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Abstract

Background:

Chronic vitamin A deficiency affects both women and children in Mozambique and populations worldwide and cannot be addressed through supplementation alone. Food-based approaches encouraging the consumption of vitamin A-rich foods, such as the orange-fleshed sweet potato (OFSP), have the potential to positively affect vitamin A status. A range of OFSP varieties have been introduced in sub-Saharan Africa in rural and urban environments and emergency and nonemergency contexts.

Objective:

To highlight the successes to date and remaining challenges of the introduction of OFSP to increase vitamin A consumption in Mozambique, collating a time line of key events.

Methods:

A systematic review of literature using The Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Results:

The systematic search resulted in 20 studies that met inclusion criteria. Data extracted include author and year, study location and duration, project partners, project title, sample size and characteristics, objectives, methods and measures, and outcomes.

Conclusions:

Orange-fleshed sweet potatoes are widely accepted by Mozambican farmers and consumers, and various studies show a positive impact on vitamin A status due to the introduction of this nutritionally superior staple crop. Remaining challenges include vine preservation, pest and disease management, market development, and storage and processing.

Keywords

food-based approach orange-fleshed sweet potato Mozambique vitamin A

Introduction

Although vital to preventing disease, disability, and death among vulnerable populations, interventions that focus on increasing micronutrient intake through a single mechanism, such as supplementation, are tenuous if not paired with complementary approaches such as food fortification and dietary diversification.¹ In countries where chronic malnutrition is widespread, food-based approaches emphasizing the consumption of a wide variety of vitamin-rich foods are crucial to reducing the occurrence of life-altering and often fatal micronutrient deficiencies.

Since 1999, the government of Mozambique has distributed supplements in order to combat high levels of vitamin A deficiency (VAD), especially among women and children.² In Mozambique, “the supply of micronutrient-rich foods is dramatically low,” resulting in persistent malnutrition.³ The ubiquity of cereals and starchy roots, particularly cassava, has led to extremely low dietary diversity, and the lack of available energy in the food system resulted in undernourishment levels³ of 38% between 2005 and 2007. In particular, VAD has been a severe public health obstacle in Mozambique, and lack of this crucial micronutrient results in xeropthalmia, blindness, growth limitations, weakened defenses, susceptibility to infection, and increased mortality.⁴ Despite government supplementation coverage, which reached 44% of children of age 6 to 59 months in 2003, VAD continues to be a major concern.² A 2005 study showed that VAD affects 71% of children between 6 and 59 months of age in Mozambique,² and the World Health Organization estimates that over 200 million women and children worldwide are affected by this preventable condition.⁵

The introduction of orange-fleshed sweet potato (OFSP) is one food-based approach that has great potential to decrease VAD in Mozambique.⁶ Although most varieties of sweet potato commonly grown in sub-Saharan Africa (SSA) are white-fleshed and lacking in vitamin A,^6,7 OFSP offers high levels of this important micronutrient and is both drought resistant and easily cultivated.⁸ Supporting data confirm that OFSP is a highly affordable source of vitamin A: “in 2004, meeting the recommended daily allowance for a child under 6 years of age (300-500 RAE) with OFSP cost less than 1 US cent.”^9(pS268)

Many published articles and reports have focused on the efficacy of OFSP as an emergency crop and/or a combatant to VAD in SSA,^6,8

–12 sensory properties and consumer acceptability of OFSP roots and enriched products,^8,9,13,14 retention of β-carotene after processing and storage of OFSP varieties,^15

–18 farmer willingness to pay for and grow OFSP,^19
–21 and consumer willingness to pay for OFSP.²² The purpose of this systematic literature review is to summarize successes and remaining challenges of the introduction of OFSP in Mozambique to date. This review collates a time line of events, beginning with the identification and distribution of varieties with high β-carotene content in the 1990s and continuing to include published evidence of success from recent years. Remaining challenges and plans for future research into the promotion of OFSP will be discussed in detail.

Methods

Study Selection

The goal of study selection was to identify published articles that contribute to building an accurate portrait of the successes and challenges of the introduction of OFSP in Mozambique to date. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram was used to guide the search for relevant literature²³ (see Figure 1). Articles identified in this systematic review were extracted from the following databases: Science Direct, ProQuest Agricultural Science Collection, Web of Science, AgEcon Search, and PubMed. The following key words and key word phrases were used: orange (or orange-flesh), sweet potato (or sweetpotato as one word), vitamin A deficiency, Africa, Mozambique. The authors also used Google search to identify reports and articles from nongovernmental organizations (NGOs) highlighting key findings of the OFSP intervention. Finally, reference list snowballing was used to further identify important sources that did not appear in research databases. The articles included in this review were chosen due to their focus on OFSP interventions and research in Mozambique. No year limitations were used as the authors intended to analyze the entire scope of the OFSP project in Mozambique since its inception. Full journal articles, conference papers, posters, and theses were considered.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram. Orange-fleshed sweet potato: successes and remaining challenges of the introduction of a nutritionally superior staple crop in Mozambique.

