Macronutrients Study Notes
Macronutrients Overview
Definition: Essential resources for growth, maintenance, and metabolism.
Requirement: Needed in large amounts, obtained through diet.
Impact: Crucial for proper body function; deficiency causes disease.
Types of Macronutrients
Proteins
Lipids (Fats)
Carbohydrates
Carbohydrates
Composition: Carbon, hydrogen, oxygen.
Main Role: Primary energy source for cellular work, cardiac, and central nervous system function; regulates protein/fat metabolism.
Groups:
Monosaccharides: One sugar unit (e.g., glucose).
Disaccharides: Two sugar units (e.g., sucrose).
Polysaccharides: Three or more sugar units (e.g., glycogen, starch, fiber).
Daily Recommendations (Adults): 135 \text{ grams} or (45-65)\% of total calories.
Simple vs. Complex: Simple provides rapid energy; complex is filling, long-lasting, and nutrient-dense.
Digestion/Absorption: Liver converts sugars to glucose -> insulin release -> glucose enters cells for ATP production. Excess stored as glycogen.
No Sugar: Body uses fats (lipolysis) and proteins (gluconeogenesis) for energy.
Excess Sugar: Increases risks for diabetes, inflammation, hypertension; excess converted and stored as fat.
Fiber: Indigestible; aids digestion, slows sugar absorption, reduces fat absorption.
Proteins
Role: Essential nutrients for growth, repair, and maintenance; building blocks (amino acids).
Composition: Polymers of amino acids linked by peptide bonds.
Amino Acids: Monomers of protein; essential ones must come from diet.
Types:
Complete: Contain all nine essential amino acids (animal sources, soy).
Incomplete: Lack one or more essential amino acids (plant sources).
Complementary: Combinations of incomplete proteins that together supply all essential amino acids.
Functions: Metabolic, tissue building/maintenance, enzymes, hormones, immune support, backup energy.
Health: Deficiency impairs cell/body function; excess amino acids converted to urea and excreted.
Lipids (Fats)
Role: Essential for cell structure/function, temperature regulation, organ protection, vitamin absorption, hormone production, nerve insulation.
Daily Recommendations: (20-35)\% of total caloric intake; (<10)\% saturated fat, (<300 \text{ mg}) cholesterol.
Types:
Triglycerides: (98)\% of dietary fat; attached to glycerol.
Phospholipids: Integral to cell membranes, aid transport (e.g., lecithin).
Sterols: Cholesterol (bile, hormones, cell membrane components).
Health: Excess stored as adipose tissue; high cholesterol (LDL) increases risk of hypertension, heart disease, stroke from plaque buildup.
Fatty Acids:
Saturated: Primarily animal sources, 'trans fats' (raise health risks).
Unsaturated: Healthier; Monounsaturated (olives, avocado), Polyunsaturated (corn, omega--3, omega--6).
Lipoproteins:
LDL (Low-Density Lipoprotein): "Unhealthy" cholesterol, transports cholesterol to cells.
HDL (High-Density Lipoprotein): "Healthy" cholesterol, removes cholesterol from cells to liver for disposal.
Macronutrients Overview
Definition: Essential organic compounds and elements required in significant quantities for the human body to carry out vital functions such as growth, maintenance of tissues, and metabolic processes including energy production and nutrient synthesis.
Requirement: Needed in relatively large amounts daily, typically measured in grams, and must be obtained through balanced dietary intake as the body cannot synthesize them sufficiently on its own.
Impact: Absolutely crucial for the proper physiological functioning of all bodily systems. Deficiencies in any macronutrient can lead to a range of severe health issues, including stunted growth, impaired organ function, reduced energy levels, chronic diseases, and compromised immune response.
Types of Macronutrients
Proteins
Lipids (Fats)
Carbohydrates
Carbohydrates
Composition: Organic compounds primarily composed of carbon (C), hydrogen (H), and oxygen (O) atoms, with a general formula of (CH2O)n.
Main Role: The body's primary and preferred energy source, particularly for high-intensity cellular work, maintaining optimal cardiac function, and providing essential fuel for the central nervous system (brain and nerves), which almost exclusively relies on glucose. They also play a critical role in regulating protein and fat metabolism, preventing ketosis and protein breakdown for energy.
Groups:
Monosaccharides: The simplest form of sugar, consisting of a single sugar unit. Examples include glucose (the body's primary fuel), fructose (found in fruits and honey), and galactose (found in milk, typically as part of lactose).
Disaccharides: Composed of two monosaccharide units linked together. Examples include sucrose (table sugar, formed from glucose + fructose), lactose (milk sugar, formed from glucose + galactose), and maltose (malt sugar, formed from two glucose units).
