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Health Benefits and Risks of Rice


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Rice is a fundamental food in many cultural cuisines around the world, and it is an important cereal crop that feeds more than half of the world's population. The two main categories are white rice and whole grain rice or bow ice. Whole grain rice is not processed very much, so it is high in nutritional value, whereas white rice is processed so that the bran or outer covering is removed, leaving it with less nutritional value. People choose different styles of rice for particular flavors, depending on their culinary needs, the availability, and the potential for healthy benefits as well.
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Chapter 10
DOI: 10.4018/978-1-5225-0591-4.ch010
Rice is a fundamental food in many cultural cuisines around the world, and it is an important cereal
crop that feeds more than half of the world’s population. The two main categories are white rice and
whole grain rice or bow ice. Whole grain rice is not processed very much, so it is high in nutritional
value, whereas white rice is processed so that the bran or outer covering is removed, leaving it with
less nutritional value. People choose different styles of rice for particular flavors, depending on their
culinary needs, the availability, and the potential for healthy benefits as well.
Rice is the seed of the grass species Oryza sativa (Asian rice) or Oryza glaberrima (African rice). As a
cereal grain, it is the most widely consumed staple food for a large part of the world’s human population,
especially in Asia. It is the agricultural commodity with the third-highest worldwide production, after
sugarcane and maize, according to 2012 FAOSTAT data (FAOSTAT, 2012). After corn, rice (Oryza
sativa, L.) is the second most widely produced cereal crop in the world, with global paddy production
reaching 720 million metric tons in 2012; yet it leads all cereals in supplying caloric energy to humans,
accounting for 20% of the global dietary energy intake (FAO, 2004). Rice is grown in over 100 countries
and on every continent except Antarctica, extending from 50° north latitude to 40° south latitude, and
from sea level to an altitude of 3000 m (Juliano, 1993; Khush, 1997; Maclean, 2002). It is also grown
under an extremely wide range of air temperatures (17–33°C) (Maclean, 2002; De Datta, 1981).
Rice is a semi-aquatic annual grass plant that includes approximately 22 species of the genus
Oryza,of which 20 are wild. Two species of rice are important for human consumption: O. sativa and
O. glaberrima. O. sativa was first grown in Southeast Asia, somewhere in India, Myanmar, Thailand,
Health Benets and
Risks of Rice
Md Zakir Hossain Howlader
University of Dhaka, Bangladesh
Hossain Uddin Shekhar
University of Dhaka, Bangladesh
Health Benets and Risks of Rice
North Vietnam, or China, between 8000 and 15,000 years ago. O. glaberrima is thought to have been
domesticated from its wild ancestor Oryza barthii by people living in the floodplains of the Niger River
in Africa about 3000 years ago. Today, rice is cultivated on every continent except Antarctica. Of the
two cultivated species, O. sativa is more widely grown, including in Asia, North and South America,
the European Union, the Middle East, and Africa. Cultivation of O. glaberrima is confined to Africa,
where it is fast being replaced by O. sativa.
Thousands of O. sativa cultivars are grown in more than 100 countries. They can be classified into
three widely cultivated ecological varieties: the long-grained indica variety grown in tropical and sub-
tropical Asia; the short/medium-grained japonica rice cultivated in temperate regions such as Japan and
northern China; and the medium grained javonica rice grown in the Philippines and the mountainous
areas of Madagascar and Indonesia (IRRI, 2013). Rice is cultivated in a variety of water regimes and soil
types, such as saline, alkaline, and acid–Sulphur soils. Irrigated lowland systems where rice is grown
in bunded fields can produce two to three crops per year, and nearly three-quarters of the world rice
production. Rain-fed lowland rice is grown in bunded fields that are flooded with rainwater. The areas of
greatest poverty in South Asia, parts of Southeast Asia, and essentially all of Africa use rain-fed lowland
farming to produce 20% of the world’s rice. Upland rice farming done in dry land conditions produces
4% of the world’s total rice production (IRRI, 2013).
The world dedicated 162.3 million hectares in 2012 for rice cultivation and the total production was about
738.1 million tonnes. The average world farm yield for rice was 4.5 tonnes per hectare, in 2012(FAO,
2014). Rice is a major food staple and a mainstay for the rural population and their food security. It is
mainly cultivated by small farmers in holdings of less than 1 hectare. Rice is also a wage commodity
for workers in the cash crop or non-agricultural sectors. Rice is vital for the nutrition of much of the
population in Asia, as well as in Latin America and the Caribbean and in Africa; it is central to the food
security of over half the world population. Developing countries account for 95% of the total production,
with China and India alone responsible for nearly half of the world output. (FAO, 2003).
