Sources of Data. Emphasis was placed on assembling original data on foods grown in various areas of Africa. Personal visits were made to nutrition institutions throughout the African continent by W. T. Wu Leung, Chief, Food Science Information (NP/NCCD) in English-speaking areas and F. Busson, Consultant (FAO), in French- and Portuguese-speaking areas Close cooperation was maintained with local representatives of FAO, the World Health Organization(WHO), and the U. S. Agency for International Development(AID), as well as with local authorities in areas visited. Numerous unpublished data were supplied by members of the Advisory Group.
Much of the unpublished information concerning foods grown or produced in the English-speaking areas was generously supplied by B. S. Platt of the Department of Human Nutrition, London School of Hygiene and Tropical Medicine, University of London, where relatively abundant data on indigenous African foods have been collected from British sources. Information on foods eaten by South African Bantu was provided by the National Nutrition Research Institute, South African Council for Scientific and Industrial Research.
Analytical data and information relating to foods grown in French-speaking areas and references to publications in French were obtained by F. Busson and Cl. Jardin from the following institutions: Centres of the Office de la Recherche Scientifique et Technique d'Outremer (ORSTOM) in Bambey, Sénégal; in Abidjan, Ivory Coast; in Yaoundé, Cameroon; and inNosy-Bé, Malagasy Republic; Laboratoire de Biochimie et Microbiologie de l‘Institut des Pêches Maritimes du Maroc in Casablanca, Morocco; Organisme de Recherches sur l’Alimentation et la Nutrition Africaines (ORANA) in Dakar, Sénégal; Laboratoire de Recherches Zootechniques de Dakar; Ministries of Agriculture and Public Health of the Ivory Coast ; Agricultural Service of Angola; and the Commission of Nutrition of Mozambique at Lourenco-Marques.
A collection of references on African foods and nutrition was published in April, 1966 as “A Selected Bibliography on African Foods and Nutrition and African Botanical Nomenclature”. The most useful references, concerning mainly the nutritive values of African foods selected from this publication and including some recent data and related references for compilation of this food table, are attached as Appendix 8.
Selection of Food Items. A comprehensive “List of Foods Used in Africa” was prepared by Cl. Jardin, FAO, to provide the basic list of foods selected for inclusion in the food table.
In general, food consumed in considerable amounts, at least periodically and in certain areas, have been selected for inclusion. These include some of the items classified in this publication as “very commonly used”. A few items which are not listed in that document or which may be classified as “uncommon” in it, but for which analytical data have been found, are also included. A total of 1,624 food items were selected to represent the most commonly used food items in Africa.
Limitations of Data. The tabulated nutritive values presented in the food composition table are derived from actual analyses reported by various investigators and probably include most of the data now available on African foods. Data for many foods are still incomplete and inadequate for defining representative values for foods commonly used in Africa. When the nutrient column is blank, it indicates that no data were available or that data are questionable and were omitted. Questionable data included are indicated by a question mark.
The number of analyses used for deriving the food values given in the food table is indicated in parentheses; but that number does not necessarily mean that all the analyses in any given entry were reported by the same laboratory. When the number of analyses is not reported, it is assumed that only one sample was analyzed. The range values are listed under each nutrient. These figures, however, are incomplete since many investigators did not report the exact number of samples analyzed or give the exact range of values.
No attempt has been made to calculate or impute the values from similar foods reported in other regions. The main purpose is to illustrate clearly the present deficiency of each nutrient of each individual food selected. Appendix 7 summarizes the gaps by indicating the approximate percentage of available data for each nutrient in each food group. There is an urgent need for immediate work to fill in these gaps.
Food Groups. Foods are grouped in the food table in a manner suggested in the FAO “Program of Food Consumption Surveys, ” 1964, with the exception of nuts and seeds which are combined into one group. The fourteen food groups are as follows:
|Group 1||--||Cereals and Grain Products|
|Group 2||--||Starchy Roots, Tubers, and Fruits|
|Group 3||--||Grain Legumes and Legume Products|
|Group 4||--||Nuts and Seeds|
|Group 5||--||Vegetables and Vegetable Products|
|Group 7||--||Sugars and Syrups|
|Group 8||--||Meats, Poultry, and Insects|
|Group 10||--||Fish and Shellfish|
|Group 11||--||Milk and Milk Products|
|Group 12||--||Oils and Fats|
Nomenclature. Where English names of foods are unknown, the scientific names or selected local names have been used.
Most of the names for edible plants were those suggested in the following publications: “Standardized Plant Names,” prepared for the American Joint Committee on Horticulture; “The Useful Plants of West Tropical Africa,” by J. M. Dalziel; “Dictionary of Economic Plants,” by J. C. TH. Uphof; other useful references listed in our previous publication “A Selected Bibliography on African Botanical Nomenclature;” and FAO's “List of Foods Used in Africa”. The scientific names used for mammals and insects and for fish and shellfish were mainly taken from FAO's “List of Foods Used in Africa”.
