TREES NURTURE NUTRITION: An insight on how to integrate locally available food tree and crop species in school gardens

Introduction

Indigenous and underutilized fruit/food trees have an important role in providing vital minerals and micronutrients to growing children, as well as the wider community. The diversity of indigenous and underutilized fruit/food trees also means that they have an important role to play in addressing seasonality and hunger periods facing many rural communities by ensuring the availability of nutritious foods for a healthier diet year-round. This chapter will highlight the role of a diversity of indigenous and underutilized fruit/food trees, and their food composition and contribution to micronutrient and wider dietary needs. It will also highlight the ‘portfolio approach’ - for addressing seasonal food and nutrient-specific gaps in local diets. And an example of the inclusion of these portfolios in school gardens initiatives is presented to highlight the relevance of such a platform for anchoring learning, providing practical demonstration space and for wide community engagement for including a greater diversity of available food trees and crops in local food systems.

Food and agriculture systems for better nutrition and health

Malnutrition in all its forms, including under-nutrition, micronutrient deficiency and over-nutrition, affects one in three people worldwide, and is the major risk factor of non-communicable disease (Development Initiatives, 2018; Forouhi and Unwin, 2019). While the causes of malnutrition are complex, a common denominator of all types of malnutrition is often a nutritionally inappropriate diet, characterized by low diversity of nutritious foods, derived from food and agriculture systems that have been shaped for delivering sufficient calories rather than a broad range of nutrients over previous decades (Hawkes, 2007; Burchi et al., 2011; Global Panel on Agriculture and Food Systems for Nutrition, 2016; HLPE, 2017a). The associations between food, health, and environment, and their role in addressing chronic vitamin and mineral deficiencies, has been discussed for some time (Johns and Eyzaguirre, 2006; Burchi et al., 2011). The need for a profound change of the global food and agriculture system away from simply supplying food, towards providing healthy diets is increasingly recognized in recent global policy frameworks and commitments (FAO and WHO, 2014; United Nations, 2015; Global Panel on Agriculture and Food Systems for Nutrition, 2016). With the Sustainable Development Goals, specifically SDG 2 - Zero Hunger, the world has committed to ending all forms of malnutrition by 2030 by simultaneously ensuring sustainable food production and maintaining the genetic diversity of seeds, plants, and animal species. To achieve a better nourished world, actions throughout the entire food system, from production, to processing, transport, and consumption and across sectors including agriculture, health, social protection, and education are required (Ruel and Alderman, 2013; FAO and WHO, 2014; Development Initiatives, 2017). Nutrition-sensitive agriculture is one part of nutrition-sensitive programming that addresses the underlying causes of malnutrition, including poverty, food insecurity, health, water, and sanitation. It is a food-based approach, recognizing the importance of nutritionally rich foods and dietary diversity for overcoming malnutrition and micronutrient deficiencies (FAO, 2014). One example is agroforestry, the integration of a diversity of trees into landscapes for greater productivity and resilience and which plays an increasingly important role in diversifying agricultural production systems (Hill- brand et al., 2017). It has received global appreciation over the past decade for its potential impact on rural livelihoods, climate-smart agriculture, biodiversity conservation, and land restoration, as stated in the recent report of the State of the World's Biodiversity for Food and Agriculture (FAO, 2019).

The role of agroforestry for diversified production, diets and improved health

Tree-based agroforestry systems and forests provide a wide variety of foods and contribute substantially to food and nutrition security in multiple ways (Jamnadass et al., 2015; Bioversity International, 2017; HLPE, 2017b). Trees provide fruits, leafy vegetables, nuts, seeds, and oils into local farming systems (Stadlmayr et al., 2013; ICRAF, 2019). Tree foods can increase the nutritional quality of local diets, mostly due to their micronutrients (mineral and vitamins), but also macronutrients (protein, carbohydrates) and phytochemicals (e.g. antioxidants) (Stadlmayr et al., 2013). Trees also provide timber, fodder, fuel, and medicinals - for home use or income generation and can contribute to the resilience of resource-constrained households (Jamnadass et al., 2015). Additionally, they enhance productivity and ecological resilience by supporting ecosystem services such as watershed management, soil health, carbon sequestration, and biodiversity while restoring degraded landscapes (Jamnadass et al., 2015; Prabhu et al., 2015). Due to their high tolerance to drought, owing to the deep and extensive roots, trees are important also at times when other food sources are not available (Jamnadass et al., 2011). Tree foods thus have the potential to complement and diversify staple-based diets throughout the year, thereby improving diet quality and health.

