaa, yes you eat, but you are tired, you gave vague descriptions of additional benefits.
think: ‘Now this is how it will be every day? eating
dagaa?’....it will become boring. You won’t get any Factors enhancing and limiting dietary diversity
pleasure [from eating], you won’t have any appetite. Agriculture and agrobiodiversity
That is why you need to frequently change. You eat When discussing factors needed to achieve and maintain
mchicha (Amaranthus spp.) today, tomorrow you eat a diverse diet, agrobiodiversity,1 as well as engaging in
kishone nguo (Bidens pilosa L.) the day after maybe agricultural activities in general (maintaining agricultural
you eat mchunga (Launaea cornuta (Hochst. ex Oliv. activities even when there is an alternative source of in-
& Hiern) C.Jeffrey)… But if you eat only one vegetable come), were some of the most commonly mentioned fac-
(or side dish) every day and ugali (stiff porridge) as tors. Links between dietary diversity and agrobiodiversity
your staple food every day, if you eat like this, only came out as a clear category or theme in 13 out of the 15
ugali and mchicha every day, you won’t have any case study households. Although local people tended to
appetite to eat… If a mama cooks the same vegetable blur the line between factors affecting dietary diversity
all the time [her family] won’t eat enough. Because and those related to having (enough) food in general,
children will eat only a little bit and leave the rest.” agrobiodiversity seemed to be especially important for en-
suring diversity of vegetables and fruit. Zaina Housseni in
Of course on the other hand, preference for diverse foods Tongwe village explained that her family’s diet was better
could motivate people to seek out a more diversified diet. than her neighbours “because, I don’t know, here in the
The importance of a varied diet for improved appetite village [other people’s] side dish is dagaa unless you have
held across various timeframes: from meal to meal, day your own garden. I have my own garden with mchicha
to day and season to season. The importance of dietary (Amaranthus spp.).”
diversity pertained not only to the diet in general, but Wealth and available cash were reported to increase
also across food groups, including carbohydrate staples, dietary diversity directly, as well as indirectly through an
side dishes and fruit (i.e., one should consume different influence on agrobiodiversity. Engaging in agriculture
types of vegetables or staples). The importance of (even when pursuing other sources of income) and
diversity for appetite and adequate intake also applied to maintenance of agrobiodiversity were seen as an impor-
varieties of a single crop – an indication that local tant strategy for overcoming seasonal variation and food
people perceived dietary diversity as intimately linked to insecurity/hunger, as well as maintaining dietary diver-
agrobiodiversity (cf. “Factors Enhancing and Limiting sity on both a short- and a long-term basis. Benjamin
Dietary Diversity” section, below). Njiku, in Shambangeda village noted:
Virtually all participants across a range in gender, age,
social and economic status were comfortable discussing “[Having many varieties of banana] helps us because
the concept of dietary diversity. This suggests that this each variety has a different taste. Also they ripen [at
concept was a salient part of local nutrition knowledge, different times].... it allows me to have bananas all the
and, more importantly, that there was a high degree of time, each time a different variety. If one variety fails,
consensus among individuals across different groups. there is another variety that continues to grow. Also…
Although appetite was overwhelmingly the first, most the time to cook [some varieties] is short, and this is
important benefit of dietary diversity discussed by local helpful. You can cook quickly, eat quickly. Other
people, the importance of having different foods in the [varieties] are a little bit hard and they need a little bit
diet was also linked to the fact that “every food has its longer.”
own importance”. For example Mathias Martin of
Kwatango village noted: “The benefit [of having many The importance of agrobiodiversity included not only
different foods] is because everything has got its own the diversity of crops in the field, but also access to
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 5 of 12

different types of fields and fields in diverse locations some places or at some times. Even if one has enough
with different ecological characteristics (i.e., land-use money, if a food item is not available, it cannot contri-
diversity or landscape heterogeneity). Although not well bute to dietary diversity. However, seasonal variation is
articulated by many, local farmers alluded to the fact perceived to affect long-term dietary diversity. Additionally,
that maintaining multiple land uses on their farms helps the varying availability of foods from the farm can be miti-
ensure their food security and dietary diversity. By main- gated by purchasing foods when they are not available from
taining different land use types, farmers reported they the farm. For example, Rehema Amiri a single mother
were able to increase their crop diversity (and therefore and successful business-woman in Shambangeda vil-
their dietary diversity and food security). Kiango Singoti, lage explained:
Bombani village said: “Because different types of fruits
need different types of fields, it has forced me to culti- “I have avocado (Persea americana Mill.), guavas
vate multiple plots [in multiple locations]”. Similarly, (Psidium guajava L.) and pineapples (Ananas comosus
Benjamin Njiku explained: “I plant some trees and some L), everything is there [in the farm]. There are many
other food crops so it is like a forest but not an ordinary guavas, we just pick them, and the children eat
forest. Because maybe this area once had trees, but not them.... They [fruits] go with their own seasons. There
when I came, so I decided to plant sugarcane (Sac- are seasons you will get many fruits, and then there
charum spp.) and it helps me. But I have planted trees are many seasons when you will get a few fruits. In
in other areas… in other areas I plant food crops which that season when fruit are scarce you will buy a few,
do not resemble forest.” like pineapple that is normally available in the field,
The few participants who did not link diet and dietary when it is not there, before it is ripe [you must buy it]
diversity to agriculture and agrobiodiversity were among or oranges (Citrus sinensis L.) and bring them home.”
