|IRC: 02/10 |
THE INTERNATIONAL RICE COMMISSION
Bangkok, Thailand, 23-26 July 2002
NUTRITIONAL CONTRIBUTION OF RICE: IMPACT OF BIOTECHNOLOGY AND BIODIVERSITY IN RICE-CONSUMING COUNTRIES
Gina Kennedy, Barbara Burlingame and Van Nguu Nguyen
RICE CONSUMPTION IN MAJOR RICE CONSUMING COUNTRIES
NUTRIENT CONTENT OF RICE
Varietal influence on nutrient composition
Influence of Agricultural Factors on Nutrient Composition
Influence of Post-harvest Factors on Nutrient Composition
NUTRITIONAL PROBLEMS IN PREDOMINANTLY RICE CONSUMING COUNTRIES
Measurement of Malnutrition in Children
STRATEGIES TO PREVENT AND ALLEVIATE MALNUTRITION
Rice is the predominate staple food for at least 33 developing countries, providing 27% of dietary energy supply, 20% of dietary protein and 3% of dietary fat. Rice can contribute nutritionally-significant amounts of thiamin, riboflavin, niacin and zinc to the diet, but lesser amounts of other micronutrients. Many factors influence the nutrient content of rice, including the cultivar, agricultural practices, postharvest conditions and handling. Traditional breeding, genetic engineering, fortification, and compositional analysis of lesser-known rice cultivars combined with nutrition education/promotion, are strategies used to improve the nutrient contribution from rice.
Rice is the predominate staple for fifteen 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, 1999). In developing countries, rice accounts for 715 kcal/capita/day; 27% of dietary energy supply, 20% of dietary protein and 3% of dietary fat. Countries in Southeast Asia are heavily reliant upon rice; in Bangladesh, Laos, Viet Nam, Myanmar and Cambodia, rice supplies more than fifty percent of per capita dietary energy and protein supply and 17-27 % of dietary fat. Rice is an important staple for several countries in Africa. In Guinea, Guinea-Bissau, Gambia, Liberia, Senegal and Cote d'Ivoire, rice supplies between 22-40 % of dietary energy and 23-39 % of dietary protein. Table one shows the average per capita supply of rice, and percent energy, protein and fat derived from rice.
Rice production has increased greatly since the 1960's. Globally, the amount of energy (kcal) per capita supplied from rice has jumped from 411 kcal/capita in 1960 to 577 kcal/capita today, an increase of 40% (Figure 1). A breakdown of regions shows that trends in dietary energy supplied from rice (kcal/capita/day) increased 90% in Sub-Saharan Africa and 28% in Asia and Latin America (FAOSTAT, 2001).
Table 1: Contribution of rice (rice-milled equivalent) as percentage of total dietary energy, protein and fat (Average 1997-1999)
|Country||per capita supply
|% per capita supply
of dietary energy
|% per capita supply
|% per capita
supply of fat
|Korea, Republic of||259.0||33.5||21.0||3.2|
|Papua New Guinea||101.6||16.1||13.6||1.8|
|United Arab Emirates||158.4||18.0||10.6||1.1|
Dietary intake surveys from China and India show an average adult intake of about 300 grams of raw rice per day (Popkin et al., 1993; FAO,1998). Using an average consumption of 300 grams of rice for an adult male and 250 grams of rice for an adult female, table two provides the amount of micronutrients supplied from rice. For a 19-50 year old male consuming the cooked equivalent of 300g of raw rice/day, white rice supplies 2-5 % RNI of calcium, folate and iron, 9-17 % RNI of riboflavin, thiamin and niacin and 21% RNI of zinc. Rice provides no vitamin C or A. Consumption of brown rice increases the RNI for all nutrients except riboflavin. The RNI's for iron, thiamin and niacin are increased by more than 10 %. The increased amount of phytate in brown rice decreases the bio-availability of many nutrients, particularly iron, zinc and calcium to which it chemically bonds. The exact implications of the amount of bio-available nutrients from brown compared to white rice requires further analysis. Rice supplies less of the RNI for women for all nutrients due to the smaller portion consumed and higher requirements for certain nutrients, particularly, iron.