Nutritional contributions of tree foods

In a World Agroforestry (ICRAF) recent research project ‘Food Trees for diversified diets, improved nutrition, and better livelihoods for smallholders in East Africa’,1 90 food tree and shrub species were identified across eight sites as important food sources from local food systems. Among the aim of the project was to target harvest and nutrient gaps through location specific food tree and crop portfolios (see section 3: How to fill harvest and nutrient ‘gaps’ through site-specific Food Tree and Crop species: An insight to the development of Food Tree and Crop Portfolios). To fill ‘nutrient gaps’ in a site, food tree and shrub species identified in local harvest calendars were mapped with food composition data from scientific articles and food composition databases. Food composition data play a key role in linking agriculture to nutrition. Knowing what people eat and which nutrients the consumed foods contain is key for assessing and improving diet quality and health, and it is equally important for agriculture, including domestication and breeding programmes, to select not only high-yielding but highlv-nutritious species (Welch and Graham, 1999; Toledo and Burlingame, 2006; Burlingame et al., 2009).

Table 6.1 provides an overview of selected food tree and shrub species and their nutrient composition. The nutrients iron, folate, vitamin A, and vitamin C were selected because of their public health concerns (iron, folate, vitamin A), their supportive functions (vitamin C supports the uptake of non-haem iron from plant foods) and their natural high quantity in tree foods. Extended nutrient profiles, including data for macronutrients, vitamins, and minerals, are available at ICRAF’s priority food tree and crop food composition database (ICRAF, 2019; Stadlmayr et al., 2019).

As shown in Table 6.1, trees and shrubs provide a variety of nutritious foods, which can be categorized in different food groups even by individual species, as they provide different edible parts. Anacardium occidentale and Vitellaria paradoxa, for example, are sources of nuts and fruits, and Vigna unguiculata is a supplier of green leafy vegetables and pulses.

While fruits and vegetables are characterized by their high micronutrient density by low energy content, pulses and nuts are known as sources of protein, energy, and minerals. Vitamin C is the main nutritive component in most fruit species, as shown in Table 6.1. The component is a good antioxidant protecting the body from radicals and it improves the absorption of non-haem iron in plant foods such as green leafy vegetables or nuts (Latham, 1997; FAO and WHO,

Food name in English

Scientific name

Water (g)

Iron (mg)

Vitamin A RE* (meg)

Folate (meg)

Vit C (mg)