Article titles were first screened by the lead author, followed by a screening of abstracts, and concluding with full-text consideration. Two other authors then independently screened the articles, first by title, then proceeding to abstracts and full-text. Articles were included or eliminated after consensus by all authors had been reached.

Studies were excluded for the following reasons: study focused on a country or region other than Mozambique or did not specify location, study focused on structure and processing of OFSP, and/or study scope was too broad, for instance, focusing on biofortification or food-based approaches overall.

Per the guidelines found in the Cochrane Handbook for Systematic Reviews of Interventions,²⁴ studies were included if they met the following quality criteria: (1) focus on key scientific developments substantiating the efficacy and effectiveness of OFSP as an intervention food for increasing vitamin A intake in Mozambique, (2) focus on sensory acceptability of OFSP to Mozambican consumers, (3) focus on farmer acceptability and market development of OFSP in Mozambique, and/or (4) detailed description of key developments surrounding the introduction of OFSP in Mozambique.

Data Extraction

The data extracted in Table 1 include first author and year, study location and duration, project partners, project title, sample size and characteristics, objectives, methods and measures, and outcomes.

Table 1.

Results from the Systematic Search for Orange-Fleshed Sweet Potato (OFSP) Interventions in Mozambique.

First Author (Year)	Location	Duration	Project Partners^a	Project Title	Sample Characteristics	Objectives	Methods/Measures	Outcomes
Low et al (2000)⁶	Mozambique	Review^b	MSU (Michigan State University)	None	Review^b	Summarize why orange-fleshed sweet potato (OFSP) is ideal to combat food insecurity and vitamin A deficiency (VAD) in Mozambique.	Review^b	• Sweet potato used as a food security crop; production controlled by women • Variety testing in Mozambique began in 1997 • OFSP varieties higher yielding, not more labor intensive • 23% population eat roots or leaves 1×/wk
Kapinga et al (2005)¹⁰	Mozambique; Uganda	Review^b	Oxfam, South African Root Crops Research Network (SARRNET), etc	Vitamin A for Africa (VITAA)	Review^b	Summarize the role of OFSP in disaster mitigation using case study from Mozambique in 2000, when worst floods in 5 decades displaced 450K and 1000 died.	Review^b	• Rapid introduction of OFSP • Widened genetic diversity • 377 000 families benefited from resistant, high-yield planting material • 34.3% farmers using OFSP
Low et al (2005)²⁵	Zambezia province, Mozambique	2003-2005	MSU, Micronutrient Initiative, the United States Agency for International Development (USAID), etc	Toward Sustainable Nutrition Improvement (TSNI)	741 households (HHs) and children (498 intervention, 243 control); children age 6 months to 4 years	Summarize key findings from TSNI project.	• Three major components to conceptual framework of intervention: agricultural; demand creation/behavior change; marketing/product dev. • Surveys • 24-Hour dietary recall • Food frequency questionnaire • Morbidity recall • Blood sampling • Anthropometric data	• 5 of the 9 varieties accepted by farmers • Increase in nutrition knowledge larger among intervention women than control women • Median vitamin A intake 8.3× higher among intervention children • VAD (defined by low serum retinol) reduced from 60% to 36% among healthy intervention children • VAD in intervention children was 10% lower compared with control • 90% intervention HHs growing OFSP in final year • 68% sweet potato grown was OFSP
Kapinga (2007)²⁶	Mozambique; other countries	2001-2006	CIP (International Potato Center), CARE, USAID, National Institute of Agronomic Investigation (INIA), International Institute of Tropical Agriculture (IITA), SARRNET, etc	VITAA	Young children and their mothers	Analyze the 5-year implementation of VITAA.	• Field assessment • HH surveys • Feeding programs • Distribution of planting material • Nutrition education and awareness campaigns	• OFSP has played a key role in food security postdisaster • Sweet potato third most important crop; used in 6 forms • Farmers consumed products 2-3× week • Sweet potato generally preserved up to 50 days • Identified culturally appropriate recipes with OFSP • Farmers exhibited product at annual agricultural shows • Rapid multiplication sites supported 377 000 families in response to drought/flood • Improving adoption depends on access to planting material, market development, and postharvest handling and processing
Mazuze (2007)¹⁹	Gaza province, Mozambique	Three planting seasons from 2002 to 2004	Agricultural Research Institute of Mozambique (IIAM)	None	150 Farmers	Assess socioeconomic and institutional factors associated with adoption of OFSP by smallholders.	• Key informant interviews and growers survey	• 83% aware of nutritional benefits • 40% reported low drought tolerance of OFSP; many reported losses of vines to drought • 70% respondents planted >75% white sweet potato (WSP) • OFSP ranked positively for yield, root size, taste, and cooking time and negatively for off-season propagation, dry matter content of roots, and tolerance to drought, pests • Positive relationship between number of OFSPs received and adoption levels
