Six Categories of Nutrients
Carbohydrates, lipids (mostly fats and oils), proteins, vitamins, minerals, and water are the six categories of nutrients that can be found in diet. The majority of the diet is made up of carbohydrates, fats, and proteins, which combined total roughly 500 grams (just over one pound) per day in real weight. These macronutrients supply the building blocks for maintaining and repairing tissues as well as the energy needed to power the numerous physiological and metabolic processes required to sustain life.
The micronutrients, on the other hand, are not themselves energy sources but rather help the body's metabolic processes. Humans require roughly 300 milligrams of vitamins and 20 grams of minerals each day, respectively, from their diets.
A nutrient is deemed "essential" if it needs to be ingested externally, typically through food. Although they are divided into categories for discussion, it's important to remember that nutrients don't function in isolation; rather, they collaborate with one another in the body.
Carbohydrates
With 4 kilocalories per gram, carbohydrates which are made of carbon, hydrogen, and oxygen are the body's main source of energy. The majority of carbohydrates include hydrogen and oxygen in the same proportion of 2:1 as water, hence the terms "carbo" (for carbon) and "hydrate" (for water).
Glucose
The brain, neurological system, and red blood cells all primarily use the simple carbohydrate glucose as fuel. Although fat is frequently employed for this purpose, glucose can also be utilized by muscle and other body cells as an energy source. Because cells require a constant supply of glucose, blood sugar is kept within a relatively small range by a number of hormones, primarily insulin, which controls the flow of glucose into cells, and glucagon and epinephrine, which release glucose from storage.
Glycogen, a complex branched type of carbohydrate that the body stores in the liver and muscle tissue in minute amounts, can be broken down to glucose and used as an energy source during brief (a few hours) fasting periods, as well as during periods of vigorous exercise or stress. Hypoglycemia, or low blood sugar, can cause weakness and lightheadedness.
The majority of carbohydrate types and protein can both be used by the body to produce glucose, despite the fact that protein is typically an expensive source of energy. At least 50 to 100 grams of carbohydrate per day are needed as a minimum in the diet. This prevents a state known as ketosis, which is the buildup of ketones in the body and spares protein while also ensuring that fats are completely digested. Although the amount and kind of carbohydrates consumed around the world varies greatly, most diets provide more than enough.
Dietary Fiber
The absence of the required enzymes prevents the human intestine from breaking down dietary fiber, which makes up the structural components of plants. These indigestible substances nonetheless support health even though they pass through the gut undigested (apart from a small portion that is fermented by bacteria in the large intestine). Insoluble fiber does not dissolve in water and adds bulk (roughage) that promotes regular bowel movements and hastens the body's elimination of chemicals from food that may be carcinogenic or otherwise toxic.
Cellulose, the majority of hemicelluloses, and lignin (a phenolic polymer, not a carbohydrate) are examples of insoluble fiber. Wheat bran, vegetables, whole grain breads and cereals are excellent sources of insoluble fiber. While soluble fiber slows down the time food travels through the gut, which is a negative consequence, it also helps lower blood cholesterol levels, which is a positive one.
Gums, pectins, certain hemicelluloses, and mucilages are the different types of soluble fiber; important food sources of soluble fiber include fruits (particularly citrus fruits and apples), oats, barley, and legumes. Both soluble and insoluble fiber work to postpone the absorption of glucose, guaranteeing a slower and more equal release of glucose into the blood. It is believed that dietary fiber can help prevent several gastrointestinal illnesses.
Lipids
Carbon, hydrogen, and oxygen are also present in lipids, but they are arranged differently and have far fewer oxygen atoms than do carbs. Lipids are insoluble in water and soluble in organic solvents like acetone or ether, a characteristic that is easily observed when an oil-and-vinegar salad dressing separates quickly after standing.
Triglycerides (fats and oils), phospholipids (such as lecithin), and sterols (such as cholesterol) are the lipids of nutritional significance. The four fat-soluble vitamins (A, D, E, and K) are transported by dietary lipids, which also aid in their absorption in the small intestine. Additionally, they transport compounds that give food sensory appeal, palatability, and satiety value—the sensation of being full and pleased after a meal.
With an energy yield of 9 kcal per gram, dietary fats are a more concentrated source of energy than carbs. The body's fat depots include adipose (fatty) tissue, which helps to cushion the internal organs and insulate the body as well as act as an energy reserve.
Proteins
In addition to carbon, hydrogen, and oxygen, which are the same elements found in carbohydrates and lipids, proteins also contain nitrogen, a part of the amino chemical group (NH2), and in some cases sulfur. Proteins play multiple roles in the body's biochemistry, including gene regulation and basic structural support.
Protein makes up the majority of muscles, bones, internal organs, skin, nails, and hair in addition to water. Protein is a crucial component of blood (such as hemoglobin) and cell membranes. Proteins are also found in antibodies, collagen in connective tissue, and several hormones, including insulin, which accelerate chemical reactions in the body.
Amino Acids
The proteins in food, such as albumin in egg white, casein in dairy products, and gluten in wheat, are disassembled into their individual amino acids during digestion and added to the body's metabolic pool after being absorbed. The genetic code and the body's current needs then direct the joining of certain amino acids via peptide links to build particular proteins.
One or more proteins, each with a distinct sequence of amino acids and a particular three-dimensional shape, are produced by each gene. Additionally, amino acids are necessary for the production of a number of significant nonprotein substances, including peptide hormones, a few neurotransmitters, and creatine.
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