Polysaccharides: Complex carbohydrates consisting of three or more, often hundreds or thousands, of monosaccharide units. Examples include glycogen (the storage form of glucose in animals, primarily in liver and muscles), starch (the storage form of glucose in plants), and fiber (indigestible plant material).
Daily Recommendations (Adults): Approximately 135 ext{ grams} per day, or (45-65) ext{%} of total daily caloric intake. This range ensures adequate energy supply and nutrient balance.
Simple vs. Complex:
Simple Carbohydrates: (Monosaccharides and Disaccharides) Provide rapid energy due to their quick digestion and absorption, leading to a quick rise in blood glucose. Often found in sugars, candies, and refined grains.
Complex Carbohydrates: (Polysaccharides) Are digested and absorbed more slowly, providing a sustained release of energy. They are generally more filling, nutrient-dense, and often contain fiber, vitamins, and minerals. Examples include whole grains, vegetables, and legumes.
Digestion/Absorption: Digestion begins in the mouth (salivary amylase), continues in the small intestine (pancreatic amylase and disaccharidases). Monosaccharides are absorbed into the bloodstream and transported to the liver via the portal vein. The liver converts all absorbed sugars (fructose, galactose) into glucose. This glucose then circulates in the blood, triggering insulin release from the pancreas, which enables glucose to enter cells for ATP (adenosine triphosphate) production through cellular respiration. Excess glucose is stored as glycogen in the liver and muscles for later use.
No Sugar (Carbohydrates): When dietary sugar or carbohydrate intake is insufficient, the body resorts to alternative energy sources. It primarily uses fats through a process called lipolysis (breakdown of lipids) and, if fat stores are low or demand is very high, proteins through gluconeogenesis (synthesis of glucose from non-carbohydrate precursors like amino acids). Prolonged carbohydrate deprivation can lead to ketosis.
Excess Sugar: Excessive intake of simple sugars and refined carbohydrates significantly increases risks for type 2 diabetes (due to insulin resistance), chronic inflammation, and hypertension. The body converts excess glucose into glycogen. Once glycogen stores are full, the remaining excess glucose is converted and stored as triglycerides (fat) in adipose tissue. This can lead to weight gain, fatty liver disease, and increased cardiovascular risk.
Fiber: Indigestible plant material that passes through the digestive system largely intact. It plays a crucial role in aiding digestion by adding bulk to stool, preventing constipation, and promoting regular bowel movements. Fiber also slows down the absorption of sugars into the bloodstream, helping to stabilize blood glucose levels, and reduces the absorption of dietary fat and cholesterol, contributing to heart health.
Soluble fiber: Dissolves in water, forming a gel-like substance (oats, beans, apples). Helps lower cholesterol and glucose levels.
Insoluble fiber: Does not dissolve in water (whole wheat, nuts, vegetables). Aids in moving material through your digestive system and increases stool bulk.
Proteins
Role: Essential macronutrients vital for growth, repair, and maintenance of all body tissues, including muscles, organs, skin, hair, and nails. They serve as the fundamental building blocks of life, composed of smaller units called amino acids.
Composition: Complex macromolecules that are polymers of amino acids linked together by strong peptide bonds.
Amino Acids: The monomer units of protein. There are 20 common amino acids. Of these, nine are considered essential amino acids (EAA) because the body cannot synthesize them and they must be obtained through the diet. The others are non-essential amino acids, which the body can produce, and conditionally essential amino acids, which become essential under specific physiological circumstances (e.g., illness or stress).
Types:
Complete Proteins: Contain all nine essential amino acids in sufficient quantities. Primarily found in animal sources (e.g., meat, poultry, fish, eggs, dairy) and a few plant sources like soy and quinoa.
Incomplete Proteins: Lack one or more essential amino acids. Abundant in most plant sources (e.g., legumes, nuts, seeds, grains, vegetables).
Complementary Proteins: Combinations of two or more incomplete plant proteins that, when consumed together within a day, collectively provide all nine essential amino acids. Examples include rice and beans, peanut butter on whole-wheat bread, or hummus with pita.
Functions: Proteins perform a vast array of functions:
Metabolic Processes: Many proteins act as enzymes, catalyzing biochemical reactions necessary for life.
Tissue Building/Maintenance: Structural components of cells and tissues, crucial for muscle growth and repair, skin integrity, and bone matrix.
Enzymes: Biological catalysts that speed up chemical reactions in the body (e.g., digestive enzymes).
Hormones: Many hormones are protein-based messengers (e.g., insulin, growth hormone) that regulate physiological processes.
Immune Support: Antibodies, which are proteins, are vital components of the immune system, defending the body against pathogens.
Transport: Proteins like hemoglobin transport oxygen, and others transport nutrients across cell membranes.