Fruits

Baobab, pulp, raw

Adansonia digitata

11.0

5.0

0

50

273

Cashew apple, raw

Anacardium occidentale

86.5

0.8

13

n.a

123

Azanza, pulp, raw

Azanza garckeana

47.2

4.4

n.a

n.a

n.a

Desert date, raw

Balanites aegyptiaca

70.4

1.6

n.a

18

51

Bird cherry, raw

Berchemia discolor

78.8

2.2

n.a

n.a

50

Papaya, pulp, raw

Carica papaya

80.8

0.7

i6i

25

58

Orange, pulp, raw

Citrus sinensis

86.8

0.1

22

30

53

Mango, pulp raw

Mangifera indica

82.7

0.7

227

25

36

Manila, pulp and skin, raw

Sclerocarya birrea

86.1

3.4

n.a

n.a

168

Sorindeia, raw

Sorindeia madagascariensis

80.5

1.9

n.a

n.a

107

Shea, fruit pulp, raw

Vitellaria paradoxa

73.3

1.9

n.a

n.a

1-196

Green leafy vegetables

Spiderwisp, leaves, boiled

Cleome gynandra

85.7

7.3

794

76

37

Cassava, leaves, boiled

Manihot esculenta

71.7

4.4

542

62

16

Moringa, leaves, boiled

Moringa oleifera

75.7

3.8

2080

26

44

Spinach, boiled

Spinacia oleracea

90.5

2.5

775

93

15

Cowpca, leaves, boiled

Vigna unguiculata

85.9

4.0

283

68

24

Pulses

Hyacinth bean, mature, whole, boiled

Lablab pnrpureus

78.6

1.4

<1

3

0

Mung bean, mature, whole, boiled

Cigna radiata

78.7

1.0

3

80

<1

Cowpea, mature, whole, boiled

Vigna unguiculata

79.7

1.1

1

80

<1

Nuts

Cashew nut, raw

A n acardinm occidentale

5.3

6.4

<1

46

<1

Macadamia, nut, raw

Macadamia integrifolia

1.4

3.7

0

11

1.2

Shea nut seed kernel, raw

Vitellaria paradoxa

6.3

3.4

0

n.a

n.a

* Vitamin A-RE expressed in retinol equivalent: retinol + 1/6 beta-carotene + 1/12 alpha-carotene + 1/12 beta-cry ptoxanthin).

2004). Tree and shrub leaves, like those of Cleome gynandra, Manihot esculenta, or Vigna unguiculate, are not only sources of iron (required for growth, cognitive development and as an oxygen carrier) but also of folate (required for growth and foetal development) and vitamin A (indispensable for the visual circle and functioning of cells) - all key micronutrients often lacking in staple-based diets (Latham, 1997; FAO and WHO, 2004).

Nutritional ditferences exist not only between food groups but between species and within species, at variety or cultivar level and for underutilized and wild foods (Charrondiere et al., 2013). Factors impacting the nutrient content of foods are manifold and include climate (Fischer et al., 2019), geography and soil, maturity stage, the preparation and processing stage (raw, cooked, dried, boiled), post-harvest handling of foods (Greenfield and Southgate, 2003), methods used for analyzing (Greenfield and Southgate, 2003; FAO/INFOODS, 2013), and the expression of components and genetics (Toledo and Burlingame, 2006; Charrondiere et al., 2013).

A focus in World Agroforestry’s (ICRAF) programmes is the promotion and cultivation of indigenous and underutilized species.2 These are foods with underexploited potential for food and nutrition security and have received little attention by researchers and private industry in the past (Hawtin, 2007; Armstead et al., 2009; FAO and Bioversity International, 2017; Dawson et al., 2018). Many of these species have the potential to provide needed micronutrients and are often also superior in minerals and vitamins compared to mainstream or exotic species. A good example is the comparison of the vitamin C values of the indigenous species Adansonia digitata (baobab fruit), Sclerocarya birred (marula fruit), and Sorindeia madagascariensis to that of the exotic species Citrus sinensis (orange), which is regarded as a reference source high in vitamin C. With on average 273 mg, 160 mg, and 107 mg/100 g EP, respectively, the indigenous species contain up to 5 times higher vitamin C values than oranges (53 mg/100 g EP). This does not mean that oranges should not be consumed anymore but rather that the diversity of locally available foods, particularly indigenous and underutilized species, has great potential to contribute to nutrient adequacy, and that these species should be further invested in and researched and promoted as locally appropriate and sustainable solutions. Important for the promotion of these foods is the knowledge of their nutrient content, but unfortunately this information, particularly on vitamins, is often missing in the literature (Stadlmayr et al., 2013). As shown in Table 6.1, data on vitamin A and folate are missing for many, particularly indigenous species. Hence, it is important that analysis of high-quality food composition data, particularly for under-researched indigenous species are conducted, so that these species can better be promoted and integrated in domestication programmes and for dietary assessments to improve diet quality from local food systems. Without this information, it could mean that certain crops rich in micronutrients are overlooked in agriculture - nutrition development planning, projects and policies. The importance of underutilized and wild species is increasingly recognized in international frameworks and guidelines (FAO and WHO, 2014; FAO, 2019).

As is the promotion of underutilized species in crop diversification explicitly stated as a recommendation3 in the Framework of Action, of the International Nutrition Conference (ICN2). Additionally, the incorporation of underutilized species into locally adapted food based dietary guidelines is recommended by the ‘Voluntary Guidelines for Mainstreaming Biodiversity into Policies, Programs and National and Regional Plans of Action on Nutrition’, endorsed by the Commission on Genetic Resources for Food and Agriculture (FAO, 2016).

 
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