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Chairman R. Ameresekere
Rapporteur Tara
Gopaldas
Ramesh Y. Bhat. National Institute of Nutrition, Hyderabad, India
Abstract
Lathyrism
Veno-occlusive disease
Mycotoxicoses
Karnal bunt wheat
Conclusion
References
To meet the increasing demands of mankind, it is essential not only to grow more food but also to conserve and utilize fully what is grown. Naturally occurring toxicants are present in some foods, and ways and means of minimizing their hazard have to be found to make them suitable for consumption. The approaches toward these include genetic means of selecting varieties that will either contain or support the least amount of toxicants and evolving technological procedures for detoxifying them.
Some of the specific examples of natural/y occurring toxicants causing disease outbreaks in man and approaches toward their prevention will be discussed in detail. These include the problems of (a) lathyrism caused by the consumption of the pulse Lathyrus sativus as staple; (b) veno-occlusive disease outbreak attributed to consumption of minor miller Panicum miliare mixed with weed seeds of Crotalaria, (c) aflatoxicosis caused by consumption of maize contaminated with aflatoxins; and (d) enteroergotism resulting from the eating of pearl millet having ergotized grains.
Although genetic and technological means of preventing/or removing these toxins have been suggested in the past. it is only a package of social management practices that will ultimately minimize the health hazard to man. This calls for strategies of interaction not only between agriculture, nutrition, and food science, but also the involvement of management, sociological, economic, and co-operative sectors.
One way of meeting the increasing food needs of mankind is to fully conserve and utilize what is grown. Utilization of certain foods is hampered through the presence in them of undesirable substances often referred to as toxicants. By trial and error people have selected for their consumption foods that generally do not pose a hazard to them. Yet, for various reasons, population groups are sometimes forced to consume foods that do contain toxicants. The reasons for such forced consumption include easy cultivation and availability, ignorace of toxins, and social and economic compulsions. Several approaches to minimize the hazards from these toxic substances have been evolved. These include the genetic approach of selecting and cultivating identified varieties that contain the least amount of toxin, the agronomic approach of allowing minimal toxin formation during cultivation. and the technological approach of either simple household or large-scale removal of toxins.
This paper describes a few specific examples of naturally occurring food toxicants known to be responsible for disease outbreaks in India.
In parts of central India and pockets in Bangladesh and Ethiopia, certain segments of the population are still known to suffer from a crippling irreversible paralytic disease popularly referred to as lathyrism. In the endemic areas of the Rewa, Satna, Durg, and Raipur districts of India, a survey carried out by the National Institute of Nutrition in 1980 indicated that there had been no fresh cases during the last seven years, although there were surviving patients of old cases.
The disease lathyrism has been attributed to the consumption of seeds of Lathyrus sativus as a staple. Cultivation of lathyrus in endemic areas has been reduced in recent years and, consequently, the proportion of lathyrus in the diet has also decreased. While this toxic pulse is also grown in parts of Maharashtra, Gujarat, and Andhra Pradesh, it is used by the local population of these areas to prepare various side dishes and not as a staple.
There are several reasons why the lathyrus crop is cultivated: ease of cultivation; drought-resistant character; good taste; high protein content; a price lower than that of other pulses; and tradition of cultivation in certain regions.
Although attempts have been made in the past to ban the sale of the crop, this approach has not met with much success. In fact prohibition of the "sale, possession for sale and exposure for sale of Lathyrus sativus or use of Lathyrus as an ingredient in the preparation of any article intended for sale" has been made in various states of the Indian Union, though not in Madhya Pradesh, Bihar, and West Bengal following certain provisions in the Prevention of Food Adulteration Act. Thus actual cultivation of lathyrus has not been banned and, in the existing agricultural situation, it would be impracticable to implement any such ban. Some varieties low in toxin that were evolved showed early promise, but the raising of these varieties was never successful for the following reasons: Grains of these low-toxic lines were shrivelled in appearance; seed multiplication facility was lacking; adaptive research in local endemic areas was not carried out; and there was no extension network in the affected areas.
