Awhole grain is agrain of anycereal andpseudocereal that contains theendosperm,germ, andbran, in contrast torefined grains, which retain only the endosperm.[1][2][3]
As part of a generalhealthy diet, consumption of whole grains is associated with lower risk of several diseases.[4][5] Whole grains are a source ofcarbohydrates, multiplenutrients anddietary fiber.
Whole grain sources include:[1][6]
Cereals
Minor cereals
Pseudocereals
Whole grains are a source of multiplenutrients anddietary fiber, recommended for children and adults in several daily servings containing a variety of foods that meet whole grain-rich criteria.[7][8][9] As components ofbreakfast cereals, whole grains are associated with improvedmicronutrient intake and lower risk of several diseases.[10] Their effects ongastrointestinal health, risk ofobesity andcognition need further evaluation.[11]
Cereal proteins have low quality, due to deficiencies inessential amino acids, mainlylysine.[12][13] Supplementation of cereals with proteins from other food sources (mainlylegumes) is commonly used to compensate for this deficiency,[13] since the limitation of a single essential amino acid causes the others to break down and become excreted, which is especially important during the period of growth.[14] In contrast, the proteins of the pseudocereals have a high nutritional value, close to those ofcasein (the main protein in milk).[6] Quinoa and amaranth are the most nutritious grains due to their high content and quality of proteins, with high levels of lysine and other essential amino acids.[6][15]
Manufacturers of foods containing whole grains in specified amounts are allowed ahealth claim for marketing purposes in the United States, stating: "low fat diets rich in fiber-containing grain products, fruits, and vegetables may reduce the risk of some types ofcancer, a disease associated with many factors" and "diets low in saturated fat and cholesterol and rich in fruits, vegetables, and grain products that contain some types of dietary fiber, particularlysoluble fiber, may reduce the risk of heart disease, a disease associated with many factors".[16][17][18] The scientific opinion of theEuropean Food Safety Authority related to health claims on gut health or bowel function, weight control, blood glucose and insulin levels, weight management, blood cholesterol, satiety, glycemic index, digestive function and cardiovascular health is "that the food constituent, whole grain, (...) is not sufficiently characterised in relation to the claimed health effects" and "that acause and effect relationship cannot be established between the consumption of whole grain and the claimed effects considered in this opinion."[19]
By supplying high dietary fiber content, as part of a general healthy diet, consumption of whole grains may lower risk of several diseases, includingcoronary heart disease,stroke and cancer, with lowerall-cause mortality.[4][20][10] Regular whole-grain consumption may lower elevatedLDL andtriglyceride levels, which are risk factors for cardiovascular diseases.[20] Whole grain consumption is associated with a lower risk oftype 2 diabetes.[10][21][22]
In 2012,Health Canada stated that "the evidence to date from clinical trials and prospective cohort studies was not sufficient to support a whole grains and coronary heart disease risk reduction claim in Canada".[23] A 2017 review of clinical trials found insufficient evidence for a relationship between whole grain consumption and lowered risk of cardiovascular diseases.[24]
TheAmerican Institute for Cancer Research andWorld Cancer Research Fund International have stated that there is strong evidence that whole grains decrease risk of colorectal cancer.[5][25][26]
In genetically susceptible people,gluten (proteins found inwheat,barley,rye,oat, and related species and hybrids)[27] can triggercoeliac disease.[28] Coeliac disease affects about 1% of the general population indeveloped countries.[28][29] There is evidence that most cases remain undiagnosed and untreated.[28] The only known effective treatment is a strict lifelonggluten-free diet.[28] Minor cereals and pseudocereals may be a reasonable alternative to replacegluten-containing cereals for people who need to follow a gluten-free diet.[6]
While coeliac disease is caused by a reaction to wheat proteins, it is not the same as awheat allergy.[28][29] Other diseasestriggered by eating gluten arenon-coeliac gluten sensitivity,[29][30] (estimated to affect 0.5% to 13% of the general population),[31]gluten ataxia anddermatitis herpetiformis.[30]
In the United States wholegrain products can be identified by the ingredients list. "Wheat flour" (as opposed to "wholegrain wheat flour" or "whole-wheat flour") as the first ingredient is not a clear indicator of the product's wholegrain content. If two ingredients are listed as grain products but only the second is listed as wholegrain, the entire product may contain between 1% and 49% wholegrain.[32] Many breads are colored brown (often withmolasses orcaramel color) and made to look like wholegrain when they are not. In addition, some food manufacturers make foods with wholegrain ingredients, but, because wholegrain ingredients are not the dominant ingredient, they are not wholegrain products. Contrary to popular belief, wholegrains arenot indicative offiber. The amount of fiber varies from grain to grain, and some products may have things like bran, peas, or other foods added to boost the fiber content.[33]
According to theAmerican Association of Cereal Chemists definition, "Whole grains shall consist of the intact, ground, cracked or flaked caryopsis, whose principal anatomical components - the starchy endosperm, germ and bran - are present in the same relative proportions as they exist in the intact caryopsis."
The following names indicate whole-grain products, in accordance with the US federal government:[34][35][36]
There are multiple grains such as cereal grains (e.g. wheat, rice, oats, barley, corn, wild rice, and rye) as well as pseudocereals (e.g. quinoa and buckwheat) that may be labeled whole grains.[37]
When wheat is milled to make flour, the parts of the grain are usually separated and then are recombined to make specific types of flour, such as whole wheat, whole grain, white cake and pastry flour, and all-purpose white flour. If all parts of the kernel are used in the same relative proportions as they exist in the original kernel, then the flour is considered whole grain.[citation needed]
Under theFood and Drug Regulations, up to 5% of the kernel can be removed to help reduce rancidity and prolong the shelf life of whole-wheat flour. The portion of the kernel that is removed for this purpose contains much of the germ and some of the bran. If this portion of the kernel has been removed, the flour would no longer be considered whole grain.[citation needed]
In the UK the legally protected term iswholemeal rather than wholegrain.[38] There are voluntary guidelines on what can be labelled a wholegrain product.[38]
Additionally, menu planners are encouraged to serve a variety of foods that meet whole grain-rich criteria and may not serve the same product every day to count for the HUSSC whole grain-rich criteria.
When compared with the WHO requirements of essential amino acids for humans, wheat, barley and rye are seen to be deficient in lysine, with threonine being the second limiting amino acid (Table 1).
{{cite journal}}: CS1 maint: multiple names: authors list (link){{cite journal}}: CS1 maint: multiple names: authors list (link){{cite journal}}: CS1 maint: multiple names: authors list (link)Similar proteins to the gliadin found in wheat exist as secalin in rye, hordein in barley, and avenins in oats and are collectively referred to as "gluten." The gluten found in all of these grains has been identified as the component capable of triggering the immune-mediated disorder, coeliac disease.
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