Harnessing traditional knowledge and experiences on food consumption in Uganda: a mixed-methods study exploring indigenous fruits and vegetables with potential cardiometabolic benefits

Abstract

Introduction

Mitigating the ongoing nutrition transition and associated risks in sub-Saharan Africa may require cost-effective and community-based approaches. Thanks to their wealth of bioactive constituents, indigenous fruits and vegetables (IFV) constitute one of such approaches. However, in Uganda, consumption of IFV is pervasively low, despite a rich diversity. Our study aimed to harness traditional knowledge on consumption of IFV and catalogue IFV reputed for cardiometabolic benefits.

Methods

In this qualitative study, we conducted focus group discussions (FGD), key informant interviews (KII) and market surveys. Participants for the FGD were recruited from the general population, while for KII, farmers, ethnobotanists, nutritionists, herbalists and health workers were interviewed. We conducted surveys in supermarkets and open-air markets together with explorative interviews with market vendors. Discussions were audio recorded, transcribed verbatim and analysed thematically. We performed phenolic profiling of the identified IFV using Phenol-Explorer and relevant publications as an initial step towards verifying the therapeutic claims ascribed to certain IFV.

Results

Eleven FGD (84 participants), 19 KII and 12 food market surveys were conducted with participants aged 19–80 years. Three of the 11 FGD were conducted among younger adults (aged 19–34 years). Tamarindus indica Linn., Cleome gynandra, Solanum anguivi and Hibiscus sabdariffa were most cited as potent against cardiometabolic risks, and their total polyphenol content (mg/100 g) was 4755, 1330, 1710 and 2920, respectively. Consumption was influenced by sensory appeal, awareness of health benefits, seasonality and social misconceptions, whereby IFV are considered food for the poor. Other barriers were low food skills, food safety concerns and the diversity of fast foods. Early adults had low knowledge of IFV and were less willing to consume IFV. A food market survey revealed a scarcity of fresh and processed IFV.

Conclusion

Our study showed that several IFV are purported to have beneficial cardiometabolic benefits, but consumption is affected by several food environment constraints.

WHAT IS ALREADY KNOWN ON THIS TOPIC

• The prevalence of non-communicable diseases, in particular, cardiometabolic diseases in sub-Saharan Africa (SSA) is high.

• This prevalence is linked to the ongoing transition characterised by a shift from traditional diets rich in fruits and vegetables to affluent diets.

• African indigenous fruits and vegetables (IFV) are rich in polyphenols with the potential to optimise cardiometabolic health, but generally, the consumption of fruits and vegetables in SSA is low.

WHAT THIS STUDY ADDS

• This study unravels barriers and facilitators to the consumption of IFV and documents health claims traditionally attributed to some IFV.

• The study harnesses the traditional experiences that can be used to optimise the consumption of these foods.

• This is a potential strategy to mitigate the effects of the nutrition transition in SSA.

• Furthermore, the study explores some strategies to mitigate the loss of diversity of IFV.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The health claims traditionally ascribed to IFV need further scientific evaluation in clinical trials.

• As such, in a separate study, we have investigated the efficacy of Tamarindus indica Linn. in optimising cardiometabolic health.

• There is a need to invest in community-based culinary workshops to enhance food skills and incorporate less appealing IFV into regular diets.

Introduction

Indigenous foods represent a large genetic diversity of ruderals and conventionally farmed food species. These foods constitute a bedrock for food diversity and food security and are a symbol of cultural identity in sub-Saharan Africa (SSA).1–3 The Food and Agriculture Organisation (FAO) of the United Nations has described indigenous foods as “foods that indigenous people have access to locally, without having to purchase them and within traditional knowledge and the natural environment from farming or wild harvesting”.4 The term African indigenous fruits and vegetables (IFV) was then coined to refer to “all categories of plants whose leaves, fruits or roots are acceptable and used as fruits or vegetables by rural and urban communities through custom, habit and tradition”.5

Aiming to accelerate food system transformation and enhance the achievement of Sustainable Development Goals, the EAT-Lancet Commission proposed a planetary health diet consisting of more plant-based foods and minimal animal-source foods.6 The proposition is partly a response to the ongoing nutrition transition and associated risks, and a means to foster environmental sustainability. The SSA is experiencing an increase in suboptimal cardiometabolic health largely due to the predominance of low-quality diets with minimal fruits and vegetables, and a steadily rising fast-food culture. This so-called nutrition transition is also shaped by several factors, including increased availability and marketing of ultra-processed foods, lower prices of these foods compared with healthier options and socio-economic changes that limit the time available for preparing meals at home.7–9 Harnessing IFV could provide a cost-effective strategy to increase the overall intake of fruits and vegetables, thereby combating the effects of nutrition transition in SSA.

Beyond conventional nutrients—macronutrients and micronutrients, IFV possess bioactive elements reputed for health-promoting benefits.10–13 The wealth of bioactive ingredients motivates the use of these foods as complementary therapy for cardiometabolic dysfunction.13–16 Evidence from human trials shows that many of these foods, either whole or extract, are potent against glucose dysregulation, high blood pressure, dyslipidaemia, central obesity, vascular dysfunction and inflammation.17–20 The efficacy of IFV is largely attributed to the abundance of polyphenols that they contain.13 21

Despite the numerous health benefits, consumption of fruits and vegetables remains generally low in low- and middle-income countries (LMICs).22–25 For example, regardless of the rich diversity of IFV in Uganda,26 27% of Ugandans do not consume any fruit or vegetable in a week while 88% never meet the WHO recommendation of at least 400 g/person/day of fruits and vegetables.27 28 Numerous reports have indicated a continuous loss of Uganda’s IFV, which presents a salient threat to food security and biodiversity.29 30 It is noteworthy that 86.4% of the IFV in Uganda have been lost in the period from 1989 to date.26 31 32 Whether the low consumption of IFV directly influences the loss of their diversity remains to be understood. However, it is tempting to suggest that both demand-side and supply-side factors likely shape the observed IFV consumption patterns. On the demand side, socio-economic and cultural drivers may play a role, while on the supply side, changes in agro-food systems could have an influence. This study investigated the barriers and facilitators of consumption of IFV among Ugandans.