Other methods of control suggested were, first, the detoxification of lathyrus through a simple household procedure, namely boiling in water and discarding the water, or the technological procedure of parboiling, such as is followed in making parboiled rice. These approaches have again not met with success for the following reasons: lack of knowledge; increased cost; increased labour; shortage of fuel; lack of time to detoxify; lack of the facility to dry the produce during the rainy season; practice of mixed crop cultivation, and marketing also as such; different taste of treated seeds; and unsuitability of treated seeds for making chapati.
In view of the drawbacks of both the approaches that were first suggested, social management strategies for lathyrism prevention have been put forward. These include the following:
Adoption of these social management approaches might enable the problem of lathyrism to be contained.
Veno-occlusive disease is of unknown aetiology, characterized by ascites and pain in the epigastrium, which resulted in the death of more than seventy people, and was reported in the Sarguja districts of Madhya Pradesh. The disease was traced to the consumption of the staple Panicum miliare contaminated with weed seeds of Crotalaria manaburn. Seeds of the weed plants. which grow along with the millet, became mixed up with the millet seeds during harvest and thus entered the human chain. On analysis in the laboratory, the weed seeds were found to contain the toxic pyrrolizidine group of alkaloids. Two approaches have been suggested for prevention of the further occurrence of disease outbreaks. First, the agronomic practice of weeding the offending plants and, second, the post-harvest method of removing the contaminating weed seeds either by winnowing or sieving. During a subsequent survey it was observed that, even though appropriate sieves were supplied to the households in the affected villages, the wire mesh of the sieves had been damaged by field rats and thus were not serving the purpose for which they were intended. This is another example of how an interaction of interdisciplinary aspects will not be effective if not properly supported by sociological measures, which must include an educational component (Krishnamachari et al. 1977).
Two major mycotoxicoses, namely aflatoxic hepatitis and enteroergotism, were reported in parts of India during 1974-1976.
Aflatoxic hepatitis claimed more than 100 people, with symptoms of jaundice, rapidly developing ascites and portal hypertension. It was traced to the consumption of maize heavily contaminated with aflatoxins (Krishnamachari et al. 1975). Maize serves as the staple food of the tribal population during certain parts of the year and was found to be improperly harvested and stored. It was noticed that the maize cobs were either: (a) kept in heaps covered with grass for a week; (b) stored in heaps inside the house; or (c) preserved along with the plant in open heaps in the fields.
Early shelling of the grains was never or rarely practised, and sometimes maize on the cobs was stored in situ in open cribs, either in open yards or inside the house, for several months. As a result the maize grains were affected with moulds.
The inhabitants were aware of the spoiled nature of the grain and resorted to one of the following practices:
Clearly, the poorest sections of the population were exposed to the greatest risk through habitually consuming unwholesome maize because of its low cost. The sequence of events that led to the disease outbreak could be summarized as follows:
The problem of aflatoxin contamination could be minimized by agricultural action programmes. These could include evolving and cultivating suitable varieties of crops that will support the least amount of fungal contamination; manufacture and distribution of cheap, easily operated machinery to achieve satisfactory drying; shelling and storage; and pursuit of a set of recommended practices that would prevent mould damage of agricultural commodities.
The problem of ergot contamination of bajra, which causes another type of mycotoxicosis, namely enteroergotism, has quite a different perspective. The agro-socio-economic structure of the affected groups is very different from that of the population affected by aflatoxic hepatitis. Ergot contamination of bajra has become more widespread following the introduction of high-yielding varieties - traditional bajra varieties were more resistant. The disease enteroergotism, occasionally reported from the rural areas of Maharashtra, Gujarat, and Rajasthan, generally occurred following the harvest of bajra, and also simultaneously in the affected villages. The clinical picture following bajra consumption was characterized by nausea, repeated vomiting, giddiness followed by drowsiness, and a prolonged phase of sleepiness that extended over 24-48 hours. Symptoms usually started within an hour following the meal, and a single meal was enough to cause the disease (Krishnamachari and Bhat 1976).