Low et al (2007)⁸	Zambezia province, Mozambique	2003-2005	MSU, Micronutrient Initiative, USAID, etc	TSNI	741 HHs and children (498 intervention and 243 control); children average age 13 months at baseline	To examine farmer willingness to adopt sweet potato varieties with a visible trait, child willingness to consume OFSP, and potential of OFSP to serve as an entry point for diversified diets.	• See Low et al²⁵	• See Low et al²⁵
Low et al (2007)⁹	Zambezia province, Mozambique	2003-2005	MSU, Micronutrient Initiative, USAID, etc	TSNI	741 HHs and children; (498 intervention and 243 control) children average age 13 months at baseline	Increase vitamin A intake and serum retinol concentrations in young children.	• See Low et al²⁵	• See Low et al²⁵
Low and van Jaarsveld (2008)¹³	Zambezia province, Mozambique	2003-2005	MSU, Micronutrient Initiative, USAID, etc	TSNI	95 tasters, 112 market shoppers	Determine whether substituting 38% of wheat flour in bread buns with OFSP from fresh roots or dried chips would produce economically viable β-carotene-rich products acceptable to rural consumers in Mozambique.	• Survey • Modification of local recipes and training of bakers to incorporate OFSP • Sensitivity analysis	• Products with 15 μg/g of trans-β-carotene are good source of vitamin A • Only chips made with Resisto yielded product with sufficient β-carotene • 110 g bun excellent source of vitamin A for children and adults • Strong preference for Golden Bread over white wheat • Boiled mashed product preferred over chips • Bakers profit increased 92% due to lower cost inputs • Use of dried chips currently not economically viable
Labarta (2009)²⁰	Zambezia province, Mozambique	January 2008	HarvestPlus	Reaching End Users (REU)	121 farmers from 6 villages; 20 HHs each village; have not participated in vine distribution in at least 3 years	Evaluate farmer willingness to pay (WTP) for OFSP planting material.	• Real choice experiment; farmers received 6 meticais to spend on 10 choice scenarios • Survey questionnaire	• Farmer WTP higher for OFSP than WSP, and higher than traditional subsidized price of vines • All OFSP varieties considered superior in terms of taste • Reported difficulty conserving vines for several varieties
Naico (2009)⁴¹	Gaza and Maputo provinces, Mozambique	June-July 2008	Ford Foundation, Willard Sparks Endowed Chair	None	308: 190 (urban); 118 (rural) market shoppers	Determine consumer WTP for sweet potato attributes (color, dry matter, size, and price) in Mozambique.	• Choice experiment administered through in-person survey	• Dry matter content most important (75% utility), then pulp color • OFSP not competitive with WSP in terms of dry matter • WTP higher for OFP in 7/8 scenarios • Participants with knowledge of nutritional benefits chose OFSP more often than those without information • Higher priced options less likely to be chosen • Smaller size roots preferred • Importance of controlling for hypothetical bias in choice experimentation • WTP for OFSP in rural areas higher than urban (21.02 MT vs 12.02 MT)
Naico and Lusk (2010)²²	Gaza and Maputo provinces, Mozambique	June-July 2008	Ford Foundation, Willard Sparks Endowed Chair	None	308: 190 (urban) and 118 (rural) market shoppers	Generate information on consumer demand for OFSP to inform market strategies and improve production using choice experiment. Determine Mozambican consumers’ willingness to consume/pay for OFSP.	• Choice experiment administered through in-person survey	• See Naico (2009) • WTP for OFSP 51.3% more when other factors constant
de Brauw et al (2010)²⁷	Uganda and Mozambique	2006-2009	World Vision (WV), Helen Keller International (HKI), HarvestPlus (International Food Policy Research Institute [IFPRI] and International Center for Tropical Agriculture [CIAT]), Gates Foundation, USAID, etc	REU	144 villages; 12 000 farm HHs; 100 HHs per unit of observation; 10 800 direct beneficiaries; children 6-35 months	Evaluate the REU project in East and Southern Africa.	• Conceptual framework adapted from TSNI • Diagnostic analysis • Randomized control trial, 2 intervention models • Qualitative interviews • Baseline and end line surveys included demographics, income, production, consumption, social networks, dietary intake, etc	• 66%-69% point increase in probability of OFSP adoption • Substantial substitution of OFSP for other sweet potato varieties • Vitamin A intakes doubled among young children (45 g/d), older children (70 g/d), and women (145 g/d) • Vitamin A intake roughly equivalent to 100% estimated average requirements • Intervention intakes higher than control • OFSP contributed 71%-84% total vitamin A intakes • Adoption probability increases as kilograms of vines received increases • OFSP 25% of sweet potato in markets • >85% consumers would purchase OFSP in future • No difference in impact in cheaper model of intervention • Yields of OFSP similar to WSP
Bechoff et al (2011)¹⁶	Mozambique	Not specified	HarvestPlus	REU	Two OFSP varieties	Evaluate carotenoid retention after simple low-cost drying and storing chips made from Resisto and MGCL01 varieties of OFSP under rural conditions, on-farm setting.	• Chip drying • Carotenoid analysis • Dry matter determination	• Total carotenoid losses during drying low, 9.2% average • Carotenoid losses during storage high after 4 months, 83.7%. • Shade drying best option for Mozambican farmers, less carotenoid loss than open air • Shade dryer not suited for thicker, handcut slices (traditional way) due to longer drying time • Chip size had a significant effect on drying but not storage • Variety affected both drying and storage • Higher level of technology does not necessarily lead to greater carotenoid retention
