Grains are seeds of various grass plants. Examples include wheat, rice, corn, rye, barley, quinoa and oats. The U.S. Department of Agriculture recommends that whole grains should make up at least half of your daily consumption of grain foods. Whole grains have more natural nutrients because they have the outer bran and inner germ layer. Refined grains made with just the starchy, white endosperm layer are fortified with vitamins, but they contain less fiber.
Macronutrients provide energy, and humans need them to live. Carbohydrates, fats and proteins are considered macronutrients, and these three components make up the human diet. Grains are naturally low in fat and a rich source of carbohydrates, which are used as the main fuel for the body. Whole grains are a rich source of fiber because they contain the fibrous outer bran layer. For example, oats, whole wheat, brown rice, bulgur and millet are all high-fiber whole grains. Fiber may help reduce cholesterol, risk for type 2 diabetes and provide bulk for bowel movements. Whole grains provide complex carbohydrates, meaning they do not raise blood sugar rapidly because the fiber slows the release from the intestines into the blood. However, refined grains such as white bread can raise blood sugar rapidly and do not provide significant fiber.
Grains are incomplete proteins, meaning they are low in at least one essential amino acid. Eating a balanced, varied diet ensures that you eat all the essential amino acids at an adequate level. This is especially important for vegetarians, who rely on grains and legumes for protein sources. Quinoa is one of the highest grains for protein content. One cup of cooked quinoa provides around 8 g of protein.
Micronutrients include vitamins and minerals. Humans need these in smaller quantities than macronutrients, and micronutrients do not provide energy. Grains are a rich source of the B vitamins, which include thiamin, riboflavin, folate, niacin and vitamin B6. B vitamins are important for the metabolism of proteins, fat and carbohydrates for energy. Folate is also especially important for pregnant females, as the fetus requires extra folate for growth and development. Whole grains contain these vitamins naturally, and refined grains are fortified with B vitamins.
Grains provide minerals such as iron, magnesium and selenium. Iron is a mineral used in oxygen transportation in the blood. Iron deficiency, called anemia, is common in adolescent females and females in childbearing years. Those at risk for anemia should eat foods high in iron, such as grains and red meat. Magnesium is used in the body for muscle contractions and energy production. Selenium acts like an antioxidant in the body to fight off free radical production.