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Nutrient impact assessment of rice in major rice-consuming countries¹

G. Kennedy^a, B. Burlingame^b and Nguu Nguyen^c

^aConsultant and ^bSenior Officer, Nutrition Planning, Assessment and Evaluation Service, FAO;
^cAgricultural Officer (Rice Agronomy), Crop and Grassland Service, FAO

INTRODUCTION

Rice is the predominate staple in at least 15 countries in Asia and the Pacific, ten countries in Latin America and the Caribbean, one country in North Africa and seven countries in sub-Saharan Africa (FAO, 1999a). In developing countries, rice accounts for 715 kcal/capita/day, 27 percent of dietary energy supply, 20 percent of dietary protein and 3 percent of dietary fat. Countries in Southeast Asia are heavily reliant upon rice; in Bangladesh, Cambodia, Lao People's Democratic Republic, Myanmar and Viet Nam, rice supplies more than 50 percent of per capita dietary energy and protein and 17-27 percent of dietary fat. Rice is an important staple for several countries in Africa. In Côte d'Ivoire, the Gambia, Guinea, Guinea-Bissau, Liberia and Senegal, rice supplies 22-40 percent of dietary energy and 23-39 percent of dietary protein. Table 1 shows the average per capita supply of rice, and percentage share of energy, protein and fat derived from rice.

A rice grain consists of the hull (including the awn, lemma and palea) and the rice caryopsis, also known as brown rice (Figure 1). The brown rice is the edible part of the rice grain. Levels of dietary fibre, minerals and B vitamins are highest in the bran and lowest in the aleurone layers; the rice endosperm is rich in carbohydrate and contains a fair amount of digestible protein, composed of an amino acid profile that compares favourably with those of other grains (FAO, 1993). Rice is a good source of the B vitamins, thiamine, riboflavin and niacin, but contains little or no vitamins C, D or beta-carotene (the precursor of vitamin A). The amino acid profile of rice is high in glutamic and aspartic acids, but low in lysine (Grist, 1986; FAO, 1993). The main antinutritional factors, most of which are concentrated in the bran, are phytate, trypsin inhibitor, oryzacystatin and haemagglutinin-lectin (FAO, 1993).

A number of factors, during production, harvest, storage and preparation, influence the nutrient composition of rice. One often overlooked factor is intravarietal differences in nutrient composition. Table 2 demonstrates that there can be wide intravarietal differences in nutrient composition.

FIGURE 1
The rice grain

INFLUENCE OF AGRICULTURAL FACTORS ON NUTRIENT COMPOSITION

Studies have shown that agricultural practices can influence the nutrient composition of the rice grain. Controlled experiments found that soil nitrogen, solar radiation, degree of plant maturation, application of fertilizer and shorter maturation periods influence protein content (Juliano and Bechtel, 1985; Iwata, in press; Graham et al., 1999). Iron and zinc content are also influenced by nitrogen application and soil quality (Senadhira, Gregorio and Graham, 1998).

Once rice has been harvested, storage, processing, washing and cooking practices can influence nutritional quality. One factor often ignored in nutritional assessment is post-harvest losses. Post-harvest losses do not affect the nutrient composition directly, but the significant amounts of rice lost during this period can have a profound impact on food security.

Post-harvest losses

Post-harvest loss is defined as a measurable quantitative and qualitative loss in a given product (FAO, 1994a). The loss can occur at any point during harvest, threshing, drying, storage or transport. An estimated 10-37 percent of total rice production is lost as a result of post-harvest factors (Saunders and Betschart, 1979). During harvest, depending on the type of machinery or human resources used, small amounts of the grain will be left in the field. Similarly, losses may occur during the drying process, which in developing countries commonly takes place on the roadside. Further losses are incurred during the storage process because of moulds, insects and rodents. Estimates from sub-Saharan Africa have shown that rodents can consume or contaminate up to 20 percent of a stored harvest (FAO, 1994b). Estimates of post-harvest rice losses in Southeast Asia are provided in Table 3. In some regions of Africa and Latin America, post-harvest losses of up to 50 percent have been documented (FAO, 1994a). Losses of this magnitude can clearly affect food security.