Amid the increasing suboptimal cardiometabolic health among Ugandans,23 27 33 IFV could offer a sustainable remedy as adjuvant therapy if underpinned by scientific evidence. This study explored the diversity of IFV locally claimed to have potential cardiometabolic health benefits. The study also used existing phytochemical databases and publications to conduct the polyphenol profiling of the identified foods as an initial step towards evaluating their therapeutic potential and ultimately promoting these foods.

Methodology

This study followed a mixed-methods research design. The qualitative part of the study is reported following the Consolidated criteria for Reporting Qualitative research.34 A three-pronged approach was used as presented in the schematic overview (figure 1). The first step focused on conceptualising indigenous foods in the Ugandan context through reviewing grey literature and Delphi rounds with experts. In the second step, we held focus group discussions (FGD) and key informant interviews (KII) to catalogue IFV with potential cardiometabolic benefits and document the barriers and facilitators to consumption. Lastly, we conducted a cross-validation for step 2. Cross-validation included conducting market surveys to assess the IFV’s diversity, availability and pricing. The surveys also aimed to understand the demographics of regular IFV consumers. Furthermore, we performed a phenolic profiling of the identified IFV to gain scientific insight into the potential cardiometabolic benefits. The study complied with the 1989 International Union for Conservation of Nature guidelines on research involving species at risk of extinction, with special reference to scientific collecting of threatened species.

Figure 1.

A schematic overview of the different steps followed to conduct the study.

Conceptualisation of indigenous food in Uganda

We reviewed the grey literature of IFV reputed for cardiometabolic benefits in Uganda. A rapid search of grey literature was performed in Google using the following keywords: (‘Food system’ AND ‘Uganda’ AND ‘environment’ AND ‘biodiversity’ AND ‘nutrition’ AND ‘culture’ AND ‘traditional knowledge’ AND ‘rural’ AND ‘food for traditional medicine’ AND ‘trade’ AND ‘wild food’ AND ‘food for hunger’ AND ‘neglected plants’ AND ‘indigenous food’). In this electronic search, organisations that extensively provided material relevant to our study were the Natural Chemotherapeutic Research Institute (NCRI), Ministry of Agriculture, Animal Industry and Fisheries, National Agricultural Research Organisation, National Council of Traditional Healers and Herbalists Associations (NACOTHA) and the National Environment Management Authority. These organisations were physically visited to access such material as reports, theses, magazines and pamphlets that could not be obtained through electronic searches. Subsequently, in multiple Delphi rounds,35 a panel of 12 experts from the fields of health, botany, herbal medicine, nutrition and food policy agreed on the definition of indigenous food in Uganda’s context, listed examples of IFV and ascribed cardiometabolic benefits. The agreed-upon definitions were used to validate responses of FGD and KII, while examples of IFV generated were incorporated into the compiled list of IFV.

Focus group discussions and key informant interviews

Study design and participants

The study involved 103 adult (≥18 years) men and women from the Greater Kampala Metropolitan Area (GKMA) regardless of their health status. Eighty-four FGD participants—30 men and 54 women—were recruited from the general population with the help of community mobilisers, health facilities and agricultural extension workers. Nineteen key informants—12 men and 7 women—were drawn from NCRI, National Crops Resources Research Institute, Plant Genetic Resource Centre, NACOTHA, Health Services, academia, freelance herbalists and district agricultural extension services. Participants were recruited using purposive and snowball sampling techniques and were physically invited for interviews through their community health workers. Older adults were intentionally targeted as these were hypothesised to have a wealth of knowledge regarding IFV and traditional food systems.

Theoretical framework

Food consumption behaviour can be explained by an array of complex interactions of intertwined factors, both at individual and environmental levels, conceptualised through theoretical models.36–38 We used a modified theoretical framework premised on the Theory of Planned Behaviour and specific constructs from the Social Cognitive Theory, Health Belief Model, Precautionary Adoption Process Model and social support theory. The modified theoretical framework (online supplemental figure) was necessary because no theory can solely describe a given behaviour.39 The model guided the development of the questioning framework and analysis of KII and FGD. Further details of the development of this modified model have been published elsewhere.40

Data collection

The investigator (TK) with experience in qualitative research moderated the FGD, and KII was assisted by a silent observer who took notes on non-verbal individual behaviour and group interactions. Using semi-structured questioning routes, open-ended questions were followed up by more specific probes to clarify and extend responses. The discussions were audio-recorded and lasted between 60 and 90 min. FGD and KII were conducted in English and Luganda (the local language in central Uganda). Before the start of each focus group, the moderator explained to the participants the reasons for conducting the FGD/KII. Participants received refreshments and a fixed transport refund of 20 000 Ugx (5€). To obtain age-related opinions and allow freedom of expression during the FGD, participants were grouped into two different age categories: early adults (18–34 years) and mature adults (≥35 years).