Brito et al (2012)²⁸	Mozambique	Review^b	EU ResIST	ResIST	Review^b	Discuss key concepts relating to sweet potato biotechnology and its diffusion in Mozambique.	Review^b	• Sweet potato largely a staple of poor households • All provinces except Niassa received distribution of OFSP cultivars in 2007 • USAID invested US$500k in OFSP tissue culture laboratory • Market for vines increasing; shortage of quality vines • Regional variation in consumption of OFSP, least frequent in Cabo Delgado • Breeding more expensive than dissemination • Informal sharing of vines key to access • Benefits from sale of OFSP not evenly distributed, larger farmers producing more for market
Hotz et al (2012)¹¹	Mozambique	2006-2009	WV, HKI, HarvestPlus (IFPRI, CIAT), Gates Foundation, USAID, etc	REU	144 villages; more than 12 000 farm HHs; 100 HHs per unit of observation; 10 800 direct beneficiaries; children 6-35 months	Learn lessons about scaling up OFSP.	• Conceptual framework adapted from TSNI • Randomized control trial, 2 intervention models • Baseline and follow-up surveys • Six OFSP varieties chosen for distribution	• Vitamin A and OFSP intake greater in both models (47%-60% of all sweet potatoes consumed) • OFSP provided 71%-84% of total vitamin A across all ages • Inadequate intakes of reference children decreased 32 and 55% in both models; similar results for women • Median intake for all intervention children 46 g • 77% HHs adopted OFSP for cultivation • 56% sweet potato grown was OFSP • Two models had similar impact
HarvestPlus (2012)²⁹	Mozambique	2006-2009	WV, HKI, HarvestPlus (IFPRI, CIAT), Gates Foundation, USAID, etc	REU	14 000 farm HHs targeted	Summarize outcomes of REU from 2006 to 2010	• Conceptual framework adapted from TSNI • Randomized control trial, 2 intervention models • Baseline and follow-up surveys	• See de Brauw et al²⁷ above
de Brauw et al (2013)¹²	Mozambique and Uganda	2006-2009	IFPRI	REU	36 community organizations in separate villages, goal 20 HHs per village—achieved in most villages. Actual at baseline: 703 HHs and 441 children. Actual at end line: 628 HHs and 409 children. Producers and consumers of OFSP.	Compare impact of REU intervention within and across Mozambique and Uganda on OFSP adoption, knowledge of vitamin A, and dietary intake of vitamin A by children.	• Randomized impact evaluations • Causal mediation analysis	• 2 of the 3 mothers named OFSP as source of vitamin A • 75%-79% farmers grew OFSP at end line (9% control) • Substantial substitution of OFSP for conventional white/yellow • Growing OFSP influences vitamin A intake regardless of amount produced • Intervention children consumed almost twice as much retinol activity equivalent (RAE) at end line compared to control (600 vs 350 μg), fully attributable to OFSP • Diffusion rate of 0.32 in Mozambique helps to lower cost of intervention
Maquia et al (2013)³⁰	Maputo province, Mozambique	2006-2008	CIP, Ministry of Science and Technology, Universidade Eduardo Mondlane (UEM), etc	None	44 sweet potato accessions, 28 genotypes	Characterize the Mozambique sweet potato germplasm collection by (1) genetic, morphological, and agronomic diversity and (2) agronomic potential toward drought tolerance.	• Field trials conducted over 2 seasons • Morphological and agronomic characterization • Random amplified polymorphic DNA analysis	• High level of diversity in Mozambique germplasm • Good source of traits for breeding • 6 Mozambican varieties and 4 others have highest drought tolerance • Majority perform best under irrigation
de Brauw and Eozenou (2014)²¹	Zambezia province, Mozambique	2009	IFPRI	REU	439 HHs, 682 farmer respondents	Explore risk preferences related to sweet potato production among Mozambican farmers.	• Uses data collected during final REU survey to test several models of risk preference	• On average, sample is risk averse but does not follow standard constant relative risk assumption utility function
Carvalho et al (2014)¹⁴	Mozambique	Not specified	Swedish International Development Cooperation Agency (SIDA)	None	134: sensory panel of 50 volunteers from UEM (students and staff). Untrained panel of 84 regular consumers of garri, or flour made of roasted cassava (farmers, market shoppers).	Develop a porridge acceptable to consumers that incorporates roasted grated OFSP and shredded sun-dried cassava.	• Roots collected, dried, and processed to create porridge • Mechanical characterization of porridge consistency • Color measurements/microscopy • Sensory ranking of consistency • Sensory acceptability of multiple attributes	• Porridge made solely from OFSP unappetizing • Sensory test of consistency: mixed OFSP and cassava porridge ranked first of 5 porridges • Overall sensory test: mixed OFSP and cassava porridge was significantly preferred over simple cassava porridge for all attributes • Flour made from grated OFSP and shredded sun-dried cassava improves perceived consistency and energy density compared to traditional cassava porridge