the most disadvantaged of the respondents; they also
struggled to articulate all aspects of their life, diet, nutri-
tion and health. For example, Tabea and Dominic John Income, cash availability and socio-economic status
of Misalai village were not cultivating their farm: they Wealth or income was reported as an important
explained it was “too difficult”, although both appeared determinant of diet and dietary diversity. It was
to be young and healthy (as an explanation, Dominic perceived to affect dietary diversity both directly
said “it’s easier to plant after hoeing (tilling), but hoeing (through purchasing power), as well as indirectly by
is what impedes me”). They were living almost entirely modifying agrobiodiversity: wealthier people could afford
off the small earnings Tabea made from the restaurant to purchase more types of seeds and other agricultural
attached to their house where she sold tea and mandazi inputs, could afford to hire help with agricultural labour,
(fried sweet dough) and very small amounts of cash from and usually had access to more land, all of which in-
Dominic’s occasional business endeavours. While it was crease their ability to grow a greater variety of crops.
unclear why exactly the family was so adverse to farming Both wealthy and poor participants identified wealth or
(perhaps social or psychological reasons), it was clear poverty as a factor limiting some people’s access to food
that there were obstacles other than physical ability and dietary diversity. For example, Tumaini and Kibua
preventing them from farming (Tabea regularly carried Daudi (recently returned to the area, making a success-
very heavy loads of firewood needed cook mandazi): em- ful living by small business, Bombani village) and Anna
phasizing the benefits of farming would have just made and Ernest Singano (poor, renting their home from the
them feel worse about the fact that they were not en- tea plantation for which Ernest works, farming with the
gaged in farming. Likewise, Mary Mathayo (a single goal of leaving the tea estate, Shambangeda village)
mother, the poorest of the 15 case study households, in talked about their lack of access to land/land tenure
Kiwanda village) did not discuss a link between agricul- affecting their agrobiodiversity, food security and dietary
ture and dietary diversity. She cultivated only maize and diversity. Trade-offs between obtaining food by way of
cassava and lived off the sale of sugarcane alcohol. The agriculture and by purchasing it were frequently
concerns and efforts of both these households were discussed. While lack of money could be made up for by
focused on small business enterprises, which produced successful agricultural endeavours, wealth gave a
small amounts of cash with which they purchased very household choice and lack of wealth required the
basic food items. household to balance more activities. Local people not
only drew connections between greater wealth and
Spatial and temporal availability of diverse foods higher agrobiodiversity supporting high dietary diversity,
Availability of different foods (both seasonally and they also identified lack of wealth and lack of crop
geographically) in general was reported as a limitation to diversity as decreasing their ability to maintain their
dietary diversity; some foods simply were not available in dietary diversity.
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 6 of 12

Livelihood diversity Other determinants of dietary diversity

In many cases, livelihood diversity was seen to support Other less prominent determinants of dietary diversity
dietary diversity in the absence of wealth or agrobiodi- included: large household size, gender, and personality
versity. Certain livelihood activities, such as livestock and family traditions.
keeping, consistently emerged as beneficial for dietary
diversity. The family of Ramadhani Juma had excellent Household size
dietary diversity, which he attributed to livelihood A number of households identified large family size as
diversity. He discussed how his black pepper (Piper an obstacle affecting diet and food security. Although a
nigrum L.) harvest gave him lump sum earnings once a larger family size increases the demands on the adults in
year, how bananas could be sold throughout the year (al- the household and decreases their ability to overcome
though only for a small amount of money), how he grew obstacles that require monetary input, in some cases it
maize and beans for home consumption, and how his may increase dietary diversity. This is because it is more
dairy cows helped him pay for his children’s school fees. difficult to get enough of any one type of food to feed a
He took occasional work as a mason, as well as tailoring large family, and less likely that there will be leftovers to
work at holidays, and his wife had a small business eat at the next meal.
