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FOOD/NUTRITION SYSTEM OF A CASSAVA-DEPENDENT CULTURE IN SOUTHERN NIGERIA

Historical Background

According to Flores (25), climate, soil, geographical location, and cultural factors play a major role in determining to what extent a population maintains the same food consumption pattern for generations. Moreover, changes in economic status, increasing education, and the advent of technology or industrialization modify food patterns. It should also be borne in mind that dietary habits are based on foods regularly grown, raised, or gathered in the region where any group of people lives. The prevailing food patterns may later be supplemented or modified by foods imported from elsewhere, as indicated by Clark (26), who goes on to emphasize that man is an opportunist in his choice of food. These observations are very pertinent in considering the complex food/nutrition system of the cassava-dependent cultures of southern Nigeria.

Historically, the original food patterns in southern Nigeria were based on the indigenous white Guinea yam (Dioscorea rotundata) supplemented with other minor yams (D. cayenensis, D. dumetorum, and D. bulbifera). The yam culture evolved after many centuries of experimentation, culminating in the domestication of yams some three to four thousand years ago. Several methods of yam preparation were developed that rendered the yam suitable for eating alone or with supplementary food items. These methods include roasting, boiling, frying, and pounding. The complexity of yam preparation and the number of complementary food items involved in yam preparations depend on whether a meal is to be eaten as a snack or as the main meal of the day. The extent to which a given yam species contains toxic principles is also reflected in the method of preparation, especially with respect to how it is cooked and for how long. Other characteristics of the different yams also determine whether they are suitable for pounding. Moreover, the occasion for which a meal is being prepared, and the socio-economic status of the people cooking or eating the yam, influence the method and elaborateness of the preparations.

Thus, yams to be eaten as snacks are usually roasted alone or boiled and eaten with as few complementary items as necessary. These items may consist of salt, palm oil, and/or pepper. When a main meal is prepared, or if there is to be a celebration, pounded yam is the traditional dish. It usually involves different kinds of soups consisting of water, salt, and oil, leafy vegetables, some ground seeds or nuts that are usually rich in protein, and animal products in the form of meat or fish. When starchy yams are eaten with soup, the overall nutritional quality is greatly improved by the complementary food items that are sources of proteins, vitamins, fats, and minerals. Some of the condiments used help to improve the flavour and also add variety to minimize monotony.

With the introduction of Asian crops (bananas, plantains, cocoyam [Colocasia spp.], water yam, mangoes, etc.}, in about the eleventh century A.D., and subsequently American crops (maize, cocoyam [Xanthosoma spp.], cassava, sweet potato, groundnuts, etc.) in post-Columbian times, the people of southern Nigeria appear to have readily adopted the new crops and grafted them into the existing farming systems where they were suited to the humid tropics and derived Savannah zones. It would also appear that those most often adopted were the most easily prepared for eating, and in much the same manner as indigenous yams were cooked. Thus bananas, plantains, cocoyams, and cassava were usually roasted, boiled, or pounded and eaten with soup as were the local yams. The same methods used for preparation of yam snacks and main meals were used for the exotic starch staples. For more complete meals, the new foods were pounded into fufu alone, or sometimes mixed with yams.

Fig. 2. Seasonal Variation in Calorie Intake of Cassava and Yam at Uboma, Imo State, 1963/64

Cassava seems initially to have been adopted with caution because of its toxicity. Even in recent times, within living memory, there have been old men in southern Nigeria who would not eat cassava. But as methods of processing and detoxifying cassava were copied from South America, the use of cassava as a staple spread far and wide in tropical Africa. The various advantages that the cassava crop has over the indigenous yams and other staples enhanced its rapid adoption. Consequently, yam lost its dominance to cassava in southern Nigeria, even though it is the preferred crop.

In Nigeria, cassava leaves never became popular as vegetables as they did in Zaire and Sierra Leone, since the nontoxic indigenous vegetables eaten in combination with yams still remained dominant. Cassava also made inroads into the rice-based cultures west of the Bandama River and attained a status second only to rice in Sierra Leone and Liberia. Cassava accounts for 41.5 per cent of the food consumed in Ogun, Oyo, and Ondo States Former Western State), as compared to 53 per cent in Bendel State (Midwest) and 45 per cent in Anambra and Imo States (East Central). Correspondingly, all starchy staples comprised 79, 69, and 79.5 per cent, respectively, of the diet compared to corresponding figures of 7, 2.8, and 1.8 per cent for cereals.