The scientific names of the edible plants, of the mammals and insects, and of the fish and shellfish are arranged alphabetically in Appendices 4, 5 and 6 with the corresponding English names, item numbers used in the food table, and the names used in the French edition.
Additional references considered useful for identification of the scientific names for edible plants, mammals and insects, and fish and shellfish are attached as Appendices 9, 10, and 11.
Moisture Content. The moisture content of African foods may fluctuate greatly with season, length of storage, etc. The need for determining moisture content whenever possible must be emphasized. More accurate values for calories and nutrient content of food can be calculated from values in the food table by using the conversion factor obtainable from the nomogram prepared by Cl. Jardin of FAO. This nomogram and its detailed explanation appear as Appendix 2.
Food Energy. The energy values of the foods in the table represent the available energy calculated by the specific Atwater factors for protein, fat, and total carbohydrate by difference, which is obtained by subtracting the sum of the figures for moisture, protein, fat, and as from 100. These factors have taken into account the losses in digestion and metabolism. The Atwater system of calculating the energy values was adopted by the FAO Committee on Calorie Conversion Factors and Food Composition Tables which met in February 1947. Since that time these factors have been expanded by Merrill and Watt, and published in 1955 by the U. S. Department of Agriculture as Agriculture Handbook No. 74, “Energy Value of Foods--basis and derivation”. These specific physiological energy factors (Appendix 1) are tentatively adopted for use in this African food table until digestibility experiments are actually made on African subjects.
The coefficient of digestibility used for deriving these energy factors is based on studies made on human subjects living in Europe or the United States, not in Africa. In view of the great variety of dietary patterns in Africa and because sufficient studies have not been made to derive the energy factors for cereals such as sorghums, millets, and teff, those for whole-grain wheat have been tentatively used.
Protein. The values for protein were computed from the nitrogen content as determined by the Kjeldahl method, multiplied by a conversion factor. From the fact that most proteins contain approximately 16 percent nitrogen, protein contents were calculated with the factor 6.25 for conversion of nitrogen to protein.
For those foods in which the protein is known to differ from this figure, the specific factors for converting nitrogen, as suggested by D. Breese Jones, and listed below, were used:
|Food||Factors for Converting|
Nitrogen to Protein
|Barley, oats and rye||5.83|
|Wheat flour, refined||5.70|
|Nuts and seeds, other||5.30|
Carbohydrate. The values refer to “total carbohydrate by difference”--that is, the sum of the figures for moisture, protein, fat, and ash are subtracted from 100. “Nitrogen-free-extract” can be obtained by subtracting the crude fiber from the total carbohydrate.
Minerals. At present only the values for calcium, phosphorus, and iron are given and refer to the total content of each of these nutrients. No deduction has been made for any unavailable portion. In some foods, reported values for iron are extremely high, possibly due to the contamination of the sample with soil. The presence of oxalic acid in many vegetables may prevent full utilization of a reported high calcium content. Moreover, in many entries the high calcium content is reported by only a single laboratory. This should not be considered as a representative value unless additional analyses are completed. Investigation on minerals is urgently needed in order to drive a sound, representative value for use.
Vitamin A. The terminology used follows the recommendation made by the FAO/WHO Expert Group on “Requirements of Vitamin A, Thiamine, Riboflavin and Niacin”, in terms of the nomenclature of the International Union of Pure and Applied Chemistry. “Retinol” is used for vitamin A alcohol, and the term “Vitamin A” signifies all compounds having vitamin A activity.
The retinol and B-carotene equivalents are listed separately in this food table, following recent recommendations by that same Expert Group. The conversion factors used (Appendix 3) for the calculation of these from International Units or from micrograms of vitamin A activity and “Estimated Distribution of Sources of Vitamin A Activity in Various Foods” are the same as were used in the INCAP/ICNND “Food Composition Table for Use in Latin America,” pages 3–4, 1961, and later accepted by this Expert Group.
Tryptophan. As suggested by the FAO/WHO Expert Group on Vitamin Requirements, one column was provided in the food table for tryptophan, with the intention of filling in, if feasible, the existing values so that the niacin equivalent (60 milligrams of tryptophan = one milligram of niacin) can be calculated.
Ascorbic Acid. Emphasis was placed on reporting the value in terms of total, instead of reduced, ascorbic acid. Findings for African foods are scanty and often the methods are not clearly specified. An asterisk is used to indicate data reported as reduced ascorbic acid.
Refuse. The percentage of refuse per 100 grams of food as purchased is listed in the last column of the food table. No description of the part of the food presently considered as refuse is given since such data are not reported. For items such as fruits, vegetables, and starchy roots and tubers, the figures would vary considerably from one consumer to another, as well as from one area to another. It is hoped that studies of this nature will be conducted locally in various areas in the near future providing sufficient and detailed description of the inedible part and making it possible to calculate values on an “as purchased” basis.