selling fried fish. Rehema Amiri, a single mother, farmer
and business owner in Shambangeda also talked about Gender
how her efforts in both business and agriculture helped For female-headed households (single father headed
her to ensure her family’s well-being, nutrition and households were extremely rare), a limited work force is
dietary diversity. often a major limitation. Mary Mathayo, a single-mother
Indeed, a lack of livelihood diversity was observed in and the most disadvantaged of the case study house-
case study households with some of the lowest dietary di- holds noted:
versity. Participants noted that households that focus all
their agricultural efforts on cash crops were more likely to “I was married and I separated. Now, I earn my living
encounter difficulties maintaining a good diet. A number by sukuma miwa (literary means pushing sugarcane,
of participants noted that those who worked as labourers refers to making and selling sugarcane alcohol)…
on the tea estates were significantly disadvantaged and Other households eat better than mine because my
had very monotonous diets if they didn’t have any other strength is that of only one person, kwasabu mkono
livelihood activities. Anna Ernest, who lived on the tea es- wangu ni mmoja (because I have one pair of hands,
tate where her husband worked in Shambangeda village i.e. she is a single parent).”
commented: “If I plant cassava like this one, I do not need
to buy it, even beans. You will find them [those who work However, the role of gender in determining dietary
for the tea company and don’t engage in agriculture] diversity in the East Usambaras is complex; gender often
drinking tea alone, or tea and boiled banana. And as for affects other factors that determine dietary diversity. For
cultivated vegetables, I will harvest leafy vegetables and example, traditional land inheritance laws which disad-
they will eat only dagaa.” vantage women can limit agriculture and crop diversity.
However, in a number of cases, certain livelihood In one household, because the wife, from the area, had
activities actually acted to decrease diet quality and diet- married a man from the West Usambara Mountains, her
ary diversity. In one (Tabea and Dominic John) of the brothers barred her from inheriting or even using her
two households where the mother of the home ran a family’s land after her father’s death. In another family,
small restaurant and prepared mandazi (fried sweet patrilineal land tenure practices limited the type of crops
dough), the dietary diversity was quite low. Mandazi the wife could plant on her husband’s land (especially
preparation is very time consuming, leaving the mother because she had sons from another marriage): perma-
with limited time to cook other meals, as well as less nent crops are seen as an assertion of tenure. It is
impetus to cook, as the family can fill up on mandazi. important to note that there were many success stories
Musa Mbwana, the head of another household, was a of women overcoming gender-based obstacles; in fact,
well-known traditional healer. His family consumed many of the most successful (in terms of diet, dietary di-
chicken frequently, as chickens are brought by versity and agriculture) households were run by women.
patients for sacrifice during treatment (and the meat
is given to the healer as part of the payment for his Personality and tradition
services). In his household, the ready access to A number of personal characteristics were also common
chicken meat seemed to act to decrease the consump- themes in discussions of what affects dietary diversity and
tion of other side dishes (especially vegetables), and nutrition. Personality emerged particularly when people
thus the dietary diversity of the family. with better diets/higher dietary diversity (especially poorer
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 7 of 12

households that still managed to maintain good dietary study that describes the importance of landscape hetero-
diversity) tried to explain why other households might not geneity for dietary diversity, a factor that has never
have the same quality and diversity in their diets. Some previously been described as a potential driver of dietary
participants simply said that people “don’t like to/don’t diversity and should be further investigated.
want to” pursue various activities needed to ensure dietary Many of the relationships between dietary diversity and
diversity. “Each person has their own thoughts or ideas or health, and dietary diversity and environment reported by
plans” was another very common explanation. An indivi- local people in this study parallel those reported in other
dual’s knowledge, determination, drive, dedication, effort studies, both quantitative and qualitative (including the
and motivation were often cited as aspects of personality, quantitative results from the same research project).
which can support improved dietary diversity. For Table 1 summarizes relationships between dietary diver-
example: “You can get many types of vegetables, but it all sity and health from the general scientific literature, quan-
depends on the effort/determination (juhudi) of the titative research from the same communities included in
mother of the house… to struggle to find them. Because this study, alongside a summary of the local knowledge
there are many mothers who don’t want to go to the bush presented herein. The same three sources of information
to look for vegetables, they get money and buy dagaa. on the drivers of dietary diversity are also presented.