Yam still remains an important crop as a co-staple, but its availability is more seasonal than that of cassava, which is of nutritionally strategic importance during February to July, the hungry season after cassava has been planted (fig. 2). Thus, cassava and yams interact with each other and with other constituents of the diet in a very complex manner. It is also interesting to note that cereals play a relatively more important role in the diets of the people of Ogun, Oyo, and Ondo States because a larger proportion of the area is almost Savannah or derived savannah compared to the land in Bendel, Anambra, and Imo States.

Characteristics of Cassava Dependency

Since cassava supplies the bulk of the energy intake in southern Nigeria as compared to other staples, there are several cassava-based food preparations for different periods of the day and various occasions. Cassava-based snacks include cassava products such as gari or cassava flakes sometimes eaten alone, but usually with a nut (e.g., coconut) or, as in the case of gari, with water or milk and sugar (table 5). The gari may, however, contain palm oil, which is used for colour and to enrich it with fat and vitamins during processing. The nutritional quality of the snack is relatively low because of the low protein content of both the cassava and the complementary foods eaten with it, except where dried fish is chewed with the cassava product.

TABLE 5. Cassava Products and Complementary Food Items Used in Cassava-Based Snacks

For main meals, cassava fufu made from gari, fermented cassava, cassava flour, or just boiled cassava, forms the bulk of the meal. It may sometimes be blended with other starchy staples such as yams (table 6). The fufu is eaten with soup that contains three main groups of food items. First, there are various seeds and nuts that are usually ground up and used to thicken the soup, either by themselves or in a mixture of some starchy staples or okra (table 6). These are high in protein, fats, and other nutrients. Second, there are leafy and fruit vegetables such as African spinach and okra that are sources of minerals, vitamins, and fibre. Their nutritional value may depend on the method of preparation, age, and other factors. There are also animal products that may come from terrestrial animals (livestock or bush meat) and/or aquatics like fish and crayfish. There are miscellaneous items such as water, salt, condiments, and oil that are common ingredients used in soup preparation. The kind of animal product used in the soup usually depends on social status or income, and the occasion for which the meal is prepared. The fufu and the soup together constitute a meal of high nutritive value. Since the soup is rich in sulfur amino acids, the toxicity of any cyanide in the cassava product used for fufu may be minimized by the detoxifying effects of the sulfur amino acids in the animal products.

Cassava products are generally not very income- or price-elastic except to the extent that increased income may result in shifts toward yams or semovita (27). Cassava itself is not very price-elastic because it is one of the least expensive of the starchy staples available. This is why cassava products such as gari are very popular with the low-income groups in urban areas. Moreover, almost every farmer can afford to grow cassava.

As for the soup and the ingredients used in making it, the whole soup may be regarded to some extent as income-inelastic, because in order to eat a main cassava meal, everyone (rich or poor) must make some soup whose ingredients have varying income elasticities. Among the ingredients used in the soup, whether egusi, crayfish, fish, or meat, the kind and amount used depend on income and socioeconomic status. The subsistence farmer in rural areas must therefore produce some surpluses to sell so he can obtain money with which to buy some of the ingredients required to balance his diet. His farming systems must be efficient and diversified enough to satisfy subsistence needs as well as the need for some ready cash. Nutrition education is also important because farmers do not always readily eat what they produce, even when the body requires it. In this regard, efforts to attain increased cassava production through breeding high-yielding and adapted cassava varieties that are resistant to pests and diseases may ensure that the farmer produces the surplus required by the urban population. This constitutes a ready source of money needed by the farmer to purchase all the complementary foods necessary for maintenance of adequate nutritional status.

TABLE 6. Cassava Products and Complementary Starchy Staples and Soup Ingredients Combined in Meals of Cassava-Dependent Peoples in West Africa

OPPORTUNITIES FOR INTERVENTION TO IMPROVE THE NUTRITIVE VALUE OF CASSAVA

Production

There are opportunities for improvement of the nutritive value of Cassava in direct Cassava improvement and production programmer. In the latter, various methods of breeding can be used to improve the protein content, overall nutritive value of roots and leaves, and reduction of cyanogenic glucoside content. Improved and more efficient crop combinations, and sequences involving relay and other intercropping systems, offer much greater opportunity for the production of a range of co-staples and complementary crops of higher nutritive value than pure crops grown sequentially, a practice fraught with risks for small farmers.

Processing

The toxicity of Cassava roots has resulted in the development of several methods of processing that minimize the danger of cyanide poisoning (table 7). For most root and tuber crops, processing could be used to produce a range of enriched, convenient foods that not only increase nutritive quality, but also increase their elasticity of demand among urban masses and higher income groups. It is the increased mobility in our urban population that has resulted in increasing demand for gari, which is a more convenient food than fermented cassava.