Milling

After harvesting, rough rice or paddy rice is dried, either mechanically or by open-air drying. Dried rice is then milled to remove the inedible hulls. Hulled rice is also called "brown" rice and consists of an average weight of 6-7 percent bran, 90 percent endosperm and 2-3 percent embryo (Chen, Siebenmorgan and Griffin, 1998). Further milling, removing the bran layer, yields white rice. On average, paddy rice produces 25 percent hulls, 10 percent bran and 65 percent white rice (Saunders and Betschart, 1979). After industrial milling, 100 kg of paddy yields about 60 kg of white rice, 10 kg of broken grains, 10 kg of bran and flour, and 20 kg of hulls (FAO, 1994b). There are several degrees of milling, depending on consumer preferences and desired degree of whiteness or opacity. Milled rice is referred to as polished or whitened rice and there are various degrees or fractions of polishing. White rice implies 8-10 percent bran removal. In general, as greater amounts of rice bran are removed from the grain during polishing, more vitamins and minerals are lost. A study in India found that up to 65 percent of thiamine and 40 percent of phosphorus were lost when rice was polished to 6.3 percent (Rao, Desikachar and Subrahmanyan, 1960). Milling loss of protein is estimated at between 10 and 15 percent (Malik and Chaudhary, in press).

Parboiling

Prior to milling or storing, rice may be parboiled, which involves soaking the rice in warm water, steaming and drying. Parboiling rice prior to cooking preserves some of the nutrient content, as micronutrients are transferred from the aleurone and germ into the starchy endosperm (Juliano and Bechtel, 1985). An analysis of six rice varieties (PR 106, PR 108, PR 109, Pb Bas I, Bas 370 and IR-8) grown in India found the content of thiamine and riboflavin to be highest in parboiled rice milled to 6 percent when compared with parboiled brown rice, parboiled rice milled to 8 percent, raw brown rice and raw milled rice (Grewal and Sangha, 1990).

Washing and cooking

Washing rice prior to cooking is estimated to lead to losses of 2-7 percent protein, 20-41 percent potassium, 22-59 percent thiamine, 11-26 percent riboflavin and 20-60 percent niacin (FAO, 1993). Losses from washing and cooking methods used in India have been calculated at 10 percent protein, 75 percent iron and 50 percent calcium and phosphorus (Grist, 1986). Cooking in excess water that is then discarded can lead to thiamine losses of 30-50 percent, riboflavin losses of 25-35 percent and niacin losses of 25-50 percent (Saunders and Betschart, 1979). High temperature frying can destroy up to 70 percent of thiamine (Saunders and Betschart, 1979).

RICE CONSUMPTION AND HEALTH

The largest nutritional problems occurring both globally and in rice-consuming countries are protein-energy malnutrition and iron, iodine and vitamin A deficiencies. Millions of children are affected by malnutrition, which contributes to half of the 10 million annual deaths in children under five years of age (Shrimpton et al., 2001). Globally, there are 3.5 billion people with iron deficiency, 2 billion at risk of iodine deficiency and millions with clinical manifestations of vitamin A deficiency (ACC/SCN, 2000). The highest prevalence of anaemia and vitamin A deficiency occurs in South Asia (Mason et al., 1999). This can probably be attributed to a combination of lack of dietary diversity, the strict vegetarian diet of a proportion of the population and unfavourable socio-economic conditions, particularly for women.

The widely accepted United Nations Children's Fund (UNICEF) causal model for childhood malnutrition identifies three underlying causes: i) insufficient access to food; ii) poor maternal and child care; and iii) inadequate health services/inferior living environments (UNICEF, 1999). Disease and inadequate intake of a diverse range of foods are the two primary factors leading to malnutrition. Life expectancy and under-five mortality rate provide a good general picture of the health of populations. The data in Table 4, however, do not show any clear relationship between rice consumption and health conditions. They show that:

• The life expectancy of the populations in countries with very high per capita rice supply ranges from 54 in Cambodia to 68 in Viet Nam; in countries with high per capita rice supply it ranges from 39 in Sierra Leone to 73 in the Republic of Korea; and in countries with moderate per capita rice supply it ranges from 47 in Côte d'Ivoire to 80 in Japan.
• The under-five mortality rate in countries with very high per capita rice supply ranges from 40/1 000 in Viet Nam to 122/1 000 in Cambodia; in countries with high per capita rice supply it ranges from 5 in the Republic of Korea to 316 in Sierra Leone; and in countries with moderate per capita rice supply it ranges from 4 in Japan to 235 in Liberia.