Figure 1. Left: O. sativa with small wind-pollinated flowers; right: O. sativa, in different growing stages
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Nowadays, food consumers are becoming more health‐conscious and shifting towards nutritious, wholesome and healthy foods, thus making manufacturers emphasize the development of functional foods. The shift from a former emphasis on survival through hunger towards functional food with nutraceutical and functional properties forced the food industry to understand functional bioactive compounds in different processed food products along with their functional and phytochemical qualities in food for humans. Functional foods are defined as foods that are containing one or more functional components/ingredients like antioxidants, carotenoids, prebiotic, probiotic, polyphenols, sterols, and/or any other components with some functional properties and provides important or limited functions in the organism, promoting welfare and health, or for a reduction in the risk and protection of cardiovascular diseases, diabetes, cancer, and osteoporosis. In a nutshell, functional foods are the healthy food products of the future. The development of functional foods and nutraceuticals from different ingredients and retention of these functional ingredients in different food products have not been adequately investigated. In industries, such products are required to increase in human life expectancy, and considering the exponential growth of health care costs, society needs to act responsively and implement new scientific knowledge, developments, and technologies that will provide beneficial results to overall health. Those adjustments will require important modifications in people's lifestyle. The advances in food science/technology are providing the food industry with increasingly effective techniques to control and improve the physical structure and the chemical composition of food products, which in turn creates functional foods. Functional foods provide lasting attributes beyond nourishing properties.
The structure of the starchy endosperm of rice (Oryza sativa) was studied by using light and transmission electron microscopy coupled with proteolytic enzyme digestions. The starchy endosperm was divided into two regions, the subaleurone and central, based on the number and types of protein bodies observed. The subaleurone region contained three different types of membrane bounded protein bodies—large spherical, small spherical, and crystalline protein bodies. The small spherical protein bodies were most numerous and the large spherical ones were least numerous. The crystalline protein bodies displayed crystal lattice fringes and were a composite of smaller angular components. The central region lacked both the small spherical and crystalline protein bodies. The large spherical protein bodies of this region were located in pockets of densely stained proteinaceous material. In contrast to the relatively well preserved cytoplasm of the subaleurone region, the central endosperm zone consistently was poorly preserved.
Rice prolamin extracted with 60 %(v/v) n-propanol from protein-rich rice bran was fractionated into individual polypeptides by SDS-polyacrylamide gel electrophoresis and isoelectric focusing. The prolamin polypeptides of 10, 13, and 16 kDa were acid hydrolized, and the amino acid composition of each polypeptide was analyzed. These prolamin polypeptides were rich in glutamic acid/glutamine and leucine but poor in lysine as reported previously for prolamins of many cereals. The 10 and 16 kDa polypeptides had a markedly high content of sulfur-containing amino acids. © 1989, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.
There are two cultivated and twenty-one wild species of genus Oryza. O. sativa, the Asian cultivated rice is grown all over the world. The African cultivated rice, O. glaberrima is grown on a small scale in West Africa. The genus Oryza probably originated about 130 million years ago in Gondwanaland and different species got distributed into different continents with the breakup of Gondwanaland. The cultivated species originated from a common ancestor with AA genome. Perennial and annual ancestors of O. sativa are O. rufipogon and O. nivara and those of O. glaberrima are O. longistaminata, O. breviligulata and O. glaberrima probably domesticated in Niger river delta. Varieties of O. sativa are classified into six groups on the basis of genetic affinity. Widely known indica rices correspond to group I and japonicas to group VI. The so called javanica rices also belong to group VI and are designated as tropical japonicas in contrast to temperate japonicas grown in temperate climate. Indica and japonica rices had a polyphyletic origin. Indicas were probably domesticated in the foothills of Himalayas in Eastern India and japonicas somewhere in South China. The indica rices dispersed throughout the tropics and subtropics from India. The japonica rices moved northward from South China and became the temperate ecotype. They also moved southward to Southeast Asia and from there to West Africa and Brazil and became tropical ecotype. Rice is now grown between 55 degrees N and 36 degrees S latitudes. It is grown under diverse growing conditions such as irrigated, rainfed lowland, rainfed upland and floodprone ecosystems. Human selection and adaptation to diverse environments has resulted in numerous cultivars. It is estimated that about 120,000 varieties of rice exist in the world. After the establishment of International Rice Research Institute in 1960, rice varietal improvement was intensified and high yielding varieties were developed. These varieties are now planted to 70% of world's riceland. Rice production doubled between 1966 and 1990 due to large scale adoption of these improved varieties. Rice production must increase by 60% by 2025 to feed the additional rice consumers. New tools of molecular and cellular biology such as anther culture, molecular marker aided selection and genetic engineering will play increasing role in rice improvement.
High- and middle-income Asian countries may not need further increase in rice production to meet domestic demand, as their population growth is slow and per capita rice consumption has been declining. Demand pressure will, however, remain strong in low-income countries that contain the bulk of Asian populations, because of continuous high population growth rates and positive income growth. Sustaining the historical growth in rice supply will be difficult if research and extension efforts target only the irrigated ecosystem, as farmers have almost achieved the maximum attainable yield for that ecosystem. The yield gap is large in the dominant rainfed ecosystems because of abiotic stresses and suboptimal use of inputs due to risks in rice cultivation.There is a need to strengthen systems-oriented rice research to develop crop management practices that avoid abiotic stresses, and high-yield varieties that can withstand temporary submergence and prolonged droughts.