Medically reviewed on August 13, 2018
Scientific Name(s): Hordeum vulgare L. Family: Poaceae
Common Name(s): Barley , hordeum , Prowashonupana
Barley is a food staple and is also brewed into beer, fermented to make miso, and processed to yield malt sugar. Although there is not a consensus, some studies indicate that barley reduces cholesterol (to a similar degree as that of oats), and a few small studies demonstrated a possible protective role in hyperglycemia.
The recommended intake of barley beta-glucan for cholesterol-lowering action is 3 g/day.
Patients with celiac disease should avoid consumption of barley products.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Hypersensitivity reactions may occur in sensitive individuals.
There is little or no information.
Barley is an annual grass grown in winter or spring. The winter annual is planted in the fall because it requires a period of exposure to cold in order to produce flowers and set seeds. It forms a rosette type of sprout in fall and winter, developing elongated stems and flower heads in early summer. Spring varieties do not have a typical rosette stage and are grown in areas with very cold winters. The stems are round and hollow between the nodes, and vary in length from 30 to 122 cm. The flowers and, later, the mature seeds are borne on spikes attached to the central stem. Depending on the variety and climatic conditions, the period from flowering until harvest lasts 40 to 55 days. 1 , 2
Barley is one of the first domesticated grains; the use of barley for food and medicinal purposes dates to antiquity. The ancient Greeks used the mucilage derived from the cereal (known as ptisane) to treat gastrointestinal (GI) inflammation. Gladiators ate barley for strength and stamina, and the Roman physician Gaius Plinius Secundus (known as Pliny the Elder, AD 23-79) used barley as part of a ritualized cure for boils. Barley is the fourth most important grain crop in the United States, and is used mainly as livestock feed. Although supplanted by wheat and rye in baking, barley is used extensively in soups, cereals, animal feed, and beer production. Protein extracted from the leaves is believed to be an adequate food supplement. Roasted seeds are used in making coffee, and fermented seeds are made into miso. Whole barley is used for animal feed and malting. For human consumption, the barley hull is removed by abrasion, producing pearl barley. 3 , 4 , 5
Barley contains about 3% to 11% dietary fiber made up of pentosans, beta-glucan, and cellulose. Beta-glucan is a highly viscous soluble polysaccharide, with a linear, unbranched structure composed of 4-O-linked beta-D-glucopyranosyl units and 3-O-linked beta-D-glucopyranosyl units; the molecular weight ranges from 0.4 to 2.3 × 10 6 Da. Beta-glucan is associated with the plant cell wall and is distributed throughout the kernel, with a slightly higher concentration in the outer portion. 6 , 7
The major nutrient in barley is starch, with smaller amounts of protein and fats also present. 8 About half of the total protein content is made up of storage proteins known as hordeins. These belong to the prolamin group and are closely related to the gluten found in wheat. Hypersensitivity to barley has been attributed to these proteins. 9 , 10 Barley bran flour consists of dried and milled brewers grain, the insoluble portion of malted barley after the removal of soluble carbohydrates. The flour contains only 1% to 3% soluble fiber, as most is lost in the processing.
Although some essential amino acids and vitamins found in the outer layers of the seed are lost during the pearling process, pearl barley is rich in B-group vitamins and is a good source of trace elements including iron, magnesium, zinc, selenium, and copper. 8 Chromium levels, up to 10 times higher than those found in brewer's yeast (generally regarded as the richest natural source of chromium), have been recorded in some cultivars. 11 Other components that have been associated with health benefits include tocotrienol, lignan, phytoestrogen, phenolic compounds, and phytic acid. 12 , 13 Barley is the source of a natural sweetener known as malt sugar or barley jelly sugar, which is high in maltose. 5
Uses and Pharmacology
Barley grass is consumed largely because of its nutritional content. Barley has been shown to lower cholesterol and has an effect on blood glucose and insulin levels. However, it is usually consumed in relatively small quantities, and incorporating sufficient barley into the diet to produce these effects is difficult. Additionally, the beta-glucan content of the grain depends on several factors, including the barley cultivar and food processing techniques. Possible methods for increasing intake of beta-glucans include the use of barley cultivars containing elevated content levels (eg, Prowashonupana barley), or encapsulation or incorporation of enriched barley flour fractions into products such as breads, pasta, and muffins. The physical form and treatment of the grain during processing appear to affect the digestion of the barley starch and the absorption of various trace elements, such as zinc. 7 , 14 , 15 , 16Hyperlipidemia