^aPartners include funders and implementers. For projects that include many partners, all may not be listed in table.

^bArticle did not specify methods but rather focused on a review of literature and/or events.

Results

The initial database search using multiple combinations of the selected key terms yielded 12 199 results (see Figure 1). The removal of 21 duplicates resulted in 12 178 results. Reference list snowballing and Google search revealed 19 other studies of potential relevance. Ten studies identified as potentially relevant through reference list snowballing were ultimately inaccessible to the authors as they were published by research institutions in Mozambique and not available on the Internet. Of these results, 71 were identified as potentially relevant. A full-text examination of these studies resulted in the exclusion of 51 studies, which did not meet the inclusion criteria. Twenty-six studies were excluded because they did not focus specifically on Mozambique. Ten studies were excluded due to focus on structure and processing of sweet potato. Fifteen studies were excluded because the scope was too broad, focusing for instance on biofortification or food-based approaches in general. Twenty studies met the inclusion criteria and are included in Table 1.

The results of this systematic review reveal that key contributors to research and reporting on the introduction of OFSP in Mozambique include Jan Low of the International Potato Center (CIP), Alan de Brauw of the International Food Policy Research Institute (IFPRI), Regina Kapinga of CIP, Abdul Naico of CIP, and Christine Hotz of Nutridemics. Of the 20 articles chosen for final review, Low was the lead author on 5, de Brauw on 3, Kapinga on 2, Naico on 2, and Hotz on 1. The interventions discussed in this body of work span 2001 to 2009 and include Vitamin A for Africa (VITAA; note 1), Toward Sustainable Nutrition Improvement (TSNI; note 2), and Reaching End Users (REU; note 3).

All of the studies took place in Mozambique, though several also examined efforts in other countries of SSA. The key organizations involved with funding and implementation (see project partners column in Table 1) include but are not limited to the Bill and Melinda Gates Foundation, the Micronutrient Initiative, the United States Agency for International Development, the Rockefeller Foundation, the HarvestPlus project led by IFPRI and the International Center for Tropical Agriculture, CIP, Michigan State University, Southern African Root Crops Research Network, World Vision, Helen Keller International, and the Agricultural Research Institute of Mozambique.

Methods and measures commonly occurring throughout the studies listed in Table 1 include household surveys, dietary recall, anthropometric measurements, and choice experiments. Common interventions include technical agricultural assistance (such as vine distribution and pest management), nutrition awareness and demand creation campaigns, and market development.

Discussion

Why OFSP

Sweet potato has long been an important food security crop in SSA,³¹ serving a key role as an energy-dense food often in postdisaster contexts.¹⁰ Sweet potato can be vegetatively propagated, or multiplied through the cutting and replanting of vine segments. It is a hardy crop that often succeeds when other crops succumb to stress and is not as labor intensive as many other staple crops.³² While the white sweet potatoes typically grown in Mozambique do not contain β-carotene,^6,7 orange varieties are high in this precursor to vitamin A.⁶ Once consumed, β-carotene is easily converted into the retinoids required by the body for eye, skin, and immune health.³³ A child who is 5-year-old or younger needs to consume only 100 g/d (half-cup) of OFSP roots in order to receive the recommended daily amount of vitamin A.³⁴

Vitamin A Intakes and Serum Retinol

Since the implementation of VITAA²⁶ from 2001 to 2006, OFSP interventions have focused on women and children as target beneficiaries due to their vulnerability to VAD and due to women’s role in the production and marketing of sweet potato. Not only has OFSP been demonstrated to be highly acceptable to Mozambicans based on its sensory and agronomic characteristics, its introduction into communities has been shown to dramatically increase vitamin A intake among children.^8,9 Toward Sustainable Nutrition Improvement, a 2-year intervention beginning in 2002, assessed the effects of OFSP availability on vitamin A intake and serum retinol concentrations especially among young children.^8,9,25 At the end of TSNI, >50% of intervention children consumed OFSP 3 or more days per week⁸ and VAD, as indicated by serum retinol levels, was reduced from 60% to 36% among otherwise healthy intervention children.²⁵ Reaching End Users, a large-scale intervention that took place from 2006 to 2009, found that vitamin A intake from OFSP increased in both models across intervention groups of all ages compared to the control.¹¹ Orange-fleshed sweet potato also accounted for a much greater overall percentage of sweet potatoes consumed in the intervention groups compared to the control, 47% to 60%, and 20% to 24%, respectively. The varieties cultivated in this trial had significant β-carotene content, higher than raw pumpkin, green leafy vegetables, mango, and ripe papaya.¹¹ The end line data collected after both TSNI and REU have helped to narrow the knowledge gap surrounding food-based approaches to nutritional improvement in Mozambique, and these experiences can be applied in other countries similarly affected by micronutrient deficiencies.