During the last decade, the highest rates of progress in reducing the under-five mortality rate have been seen in Bangladesh, Ecuador, the Gambia, Indonesia, the Republic of Korea and Malaysia, whereas the least progress has been made in Cambodia, Côte d'Ivoire, Papua New Guinea and Sierra Leone. The three most commonly used indicators of childhood malnutrition are stunting, wasting and underweight. The high-very high prevalence rate for stunting is 30-40 percent, for wasting is 10-15 percent and for underweight is 20-30 percent (Dean et al., 1995). Data in Table 4 show that the percentages of children under five years who suffer from stunting, wasting or are underweight are generally high in the countries with very high per capita rice supply.

STRATEGIES TO PREVENT AND ALLEVIATE MALNUTRITION

There are several broad categories of interventions that can alleviate malnutrition. Improvements in the quality of and access to health care, increased literacy rates, access to clean water and improvements to the status of women all contribute to declines in the number of malnourished people. There are four categories of direct interventions believed to be successful in reducing micronutrient malnutrition: supplementation, fortification, dietary diversification and disease reduction (Bouis, 1996). While all of these strategies are important, the following sections will focus on the potential for improving malnutrition, primarily micronutrient malnutrition, through nutritional improvement of rice.

Progress in improvement of the nutritional content of rice

Recently, there has been a new research impetus towards improving the nutritional status of populations through improvements in staple crops. While it is understood that a variety of foods are needed to meet nutrient requirements, the rationale for improvement of the nutrient content of staple foods is based upon the premise that staple foods are widely available and affordable for the majority of the world's population, particularly the poor. Foods naturally rich in micronutrients - animal products and vegetables - are generally more expensive than staple foods, subject to seasonal availability and lack the potential to be stored for long periods (Graham, Senadhira and Ortiz-Monasterio, 1997). Additionally, the diets of the most economically disadvantaged people contain a greater proportion of calories from staple foods; increasing the micronutrient density of these foods is seen as a strategy to improve their nutritional profile.

The proceedings of the 19th Session of the International Rice Commission called for an increased focus among rice scientists on strategies to combat malnutrition (FAO, 1999b). Historically, improvements in rice breeding focused on increasing the quantity of the food source; the importance of the quality of the food source in reducing micronutrient deficiencies is now coming to the forefront (Ruel and Levin, 2000). There is greater recognition of the global prevalence of many forms of micronutrient malnutrition such as iron, vitamin A and zinc deficiencies. Improvements in rice technology include a variety of approaches, namely, enhancing nutritional quality through plant breeding, increasing micronutrient content of the grain through genetic modification and improving rice fortification techniques.

Breeding for nutritional improvement

In an effort to create nutritionally superior cultivars, scientists at the International Rice Research Institute (IRRI), in the collaboration with the University of Adelaide, Australia, have been systematically documenting the iron and zinc content of hundreds of rice varieties (Graham et al., 1999). This work has led to the identification of varieties with above-average levels of iron and zinc content. Trials are currently under way to combine the traits of high zinc and iron with improved yield. The initial focus is to breed a rice variety containing higher absolute mineral content. The true test of the success of this strategy will be the bioavailability of the increased nutrient content. In order to achieve higher bioavailability, three approaches are possible: i) increase the concentration of the nutrient in the grain; ii) increase the percent bioavailability (by decreasing material that inhibits nutrient uptake); or iii) a combination of these two strategies (Graham, Senadhira and Ortiz-Monasterio, 1997). Currently, the most feasible strategy is breeding a variety with increased nutrient content in the grain. The alternative, decreasing the antinutrient content of the grain, is currently not recommended owing to the crucial role of the antinutritional factors in plant growth (Bouis, 1996).

Similar research, at the West Africa Rice Development Association (WARDA), has encountered success with breeding for specific traits. While not directly aimed at improving the nutrient content of rice, the WARDA project hopes to improve household food security through use of improved rice varieties, by combining the desirable traits of two very different species, Oryza glaberrima and Oryza sativa. The low yield and tendency towards brittle grains of Oryza glaberrima have led to its increased marginalization in favour of Oryza sativa varieties native to Asia. These varieties were introduced in Africa, cultivated and popularized because of their potential for greater yields. The drawback to the cultivation of Oryza sativa species in Africa has been its increased susceptibility to pests and diseases, which over the years has led to increasing amounts of pesticides and fertilizers being necessary to maintain high yields. Using conventional and modern techniques, scientists at WARDA were able to combine the beneficial traits of both glaberrima and sativa. The new varieties have been named "NERICAs" (NEw RIce for AfriCA). By combining the beneficial traits of the African and Asian species, NERICAs have the potential for higher yields, better resistance to disease and drought and higher protein content than the Oryza sativa varieties commonly grown in the region (WARDA, 1999).

