Influence of seasonal on-farm diversity on dietary diversity: A case study of smallholder farming households in Western Kenya
This supplementary file summarizes in more details the measurement tools used in the study (described in the methodology section of the main document), by showing an overview of the tools and the data needed for the calculation of the values. The measurement tools detailed below are:
- Household hunger scores
- Agrobiodiversity indicators
- Dietary Diversity Scores (DDS)
- Food Consumption Scores (FCS)
- Wealth index
1. Household hunger scores
Household hunger scores serve as an indicator for household food security, and they were calculated in two key stages, according to Ballard et al. (2011):
a. At the data collection stage, responses to four variables were sought:
Variables used / Full questionsFOODWOR / In the past one month, did you worry that your household would not have enough food?
HRES / In the past one month, was there ever no food to eat of any kind in your house because of lack of resources to get food?
HRESFREQ / How often did this happen in the past one month?
HHUN / In the past one month, did you or any household member go to sleep at night hungry because there was not enough food?
HHUNFREQ / How often did this happen in the past one month?
HHUNG / In the past one month, did you or any household member go a whole day and night without eating anything at all because there was not enough food?
HHUNGFREQ / How often did this happen in the past one month?
b. The household hunger scores were then computed according to Ballard et al 2011. The first step entailed recoding of the above three frequency-of-occurrence questions (from HRESFREQ, HHUNFREQ and HHUNGFREQ, to new HRESFREQ, new HHUNFREQ and new HHUNGFREQ, respectively), corresponding to responses to each of these three frequency-of-occurrence categories: 0- ‘no’, 1- ‘rarely’ or ‘sometimes’, and 2-‘often’. For each household, the above values were then summed up to calculate the household hunger score (which should range between 0 and 6). The summed values were then used to generate the household hunger categorical indicators, which are: 0 to 1 representing little to no hunger, 2 to 3 representing moderate hunger, and 4 to 6 signifying severe hunger (Ballard et al. 2011).
2. Agrobiodiversity indicators
The seven seven farm diversity indicators utilized in this study were:
· Species richness: it shows the number of species available in a farm, for example, a farm with Zea mays and Sorghum bicolor has a plant species richness of 2.
· Individual density: it refers to the number of individuals per 1000m2. For example, if a farm of 5000m2 has 10000 individual numbers of Zea mays and Sorghum bicolor, then the individual density is 2000 per 1000 m2.
· Shannon evenness: it quantifies how equal the distribution of individuals per species is (Beals, Gross, and Harrell 2000). With the value of the index ranging from 0 to 1, the greater the value the greater the evenness.
· Shannon diversity index: It accounts for both species abundance and evenness (Beals, Gross, and Harrell 2000). A high Shannon index shows that the individuals are more or less equally distributed between the species while if the Shannon index is low, there may be dominance of a species.
· Simpson’s index of diversity (1-D): It takes into account species richness, abundance and evenness (Beals, Gross, and Harrell 2000; Kovach Computing Services 2013). The value of this index ranges from 0 to 1, and the greater the value the higher the probability that two individuals randomly selected from a sample will belong to different species (Offwell Woodland & Wildlife Trust 2004).
· Combined crop and livestock count: it shows the number of crop and livestock species available in a farm (Jones, Shrinivas, and Bezner-Kerr 2014). For example, a farm with Zea mays (maize), Sorghum bicolor (sorghum) and Gallus gallus domesticus (chicken) has a combined crop and livestock count of 3.
· Relative nutrient functional diversity: it computes the nutrient diversity of a farm based on the nutrient composition and abundance of both food plants and livestock, relative to that of other farms in the sample (Remans et al. 2011).
3. Dietary Diversity Scores (DDS)
As an indicator of dietary quality, 1-day recalls of food consumption consumed at household level and by women only were utilized to compute dietary diversity scores (DDS).