Sensory Qualities of OFSP

The introduction of nutritionally superior varieties of staple foods, also known as biofortified foods, can be complex due to a variety of factors including culture, tradition, and dietary preferences.^35,36 Various studies have shown that OFSP is accepted in Mozambique^{14,20,22,25,37,38} and will not be rejected due to its orange color.^9,11 However, the image of sweet potato as a staple of poor households and a women’s crop persists in Mozambique²⁸ due to its use in postdisaster contexts to improve food security.¹⁰ It is also important to note that consumer perception of existing varieties is geographically specific. For instance, the Resisto variety that is cultivated widely in SSA is well liked in Mozambique,⁹ considered to be watery in Tanzania,³⁹ and was determined to be less watery than several cream flesh varieties in a South African study.⁴⁰

In 2002, the TSNI project was launched in Mozambique to promote OFSP as a food-based approach to combatting VAD.⁹ This was based on a conceptual framework that included 3 pathways: access to high-yielding, β-carotene-rich OFSP planting material, demand creation and empowerment through knowledge, and market development for fresh roots and processed products to ensure sustained adoption.²⁵ The results of TSNI demonstrated that 5 of the 9 varieties introduced were acceptable to both men and women based on taste and agronomic performance.^8,9,25 Further, the Golden Bread that is made by substituting 38% of wheat flour with boiled and mashed OFSP was popular and profitable among participants in TSNI,^9,13,25 who demonstrated “a strong preference for Golden Bread over white wheat flour bread because of its heavier texture … superior taste, and attractive golden appearance.”^13(p103)

Varieties and Breeding

Research has shown that consumers are willing to pay >50% more for varieties of OFSP that possess similar eating qualities to traditional varieties, the most important of which is dry matter content.^22,41 Multiple studies have shown that African consumers typically prefer sweet potatoes with high dry matter and low water content.^42
–44 A choice experiment conducted in 2008 in 2 provinces of Mozambique revealed that willingness to pay for high dry matter content (associated with a firm, starchy potato) was almost twice that of willingness to pay for the color of pulp, even when consumers received information about the health benefits of consuming OFSP.^22,41 The Resisto variety has been shown to be popular in Mozambique due to its taste, dark-orange color, growth structure, and high yields but was found to be less drought-tolerant than the light-orange Jonathan variety.^9,25 These findings have been essential for sweet potato breeders who have subsequently worked to create new OFSP varieties that are high in β-carotene, drought tolerant, resistant to pest and disease, and suitable for Mozambican dietary preferences. In response to the lack of drought tolerance observed in the first 8 varieties released in Mozambique in 2001, breeding trials were undertaken from August 2005 to December 2009, resulting in the release of 15 improved varieties⁴⁵ in 2011. The time required to create new varieties has been reduced from 8 to 4 years due to a new technique known as “accelerated breeding,” and from 2000 to 2012, the number of countries in SSA with sweet potato breeding programs grew from 2 to 12.⁴⁶

Market Dynamics

Several studies included in this review emphasize the importance of including a market development component to ensure the successful introduction of OFSP into communities.^8,9,11,13,25 Although many Mozambican consumers have demonstrated a preference for OFSP, low-purchasing power is a major constraint for enhancing dietary diversity.¹³ One key challenge identified during TSNI was the creation of a market development strategy that assures significant home consumption of OFSP while still allowing surplus for sale at markets.⁹ Proximity of households to markets and agroecological conditions are both key variables to the success of market development. The success of the pilot marketing component of TSNI encouraged researchers to suggest the inclusion of a strong marketing component in future efforts to scale-up the production and consumption of OFSP.⁹

By the end of the TSNI project: 90% of intervention households were growing OFSP, 30% of which were selling OFSP (up from 13%); sweet potato plot sizes were nearly 10 times larger, and OFSP was the cheapest source of vitamin A on local markets.⁸ This last finding is especially important, as a very slight price increase in OFSP has been associated with a decrease in utility for potential consumers.²² However, the final report for the REU project, which employed a conceptual framework adapted from that of TSNI, indicates that the market development component did not significantly affect adoption rates or vitamin A intake.²⁷

Storage and Processing

Orange-fleshed sweet potato is generally available in Mozambique between March and August; mangos are an important complementary source of β-carotene but are usually available only between December and February. Because seasonality is a limiting factor of OFSP availability and consumption,¹¹ it is important to understand methods of storing, cooking, and processing that maximize β-carotene retention. Fresh roots can be stored in protected pits for 1 to 5 months, but this practice is not common in Mozambique.¹³ While β-carotene content of some varieties remains relatively stable during storage, it begins to decline after 12 weeks of indoor storage and 22 weeks of in-ground storage. An on-farm evaluation in Mozambique in 2011 found high losses of carotenoids during storage of dried OFSP chips, leading to a recommendation that chips be stored no longer than 2 to 4 months depending on the variety.¹⁶ Staggered planting and improved fresh root storage, therefore, are important solutions to extending the availability of this nutritious crop.¹³

The bioavailability of β-carotene is affected by the method of processing: for OFSP, “raw < baked < steamed/boiled < deep fried”⁴⁷. Consumption of OFSP in conjunction with small amounts of fat can increase β-carotene bioavailability by up to 20-fold. A 2006 study examined β-carotene retention in boiled, mashed OFSP of the popular Resisto variety.⁴⁸ Results showed that the most successful way to retain β-carotene (up to 92%) was by boiling for 20 minutes with the lid on. When boiled with the lid off, the potatoes took longer to cook through and lost slightly more β-carotene (retention of 88%).