Genetic engineering for nutritional improvement

Nutritional genomics is a new term referring to a combination of biochemistry, genetics, molecular biology and genome-based technologies to investigate and manipulate plant compounds with nutritional value (Tian and DellaPenna, 2001). This new technology has been applied to rice in two instances - the development of golden rice and iron-enhanced rice. In the case of golden rice, an entire biosynthetic pathway for beta-carotene was introduced through the use of a technique called agrobacterium-mediated transformation, which resulted in rice grains containing significant amounts of previously non-existent carotenoids, the precursors of vitamin A. The most promising experimental line contained 1.6 µg/g carotenoid, providing evidence that the goal of achieving provitamin intake of 100 µg retinol equivalent from a daily rice intake of 300 g is attainable (Ye et al., 2000). In a similar experiment, again using genetic modification, via utilization of a ferritin gene from Phaseolus vulgaris, the iron content of rice grains was doubled (Lucca et al., 2000). Additionally, to boost absorption of the iron by humans, a heat-tolerant phytase from Aspergillus fumigatus was engineered into the rice (Lucca et al., 2000). The role of the phytase will be to degrade phytic acid which, when present, inhibits the absorption of iron. There is hope that these new technologies will translate into improved micronutrient intakes for large segments of the population currently suffering from deficiencies. Questions remain as to the extent to which the increased levels of micronutrient in the grain will increase levels of bioavailability in humans. Likewise, there remain numerous questions regarding the yield, disease resistance and palatability of these new lines.

Fortification of rice

The success of various fortification strategies, particularly those involving fortification with iron, is mixed. The fortification of foods with iron remains technically complex. Those iron compounds with the greatest bioavailability (ferrous sulphate and ferrous fumarate) significantly alter the palatability of food, whereas large declines in the uptake of iron are seen when a more palatable iron compound (elemental iron or ferric orthophosphate) is used (Dary, 2001). There are technical, logistical and practical barriers to be addressed in order to have a successful fortification programme. The level of technical difficulty encountered in fortification programmes depends on the nutrient to be added. Logistical and practical elements that make a fortification programme successful include: ensuring supply of and access to the product; monitoring and support from the government; and consumer knowledge and demand for the product (Maberly, 2000). Another key element is involvement of the appropriate industry sector - millers in the case of rice. Lastly, on a practical level, the enriched product must be available, affordable and palatable.

In the Philippines a type of fortified rice has successfully undergone consumer acceptability tests. The iron-fortified rice was tested for effectiveness in a clinical trial of 218 schoolchildren. After six months, the experimental group showed significantly higher mean haemoglobin levels and a significant reduction in the prevalence of anaemia when compared with controls (Florentino, 2001). A government-sponsored programme is supporting the nationwide production and distribution of the iron-fortified rice and efforts are also under way to improve the technology by reducing the cost and losses associated with the fortification process.

CONCLUSION

Rice is a good source of carbohydrates, and B vitamins, and with current technological breakthroughs, may have the potential to also supply greater amounts of other nutrients. Caution, however should be exercised when promoting any single food source. One food, no matter how modified, cannot provide all necessary nutrients required to maintain health. In addition to sufficient dietary supply of energy, protein and fats, adequate nutrition requires the consumption of a wide range of vitamins and minerals. In predominantly rice based diets adequate nutrition can only be achieved through the addition of other nutritious foods. Animal foods such as poultry, meat, fish, eggs and milk can supply needed amounts of protein, fat, vitamins and minerals, particularly vitamin A and iron. Similarly, green leafy vegetables and fruits can provide substantial amounts of vitamin A, vitamin C and iron.

Numerous factors influence the nutrient composition of rice. These can be classified into agricultural influences, such as application of fertilizer and crop spacing, and post-harvest influences of storage and cooking. Both agriculture and nutrition scientists should work towards understanding the ways in which nutrient composition is affected and, more importantly, work together to optimise the nutrient composition of the final consumed product. One step toward this goal would be increased awareness in the nutritional and agricultural communities of the factors influencing nutrient composition. Greater documentation of the influence of variety on nutrient composition should be undertaken. At a minimum, all new rice varieties should undergo complete nutrient analysis. This basic information is essential for the assessment of the adequacy of nutrient intake and to provide a benchmark for assessing the impact of the new varieties.

A large number of persons living in predominantly rice-eating countries suffer from various forms of malnutrition. Understanding the causes of malnutrition is the only way to bring about sustained improvements in overall health and well-being. Current advances in rice technology may be able to alleviate the severity of malnutrition currently experienced. These advances must also be accompanied by actions that alleviate the core causes of malnutrition, namely, improvements in health care, sanitation and hygiene and education.