A final ruling on permissible health claims for the role of barley soluble fiber in reducing the risk of cardiovascular disease was issued by the Food and Drug Administration in August 2008, and barley now joins oats and other soluble fibers regarded as low-density lipoprotein (LDL), cholesterol-lowering agents. 17 Although the precise mechanism is unclear, it is thought that beta-glucan regulates the rate and site of lipid and carbohydrate digestion and absorption. Postulated mechanisms include increased viscosity in the GI tract, delay in cholesterol absorption, and increased conversion of cholesterol into bile acids. The cholesterol-lowering activities of barley are usually attributed to the beta-glucan fraction of the grain; however, barley oil also has shown cholesterol-lowering properties. 18Animal data
Concentrated beta-glucan preparations from barley lowered serum cholesterol in animal models. The effects of concentrated beta-glucan on plasma lipids and lipoprotein, hepatic cholesterol, fecal excretion of neutral steroids, and atherogenesis were studied in hamsters consuming a hypercholesterolemic diet. 19 Improvements in all parameters occurred and were dose dependent. Lipid metabolism was significantly better in diabetic rats fed a barley diet than those receiving low fiber, rice, or cornstarch diets in another study. 20 The fiber content of the barley diet was very high (1.79 g/day); this corresponds to a human dosage of about 42 to 73 g/day.Clinical data
The results of clinical studies have been mixed, but largely demonstrate positive findings. Reductions in LDL and total cholesterol, as well as reductions in cholesterol and high-density lipoprotein ratios, have been shown in a number of trials conducted in hypercholesterolemic patients. 16 , 18 , 21 , 22 , 23 However, a number of studies have been unable to demonstrate changes in lipid profiles. 24 , 25 , 26 One reason proposed for the negative findings is the molecular weight of the beta-glucan used in the trial, with positive results being attributed to higher molecular weight glucan content. 24 , 27Diabetes mellitus
Meals high in soluble fiber reduced the rise in postprandial blood glucose and insulin concentrations. These effects were attributed to an increase in the viscosity of the contents of the stomach and small intestine, thus reducing the absorption rate of the digested nutrients. 6 , 16Animal data
Long-term improvements in glucose tolerance, fasting plasma glucose, and glycosylated hemoglobin levels were demonstrated in diabetic rats receiving a barley diet for 9 months, and attributed to the high fiber content of the barley diet. Results from rats fed rice and cornstarch diets that differed from the test diet only in fiber content were worse after the third month of the study. 20Clinical data
Few trials have been conducted using barley beta-glucan in diabetic populations, with most available data based on trials in healthy volunteers.
Most trials evaluated the postprandial effect of a barley-enriched breakfast meal (30% of the carbohydrates in the control diet were replaced by barley) and consistently found positive effects on blood glucose and insulin responses. 28 , 29 , 30 , 31 , 32 , 33 , 34 Similarly, trials conducted in patients with type 2 diabetes have shown reduced glycemic responses to barley-enriched breakfast meals. 16 , 35 A limited number of trials have not established a positive response, notably when using barley beta-glucan as a drink rather than a grain-based meal. 12 , 24 , 35Other uses
Beta-glucan is fermented by the intestinal microflora to form short-chain fatty acids important for the protection of colonic mucosa. Additionally, the starch in barley is an important precursor of butyric acid, a substance that has an essential function in maintaining the health of the colonic mucosa, particularly against inflammatory conditions and those associated with abnormal cell proliferation. 24 Limited trial data exist to support GI therapeutic claims. 12 , 36Prostate
A diet high in soluble fiber, including barley, resulted in a small but statistically significant reduction in serum prostate specific antigen in healthy men with hyperlipidemia. 37 The test diet consisted of precooked barley, dried lentils, peas, and beans, plus oat bran and a commercial breakfast cereal enriched with psyllium.
Most trials evaluating effects on cholesterol have used dosages ranging from 3 to 10 g/day barley beta-glucan. 16 An intake of at least 3 g/day of barley beta-glucan is suggested for lowering cholesterol. 6
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Urticaria from beer is an immunoglobulin E–mediated hypersensitivity reaction induced by a protein component of approximately 10 kDa derived from barley. 42 Beer contains hordein at a concentration of 1.12 g/serving, 43 an amount sufficient to exacerbate symptoms of celiac disease in some individuals.
Like gluten, hordein belongs to the group prolamins, a family of cereal grain storage proteins rich in glutamine and proline. Cross-reactivity between gluten peptides and related hordein peptides has been established. 9 , 10 Hordeins have been implicated as a trigger for celiac disease, and barley should be avoided by people with this disorder.
There is little or no information regarding the toxicology of barley.
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