Data analysis

Audio recordings were transcribed verbatim, translated into English for the FGD and KII conducted in Luganda and cross-checked by two researchers. Using the thematic content data analysis, two investigators independently read the transcripts and developed the initial coding framework. The framework was discussed among the two researchers to identify similarities and contrasts. In the case of disagreements on the coding, a third researcher was consulted. The resultant codebook was used to work through all the transcripts. NVivo software (V.12.0) was used for the data coding process. Generated codes from all transcripts were organised together into a second coding framework. Codes with overlapping content were grouped into categories. The categories of codes were then grouped into themes using the theoretical framework to generate the final codebook. Two researchers synchronised the final coding frameworks, which were then shared with the third researcher. The inclusion of factors/codes was based on frequency of citation by participants. The non-verbal behaviour and group interactions were equally considered. The interaction of these themes was shaped by three ecological levels, and therefore, findings are reported accordingly:

1. Intrapersonal level: internal characteristics and psychological elements that influence a person’s eating habits. These factors include personal beliefs, attitudes, knowledge, preferences, motivation and self-efficacy (the confidence in one’s ability to make healthy choices). Additionally, they encompass emotions and perceptions regarding food and health.

2. Interpersonal level: factors influencing eating habits, including age, gender, culture, socioeconomic status, personal preferences, attitudes towards food, psychological and physiological aspects and social influences.

3. Environmental level: external conditions and elements influence an individual’s food choices and eating habits. These include the physical availability of food—whether healthy or unhealthy options are easily accessible. Social influences (family, friends and cultural norms, economic considerations like the cost of healthy foods). Other factors are marketing, advertising and proximity to food markets. Finally, policies that affect food accessibility and choices contribute to shaping eating habits.

Both FGD and KII factors are presented together, except where views were divergent. The most commonly used IFV for traditional cardiometabolic therapies was determined by the frequency of citation in both FGD and KII.

Cross-validation

Market survey

Six open-air food markets and six supermarkets were purposively selected around GKMA. Open-air food markets were Mukono, Seeta, Kireka, Kajjansi, ST. Balikuddembe (Owino) and Nakasero. In addition, a pragmatic sample of three vendors in each market selling at least 10 different IFV was chosen for a structured interview. The interview themes included pricing, seasonality of IFV, the demographics of the ardent customers of IFV, the variations in sales at different times of the day, storage techniques and knowledge of potential cardiometabolic benefits of IFV they sell. Furthermore, vendors were asked to report on the customers’ perceptions of IFV relative to other exotic fruit and vegetable varieties. Availability of IFV in open-air food markets is reported as the proportion of surveyed food stalls selling a given IFV in each market location. In the supermarkets, we registered all food products containing IFV as either principal products or ingredients in another product, pricing, nutrition information and health claims included on the product package. Comparison of IFV prices between open-air food markets and supermarkets was not feasible due to large variations in weight and form. In addition, we collected data through transect walks in open-air markets and supermarkets to gain a spatially referenced understanding of the availability, diversity and purchasing patterns of IFV. With the assistance of the market warden, the research team developed a transect diagram to navigate the fruits and vegetables section, taking notes on the parameters of interest. This information would later reinforce the data obtained from FGD, KII and vendor interviews.

Phenolic profiling of IFV

The phenolic profiling was done in two steps. First, we conducted taxonomic classification and verification of local and scientific names of the identified IFV. The compiled list of the local names and a photograph of each IFV was reviewed by a herbarium specialist for taxonomy. The specialist also identified the potential availability of other varieties of given species. The correctness of scientific names was checked using the International Plant Names Index database.41 In the second step, we searched in databases such as Phenol-Explorer42 and PhytoHub43 and other publications to determine the polyphenolic composition of the identified IFV.

Results

After 11 FGD and 19 KII were conducted, no new themes were emerging—this was defined as reaching data saturation. Each focus group consisted of six to eight participants, totalling 84 with an average age of 43 years. Three out of the 11 FGD were conducted among younger adults. The sociodemographic characteristics of participants are presented in table 1.

Table 1.

Sociodemographic characteristics of participants of both FGD and KII

Parameter	Participants in FGD (n=84)	Participants in KII (n=19)
	N, %	N, %
Gender
Male	30 (35.7)	12 (63.2)
Female	54 (64.3)	7 (36.8)
Age (years)
18–34	32 (38.1)	4 (21.1)
≥35	52 (61.9)	15 (78.9)
Employment status
Employed	55 (65.5)	19 (100)
Not employed	29 (34.5)	0 (0)
Marital status*
Single	25 (31.3)	4 (21)
Married	44 (55)	14 (73.7)
Widowed	11 (13.7)	1 (5.3)
Education level
None	14 (16.7)	0 (0)
Primary level certificate	23 (27.4)	1 (5.2)
Secondary level certificate	27 (32.1)	1 (5.3)
University/Tertiary	20 (23.8)	17 (89.5)
Region of origin
Central	49 (58.3)	10 (52.6)
Eastern	19 (22.6)	3 (15.8)
Western	10 (11.9)	3 (15.8)
Northern	6 (7.2)	3 (15.8)
Household size
Single-person household	11 (13.1)	3 (15.8)
Multiple-person household	73 (86.9)	16 (84.2)
Average monthly income (US$)	56†	1191‡

*N=80 for FGD participants (four participants did not disclose their education background).

†N=60 FGD participants (24 participants did not disclose their income).