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Evaluation de la valeur nutritive du riz dans les principaux pays consommateurs

Le riz est la principale denrée de base en Asie et dans le Pacifique ainsi que dans un certain nombre de pays d'Amérique latine et des Caraïbes et en Afrique. Le riz brun est la part comestible des grains de riz. Les fibres, les minéraux et les vitamines du groupe B sont plus élevés dans le son que dans la couche d'aleurone. L'endosperme du riz est riche en hydrates de carbone et contient une quantité importante de protéines digestibles dont la teneur en acides aminés est au moins aussi bonne que celle d'autres céréales. Le riz est riche en vitamine B, en thiamine, en riboflavine et en niacine mais sa teneur en vitamine C, D ou en beta-carotène, (précurseur de la vitamine A) est faible ou nulle. S'agissant des acides aminés, le riz est riche en acides glutamiques et aspartiques, mais pauvre en lysine. Un certain nombre de facteurs, au cours de la production, de la récolte, du stockage et de la préparation influencent la teneur en nutriments du riz.

Les principaux problèmes nutritionnels, tant à l'échelle mondiale que dans les pays consommateurs de riz, sont la malnutrition protéino-énergétique, les carences en fer, en iode et en vitamine A. Des millions d'enfants sont touchés par la malnutrition, qui est chaque année responsable de la moitié des 10 millions de décès d'enfants de moins de cinq ans. Les données disponibles, toutefois, n'établissent pas un lien évident entre la consommation de riz et les conditions de santé, mais le pourcentage d'enfants de moins de cinq ans qui souffrent de retard de la croissance, d'émaciation ou d'insuffisance pondérale est généralement élevé dans les pays où la consommation de riz par habitant est très élevée. La dix-neuvième session de la Commission internationale du riz a demandé que les spécialistes s'intéressent davantage aux stratégies visant à combattre la malnutrition. Les améliorations de la technologie du riz comprennent diverses méthodes, comme l'amélioration de la qualité nutritionnelle par la sélection, l'accroissement de la teneur en micronutriments des grains par le biais de la modification génétique et l'amélioration des techniques d'enrichissement du riz.

Evaluación del impacto nutritivo del arroz en importantes países consumidores de arroz

El arroz es el principal alimento básico en Asia y el Pacífico, así como en varios países de América Latina y el Caribe y de África. El arroz descascarado es la parte comestible del grano de este cereal. Donde más fibra dietética, minerales y vitamina B hay es en el salvado y donde menos, en la capa aleurónica, mientras que el endosperma es rico en carbohidratos y contiene una notable cantidad de proteína digestible, compuesta de un perfil de aminoácidos que es superior al de otros cereales. El arroz es una buena fuente de vitaminas B; tiamina, riboflavina y niacina, pero contiene poca o ninguna vitamina C, D o betacaroteno, precursora de la vitamina A. El perfil de aminoácidos del arroz es elevado en ácidos glutámico y aspártico, pero es bajo en lisina. Hay varios factores que, durante la producción, cosecha, almacenamiento y preparación, influyen en la composición de nutrientes de arroz.

Los mayores problemas nutricionales que se presentan tanto a nivel mundial como en los países consumidores de arroz son la malnutrición proteinoenergética y la carencia de hierro, yodo y vitamina A. Millones de niños padecen malnutrición, la cual contribuye a la mitad de los 10 millones de muertes anuales de niños menores de cinco años. Sin embargo, los datos disponibles no muestran una relación clara entre el consumo de arroz y condiciones de salud, a pesar de lo cual los porcentajes de niños menores de cinco años que padecen retraso del crecimiento, emaciación y peso inferior al normal son generalmente elevados en los países con un elevado suministro de arroz per cápita. La Comisión Internacional del Arroz, en su 19ª reunión, pidió que los científicos arroceros hicieran más hincapié en las estrategias para combatir la malnutrición. Las mejoras en la tecnología arrocera incluyen distintos enfoques, tales como el fortalecimiento de la calidad nutritiva mediante el mejoramiento genético, el aumento del contenido en micronutrientes del grano por medio de la modificación genética y la mejora de las técnicas de enriquecimiento del arroz.

¹ This article is a result of a study conducted jointly between the Crop and Grassland Service (AGCP) and the Nutrition Planning, Assessment and Evaluation Serivce (ESNA) of FAO.