TABLE 7. A Tentative Classification of Traditional Cassava Processing

I. No special detoxification techniques applied

1.1 Totally unprocessed (i.e., eaten raw)

1.2 Simple cooking techniques only (as used for non-toxic starchy staples)

1.21 Boiling, stewing, etc.
1.22 Roasting, baking
1.23 Frying

1.3 Sun-drying

1.31 Sun-drying without subsequent processing
1.32 Sun-drying with subsequent processing

1.321, etc. Different types of milling, grinding, etc.

1.4 Kiln or hot-air drying (Subdivide as for 1.3)

II. Special detoxification techniques applied

2.1 Detoxification by solution

2.11 Soaking of whole roots or large pieces

2.111 Soaking in static water
2.112 Soaking in running water
2.113 Soaking in salt water

2.12 Soaking after comminution (Subdivide as for 2.11)

2.13 Boiling

2.131 Simple boiling
2.132 Repeated boiling, in changes of water

2.14 Wet extraction processes for starch

2.141 Starch extraction without subsequent gelatinization
2.142 Starch extraction with subsequent gelatinization

2.2 Detoxification by fermentation

2.21 Spontaneous fermentation

2.211 Fermentation followed only by washing
2.212 Fermentation followed by washing and heat treatment

2.2121 Roasting
2.2122 Steaming
2.2123 Drying in hot air

2.22 Fermentation with use of inoculum from earlier preparations (Subdivide as 2.21)

Source: Ref. 11

Marketing

Where there are adequate marketing facilities, suitable pricing arrangements, and effective farmers' organizations that can handle marketing, smallholders derive maximum incentive from farming. They are not left at the mercy of middlemen who have to perform certain functions that increase their returns from collection, distribution, and marketing at the expense of the farmer. Wholesale and retail markets are necessary for ensuring availability of foods where consumers require them.

Home Preparation and Consumption

Nutritional training is necessary to ensure that everyone recognizes the need for a balanced diet, and that losses in food quality and wastage are minimized. Knowledge of nutrition is also necessary for the elimination of superstition that may constitute a stumbling block to achievement of nutritional well-being. With good nutritional training, it is not enough to achieve a balanced diet and ensure that foods are well prepared; there is also the need to make sure that there is sufficient food of good quality properly distributed among all the individuals in different parts of the country, and within each household, according to need. It is as important to eliminate undernutrition as it is to avoid consuming more than is required.

Storage and Transportation

Storage and transportation activities are necessary to facilitate processing, distribution, and provision of food to everyone in any part of the country and throughout the year. The occurrence of mycotoxins in mouldy food constitutes a health hazard that should be avoided by proper handling and preservation. Adequate measures should be taken to minimize losses in transit and storage while maintaining quality.

CASSAVA AND SOIL FERTILITY

The cassava plant has often been label led a soil-depleting crop, but it does not remove nutrients from the soil more than do any of the common tropical crops such as sugarcane, orange trees, or maize, especially considering the high yield of the cassava plant and the fact that it is usually harvested one year or more after planting. Although it removes large quantities of potassium from the soil, the amount compares favourably with that taken out by other roots crops, sugarcane, tomatoes, and Bermuda grass grown for forage.

It should, however, be borne in mind that cassava is adapted to marginal or even impoverished soils. It is also a common practice to grow cassava last in the rotation before fallow. Consequently, the depleted condition of soils on which cassava is often grown in traditional agriculture is the result of nutrient uptake by crops other than cassava, except where several cassava crops are involved. Recent studies also indicate that cassava is associated with mycorrhiza and is able to extract phosphates from soil in which they exist in a fixed, usually unavailable form. This may partly explain the cassava plant's ability to thrive on poor soils where other crops fail.

SUMMARY

Cassava has attained the status of either dominant staple or co-staple in certain parts of the world where it contributes more than 50 per cent of the energy requirements of a bulk of the population.

The nutritional hazards of cassava dependency require careful attention. It is necessary to adopt a systems approach and study the whole, often complex, food/nutrition system so as to understand it and arrive at a more realistic appraisal of the problems of cassava-dependence

However, increasing dependence on cassava may result in gradually increasing quantities of its products being fed to young children. Replacement of more protein-rich weaning foods by cassava products should be avoided in order to safeguard young children from cassava toxicity and protein deficiency.

Increased production of cassava as part of a food system should also involve the production of complementary foods to be consumed with cassava. Alternatively, the strategy should involve farming systems that ensure enough increases in cassava production to allow the resulting profit to be used to purchase all of the food that the farmer needs.

