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Refined grains refers to grain products consisting of grains or grain flours that have been significantly modified from their natural composition.
Grain modification involves the mechanical removal of bran and germ.
Modifications include:
grinding, sifting, mixing, bleaching, and brominating.
Thiamin, riboflavin, niacin, and iron are often added back in to nutritionally enrich the grain, but such added nutrients represent a fraction of the nutrients removed.
Some nutrients, including iron and B vitamins, are added back to refined grains and flours during manufacturing but still represents only a fraction of what is initially removed from the grain.
For these reasons, refined grains do not provide the same health benefits as whole grains.
Refined grains are nutritionally inferior to whole grains, but for some grains the removal of fiber coupled with fine grinding results in a slightly higher availability of grain energy for use by the body.
Chemical form of refinement yields a improvement in the bioavailability of niacin.
Nutritional effects of refining or enriching wheat and rice
Refined grains are missing fiber and key nutrients that their whole-grain counterparts retain.
Refined grains include white rice, white bread, regular white pasta, and other foods that have been made with white flour (enriched wheat flour or all-purpose flour), including many cookies, cakes, breakfast cereals, crackers, and snack foods.
Whole grains contain three parts: the bran (outer layer), endosperm (middle layer), and germ (inner layer).
Refined grains, which retain only the endosperm.
The bran and germ are the most nutritious parts of the grain.
Bran and germ contain concentrated amounts of fiber, vitamins, minerals, and antioxidants.
During the refining process, the bran and germ are removed from the whole grain.
The endosperm, is the part of the grain that is left after the refining process.
Endosperm is soft, easy-to-chew and rich in starch.
Endosperm is primarily composed of starchy carbohydrates and is low in nutrients.
Refined grains are quickly digested into simple sugars.
Refined grains are absorbed into the bloodstream, and can cause blood-sugar levels to spike and then quickly crash, altering energy levels and mood.
The high-quality carbohydrates in whole grains are rich in fiber, which helps temper blood sugar levels by slowing the absorption of sugar into the bloodstream after meals.
Carbohydrates in whole grains provide long-lasting energy.
Diets rich in nutritious whole grains reduce your risk of type 2 diabetes, cardiovascular disease, and high blood pressure.
A diet high in refined grains can contribute to high triglycerides, increase inflammation and which may worsen symptoms of arthritis.
Refined grains may also impair weight loss; because they are low in fiber, less filling than whole grains and are is associated with overeating.
White bread, and regular pasta made with enriched wheat flour or all-purpose flour are wheat-based and therefore contain gluten, so they should be avoided by people with celiac disease.
With whole grains, processing removes only the indigestible outer hull, preserving the nutrition-packed bran and germ, and the endosperm.
With refined grains, processing strips away the bran and germ.
Refined grains are an important part of many food cultures and experiences and can be part of a healthy overall diet.
Adults who eat three slices of white bread daily have a significantly increased risk for dying from cardiovascular causes.
study (Prospective Urban Rural Epidemiology (PURE) of more than 137,000 people in 21 countries documented a clear link between a high level of consumption of refined grains and a significantly increased risk for death from any cause or major cardiovascular disease (CVD) event during a median follow-up of 9.5 years.
People who reported eating at least 350 g (7 servings) of refined grain daily had a significant 29% increased risk of either death or a major CVD event of MI, stroke, or heart failure, compared with those who consumed less than one serving per day, fewer than 50 g. of refined grain.
No significant association between levels of whole grains or white rice in the diet and CVD events.
A reduction in the quantity of refined grains and sugar, and improvement in the quality of carbohydrates is essential for better health outcomes.
U.S. dietary guidelines recommend that refined grains constitute less than half of a person’s carbohydrate consumption, but a much safer daily consumption limit would cap refined grains to no more than one serving a day.
The data for the current PURE analysis came from more than 148,000 people aged 35-70 years at entry in 21 geographically and economically diverse countries, excluding patients with known CVD at baseline left a cohort of 137,130 people.
There was no significant association between the quantity of whole grains consumed and the main outcome, nor a link between higher amounts of white rice consumption and the main outcome.
Rice such as long-grain rice and especially parboiled white rice may have both a definite glycemic advantage and an overall nutritional advantage over refined wheat products.
Refined grains undergo rapid action by digestive enzymes and quick absorption from the small intestines leading to an increase in postprandial blood glucose concentrations.
Refined grain is similar to eating sugar, as refined grain is 100% glucose.
Whole grains differ by entering the gut packaged in cell structures that slow digestion and avoid delivering sugar in an unnaturally rapid way.