Others are determined to look for vegetables.” explained Local knowledge about the importance of dietary
Saidi Kombo.... “[I am more able/determined than other diversity recorded is well-aligned with scientific findings:
women] because I really like leafy vegetables.” continued participants’ emphasis of the role of dietary diversity for
Amina, his wife. appetite, over its importance for vitamin and mineral in-
Other participants linked a person’s choices and habits take or other nutrition-related health outcomes, was likely
to their family’s traditions and commitment to culturally due to the fact that vitamins and minerals are concepts
held food preferences and taboos. While in some set- that are not well integrated into existing local knowledge
tings, cultural taboos are universally held and adhered systems. Older nutrition and nutritional anthropology re-
to, in the East Usambara Mountains many food taboos search has similarly reported that diets that lack diversity
varied from one family to another. Only a few taboos, induce boredom and undereating, especially in children
like those against eating snails and monkeys, were held [51]. The fact that many participants talked about dietary
by the majority of people. diversity and having (enough) food in general somewhat
Rarely did people say that others lacked dietary diversity interchangeably, suggests not only that food security is
because they were in some way poorer or disadvantaged, important to people, but that it is associated with dietary
suggesting that dietary diversity was perceived as some- diversity (as in the scientific literature).
thing all people in their community (rich and poor) can Scientific evidence of the drivers of dietary diversity
achieve. vary between sites and studies (first column Table 1).
Local knowledge in this study suggests that land use
Discussion diversity and landscape heterogeneity are important for
These data demonstrate that dietary diversity is perceived dietary diversity; factors which have not, to date, ever been
as important for appetite and overall food consumption. examined using dietary survey data [52]. Local knowledge
There was a high degree of agreement among participants that crop diversity is important for food security and re-
from a range of backgrounds about the concept of dietary silience has been previously described: farmers around the
diversity and its benefits for enhancing appetite. These world report that crop diversity and agrobiodiversity
findings suggest that the concept is a salient part of local provide them with security in the face of environmental,
nutrition knowledge. These results also contribute to the climate, economic and social change (e.g., in Nepal [53]).
growing understanding of how dietary diversity is asso- One recent research project has also looked at local know-
ciated with biodiversity. Agriculture, agrobiodiversity and ledge of the importance of agrobiodiversity in Rwanda,
landscape heterogeneity, along with wealth were some of with remarkably similar results to this study [37]. The re-
the most commonly reported determinants of dietary search in Rwanda reported that local people identified
diversity. Household size, livelihood diversity, and gender dietary diversity as one of the two most important reasons
were also perceived to affect dietary diversity. they valued agrobiodiversity (along with income gene-
Figure 1 represent our effort to visualize the reported ration), and dietary diversity was perceived as important
determinants of dietary diversity and their interactions. for health and nutrition: “farmers said they liked to grow
The figure highlights our interpretation, based on the diverse crops because they wanted to eat different foods,
results presented herein and our wider understanding of that eating the same food caused health problems, and di-
the field site, of how the drivers of dietary diversity are verse foods are important for nutrition” [37]. For example,
situated and interact within the larger complex social- one of the farmers interviewed by Isaac et al. [37] stated:
ecological system. To our knowledge this is the first ‘If you have production from all of these [crops] there’s no
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 8 of 12

Fig. 1 Diagram of the most salient relationships between determinants and outcomes of dietary diversity, showing an interpretation of how they
interact within the social-ecological system (arrows indicate associations that can be either positive or negative, they are not meant to
indicate causation)

Table 1 Summary of knowledge about the importance and drivers of dietary diversity (DD) from three different sources
(local knowledge, scientific knowledge/quantitative results from same study, scientific knowledge/quantitative results from
other studies)
Scientific literature Quantitative data from the study communities Qualitative data from local people in this study
Importance of Dietary Diversity
• DD associated with overall food consumption, • DD associated with overall energy intake [46] • DD important for appetite and enjoyment
energy intake and satiety [51, 64–69] • DD associated with intake of most nutrients of food
• DD associated with dietary quality, nutrient and nutrient adequacy (Mean Adequacy Ratio, • DD important because “each food has its
intake, nutrient density (likely explaining links MAR) [46] own value”
to child growth and other anthropometric and • After controlling for energy intake, DD no
biochemical markers of nutrition) [68–71] longer associated with intake of most
nutrients [46]
Drivers of Dietary Diversity
• DD linked to agrobiodiversity in at least • DD associated with agrobiodiversity (crop • Agriculture, agrobiodiversity