One use for boiled, mashed OFSP is as a partial substitute for wheat flour in Golden Bread. In addition to being well liked by consumers and an excellent source of vitamin A, Golden Bread can provide an important source of income for bakers, whose profit has been shown to increase by up to 92% as the result of using locally available sweet potato to replace expensive imported wheat flour.¹³ Using dried OFSP chips to make Golden Bread is currently not cost effective as 4 kg of fresh roots are required to produce 1 kg of chips, and revenues are greater from selling fresh roots. However, seasonal fluctuations in supply could be largely mitigated if the use of dried chips from darker orange varieties with higher β-carotene content became economically viable.¹³

Farmer Networks

While sexual propagation is used to create new varieties of OFSP, the crop is commonly propagated vegetatively, meaning the vines can be cut and replanted to create new root systems. Researchers of OFSP integration into rural Mozambican communities have recognized that free vine distribution by third parties, such as NGOs, has the potential to discourage vine preservation by farmers with limited resources.⁹ However, these vine distributions are critical to introducing improved OFSP planting material into communities, and research shows that OFSP technology may be diffused from direct beneficiaries to reach indirect beneficiaries,¹¹ helping to control the cost of interventions.²⁷

Agronomic Challenges: Vine Preservation and Weevil Infestation

Various studies included in this review indicate that one of the greatest remaining challenges involved in the introduction of OFSP is limited access to quality vines for planting due to drought and flood and lack of sufficient planting material at the beginning of the season.^{12,19,20,25,28,27} Multiplying vines requires considerable labor and access to water. Farmers have been encouraged to reproduce and share vines through small-scale commercial networks,²⁵ but reoccurring drought and flooding makes maintaining vines in the off-season difficult. In the third year of REU, the use of trained decentralized vine multipliers was determined to be a successful mechanism for increasing the availability of planting material at the community level.²⁹ A promising new method known as “Triple S” also enables farmers with limited access to water to preserve small, healthy sweet potato roots in buckets of sand during the dry season, with the intention of re-sprouting the roots in protected seed beds before the rains begin.⁴⁹ The 2011 release of 15 improved varieties of OFSP in Mozambique was an important step toward improving the quality of available planting material and increasing the utility of the crop for producers; recent research has highlighted the importance for breeding efforts to continue to focus on greater drought tolerance.³⁰ Additionally, sweet potato is highly susceptible to pest and disease,^25,27,28 necessitating preventive measures such as disinfection of vines and hilling-up (note 4) of sweet potato plots.²⁷

Models of Different Intensity Produced Similar Results

The TSNI project operated for 4 growing seasons from 2002 to 2005 and was designed to test the efficacy of OFSP in maintaining vitamin A status among children who received capsules.²⁵ In 2006, a 1-year financing arrangement known as Eat Orange was implemented to test a new approach and serve as a bridging project between TSNI and REU.²⁷ Although Eat Orange incorporated changes to lower the cost per beneficiary, the conceptual framework for TSNI was used to design the subsequent REU project, a scaled-up intervention implemented¹¹ from 2006 to 2009. The REU project employed 2 intervention models of different levels of intensity, which produced similar results at end line, leading researchers to conclude that the lower intensity model was more cost effective and should be used in future interventions to encourage the production and consumption of OFSP.^11,27 A 2013 report on the impacts of REU in Mozambique in Uganda showed that by the end of the project, 75% of Mozambican farmers in model 1 and 79% in model 2 were growing OFSP, compared to only 9% of farmers in the control group.¹² This study concluded that access to vines was the most important factor in the impact of OFSP on vitamin A intakes, and that the effect of nutritional knowledge on adoption of OFSP was very limited.

Conclusion

Through conversations with individuals currently working to promote OFSP in Mozambique and exploration of the Sweetpotato Knowledge Portal,⁵⁰ the authors were able to identify several recent interventions focusing on OFSP, including the Sweet Potato for Profit and Health Initiative, The Sweetpotato Action for Security and Health in Africa (phases 1 and 2), the Office of US Foreign Disaster Assistance distribution of planting material in response to drought and flood, Reaching Agents of Change, Nutritious Orange-Fleshed Sweet Potato for Niassa, and Scaling Up Sweetpotato Through Agriculture and Nutrition. Reports on these interventions are not included in Table 1, as they did not appear during the systematic search for literature; however, these interventions are included in the time line in order to help develop a clear picture of OFSP activities in Mozambique from the 1990s to date (see Figure 2). Although she was not captured as a lead author in the systematic search for literature, the work of Maria Andrade of CIP has been essential to OFSP breeding and supported the work of many key contributors in this review.

Figure 2.

Time line of orange-fleshed sweet potato (OFSP) in Mozambique.

