Rice is the staple food of over half the world's population. It is the predominant dietary energy source for 17 countries in Asia and the Pacific, 9 countries in North and South America and 8 countries in Africa. Rice provides 20% of the world's dietary energy supply, while wheat supplies 19% and maize (corn) 5%.
Cooked unenriched long-grain white rice is composed of 68% water, 28% carbohydrates, 3% protein, and 1% fat (table). A 100-gram (3+1⁄2-ounce) reference serving of it provides 540 kilojoules (130 kilocalories) of food energy and contains no micronutrients in significant amounts, with all less than 10% of the Daily Value (DV) (table). Cooked short-grain white rice provides the same food energy and contains moderate amounts of B vitamins, iron, and manganese (10–17% DV) per 100-gram serving (table).
A detailed analysis of nutrient content of rice suggests that the nutrition value of rice varies based on a number of factors. It depends on the strain of rice, such as white, brown, red, and black (or purple) varieties having different prevalence across world regions. It also depends on nutrient quality of the soil rice is grown in, whether and how the rice is polished or processed, the manner it is enriched, and how it is prepared before consumption.
A 2018 World Health Organization (WHO) guideline showed that fortification of rice to reduce malnutrition may involve different micronutrient strategies, including iron only, iron with zinc, vitamin A, and folic acid, or iron with other B-complex vitamins, such as thiamin, niacin, vitamin B6, and pantothenic acid. A systematic review of clinical research on the efficacy of rice fortification showed the strategy had the main effect of reducing the risk of iron deficiency by 35% and increasing blood levels of hemoglobin. The guideline established a major recommendation: "Fortification of rice with iron is recommended as a public health strategy to improve the iron status of populations, in settings where rice is a staple food."
Rice grown experimentally under elevated carbon dioxide levels, similar to those predicted for the year 2100 as a result of human activity, had less iron, zinc, and protein, as well as lower levels of thiamin, riboflavin, folic acid, and pantothenic acid. The following table shows the nutrient content of rice and other major staple foods in a raw form on a dry weight basis to account for their different water contents.
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