Friday, January 3, 2014

Human Nutritional Requirements

Energy-Rich Carbohydrates

Fresh fruits, whole grains, and vegetables—especially legumes such as peas and beans—provide abundant complex carbohydrates . The body breaks the starch in these foods into glucose, your primary source of energy. These foods also provide essential vitamins and fiber. Eating foods high in soluble fiber helps lower one's cholesterol level and may reduce the risk of heart disease. A diet high in insoluble fiber helps prevent constipation.
Foods rich in processed carbohydrates such as white flour, refined sugar, and corn syrup are sometimes said to be lull of "empty calories/' This is a way of saying that these foods provide little in the way of vitamins or fiber.
You may have noticed breads and other grain-based foods labeled as "gluten-free." Gluten is a protein found in  wheat and many other grains. An estimated 1 percent of the population has a genetic disorder called celiac disease, in which gluten causes an autoimmune reaction that harms the small intestine's villi. Celiac disease is treated by eliminating gluten from the diet.

Good Fat, Bad Fat

Your body uses lipids to build cell membranes, as energy stores, and as a reservoir for fat-soluble vitamins.
Linoleic acid and alpha-linolenic acid arc essential fatty acids, meaning the human body needs them but cannot make them, so they are required in the diet. Both are polyunsaturated fats; their long carbon tails include two or more double bonds. Unsaturated fats are liquid at room temperature.
We divide the polyunsaturated fatty acids into two categories: omega-3 fatly acids and omega-6 fatty acids. Omega-3 fatty acids, the main fat in oily fish such as sar dines, seem to have special health benefits. Studies suggest that a diet high in omega-3 fatty acids can reduce the risk of cardiovascular disease, lessen the inflammation associated with rheumatoid arthritis, and help diabetics control their blood glucose. Oleic acid, the main fat in olive oil. may also have health benefits. It is monounsaturated, which means its carbon tails have only one double bond. A diet in which olive oil is substituted for saturated fats helps prevent heart disease.
Dairy products and meats are rich in saturated fats and cholesterol. Overindulging in these foods increases one's risk for heart disease, stroke, and some cancers.
Trans fatty acids, or trans fats, are manufactured from vegetable oils. However, they have a molecular structure that makes them even worse for the heart than saturated fats. All food labels are now required to show the amounts of trans fats, saturated fats, and cholesterol per serving.

Body-Building Proteins

Amino acids are building blocks of proteins. Your cells can make some amino acids but you must get eight essential amino acids from food.Most proteins in meat are "complete," meaning their amino acid ratios match a human's nutritional needs. By contrast, most plant proteins are "incomplete," meaning they lack one or more amino acids essential for the human diet.
The American Dietetic Association states that, with careful planning, a vegetarian diet can provide all essential nutrients for people in any stage of life. To obtain all the required amino acids from plant sources alone, one must combine foods so that the amino acids missing from one component are present in some oth ers. As an example, rice and beans together provide all necessary amino acids, but rice alone or beans alone do not. You do not have to eat the two complementary foods at the same meal, but both should be consumed within a 24-hour period.

Vitamins and Minerals

Vitamins are organic substances that are essential in very small amounts; no other substance can carry out their metabolic functions. At a minimum, human cells require the thirteen vitamins. Minerals are inorganic substances that are essential for growth and survival because no other substance can serve their metabolic functions. Red blood cells require iron to make oxygen-transporting hemoglobin. Iodine is essential for development of a healthy nervous system and to make thyroid hormone.