The occurrence of the disease could be prevented by the cultivation of resistant varieties of bajra, or through suitable agronomic practices, such as changing the sowing season. Once contamination of harvested bajra is noticed, decontamination measures such as winnowing, sieving, and hand-picking could be resorted to. The salt flotation technique of washing ergotized bajra in a 5 to 10 per cent common salt solution has been successfully utilized by many villagers in the affected areas.
Subsequent to the popularization of certain Mexican dwarf wheat varieties in India, the disease Karnal bunt of wheat caused by the fungus Neovossia indica had in recent years assumed epiphytotic proportions in parts of north-western India. The affected grains lacked lustre and were black in colour, especially at the tip and all along the longitudinal furrow on the central side. Severely affected grains retain only the outer pericarp and the aleurone layer, and hence the name bunt. The affected grains emit an odour similar to that of rotten fish because of the presence of trimethylamine, which is known to pose hazards to human and animal health (Bhat et al. 1978). Hence there was considerable anxiety as to whether the use of Karnal bunt wheat was safe.
The nutrient composition of Karnal bunt wheat grains was similar to that of normal wheat, except that the thiamine and lysine contents of affected grains were appreciably lower. Short-term toxicity studies in rats fed up to 50 per cent of Karnal bunt wheat over a period of 45 days, and acute toxicity studies in chicks by oral administration of various extracts of such affected wheat, did not indicate any adverse effect (Bhat et al. 1980). Short-term toxicological studies carried out in monkeys fed a diet containing 70 per cent Karnal bunt wheat did not also indicate any adverse effects, as judged by weight gain. food intake, various haematological parameters and liver enzyme levels. Based on these studies, a tentative tolerance limit of 1 per cent Karnal-bunt-affected grains in good grains, which is within the overall limit of 5 per cent damaged grains, has been suggested (Bhat et al. 1981).
Although genetic and technological means of preventing or removing toxins from various food grains have been suggested in the past, it is only a package of social management practices that will ultimately minimize the health hazard to man. This calls for strategies of interaction not only between agriculture, nutrition, and food science, but also the involvement of management, sociological, economic, and cooperative sectors of the total system.
Bhat, R.V., S. Rao Bapu, D.N. Roy. V. Malini, and P.G. Tulpule. 1981. Toxicological Evaluation of Karnal Bunt Wheat in Monkeys - A Report. National Institute of Nutrition, Hyderabad.
Bhat, R.V., Y.G. Deosthale, D.N. Roy, V. Malini, and P.G. Tulpule. 1980. "Nutritional and Toxicological Evaluation of Karnal Bunt Wheat." Indian Journal of Experimental Biology, 18: 1333-1335.
Bhat, R.V., V. Nagarajan, and P.G. Tulpule. 1978. Health Hazards of Mycotoxins in India, p. 58. Indian Council of Medical Research, New Delhi
Krishnamachari, K.A.V. R., and R.V. Bhat. 1 976. "Poisoning by Ergoty Bajra (Pearl Millet) in Man " Indian Journal of Medical Research, 64: 1624 1628.
Krishnamachari, K.A.V.R., R.V. Bhat, D. Krishnamurthy, K. Kamala, and V. Nagarajan. 1977. "Aetiopathogenesis of Endemic Ascites in Sarguja District of Madhya Pradesh." Indian Journal of Medical Research, 65: 672-678.
Krishnamachari, K.A.V.R., R.V. Bhat, V. Nagarajan, and T.B.G. Tilak. 1975. "Hepatitis Due to Aflatoxicosis: An Outbreak in Western India." Lancet, vol. 1 (7915): 1061-1063.
Nagarajan, V. 1973. "Prevention of Development of Toxins in Foods: Some Approaches for (a) Prevention of Aflatoxin Contamination and (b) Reducing the Neurotoxin in Lathyrus sativus." In S.V. Pingale, A. Austin, and M.T.R. Nair. Post-harvest Technology of Cereals and Pulses, pp. 323-326. INSA/ICAR/CSIR/FCT, New Delhi.