seven studies [46, 52, 72–78], diversity) [46] • Land use diversity/landscape heterogeneity
• DD associated with forest cover in three • DD associated with forest cover [46, 47]. • Different foods eaten seasonally
studies [47, 52, 79, 80]. • No differences in DD between wet and dry • Wealth, available cash, land tenure
• DD linked to vegetable production [81] season, but difference in sources of • Livelihood diversity
• DD linked to home gardens [52, 82] foods [46, 48] • Family size
• Season may increase/decrease • DD associated with wealth and market access • Gender
DD [83, 84] but not with sex or education of the head of • Personality, family tradition, taboos
• Wild food use associated with higher the household (unpublished data from the
DD [54] study) [46]
• DD also associated with wealth, household
size, education and other economic and
demographic variables
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 9 of 12

hunger. And to change the food – today if we eat squash the primary school science curriculum and participants
and beans the next day we can eat something else…Life is reported school as a source of information. Compared
strong – there’s no disease in the body and children don’t to scientific approaches to many health issues (which
get sick because they change the food every day’ [37]. often focus on causes and treatment of disease or defi-
Interestingly, despite wild food being widely consumed ciency), scientific discourse about dietary diversity focus
in the study site [48], and having been shown to be more on health (and how to maintain it) [55]. Similarly,
associated with greater dietary diversity [54], there was the local knowledge examined in this research tended to
limited mention of wild foods by local people in their focus on the health-giving components of diet and food.
discussion of the drivers of dietary diversity. Compared to other forms of nutrition knowledge which
Discrepancies between scientific knowledge and local are often heavily nutritionalized and medicalized [59],
knowledge of dietary diversity presented herein should dietary diversity presents an ideal starting place and
not in any way reduce the validity of local knowledge. foundation for education about healthy diets.
The assessment of local knowledge against “scientific
truths” perpetuates a dichotomy, in which local Conclusions
knowledge is qualified relative to a ‘superior’ knowledge; Shell-Duncan and McDade [60] highlight the import-
dichotomies which maintain colonial cultural suprema- ance of ethnographic data on health and nutrition know-
cies and perpetuate hegemony [55, 56]. In this case, the ledge for interpretation of nutrition survey results: they
discrepancies between local knowledge and the other re- describe higher rates of inadequate iron intake among
search findings from this study could easily be a result girls than boys in a Rendille community in northern
of the well-known imperfections in dietary data collec- Kenya and link this to cultural classifications of ‘soft’
tion tools [46]. In fact, this qualitative research may have foods (including rice, maize porridge, and tea), import-
identified drivers of dietary diversity that have simply ant for girls, and ‘hard’ foods (including meat, blood,
not been identified or tested yet using quantitative and beans) important for boys. Worsley [34] points out
methods (e.g., land-use diversity). that “…‘messages’ are often accepted or rejected accord-
At the same time, we acknowledge the subjective nature ing to their consonance with prior beliefs”. The gap be-
of qualitative analysis, the possibility that other themes/ tween scientific and local knowledge systems remains a
categories could be apparent to other researchers or that major, and rarely addressed, issue in nutrition interven-
the relative importance of themes/categories could be tions with education or behaviour change components.
judged differently. The fact that the first author intro- Unlike Shell-Duncan and McDade [60], which describes
duced herself as a nutrition researcher, could have led par- local nutrition knowledge that is quite different from sci-
ticipants to give responses which they perceived to align entific knowledge, in this study, local knowledge of diet-
with the scientific knowledge system. However, she was ary diversity was well aligned with scientific knowledge.
able to elicit a diverse range of responses from local The universal use of the Swahili language and primary
people, including many that were not close to scientific school education are legacies of Tanzania’s socialist era
concepts (and was able to do this when Tanzanian [61, 62], and have likely been a driving force behind the
members of the team with university degrees in science creation of consensus among local people on nutrition
often were not able to) suggesting that this aspect of knowledge. These are strengths that future public health
researcher bias was largely overcome. policy and programs should seek to build on. There is
The fact that “personality” emerged as an explanation room to incorporate ethnonutritional concepts in the
given as to why some members of the community were un- National Primary School science curriculum, and to adapt
able to maintain a diverse diet highlights one of the limita- the curriculum to local contexts. In the face of changing
tions of drawing on local perceptions of determinants of dietary patterns and nutrition burdens across Africa, at-
health: poor people are often blamed for making bad deci- tention to the diet and nutrition information in school
sions, or being lazy, when in reality there are structural bar- curriculums should be prioritized.