As women DDS serve as indicator of nutritional adequacy while household DDS is a proxy for a household’s economic access to foods, different food groups are required for computation of the two scores (FAO, 2011). Nine food groups were selected for the women DDS and 12 food groups for the household DDS, according to FAO (2011), as shown below:
/ Food groups for DDS / Food groups aggregated to create women DDS / Examples of food items /1 / Cereals and white tubers (starchy staples) / Cereals / Ugali, chapatti, porridge, bread, spaghetti, scones, biscuits, rice, boiled whole maize grain, doughnuts, maize-banana pancake, or any food made from finger millet, sorghum, maize or wheat
White roots/tubers / Irish potatoes, white sweet potatoes, white yams, coco yams, cassava or any white roots and tubers or foods made from these
2 / Dark green leafy vegetables / None / Dark green leafy vegetables and indigenous vegetables eg amaranth, pumpkin leaves, cassava leaves, sweet potato leaves, cowpea leaves, spiderplant, ‘murere’, ‘mito’ etc
3 / Eggs / None / Eggs from chicken, ducks, guinea fowl or any other eggs
4 / Legumes/nuts/seeds / None / Beans, lentils, peas, cow peas, pigeon peas, bambara groundnuts, soya beans, groundnuts, green grams, chick peas, any seeds
5 / Meat/fish / Flesh meat / Beef, pork, lamb, mutton, goat, rabbi, wild game, chicken, duck or other birds
Fish / Fresh or dried fish
6 / Milk/milk products / None / Milk, sour milk (‘maziwa lala’), yoghurt, cheese or other milk products
7 / Other fruits/vegetables / Other fruits / Any other fruits eg watermelon, orange, tangerine, lemon, tamarind, avocado, pear, banana, wild fruits eg guavas etc
Other vegetables / Other vegetables eg tomato, onion, eggplant, other locally available vegetables eg okra, cabbage, green pepper, green beans, wild vegetables, mushrooms
8 / Organ meat / None / Intestines(‘matumbo’), liver, kidney, heart or other organ meats or blood-based foods
9 / Vitamin A rich fruits/vegetables / Vitamin A rich vegetables and tubers / Pumpkin, carrots or sweet potatoes that are orange inside, and other locally available vitamin A rich vegetables eg red sweet pepper
Vitamin A rich fruits / Pawpaw, ripe mangoes, tree tomato
Source: FAO (2011) and adapted to food items found during the survey
/ Food groups for DDS / Food groups aggregated to create household DDS / Examples of food items /1 / Cereals / None / Ugali, chapatti, porridge, bread, spaghetti, scones, biscuits, rice, boiled whole maize grain, doughnuts, maize-banana pancake, or any food made from finger millet, sorghum, maize or wheat
2 / Eggs / None / Eggs from chicken, ducks, guinea fowl or any other eggs
3 / Fish / None / Fresh or dried fish
4 / Fruits / Vitamin A rich fruits / Pawpaw, ripe mangoes, tree tomato
Other fruits / Any other fruits eg watermelon, orange, tangerine, lemon, tamarind, avocado, pear, banana, wild fruits eg guavas etc
5 / Legumes/nuts/seeds / None / Beans, lentils, peas, cow peas, pigeon peas, bambara groundnuts, soya beans, groundnuts, green grams, chick peas, any seeds
6 / Meat / Organ meat / Intestines(‘matumbo’), liver, kidney, heart or other organ meats or blood-based foods
Flesh meat / Beef, pork, lamb, mutton, goat, rabbi, wild game, chicken, duck or other birds
7 / Milk/milk products / None / Milk, sour milk (‘maziwa lala’), yoghurt, cheese or other milk products
8 / Oils/fats / None / Oils, fats or butter added to food or used for cooking
9 / Spices/condiments/beverages / None / Spices (black pepper, salt), condiments (soy sauce, hot sauce), coffee, tea, alcoholic beverages such as locally brewed beer, bottled beer, spirits, wine, traditional spirits, traditional brews
10 / Sugars / Sweets / Sugar, honey, sweetened soda or sugary foods such as chocolates, sweets or candies
High-sugar foods / Sugarcane
11 / Vegetables / Vitamin A rich vegetables and tubers / Pumpkin, carrots or sweet potatoes that are orange inside, and other locally available vitamin A rich vegetables eg red sweet pepper
Dark green leafy vegetables / Dark green leafy vegetables and indigenous vegetables eg amaranth, pumpkin leaves, cassava leaves, sweet potato leaves, cowpea leaves, spiderplant, ‘murere’, ‘mito’ etc
Other vegetables / Other vegetables eg tomato, onion, eggplant, other locally available vegetables eg okra, cabbage, green pepper, green beans, wild vegetables, mushrooms
12 / White tubers/roots / None / Irish potatoes, white sweet potatoes, white yams, coco yams, cassava or any white roots and tubers or foods made from these
Source: FAO (2011) and adapted to food items found during the survey
4. Food Consumption Scores (FCS)
So as to offer a more complete picture of weekly dietary patterns during the 2014 survey, 7-day recalls of food groups consumed at household level and by women only were utilised to compute Food Consumption Scores (FCS).