Many organizations have worked in partnership to promote OFSP as a nutritionally superior staple crop in Mozambique over the past 15 years, including NGOs, government organizations, and private funders. There have been notable improvements in the vitamin A status of the participants involved in these projects, and the food environment has benefited from the addition of this β-carotene-rich crop. However, VAD persists, and many Mozambicans do not have regular access to or knowledge of OFSP and its potential markets.

In a 2013 case study provided by reviewers of the current manuscript but not captured in the systematic search, 4 major lessons are identified as emerging from the OFSP experience in Mozambique to date: OFSP is acceptable to people of all age groups and can have an important impact on vitamin A intake and status; adults and children may have different varietal preferences, as adults tend to prefer higher dry matter content; the availability of high-quality planting material at the beginning of the rainy season is a key constraint to OFSP expansion; and breeding efforts in Africa should be enhanced to ensure a supply of regionally appropriate varieties.⁴⁹ A chapter from the 2013 Handbook of Food Fortification and Health also offers a concise summary of the lessons learned from 14 years of OFSP implementation in Mozambique as well as 10 critical steps to guide the design of OFSP interventions.⁴⁶

Future research should include follow-up studies to determine which OFSP varieties are accepted in specific communities, as varietal preference has been demonstrated to vary significantly across regions of Mozambique.¹¹ In addition to the baseline and end line surveys that are typically conducted during project implementation, researchers should interview key informants to better understand the social and technical challenges associated with long-term retention of OFSP planting material after distributions. These interviews will help to determine the factors that may affect farmer willingness and ability to conserve and distribute vines within their own networks, such as access to water, cost of labor, pests and disease, gender dynamics, consumer preference, market potential, and dependence on distribution of vines from NGOs.

Awareness of OFSP and its nutritional benefits exists in some regions of Mozambique; however, the market for OFSP must be formalized in order to improve access to OFSP and its derivatives. Innovation in product development, such as bread and juice, as well as commercialization facilitated by grading of sweet potatoes according to variety and quality are important methods for stabilizing these markets.²⁵

Preventive measures must be taken to control weevil infestation,²⁷ in addition to continued efforts to improve drought tolerance.³⁰ There is also a considerable need for continued research in the area of storage and processing of OFSP to better understand the retention and loss of β-carotene.^13,51 Future studies should focus on improved storage technology for fresh roots, staggered planting as a mechanism to extend availability, and crop rotations that maximize the growing potential of OFSP. Formal studies should also be conducted to analyze the rate of conversion of β-carotene from sweet potato leaves into retinol, as well as studies to clarify the effect of environmental variation and time of harvesting on β-carotene content of popular sweet potato varieties.⁵¹

Linking OFSP promotion with other health interventions including increased fat consumption and deworming has been shown to have positive outcomes in clinical settings⁵² and could therefore be a useful strategy at the community level in Mozambique.⁵¹ The OFSP can also potentially play a greater role in supporting the nutrition and income of households affected by HIV/AIDS.

Finally, recent broad-scale disseminations of OFSP in Mozambique have taken place without adequate resources to measure impact at the household level.⁴⁹ Research must be conducted to determine the best pathways for scaling-up OFSP delivery systems, with an emphasis on developing monitoring and evaluation plans that ensure that impact can be accurately measured.⁵¹

As key donors begin to recognize the need for integrated approaches to improving agriculture and nutrition, OFSP is increasingly recognized as an important mechanism to improving food security.⁴⁶ Food-based approaches to alleviating micronutrient deficiencies are complex due to the initial setup involved and the behavior change required to measure success; however, proponents of this approach believe that it has greater potential to affect long-term health outcomes than an approach that relies solely on supplementation.⁴⁶ Radio and television coverage, demonstration events, and farmer testimonies have all helped to increase government support for OFSP in Mozambique, thereby encouraging continued donor investment. Understanding the production, distribution, and consumption of vitamin A-rich OFSP in Mozambique has important implications for other food-based interventions focused on increasing micronutrient intake within regionally specific cultural contexts. Agronomic challenges, regional differences in consumer preference, postharvest handling and the creation of value-added products, and linkages between food producers and consumers through marketing efforts all make a distinct difference in the likelihood of adoption. Population-level improvement in the intake of specific micronutrients through food-based interventions requires consideration of regional, community, and individual contexts to provide long-term solutions to decreasing chronic micronutrient deficiencies.

Footnotes

Authors’ Note

Mica Jenkins is the lead author on this article and was responsible for literature search,screening and final selection of articles,structure and content of the manuscript,creation of tables and figures,editing,and final submission. Carmen Byker Shanks provided disciplinary expertise,constant guidance in literature search,screening and final selection of articles,and multiple edits of the manuscript,figures,and tables. Bailey Houghtaling assisted in article screening and final selection and provided multiple edits of the manuscript,figures,and tables.

Acknowledgment

The authors are grateful for the generous support from the Montana State University author fund for publishing this article as SAGE Choice (Open Access).

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research,authorship,and/or publication of this article.

Funding

The author(s) received no financial support for the research,authorship,and/or publication of this article.

Notes

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