‡N=13 KII participants (six participants did not disclose their income).

FGD, focus group discussion; KII, key informant interview.

Identified IFV species and the ascribed cardiometabolic benefits

A total of 64 IFV species were identified (online supplemental table 4, supplementary excel file 1), and these were either farmed or gathered from the wild. Tamarindus indica Linn. (tamarind), Cleome gynandra Linn. (spider plant), Solanum anguivi Lam. (bitter berries) and Hibiscus sabdariffa Linn. (hibiscus) were most frequently cited IFV used as local therapies for cardiometabolic dysfunction.

Barriers and facilitators to consumption of IFV

Altogether, 38 factors and 19 themes were drawn from FGD and KII as barriers and facilitators to the consumption of IFV (online supplemental tables 1 and 2). A summary of these factors and the frequency of citations is presented in table 2.

Table 2.

Summary of the barriers and facilitators for the consumption of IFV

Ecological levels	Categories of factors	Frequency of citation
Intrapersonal level	Sensory appeal (eg, colour, taste, texture)	FGD (1–11), KII (6 and 11)
	Physiological attributes (IFV are associated with low satiety)	FGD (3 and 8)
	Knowledge of potential cardiometabolic health benefits	FGD (1–8)
	Convenience and time implications of food preparation	FGD (1, 9–11)
	Nutrition knowledge and food preparation skills	FGD (1–11), KII (4–10)
interpersonal level	Sociocultural norms
	IFV are food for the poor, medicine, not food, food for the mature adults, a symbol for backwardness, food for village people, food during food scarcity	FGD (1–11)
	IFV are associated with witchcraft, superstition	FGD (1,3, 8)
	IFV are associated with weight loss	FGD (1, 4, 7)
	Food taboos, foods linked to tribes	FGD (1, 3, 8), KII (16–19)
	Increased drive towards nutrition for longevity	FGD (1, 7), KII (1–19)
Environmental factors	Physical food environment
	Scarcity of IFV, proximity to food market, seasonality of IFV	FGD (1, 2, 5, 6, 8–11)
	Limited availability of ready-to-eat IFV	FGD (2–5)
	Social food environment
	Family size	1–8, 10
	Family composition	1–8, 10
	Peer influence	1, 9–11
	Influence of women and children	1, 2, 6–8
	Information environment
	Health claims related to IFV	KII 5, 6, 10, 13, 14
	Food adverts-related fast foods	KII 15, 17, 18
	Food safety concerns (pesticide/herbicide residues, microbial contamination, aflatoxin)	FGD (1, 4, 6–8), KII (3–5, 9, 16)
	Economics Financial considerations (limited budget to be spent on food)	FGD (1–11)

FGD, focus group discussion; IFV, indigenous fruits and vegetables; KII, key informant interview.

Intrapersonal factors

Behavioural beliefs

1. Psychological and physiological perceptions. Participants reported that IFV is often bland or bitter and lacks the visual appeal compared with fast foods. There was a strong preference for exotic fruits and vegetables due to their reportedly superior sensory characteristics.

“Bitter berries, spider plant, cherry tomatoes…have a bitter taste, so I wouldn’t eat them, I prefer meat, fries, and if you go out you can’t order IFV, you just want to eat tastier fast foods because they even look nice.” (FGD 9 and 10, KII 6 and 11)

Additionally, participants noted that IFV are low in satiety and less desirable for intense activities, which is why energy-dense staples are prioritised.

“We work at a construction site, we dig, these jobs require a lot of energy…We choose posho and cassava to provide energy throughout the day. So, we cannot choose IFV, those indigenous foods can only be snacks or tea accompaniments.” (FGD 3 and 8)

However, participants involved in sports activities indicated that they regularly eat IFV to boost their performance.

1. Knowledge of cardiometabolic risks. Participants acknowledged the rising trend of cardiovascular diseases, which they largely attributed to unhealthy eating. However, healthful eating was essentially construed as a moderate intake of fats, soda and alcohol, with very little attention to fruits and vegetables.

2. Potential cardiometabolic health benefits. Participants drew a link between the consumption of IFV and the prevention of cardiometabolic risks. The older participants referred to some of the IFV as direct remedies for overweight, diabetes and hypertension.

“When our parents ate these foods, they lived longer and healthier, but nowadays we see young people with diabetes and heart diseases, overweight. Foods like katunkuma, jjobyo, and all those bitter vegetables can’t allow accumulation of body fat, but young people don’t care, all they want fast foods…we are surely dying.” (FGD 1, 2, 3, KII 1–6, 13–17)

1. Convenience and time implications. The difficulty in preparation of IFV was heavily cited as an impediment for their consumption. Some indigenous vegetables like lima beans and pigeon peas take a long time to cook, which is an inconvenience, especially in the case of busy schedules. Moreover, participants noted the limited supply of safe ready-to-eat/prepacked IFV.

2. Nutrition knowledge and food preparation skills. Vegetables like bitter berries and spider plant were cited as difficult to prepare in a way that makes them palatable. The cited preparation methods included boiling, frying, steaming, grinding, sun drying and seldom pasting. Participants expressed that traditional methods formerly used to prepare most indigenous vegetables are no longer convenient. Frying has replaced boiling and steaming. Vegetable preparation skills were limited, and vegetables were reported to be cooked for longer periods.

