Grains such as rice, corn and wheat are staple food of human around the world. The countries with low morbidities due to diabetes and coronary heart disease such as Japan consume higher calories from grain (60-80% of total calories). Whereas, the countries with high morbidities rate of diabetes and coronary heart disease such as USA consume fewer calories from grain (20% of total calories).
Evolution of the food has led to milling of whole grains before consumption. For example if rice is milled 1 time for removing inedible husk and remaining 100% of germ (embryo) and bran (seed coat and pericarp), it is called whole grain. If this process is repeated until whole bran is removed and turned into white rice that primarily consists of starchy endosperm, it is called refined grain.
There are 3 types of rice which are classified as whole grains for consumption as follow- Brown rice is made from 1 time milling with a rice milling machine for removing their hulls and remaining germ and bran which are yellow in color.
1. Red rice is made from Sangyod rice or Munpoo rice which is red in color by 1 time milling, similar to brown rice, but the colour of rice is brown-red because of brown-red seed. The colour of rice may differ depending on species of rice such as Riceberry rice is deep purple in color. The unique color is not related with 1 time or repeated milling. That means Riceberry rice may be milled 1 time, similar to brown rice, or several times as white rice.
2. Coarse rice is made from pounding paddy with a wooden pestle (no use of rice milling machine). Pounded paddy is winnowed with a threshing basket (throw it up in the air, then let the husk fly with the wind and get remaining seeds with a threshing basket). Nowadays, there are no manufacturers merchandising coarse rice because of low demands and high labor costs.
3. White rice is the result of through refining processes by removing the outer bran and germ portions of brown rice. White rice is classified as refined grain.
Oats is classified as whole grain. There are 5 types of oats as follow;
1. Whole oats is comparable with paddy. No one can consume whole oat except when using germinated oat.
2. Oat groats are the result of 1 time milling for removing their inedible husk and remaining oat germ and bran coating the seed under the husk. Sometimes, oat groats are steamed and then rolled into ﬂakes called rolled oats.
3. Steel-cut oats sometimes called Scotch, are the result of oat groats cutting into two pieces for easier cooking. Sometimes, steel-cut oats are steamed and then rolled into ﬂakes called quick oats for quicker cooking.
4. Oat bran is made from the outmost bran or edible covering of the oat which is comparable with rice bran. Thai people normally do not consume rice bran but Western people consume oat bran In terms of nutrition, oat bran is the best part of oat because it contains protein, vitamins, minerals, the highest fiber, and low calories
5. Oat flour is made from oat crushing into powder.
There are 2 forms; oat flour from oat groats and oat flour from polished oat.
Wheat is popularly consumed in form of flour such as bread. The classification of flour either whole grain or refined grain is based on the same principle. Flour which is the result of 1 time milling for removing specifically the inedible husk and remaining all parts ground is called whole wheat flour. Nevertheless, winnowing of whole wheat flour to separate fine powder from coarse powder (most of them are embryo and seed coat) results in the property of whole wheat flour changing to become white flour, although it is called whole wheat flour. The consumers have to consider the color and texture of bread or products from those flours so they can make the decision of how much percentage of whole wheat flour is literally present.
Seeds of grain constitute of the hulls, bran (seed coat and pericarp), and starchy endosperm. The most nutritionally important part is bran because it contains protein, vitamins, minerals, and fiber that are necessary for the body. The endosperm is starch providing calories which is the part of over consumption in most of people in present. Refining processes of whole grains to increase calories density, enhance flavor, extend shelf life has led to products such as white rice, white bread and white flour and food industries such as cakes, cookies, doughnuts, croissants, noodle, and spaghetti. The harmful effects of under nutrition of bran had lead to nutritional deficiency diseases like beriberi in early era and non-communicable diseases such as diabetes and coronary heart disease in current times. The subsequent studies found that reﬁned grains consumption causes diseases but whole grains consumption reverses diseases. Benefits of consuming whole grains are summarized below-
Reﬁned grains intake increase type 2 diabetes risk while whole grains intake reverse type 2 diabetes
The analysis of prospective cohort studies: the Health Professionals Follow-up Study and the Nurses’ Health Study at Harvard Medical School found that higher intake of white rice (5 servings per week) was associated with a higher risk of type 2 diabetes. In contrast, high brown rice intake (2servings per week was associated with a lower risk of type 2 diabetes A systematic review and meta-analysis of European cohort studies to determine the relationship between whole grains intake and reﬁned grains intake on type 2 diabetes risk found that a high whole grain intake was associated with reduced type 2 diabetes risks while a reﬁned grain intake was associated with a higher type 2 diabetes risk.