Table 2: Amount and percent of RNI (recommended nutrient intake) of certain micronutrients supplied from an average rice intake (300g Male /250g Female)
The figures were obtained by using 300 grams of raw rice, converted into cooked equivalent using the conversion factors of 2.63 for brown rice and 2.32 for white rice (Banjong, 1995). Percent requirement was calculated for a male 19-50 years old and a non pregnant non lactating female 19-50 years old using provisional RNI (Recommended Nutrient Intakes). Lowest % bioavailability assumed for iron and zinc FAO (2000) Nutrient composition data from USDA Release 14 Rice, brown medium grain cooked and Rice, white, medium grain cooked, unenriched. (USDA 2001.)
The different layers of rice seed; outer hull, caryopsis, aleurone, subaleurone, endosperm; and embryo contain differing amount of nutrients. Dietary fiber, minerals and B vitamins are highest in the bran and lowest in the aleurone layers, rice endosperm is rich in carbohydrate and contains a fair amount of digestible protein, composed of an amino acid profile which compares favorably to other grains (Juliano,1993). Rice is a good source of the B vitamins; thiamin, riboflavin and niacin but contains little to no vitamin 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; Juliano, 1993). The main antinutritional factors, most of which are concentrated in the bran, are phytate, trypsin inhibitor, oryzacystatin and haemagglutinin-lectin (Juliano, 1993 ).
A number of factors influence the nutrient composition of rice. Diagram one outlines these different influences.
Intra-varietal differences within rice are often overlooked, however research undertaken predominately at the International Rice Research Institute (IRRI) has shown that the nutrient composition can significantly differ between varieties (Juliano and Villareal, 1993, Chandrasekhar and Mulk, 1970). The protein content of over two thousand rice varieties was tested at IRRI. Protein ranged from 4-14 % in Oryza sativa varieties and 9-14% in Oryza glaberrima varieties (Table 3). In Oryza sativa, Asian rice varieties exhibited the greatest overall variation in protein content (4-14%), while South American varieties had the highest average protein content (7.9%).
Table 3: Summary by region of protein content in O. sativa and O. glaberrima
|Source||Sample number||Protein Range (%)||Protein Mean (%)|
|Oryza sativa L.|
Source Juliano and Villareal, 1993
Since the early 1990's IRRI in cooperation with the University of Adelaide has been analyzing variations in iron and zinc content in rice varieties. Rice grown under uniform conditions at the IRRI research center ranged in iron content from .75-2.44 mg/100g, with a mean of 1.21 mg/100g. Zinc content ranged from 1.59-5.84 mg/100g with a mean of 2.54 mg/100g (Graham et al., 1999). A sample of varieties grown under greenhouse conditions at IRRI is presented in table four. This table demonstrates that some traditional rice varieties contain 2 and ½ times more iron content than commonly grown high yielding counterparts. Four of the top five varieties richest in iron and zinc content are traditional rice varieties, while the varieties at the lower end of the scale in terms of iron and zinc density are the popular, modern high yielding varieties.
Table 4: Iron and Zinc content of selected varieties grown in greenhouse conditions
(Average of 3 replications)
|Variety||Iron mg/100g||Zinc mg/100g|
|Xue Bue Nuo||2.25||4.66|
Source: Adapted from Senadhira, Gregorio and Graham,1998
Studies have shown agricultural practices can influence the nutrient composition of the rice grain. Controlled experiments found soil nitrogen, solar radiation, degree of plant maturation, application of fertilizer and shorter maturation periods, influenced 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 et al., 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 effect the nutrient composition directly, but the magnitude 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 (De Lucia and Assennato, 1994). The loss can occur at any point during harvest, threshing, drying, storage or transport. An estimated 10-37 % of total rice production is lost due to post harvest factors (Saunders, 1979). During harvest, depending on the type of machinery or manpower 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 due to molds, insects and rodents. Estimates from Sub-Saharan Africa have shown rodents can consume or contaminate up to 20% of a stored harvest (FAO, 1994). Estimates of post harvest rice losses in Southeast Asia are provided in table five.
Table 5: Estimates of the quantitative losses of rice for each stage in the post-harvest system in Southeast Asia.
|Threshing||2 %||6 %|
|Storage||2 %||6 %|
|Transport||2 %||10 %|
Source: De Lucia and Assennato, 1994.