“For us indigenous vegetables are not just simply vegetables, there’s a cultural dimension to them. For example, there’s a traditional way of preparing them which involves wrapping vegetables in a banana leaf and steaming them on top of the main food, unfortunately, all that is lost now; people use plastic bags and polyester sacks, but mostly they simply fry. This makes me sad.” (FGD 1, 6, 7, 8)

“…the way you prepare them matters. These self-styled herbalists may not understand, but the bioactivity of phytochemicals in food is influenced by processing methods, for example, the effect of heat, pH among other factors, so if these processing conditions are not controlled, the phytochemicals could be affected.” (KII 4)

1. Self-efficacy. Equipping meal planners with food preparation skills was identified as a key facilitator for the consumption of IFV. Women, who are essentially the meal planners of households, often lack the food skills to prepare palatable dishes from indigenous vegetables that are deemed unpleasant.

“…I think the focus of sensitization should be on women is because they are the meal planners of the homes, and if they don’t know the health benefits of these foods or skills to prepare them in a better way, then we won’t eat them.” (KII 10)

Interpersonal factors

1. Injunctive norms. IFV were associated with several sociocultural misconceptions. For example, IFV were regarded as food for poor and low social class people. Early adults considered IFV a symbol of backwardness, food for older adults and medicine for certain ailments.

“If the neighbors see you eating katunkuma, cherry tomatoes, jjobyo, nsugga…they will laugh at you saying that the poverty at your house stinks. One day I packed these foods for my children for school, but their peers mocked them, saying they are very poor, backward, and eating medicine for old people.” (FGD 1)

Participants regarded IFV as a coping strategy for food insecurity.

“…these are foods we eat when we don’t have anything else to eat, as for me, if I see people eating these foods, it’s an indication that hunger and poverty have struck.” (FGD 8)

Participants reported certain cultural beliefs where IFV are associated with witchcraft and superstitions or are only consumed during particular cultural ceremonies.

“…you see, some fruits like jackfruits are thought to be resting places for ancestral spirits, steamed unripe indigenous bananas and mushrooms are used for cleansing after the birth of twins, jjobyo induces labour pains, while rosary peas are used for love charms. If you eat meat or fish together with yams/yam leaves as vegetables, the yams in your garden will all die.” (FGD 3 and 8)

Some IFV, like bitter berries, spider plant, hibiscus and black nightshade, were linked to weight loss or prevention of weight gain. Participants expressed a positive perception of large body sizes, which they linked to health, wealth and prosperity.

“…those foods can make you lose weight, or if you eat them regularly, or you won’t gain weight. I can’t imagine myself losing weight; in fact, I always want to add weight to look good because when you lose weight, people think you are poor or have health problems.” (FGD 1)

1. Descriptive norms. Participants agreed that there is a strong tradition that leads individuals to primarily consume the food they grew up eating. Typically, the main meal consists of carbohydrate-based staples with a small portion of vegetables. Some IFV were culturally connected to specific tribes, and other tribes are reluctant to consume them.

“In the central here, food is carbohydrate staples and occasionally little vegetables at the side…but the Luos eat a lot of vegetables, then you have vegetables like malakwang, okra, otigo, which are culturally for the Luos, also the way they cook their vegetables like pasting with pea nuts, Hmmm, all these are alien to our culture.” (FGD 1 and 3)

The existence of food taboos was presented as another barrier.

“We have clans in Buganda and each clan has a totem, so you find some indigenous vegetables like Kkobe, Butiko, and Empindi, which means for the people belonging to these clans, such foods are taboos.” (FGD 8)

Individuals from higher socio-economic groups are becoming increasingly focused on nutrition for longevity, and this has reportedly driven up the demand for IFV.

“My clients are scared of the raging cardiovascular diseases and are seeking remedies in natural foods, especially these indigenous foods; katunkuma, pomegranates, tamarind, jobbyo… everyone wants to live a longer disease-free life, so I always say why take synthetic food supplements when we have these foods here.” (KII 16)

Environmental factors

The environmental factors were influenced by the physical and social aspects of food environments.

1. Physical food environment. Participants reported scarcity of IFV and the ubiquitous availability of exotic fruits and vegetables in urban areas. The main sources of IFV were open-air food markets; however, the availability and diversity of IFV were reported to be erratic during the day. The food markets were said to be far from residences, yet IFV are almost unavailable in the supermarkets.

“Hmmm IFV are so rare, maybe they exist in villages but here in town, markets rarely have them except very early in the morning or late in the evening. But also, markets are far from us, you need a taxi or bodaboda to reach there, that is already money spent.” (FGD 2 and 6)

There is minimal availability of ready-to-eat IFV reportedly because the drive towards processing of IFV is still low. Restaurants do not always prepare IFV, as there is a social preference for fast foods and exotic fruit and vegetable varieties such as apples, grapes, French beans and watermelons. Most IFV are still gathered as ruderals from the wild and efforts to conventionally farm these foods are still inadequate. The participants agreed that certain types of fruit and vegetable plants are currently rare or completely unavailable in their area. They mentioned that the ability to cultivate fruit and vegetables is hindered by a lack of land, knowledge of urban or backyard gardening and access to high-quality seeds.

“We used to collect IFV from forests and swamps where naturally they grow, these places have been cleared for settlement and industrial activities…,now if you want a fruit like Ttungulu you can’t find it. Maybe if we had space and seeds, we could grow them at home but it’s hard because they aren’t adapted to conventional farming conditions.” (FGD 2–5)

Seasonality of IFV was cited as a key determinant of consumption.