A systems approach to the study of a cassava-dependent culture reveals many intervention opportunities in production, harvesting, processing, storage, marketing, home preparation, and transportation that can significantly minimize nutritional hazards while holding high potential for improving human welfare.

REFERENCES

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2. D.E. Kay, Root Crops (Tropical Products Institute, London 1973).

3. T.P. Phillips, "Cassava Utilization and Potential Markets" (International Development Research Centre, Ottawa, Canada, 1 974).

4. Food and Agriculture Organization, Production Yearbook, 1972 (FAO, Rome).

5. S.G. Appan et al., "A Strategic Program for Genetic Engineering of Cassava," in: Tropical Foot and Tuber Crops Tomorrow, vol. 1, Proceedings of 2nd International Symposium on Tropical Root and Tuber Crops (Ibadan, Nigeria, 1970), pp. 79-82.

6. Food and Agriculture Organization, Production Yearbook, 1977 (FAO, Rome).

7. O.L. Oke, "Cassava as Food in Nigeria," World Rev. Nutr. Dietet., 9: 227 (1968).

8. C.A. DeVries, J.D. Ferwerda, and M. Flach, "Choice of Food Crops in Relation to Actual and Potential Production in the Tropics," Netherl. J. Agric. Sci., 5: 241 (19671.

9. B. Brouillette et al., African Geography for Schools: A Handbook for Teachers (Longmans, Green & Co., Ltd., London, and UNESCO, Paris, 1974).

10. W.O. Jones, Manioc in Africa (Stanford University Press, Stanford, Calif., USA, 1959).

11. D.G. Coursey and P.H. Haynes, "Root Crops and Their Potential as Food in the Tropics," World Crops, 261 - 265 (1970).

12. B. Nestel, "Current Utilization and Future Potential for Cassava," in B. Nestel and R. McIntyre, eds. Chronic Cassava Toxicity: Proceedings of an Interdisciplinary Workshop, London, England, 29 - 30 January, 1973 (International Development Research Centre, Ottawa, Canada, 19731, pp.11 -26.

13. F. Nartey, "Manihot esculenta (Cassava): Cyanogenesis, Ultrastructure and Seed Germination," D.Sc. thesis, University of Copenhagen (Munksgaard, Copenhagen, Denmark, 19771.

14. C.H. Hendershot et al., eds, A Literature Review and Research Recommendations on Cassava (Manihot esculenta, Crantz) (University of Georgia, Athens, Georgia, USA, 19721.

15. M.C. Latham, Human Nutrition in Tropical Africa (FAO, Rome, 1969).

16. A.A. Adegbola, "Methionine as an Addition to Cassava-Based Diets," in B. Nestel and M. Graham, ads., Cassava as Animal Feed: Proceedings of a Workshop held at the University of Guelph, 18 - 20 April 1977 (international Development Research Centre, Ottawa, Canada, 19771, pp. 9 - 17.

17. F. Delange, M. van Der Velden, and A.M. Ermans, "Evidence of an Anti-Thyroid Action of Cassava in Man and Animals," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp. 147- 157.

18. G.W. Butler, J.F. Relay, and B.A. Tapper, "Physiological and Genetic Aspects of Cyanogenesis in Cassava and Other Plants," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp. 65 - 71.

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20. O.L. Oke, "The Role of Hydrocyanic Acid and Nutrition," World Rev. Nutr. Dietet., 11: 170 - 198 (1969).

21. B.O. Osuntokun, "Ataxic Neuropathy Associated with High Cassava Diets in West Africa," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp.127 - 138.

22. O.L Ekpechi, "Endemic goitre and High Cassava Diets in Eastern Nigeria," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp. 139 - 145.

23. D.G. Coursey, "Cassava as Food: Toxicity and Technology," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp. 27-36.

24. J.H. Maner and G. Gomez, "Implications of Cyanide Toxicity in Animal Feeding," in Nestel and McIntyre, eds., Chronic Cassava Toxicity, pp. 113 - 120.

25. M. Flores, in International Encyclopedia of Food and Nutrition, vol. 5, chap 3, p. 63.

26. F.L G. Clark, "Food Habits as Practical Nutrition Problem," World Rev. Nutr. Dietet., 9: 58 - 84 (1968).

27. J.E. April, G.N. Hersh, D.J. Rogers, and C.C. Slater, "Cassava's Role as a Food Staple: A Cross Disciplinary Systems Analysis of Nutrition Problems in a Cassava-Dependent Culture" (Bureau of Technical Assistance, Office of Nutrition, USAID, Washington, D.C., 1968).

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