Fluid Balance: Help maintain fluid balance between blood and tissues.
Backup Energy: In situations of extreme calorie or carbohydrate deficit, proteins can be broken down for energy through gluconeogenesis.
Health: Protein deficiency, known as malnutrition, impairs virtually all cell and body functions, leading to muscle wasting, weakened immune system, edema, and impaired growth and development. Conversely, excess amino acids are deaminated (nitrogen removed), converted into ammonia (toxic), then into urea in the liver, and finally excreted by the kidneys. While generally harmless in healthy individuals, chronically high protein intake can potentially stress the kidneys or lead to dehydration if water intake isn't sufficient.
Lipids (Fats)
Role: Essential macronutrients for numerous critical bodily functions. They are integral to cell membrane structure and function, regulate body temperature by providing insulation, protect vital organs from shock, facilitate the absorption of fat-soluble vitamins (A, D, E, K), are precursors for hormone production (steroid hormones), and insulate nerve fibers (myelin sheath) for efficient nerve impulse transmission. Also, they are a concentrated source of energy.
Daily Recommendations: Constitute (20-35) ext{%} of total daily caloric intake. Specifically, less than (10) ext{%} of total calories should come from saturated fat, and cholesterol intake should be kept below (300 ext{ mg}) per day for most adults to promote cardiovascular health.
Types:
Triglycerides: The most common type of fat found in food and in the body, making up about (98) ext{%} of dietary fat. They consist of a glycerol backbone linked to three fatty acid molecules. They are the primary form of energy storage in adipose tissue.
Phospholipids: Similar to triglycerides but with one fatty acid replaced by a phosphate group. They are integral components of all cell membranes, forming a lipid bilayer, and play a crucial role in emulsification and aid in the transport of fats in the blood (e.g., lecithin, found in egg yolks and soybeans).
Sterols: Complex lipids characterized by a four-ring carbon structure. Cholesterol is the most well-known sterol and is vital for many functions, including the production of bile acids (for fat digestion), steroid hormones (e.g., estrogen, testosterone, cortisol), and vitamin D, as well as being a structural component of cell membranes.
Health: Excess dietary fat, especially saturated and trans fats, is stored as adipose tissue, leading to weight gain and obesity. High levels of low-density lipoprotein (LDL) cholesterol significantly increase the risk of atherosclerosis (plaque buildup in arteries), hypertension (high blood pressure), heart disease, and stroke. Chronic inflammation and damage to blood vessel walls are also associated with unhealthy fat profiles.
Fatty Acids: The basic units of fat, differing in length and degree of saturation (number of double bonds).
Saturated Fatty Acids: Primarily found in animal sources (e.g., red meat, butter, cheese) and some tropical oils (e.g., coconut oil, palm oil). Their carbon chains contain no double bonds, making them 'saturated' with hydrogen atoms, which contributes to their solid state at room temperature. High intake is generally associated with increased 'bad' (LDL) cholesterol levels and higher risk of heart disease. Trans fats, formed through hydrogenation of unsaturated fats, are a particularly harmful type of saturated fat.
Unsaturated Fatty Acids: Contain one or more double bonds in their carbon chains, giving them kinks that prevent tight packing, making them liquid at room temperature. Generally considered healthier.
Monounsaturated Fatty Acids (MUFAs): Contain one double bond. Found in olives, olive oil, avocados, nuts (almonds, peanuts, pecans), and seeds. They can help lower LDL cholesterol while increasing HDL ('good') cholesterol.
Polyunsaturated Fatty Acids (PUFAs): Contain two or more double bonds. Found in corn oil, soybean oil, safflower oil, and fatty fish. This category includes essential fatty acids: omega--3 (alpha-linolenic acid, EPA, DHA) and omega--6 (linoleic acid). Omega--3 fatty acids are crucial for brain function, growth, and reducing inflammation, found in fatty fish (salmon, mackerel), flaxseeds, and walnuts. Omega--6 fatty acids are important for skin health and cell membranes but high intake relative to omega--3 can promote inflammation.
Lipoproteins: Complexes of lipids and proteins that transport fats in the blood.
LDL (Low-Density Lipoprotein): Often referred to as "unhealthy" or "bad" cholesterol. Its primary function is to transport cholesterol from the liver to cells throughout the body. High levels can lead to cholesterol deposition in arterial walls, forming plaque, which contributes to atherosclerosis and cardiovascular disease.
HDL (High-Density Lipoprotein): Often referred to as "healthy" or "good" cholesterol. Its primary function is to remove excess cholesterol from cells and arterial walls and transport it back to the liver for disposal or reprocessing. Higher levels of HDL are associated with a lower risk of heart disease due to its role in reverse cholesterol transport.