“…definitely, most of these indigenous vegetables are seasonal and are more available/accessible during rainy seasons, if they are out of season, usually the prices are so high you cannot afford them.” (FGD 1, 2, 8)

1. Social food environment. It was discussed that the size and composition of the family, the influence of children and women and peer influence are key determinants of IFV consumption. In multiperson households, priority was given to presumably more satisfying foods such as carbohydrate staples.

“…we are about seven people in the house, so with the little money we have to spend on food, priority is given to more satisfying foods like posho. You cannot start spending on IFV because they cannot make people feel full.” (FGD 4)

Participants from single-person households reported often choosing ready-to-eat street foods.

“I am alone in my house, so I choose ready-to-eat street foods like potato chips, sausages, soda… I can’t start cooking or making juice”. (FGD 10)

Food choices were also dictated by what children liked to eat.

“Children don’t like such foods, some think IFV are foods for the mature adults, for example, my children don’t eat bitter berries, jjobyo, so it’s hard to eat it when they are just looking on, so we end up entirely not buying these foods.” (FGD 1 and 3).

1. Women’s role and influence. It was reported that culturally, women are responsible for meal planning and preparation, while men typically do not cook or make decisions about what should be cooked and how it should be prepared.

“What the wife cooks is what we eat, in our culture, men don’t go to the kitchen or plan what is cooked at home. Women will always cook the way their mothers taught them. Besides, our wives get annoyed when we tell them to prepare vegetables at home because they feel we have become so poor.” (FGD 8).

Female participants noted that preparing vegetables depends on how much money their husbands allocate for food purchases. Priority is given to animal protein sources like meat and fish, while vegetables are considered only if the funds allow. In urban areas, it was also reported that men largely prefer animal-source foods over vegetables.

“…sometimes you have no choice but to prepare the food that your husband likes, not only considering the health benefits, because if you prepare let’s say bitter berries or jjobyo, he will choose not to eat.” (FGD 1 and 2)

1. Peer influence. Younger adults cited being influenced by their friends to frequent fast food outlets. The mature adults claimed to learn from each other’s dietary aspects, such as reducing intake of fried foods and eating fruits and vegetables regularly.

“…I learned how to vary my dishes and not eat the same food all the time, not to prepare food without greens, to eat some fruits during breakfast from my neighbour, while friends teach us to eat boiled foods instead of frying all the time.” (FGD 1)

1. Information environment. Participants reported obtaining information on the cardiometabolic benefits of IFV from herbalists, older adults, testimonies of previous users and non-communicable disease clinics. Younger adults particularly claimed to receive such information through social media. However, participants demonstrated difficulty in verifying the authenticity of the shared information.

“There are so many self-styled herbalists and nutritionists nowadays giving all sorts of health and nutritional advice, promoting some IFV and forbidding others, making all sorts of health claims, it is actually sad that you will also find these baseless claims on some food products in supermarket shelves and our people are not protected from this harmful information.” (KII 5, 6, 10, 13, 14)

It was noted that adverts on billboards and mainstream media mainly promote fast foods and fizzy drinks.

“…I personally feel our people would make attempts, for example, to drink the juice from let’s say hibiscus or tamarind if there was a deliberate effort by the media to promote these foods, but all the adverts you see are promoting soda brands and synthetic drinks.” (KII 15, 17, 18)

1. Food safety concerns. Participants expressed chemical and microbiological food safety concerns. Chemical food safety concerns included pesticide residues and metal debris in powdered IFV. Indigenous vegetables usually grow as ruderals or are cultivated in polluted areas and are often sold under unhygienic conditions. There were also concerns about the influx of genetically modified fruits and vegetables and questions regarding their safety.

“These indigenous vegetables often grow in very unhygienic places for instance in sewage polluted areas, then you find vendors selling them in very unhygienic conditions, you can imagine a vegetable stall mounted above an open drainage channel.” (FGD 9)

“…from having our indigenous foods turned into genetically modified variants to the uncontrolled use of all sorts of agricultural chemicals, certainly death is on our doorsteps. Everything is sprayed, even at the point of harvesting.” (KII 3, 4, 16)

It was emphasised that traditional drying and storage practices of IFV may expose them to mycotoxin contamination.

“…the way these herbalists and farmers handle these products after harvesting for example, you find them drying hibiscus calyxes, katunkuma or ggobe on bare ground, no quality control on storage moisture or temperature, all this could attract mycotoxins and aflatoxins.” (KII 5 and 9)

1. Financial considerations. Participants perceived that IFV are expensive and cannot be prioritised given the limited financial resources.

“Absolutely! without doubt we don’t really eat what we want, finances dictate what we choose to eat, we can’t spend the little money we have got on fruits and vegetables, and we can only buy energy-dense foods. IFV are quite costly from the market.” (FGD 1–11)

Cross-validation

Concerning the phenolic composition, the identified IFV demonstrated varying concentrations and a diversity of polyphenol classes. Among the four most frequently mentioned IFV, T. indica L. had the highest total polyphenol content (mg/100 g) at 4755, followed by H. sabdariffa at 2920, S. anguivi at 1710 and C. gynandra at 1330. The most abundant flavonoids were flavanols, flavones, flavanones and anthocyanins, while the primary non-flavonoids included hydroxybenzoic acid, hydroxycinnamic acid and lignans (online supplemental table 5, supplementary excel file 2).