riers, including social, cultural and environmental barriers, The qualitative approach to ethnonutrition used in this
that prevent them from making healthy choices [57, 58]. research has revealed that local people perceive a strong
In the face of changing food systems and dietary pat- link between agriculture and agrobiodiversity (and by ex-
terns [13], public health nutrition policy and programs tension environmental health in general) and human diet
will need to find messages that support cultural dietary and nutrition. Landscape heterogeneity was reported as
traditions, promote healthy dietary behaviour and are important for dietary diversity. Maintenance of agricul-
easily integrated into existing knowledge systems. The ture when households shift to other sources of income
Tanzanian primary school curriculum has been an effi- was also reported as important. Crop varietal diversity
cient means for promoting healthy diets in this site. was reported as important for maintaining dietary diver-
Many of the concepts seen in this research also seen in sity across seasons. Income, livelihood diversity and
Powell et al. Journal of Ethnobiology and Ethnomedicine (2017) 13:23 Page 10 of 12

household size were also reported as important. Nutri- Funding

tion research has struggled to accept other ways of This research was funded by the International Development Research Center
(IDRC), Canada (Doctoral Award to BP). SLY was supported by K01 MH098902
knowing as equal to knowledge generated through scien- from the National Institute of Mental Health, USA.
tific enquiry. New paradigms are needed to achieve
greater and more efficient knowledge communication in Availability of data and materials
The data for this paper are in the form of qualitative transcripts which are
nutrition interventions and public health nutrition. stored and backed-up by the lead author (BP); they are available on request
Overlaps between scientific and local knowledge systems to the lead author (BP) with a privacy and confidentiality agreement. The
(such as dietary diversity) offer an excellent platform to qualitative transcripts contain sensitive personal information (including some
which research participants indicated they would prefer not be made
provide novel health and nutrition information to publically available).
local communities; such an approach should enable
novel information to be more readily integrated into Authors’ contributions
Research was designed and funding was secured by BP and TJ Data
existing local knowledge systems. collection was conducted by BP Data analysis and paper preparation was
done by BP with support from SLY and RBK. All coauthors contributed to the
final draft of the paper. All authors read and approved the final manuscript.
Endnotes Competing interests
1
Definitions of agrobiodiversity vary; the Convention The authors declare that they have no competing interests.
on Biological Diversity (CBD) defines it as all living or-
Consent for publication
ganisms associated with agriculture, crops and livestock All authors have reviewed and confirmed that the paper is ready for
and the ecosystem of which they are a part, while others, publication. All research participants gave free and informed consent for
including (Bioversity International) it includes only culti- their words and names to be published.
vated species, herein we use crop diversity to specify and Ethics approval and consent to participate
agrobiodiversity to refer to both the more specific and Research underwent ethics approval at McGill University (IRB #916-0708) and
the more general definitions combined. It is important the National Ethics Board in Tanzania (COSTECH) and research agreements
were signed with village governments. Informed consent was obtained
to note that plant taxonomy in local knowledge systems verbally from adults and guardians of children; was recorded by an
often differs from scientific classifications [63]. In this enumerator; and, confirmed by the lead researcher (BP) prior to participation
work when “type” in “type of food” “type of vegetable” in the study. No payment was offered to the 15 case study households for
their participation in the qualitative work.
or “type of fruit” was discussed with local people, the
definition of “type” was left to the informant’s discretion.
Generally “type” used by participants matches traditional Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in
agricultural classification of crops, and does not refer to published maps and institutional affiliations.
variety unless specified.
Author details
1
Department of Geography and African Studies Program, Pennsylvania State
University, State College, PA, USA. 2Center for International Forestry Research,
Bogor, Indonesia. 3Department of Development Sociology, Cornell University,
Ithaca, NY, USA. 4Department of Anthropology, Institute for Policy Research,
Additional files Northwestern University, Evanston, Illinois, USA. 5School of Dietetics and
Human Nutrition, McGill University, Montreal, Canada.
Additional file 1: Info Brief: Diet and Nutrition in the East Usambaras
(in Swahili). (PDF 242 kb) Received: 10 December 2016 Accepted: 31 March 2017
Additional file 2: Info Brief: Nutrition and Environment in the East
Usambaras (in Swahili). (PDF 567 kb)
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