In some regions of Africa and Latin America, post harvest losses of up to 50 percent have been documented. (De Lucia and Assennato,1994). Losses of this magnitude can clearly affect food security.
After harvesting, rough rice or paddy rice is dried, either mechanically or by open-air. Dried rice is then milled to remove inedible hull. Hulled rice is also called "brown" rice and consists of an average weight of 6-7% bran, 90% endosperm and 2-3 % embryo (Chen et al., 1998). Further milling removing the bran layer yields white rice. On average, paddy rice produces 25% hulls, 10% bran, and 65% white rice (Saunders, 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, 1994).
There are several degrees of milling which can take place, depending on consumer preferences and desired degree of whiteness or opacity. Milled rice is referred to as polished or whitened and there are various degrees or fractions of polishing. White rice implies 8-10% 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 up to 65 % of thiamin and 40% of phosphorus were lost when rice was polished to 6.3% (Rama et al., 1960). Milling loss of protein is estimated at between 10-15% (Malik and Chaudhry in press).
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 (PR106, PR 108, PR 109, Pb Bas I, Bas 370 and IR-8) grown in India found the content of thiamin and riboflavin to be highest in parboiled rice milled to 6 % when compared to both parboiled brown rice, parboiled rice milled to 8%, 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 % protein, 20-41 % potassium, 22-59 % thiamin, 11-26 % riboflavin and 20-60 % niacin. (Juliano,1993).
Losses from washing and cooking methods used in India were calculated at 10% protein, 75% iron, and 50 % calcium and phosphorus (Grist, 1986). Cooking in excess water that is discarded can lead to thiamin losses of 30-50%, riboflavin loss of 25-35% and niacin loss of 25-50% (Saunders, 1979). High temperature frying can destroy up to 70% of thiamin (Saunders, 1979).
Table six compares the nutrient value of equal portions of raw and cooked rice. Rice expands during cooking as water is absorbed. One hundred grams of raw white rice yields approximately 232 grams of cooked white rice, and 100 grams of raw brown rice yields 263 grams of cooked brown rice (Banjong et al., 1995).
Table 6: Energy in 100 g raw and cooked rice.
|Type of Rice||Energy kJ/100g||Energy kcal/100 g|
Source: Adapted from Saunders 1979. (Conversion 1kcal=4.184 kJ)
As noted in table five, 2-6 % of rice harvest may be lost during storage. These losses are incurred due to infestation by insects, mold and consumption or contamination of the grain by rodents and birds. Parboiling rice has been shown to decreases post-harvest losses during storage due to insects (Bhattacharya, 1985). Similarly, certain traditional rice varieties have proven to be less vulnerable to attack by insects when compared to high yielding varieties (FAO, 1994). Vitamin content, particularly thiamin, has been seen to decrease during rice storage (Juliano et al., 1985). However, it was found that the loss of B vitamins during storage was less in parboiled rice (Bhattacharya, 1985).
The largest nutritional problems occurring both globally and in rice consuming countries are protein-energy malnutrition, and iron, iodine and vitamin A deficiency. 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 persons with iron deficiency, 2 billion at risk of iodine deficiency and millions with clinical manifestation of vitamin A deficiency (ACC/SCN, 2000). The highest prevalence of anemia, vitamin A deficiency occur in South Asia (Mason et al, 1999). This is most likely due to a combination of lack of dietary diversity, strict vegetarian diet of a proportion of the population, and unfavorable socio-economic conditions, particularly for women.
The widely accepted UNICEF causal model for 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.
Basic indicators such as life expectancy, infant mortality rate and literacy rates of men and women provide a reasonable picture of the health and sanitation conditions and gender equality in a given country. A profile of basic health and living standards in predominately rice eating countries is shown in table seven. Countries with the best indicators of life expectancy and under five mortality rate, include, Japan, Costa Rica, United Arab Emirates and Jamaica. Those with the lowest life expectancy and infant mortality rates are Sierra Leone, Malawi, Guinea and Cote d'Ivoire, during this assessment period, many of these countries experienced civil unrest.