Only five types of fresh IFV (tamarind, bitter berries, hibiscus and pomegranates) were identified in supermarkets. Mainly, exotic vegetables and fruits could be identified across the surveyed supermarkets. Supermarkets had several products processed from IFV, and these were mainly wines, vegetable powders, tea infusions, juice blends, kombucha and porridge formulations, essentially from such foods as hibiscus, tamarind, bitter berries, okra, amaranthus, avocado seeds, pigeon peas and pumpkin seeds. The prices of IFV-based products were three to four times higher than their raw forms.

Only 21 out of the 64 IFV cited during FGD and KII were identified in the open-air food markets (online supplemental table 3). The availability and diversity of IFV varied erratically throughout the day, with peaks in the morning and evening. Hibiscus, tamarind, amaranthus varieties, pigeon peas and scarlet eggplant were the most common IFV. Pomegranates, spider plant, alligator pepper and chayote were scarce, while Java plum, black nightshade and cherry tomatoes were completely unavailable. The interviewed vendors reported that older adults were the most frequent buyers of these foods, while the younger adults were ardent buyers of exotic varieties. Peak sale hours were early morning and late evening. In terms of food handling, no specialised structures were observed, IFV were vended on open stalls with no cooling system and very often, exposed to the sun.

Discussion

The findings showed a fair understanding of the interface between the consumption of IFV and the prevention of cardiometabolic risks. Although several IFV were linked to potential cardiometabolic benefits, T. indica L. fruits were the most popular potential adjuvant therapy for cardiometabolic disturbances. Interestingly, the phenolic profile of T. indica L. fruits relative to other identified IFV seems to corroborate purported health benefits. The main hindrances to IFV consumption were financial limitations, convenience and time barriers, food safety concerns, lack of knowledge about food and nutrition, physical environment of food, food skills and self-efficacy, sociocultural norms and physiological and psychological satisfaction. A cross-check of market availability and variety of IFV revealed a shortage of these food items, both fresh and processed. From a conceptual viewpoint, the study is in tandem with the current National Biodiversity Strategies and Action Plan for Uganda, which seeks to conserve indigenous plant genetic resources30 by raising awareness of the potential health benefits of these neglected foods. The study generates novel evidence on drivers and barriers to IFV consumption in LMIC settings, a pathway to curbing cardiometabolic risks by emphasising the so-called planetary healthy diets.44

Sociocultural perceptions of indigenous fruits and vegetables

The sociocultural norms—where IFV are regarded as food for the poor or weeds and associated with several myths—are believed to affect consumption. The works of Yiga et al40 45 corroborate our findings that vegetables are generally regarded as food for the poor. In addition, it was claimed that consumption of IFV promotes weight loss or hampers weight gain, which is undesirable in many African communities. Findings have revealed a culturally entrenched affinity for large body size in SSA as an indicator of health and prosperity.40 45 This health-beauty paradox is a potential impediment to the consumption of IFV. In several SSA communities, food consumption relates to many sociocultural practices and connotations that are often restrictive.2 46 47

Socioeconomic aspects of indigenous fruits and vegetables

Food choices were largely influenced by financial status and convenience rather than health considerations. Although it was widely reported that IFV are particularly expensive, the general fruit and vegetable consumption culture among Ugandans is far from optimal.23–25 28 While it is tempting to assume that a good financial status would predict healthful eating, our findings corroborate earlier reports from Uganda40 and Tanzania48 that a higher financial status may instead trigger unhealthy food choices. Across SSA, a low financial status increases the propensity to consume only carbohydrate staple-based diets, devoid of fruits and vegetables and ultra-processed foods.45 This seems to invalidate the traditionally ingrained assertion in SSA that vegetables are foods for the poor. Furthermore, some indigenous vegetables take hours to prepare, making them unsuitable in the face of convenience.2 Moreover, the hard-to-cook effect of some indigenous vegetables poses a sustainability challenge through increased demand for fuel.

Physiological and psychological satisfaction is influenced by satiety, food sensory attributes and peer influence. Findings from SSA show that multiperson households are more focused on providing foods with high satiety and desirability to children.45 Single persons presented a propensity to eat out of home and were more likely to be influenced by their peers to eat fast food. Emotional satisfaction was linked to the consumption of fast foods, while IFV were considered not tasty and visually unappealing even after cooking. In the wake of the nutrition transition, eating from fast food outlets is perceived to be emotionally satisfying, especially for early adults.40 It is imperative to note that the high value attached to energy-dense foods across SSA, compounded by the bitter taste and peculiar colour of IFV, is a mainstay hindrance to the consumption of IFV.2 45 On a positive note, participants reported learning from each other the health benefits of foods like S. anguivi, C. gynandra, T. indica and H. sabdariffa during community group meetings.24 This highlights the importance of community structures as instrumental conduits of nutrition knowledge, and such structures could be harnessed to promote the consumption of IFV.

Avenues and possible trade-offs to increase the consumption of indigenous fruits and vegetables

Generally, food safety is a key deterrent to the consumption of IFV. In particular, indigenous vegetables are regarded as ruderals growing in polluted places.49 50 Moreover, there is empirical evidence of the presence of high pesticide residues on Ugandan fruits and vegetables.51 52 Postharvest handling systems for IFV are still substandard, for example, drying vegetables on bare ground, poor storage and vending are precursors of food mycotoxin contamination. Particularly, aflatoxin contamination in fruits and vegetables is a rampant threat in SSA.53 54 Consequently, increased consumption of such IFV introduces another layer of complexity. This delicate balance highlights the necessity for technological and educational intervention to ensure good agricultural practices, safe food processing and handling practices. Without these measures, efforts to enhance diet quality could inadvertently pose new health risks, undermining the overall objective of promoting healthy and sustainable diets in SSA.

