Rice is a dietary staple for more than half of the world’s population, making its nutritional content a subject of public health importance. One nutrient is iron, a mineral used to transport and store oxygen in the body. The amount of iron in rice can vary widely, influencing the nutritional impact on populations that rely on it as a primary food.
Iron Levels in Common Rice Varieties
The natural iron content of rice differs considerably among its varieties, a difference largely dictated by processing. Whole grain rice, such as brown, black, and red varieties, retains its outer layers—the bran and the germ—where most of its minerals are stored. Consequently, these colored rices have a higher iron content than white rice, which has these layers removed during milling.
For example, black rice may contain around 1.8 milligrams of iron per 100-gram serving, while red rice has about 0.7 milligrams. Brown rice offers approximately 0.4 milligrams per serving. In contrast, a typical serving of white rice might only contain about 0.2 milligrams of iron.
The variation in iron levels is not solely due to milling. The specific cultivar of rice and the soil conditions in which it is grown also contribute to the mineral content of the grain. This inherent genetic diversity means that even within the same category, such as red or black rice, there can be a range of iron concentrations.
The Process of Iron Fortification
To address the nutritional shortcomings of polished white rice, the practice of iron fortification was developed. Fortified rice is designed to reintroduce micronutrients lost during milling and to help combat iron-deficiency anemia on a large scale. This strategy involves adding iron, often with other vitamins and minerals like folic acid and vitamin B12, to the rice grains.
One of the most widely used methods for fortification is extrusion. In this process, a dough is made from rice flour, a concentrated micronutrient premix, and water. This dough is passed through an extruder, which uses heat and pressure to form reconstituted kernels shaped like regular rice grains. These fortified kernels are then blended with standard polished rice at a ratio of 0.5% to 2%.
Another technique is coating, where rice grains are sprayed with a liquid mixture containing the iron premix. A simpler method is dusting, which involves applying a fine powder of micronutrients directly to the rice. Dusting is less effective because the added nutrients can be easily washed off if the rice is rinsed before cooking. The extrusion method is preferred as it better protects the nutrients, ensuring they are retained.
Improving Iron Absorption from Rice
The mere presence of iron in rice does not guarantee that the body can use it efficiently. The bioavailability of iron, or the amount that is absorbed and utilized, is influenced by several dietary factors. Rice, particularly whole grain varieties like brown and red rice, contains a compound called phytic acid. This compound, located in the bran, binds with minerals like iron, making them less available for absorption.
A strategy to counteract the effects of phytic acid and boost iron absorption is to consume rice with foods rich in vitamin C. Vitamin C captures non-heme iron—the type found in plant-based foods like rice—and converts it into a form that is more easily absorbed. Pairing a rice-based meal with ingredients such as bell peppers, broccoli, tomatoes, or a glass of citrus juice can increase the uptake of iron.
Another way to enhance iron absorption is by including a source of heme iron, found in animal products, in the same meal. Heme iron, from meat, poultry, or fish, is more readily absorbed than non-heme iron. Consuming heme iron alongside non-heme iron sources like rice has been shown to improve the absorption of the non-heme iron as well.