The highest rates of progress in reducing the under five mortality rate have been seen in Malaysia, Republic of Korea, Indonesia, Gambia, Ecuador and Bangladesh. The least progress has been made in Cambodia, Sierra Leone, Cote d'Ivoire and Papua New Guinea.
Table 7: Basic Indicators of Health and Well-being
|Country||Life Expectancy (yrs)||Under 5 mortality rate||Infant Mortality Rate||% population with
Adult Literacy rate
|GNP per capita (US$)|
|Korea, Republic of||73||5||5||92||99||98||8490|
|Papua New Guinea||59||112||79||42||81||63||800|
Source UNICEF, 2001.
- Data not available
x Data refer to years or periods other than those specified, differ from the standard definition, or refer to only part of the countries
Under five mortality rate- probability of dying between birth and five years of age expressed per 1,000 live births
Infant Mortality rate- probability of dying between birth and one year of age expressed per 1,000 live births
Adult Literacy rate- percentage of persons aged 15 and over who can read and write
There are three key indicators of childhood growth used to assess the prevalence of malnutrition in children under five years of age; stunting, wasting and underweight. Stunting is a measure of height for age and is considered a good indicator of chronic malnutrition. Wasting is measured in terms of weight for height and indicates acute malnutrition. Underweight is measured in terms of weight for age and is the indicator most commonly used in growth monitoring programs. All three indicators are assessed using growth reference curves, and include all children falling below an established reference cut-off point. (UNICEF, 2001).
High-Very High prevalence rates for the stunting, wasting and underweight are 30-40%, 10-15% and 20-30 % respectively. (Dean et al., 1995). The highest prevalence rates of children suffering from stunting are seen in Korea, Bangladesh, Cambodia and Nepal. Twelve countries have a prevalence rate of above 30 %, which is considered high. Wasting or acute malnutrition is the most severe in Bangladesh, India, Cambodia and Suriname; seven countries show a high to very high rate of wasting. In terms of underweight, Bangladesh, Cambodia and India have the highest prevalence rates; sixteen countries have high to very high prevalence rates.
There are several broad categories of interventions that can alleviate malnutrition. Improvements in the quality and access to health care, increased literacy rates, access to clean water and improved women's status all contribute to declines in the number of malnourished. 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 remainder of this paper will focus on the potential for improving malnutrition, primarily micronutrient malnutrition through agricultural improvement of rice.
Recently, there has been a new research impetus toward improving 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. Additionally, the diets of those most economically disadvantaged 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 increase in focus among rice scientists on strategies to combat malnutrition (Swaminathan, 1999). 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 IRRI with the collaboration of the University of Adelaide have been systematically documenting iron and zinc content of hundreds of rice varieties (Graham et al., 1999). This work has lead to the identification of varieties with above average levels of iron and zinc content. Trials are currently underway to combine the traits of high zinc and iron with improved yield. The initial focus is to successfully 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 which inhibits nutrient uptake) iii) a combination of these two strategies (Graham et al., 1997). Currently, the most feasible strategy is breeding a variety with increased nutrient content in the grain, as the alternative, decreasing antinutrient content of the grain is currently not recommended due to the crucial role of the anti nutritional 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 toward brittle grains of Oryza glaberrima have led to its increased marginalization in favor of Oryza sativa varieties native to Asia. These varieties were introduced in Africa, cultivated and popularized due to 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 required increasing amounts of pesticides and fertilizers 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, NERICA's have the potential of 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 amount 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 300g 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 sulfate 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 program. The level of technical difficulty encountered in fortification programs depends on the nutrient to be added. Logistical and practical elements which make a fortification program successful include; ensuring supply and access of 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 school children. After 6 months, the experimental group showed significantly higher mean hemoglobin levels and a significant reduction in the prevalence of anemia when compared to controls (Florentino, 2001). A government-sponsored program is supporting the nationwide production and distribution of the iron-fortified rice and efforts are also underway to improve the technology by reducing the cost and losses associated with the fortification process.
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, can not 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.
There are numerous factors which 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 toward understanding the ways in which nutrient composition is affected and more importantly work together to optimize 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 which alleviate the core causes of malnutrition, namely, improvements in health care, sanitation and hygiene and education.
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