The claim that IFV have inferior sensory appeal is a salient hindrance to consumption. However, such claims could reaffirm the fact that low food skills and self-efficacy often mediate the exclusion of healthy foods on account of their unpleasant taste.2 55 Alienating indigenous foods due to their claimed inferior taste has been reported, especially among early adults in South Africa.2 Participants from northern Uganda reiterated that simple innovations, such as pasting with peanut butter, could ameliorate the taste of indigenous vegetables. Such simple innovations to offset unpalatable tastes have also been reported in Ghana.56 While such culinary innovations may enhance palatability, they may increase energy intake, potentially compromising nutritional goals aimed at mitigating diet-related metabolic risks. It has been shown that training sessions built around the concept of food literacy can improve food skills and self-efficacy and consequently increase fruit and vegetable intake.24 Other potentially effective innovations could focus on improving IFV convenience and appeal by stimulating minimally processed ‘ready-to-eat’ products. Noteworthy, the traditional culinary and preservation practices, where vegetables are customarily steamed for long hours, uncontrolled drying and roasting, among others, could be detrimental to the integrity of phytochemicals.57 58

The scarcity of IFV is a barrier to consumption. Previous studies have documented an apparent lack of healthier food options, such as prepackaged fresh fruits and vegetables in Uganda and SSA.2 40 59 For instance, only 62.2 kg and 105.5 kg of fruits and vegetables are available per person per year for Uganda and the entire African region, respectively.25 This threshold falls short of the WHO and FAO recommendation of 146 kg/person/year.59 The scarcity can be attributed to the seasonality of IFV,60 as well as the ubiquitous presence of exotic varieties in the retail food environment.30 The inherent characteristics of IFV, such as low yields and long growth periods, among others, often discourage large-scale production.2 61 62 Moreover, there is little doubt that the commercialisation of fruits and vegetables has coincided with the desire to cultivate exotic species with superior agronomic qualities.63

Regarding information on IFV, we observed age-related disparities in the knowledge of IFV. Culturally, the older adults are the custodians of knowledge about indigenous food, which cascades to younger generations over time. However, lifestyle changes marked by rapid urbanisation have caused a shift in nutrition patterns, the so-called nutrition transition.64 Consequently, such indigenous knowledge has plummeted among the early adults.2 Hence, younger adults were less enthusiastic about IFV in our study. The age-related difference in knowledge of IFV could be critical to developing age-tailored interventions to increase IFV consumption. Participants highlighted that food preparation is traditionally seen as a woman’s role. However, promoting community-wide awareness and family-inclusive cooking sessions can help encourage a more equitable sharing of responsibilities.

Cardiometabolic potentials of indigenous fruits and vegetables

Regarding the nutraceutical potential, the study revealed an array of scientifically unsubstantiated health claims related to IFV. Although T. indica L. was widely purported to have putative cardiometabolic benefits, there is a dearth of clinical studies to confirm the claimed efficacy. However, the phytochemical profile of T. indica L. shows a wide range of bioactive components such as polyphenols (flavonoids and phenolics), alkaloids and saponins.65 The abundance of polyphenols (flavanols—epicatechins and catechins) is reportedly responsible for the antilipidaemic, antidiabetic, hypotensive and anti-inflammatory properties of T. indica L.66 Based on this study, we conducted a clinical trial that showed that consumption of T. indica L. juice could improve lipid metabolism and optimise blood pressure in people living with HIV.67 Furthermore, dietary guidelines for bioactives recommend a daily intake of 400–600 mg of flavanols for cardiometabolic protection,68 while the European Food Safety Authority approved a health claim that 200 mg/day intake of cocoa flavanols is important for vascular homeostasis.69 On the other hand, H. sabdariffa L. powder, beverages or refined extract are gathering a lot of attention, with several epidemiological studies attesting to the cardiometabolic benefits of such food materials.17 70 71

Study strengths and limitations

The study employed a modified theoretical framework as a basis for the design of questioning routes for both KII and FGD. The combination of multiple health behavioural theories has been advocated as no single theory can solely describe behaviour.39 The use of probes in the questioning route allowed for flexibility in capturing new, emerging themes. The inclusion of food market surveys was an essential component to validate some of the claims from FGD regarding the availability and diversity of IFV. However, the time of the study could have influenced the findings of the market survey since seasonal variation has a huge bearing on food availability and diversity.60 72 Polyphenolic profiling of IFV was not fully complete since a large diversity of IFV has not yet been characterised, and hence is unavailable in the databases used.

Conclusion and recommendations

The consumption of IFV is influenced by a plethora of complex intrapersonal, interpersonal and environmental factors. At an intrapersonal level, there is a need to improve food knowledge, skills and self-efficacy to prepare tasty diets involving IFV through community-based culinary workshops. At the environmental level, there is a need to stimulate the production of IFV by empowering communities with skills in backyard farming. In addition, the food market chain of IFV needs to be streamlined to enhance access to IFV. There is a need to underpin cardiometabolic health claims associated with IFV through clinical trials. The food marketing environment often promotes unhealthy options, so it is vital to implement policies that encourage IFV and limit ultra-processed products. Strategies could include financial incentives like subsidies, support for local producers and regulatory measures to make IFV more appealing and accessible while disincentivising unhealthy alternatives.

Data availability statement

Data are available on reasonable request. Requests should be made to the corresponding author.

Data availability statement

The datasets of this study are available on reasonable request from the corresponding author. Requests should be made to the corresponding author.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).