Refined grains have been significantly modified from their natural composition, in contrast to

whole grains A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm. As part of a general healthy diet, consumption of whole grains is associated wit ...

. The modification process generally involves the mechanical removal of

bran Bran, also known as miller's bran, is the hard outer layers of cereal grain. It consists of the combined aleurone and pericarp. Corn (maize) bran also includes the pedicel (tip cap). Along with germ, it is an integral part of whole grains, ...

and

germ Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embryo ...

, either through grinding or selective sifting.

Overview

A refined grain is defined as having undergone a process that removes the bran, germ and

husk Husk (or hull) in botany is the outer shell or coating of a seed. In the United States, the term husk often refers to the leafy outer covering of an ear of maize (corn) as it grows on the plant. Literally, a husk or hull includes the protective ...

of the grain and leaves the

endosperm The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the embryo and ...

, or starchy interior. Examples of refined grains include

white bread White bread typically refers to breads made from wheat flour from which the bran and the germ layers have been removed from the whole wheatberry as part of the flour grinding or milling process, producing a light-colored flour. This milling pro ...

white flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...

, corn

grits Grits are a type of porridge made from boiled cornmeal. Hominy grits are a type of grits made from hominy – corn that has been treated with an alkali in a process called nixtamalization, with the pericarp (ovary wall) removed. Grits are ofte ...

and

white rice White rice is milled rice that has had its husk, bran, and germ removed. This alters the flavor, texture and appearance of the rice and helps prevent spoilage, extend its storage life, and makes it easier to digest. After milling (hulling), the ...

. Refined grains are milled which gives a finer texture and improved shelf life. Because the outer parts of the grain are removed and used for animal feed and non-food use, refined grains have been described as less

sustainable Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...

than whole grains. After refinement of grains became prevalent in the early 20th-century, nutritional deficiencies (

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...

thiamin Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thia ...

riboflavin Riboflavin, also known as vitamin B2, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are involved in e ...

and niacin) became more common in the United States.Sizer, Frances; Whitney, Ellie. (2013). ''Nutrition: Concepts and Controversies''. Cengage Learning. pp. 125-126. Edelstein, Sari. (2019). ''Food Science: An Ecological Approach''. Jones & Bartlett Learning. p. 480-482. To correct this, the Congress passed the U.S. Enrichment Act of 1942 which requires that iron, niacin, thiamin and riboflavin have to be added to all refined grain products before they are sold.

Folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...

(folic acid) was added in 1996. Refining grain includes mixing, bleaching, and brominating; additionally, folate, thiamin, riboflavin, niacin, and iron are added back in to nutritionally enrich the product. Enriched grains are refined grains that have been fortified with additional nutrients. Whole grains contain more

dietary fiber Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...

than refined grains. After processing, fiber is not added back to enriched grains. Enriched grains are nutritionally comparable to whole grains but only in regard to their added nutrients. Whole grains contain higher amounts of minerals including

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium ...

, and

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic ta ...

and vitamins such as

Vitamin B6 Vitamin B6 is one of the B vitamins, and thus an essential nutrient. The term refers to a group of six chemically similar compounds, i.e., " vitamers", which can be interconverted in biological systems. Its active form, pyridoxal 5′-phospha ...

and

Vitamin E Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vit ...

. Whole grains also provide

phytochemical Phytochemicals are chemical compounds produced by plants, generally to help them resist fungi, bacteria and plant virus infections, and also consumption by insects and other animals. The name comes . Some phytochemicals have been used as poisons ...

s which enriched grains lack. In the case of

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

, the process of

nixtamalization Nixtamalization () is a process for the preparation of corn, or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater (but sometimes aqueous alkali metal carbonates), washed, and then hulled. The term ...

(a chemical form of refinement) yields a considerable improvement in the bioavailability of niacin, thereby preventing

pellagra Pellagra is a disease caused by a lack of the vitamin niacin (vitamin B3). Symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth. Areas of the skin exposed to either sunlight or friction are typically affected first. Over ...

in diets consisting largely of maize products. Similar to whole grains, refined grains are a good source of starch, including

resistant starch Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods, but it can also be added as part of dried raw foods, or use ...

Research

The dietary guidance of many countries is to replace refined grains with whole grains. The

Dietary Guidelines for Americans The Dietary Guidelines for Americans (DGA) provide nutritional advice for Americans who are healthy or who are at risk for chronic disease but do not currently have chronic disease. The Guidelines are published every five years by the US Department ...

(2020-2025) advises people to limit their intake of refined grains to be no more than half of total daily grain consumption.

Cardiovascular disease

According to a 2020 review there is insufficient evidence to recommend "whole grains as opposed to refined grains for the prevention and treatment of CVD". A 2022 review found that refined grains do not contribute to a higher CVD risk and suggested that it is other unhealthy foods in the Western dietary pattern such as

red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...

and

processed meat Processed meat is considered to be any meat which has been modified in order to either improve its taste or to extend its shelf life. Methods of meat processing include salting, curing, fermentation, smoking, and/or the addition of chemical pr ...

, and sugar-sweetened beverages that increase higher CVD risk.

Obesity

There is no strong scientific evidence associating refined grains with

obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...

Nutrition

References

External links

''The History of Bread'', UK Bakers Federation, 2002
{{Wheat Cereals Food science