Both household and women FCS were computed by multiplying the frequency of consumption of eight food groups (shown below) in the last seven days by weight assigned to each food group (WFP, 2008):
Food groups / Examples of food items / Weight1 / Cereals and tubers / Maize, maize porridge, rice, sorghum, bread and other cereals, cassava, potatoes and sweet potatoes / 2
2 / Pulses / Beans, peas, groundnuts and cashewnuts / 3
3 / Vegetables / Vegetables and leaves / 1
4 / Fruits / Fruits / 1
5 / Meat and fish / Beef, goat, poultry, pork, eggs and fish / 4
6 / Milk / Milk yoghurt and other dairy / 4
7 / Sugar / Sugar and sugar products / 0.5
8 / Oil / Oils, fats and butter / 0.5
Source: WFP (2008)
5. Wealth index
The wealth index is a socio-economic variable used as a wealth status proxy. In this study, 13 variables on living conditions and household assets were collected for the wealth index calculation: type of (i) house roof (ii) toilet facility (iii) main source of drinking water, and if household possessed (iv) electricity/solar (v) radio (vi) mobile phone (vii) watch or clock (viii) television (ix) crop or animal sprayer (x) animal cart (for example, ox or donkey cart for transport purposes) (xi) bicycle (xii) motorcycle (xiii) car or lorry.
The wealth index was then computed using SPSS, through the standardised Principal Component Analysis method (Filmer and Pritchett 2001). To apply this method:
1. The 13 asset variables were recoded to binary form (either 0 or 1).
2. So as to get weights/scoring factors for each of the 13 asset variables, standardized Principal Component Analysis method in SPSS was then carried out to create the wealth index per household.
References
Ballard, T., J. Coates, A. Swindale, and M. Deitchler. 2011. Household hunger scale: indicator definition and measurement guide. Washington, D.C.: FANTA-2 (Food and Nutrition Technical Assistance).
Beals, M., L. Gross, and S. Harrell. Diversity Indices: Shannon's H and E 2000 [cited 17 September 2015. Available from http://www.tiem.utk.edu/~gross/bioed/bealsmodules/shannonDI.html.
FAO (Food and Agriculture Organization of the United Nations). 2011. Guidelines for measuring household and individual dietary diversity. Rome: FAO.
Filmer, D., and L. H. Pritchett. 2001. Estimating wealth effects without expenditure data - or tears: an application to educational enrollments in states of India. Demography 38 (1):115-132.
Jones, A. D., A. Shrinivas, and R. Bezner-Kerr. 2014. Farm production diversity is associated with greater household dietary diversity in Malawi: Findings from nationally representative data. Food Policy 46 (1):1-12.
Kovach Computing Services. 2013. Multi-Variate Statistical Package (MVSP), Version 3.22. Anglesey: Kovach Computing Services.
Offwell Woodland & Wildlife Trust. Simpson's Diversity Index 2004 [cited 16 June 2015. Available from http://www.countrysideinfo.co.uk/simpsons.htm.
Remans, R., D. F. Flynn, F. DeClerck, W. Diru, J. Fanzo, K. Gaynor, I. Lambrecht, J. Mudiope, P. K. Mutuo, and P. Nkhoma. 2011. Assessing nutritional diversity of cropping systems in African villages. PLoS One 6 (6):e21235.
WFP (World Food Programme). 2008. Food consumption score: construction of the FCS.
1