2.1 Carbohydrates
3 min read•june 18, 2024
are essential nutrients that fuel our bodies. They're broken down into , which provides energy for cells. The body regulates levels through various processes, storing excess glucose as for later use.
Simple carbs are quickly digested, causing rapid blood sugar spikes. Complex carbs and offer slower digestion and more stable energy. also supports digestive health, lowers cholesterol, and may reduce cancer risk. Understanding carb helps make informed dietary choices.
Carbohydrate Metabolism and Nutrition
Carbohydrate metabolism in the body
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- Digestion begins in the mouth with (enzyme) breaking down carbohydrates into smaller units
- continues digestion in the small intestine, further breaking down carbohydrates into (glucose, , )
- Monosaccharides are absorbed through the walls of the small intestine and transported to the liver via the portal vein
- In the liver, fructose and are converted into glucose, which is then stored as (storage form of glucose) or released into the bloodstream to maintain blood sugar levels
- Glucose enters cells via -mediated transport using ()
- Inside cells, glucose undergoes , producing (3-carbon molecule) and (energy currency)
- Pyruvate enters the and in the mitochondria, generating more ATP to power cellular functions
Glucose regulation and storage
- : The process of converting excess glucose into glycogen for storage in the liver and muscles
- : The breakdown of stored glycogen into glucose when blood sugar levels are low
- : The production of glucose from non-carbohydrate sources (e.g., amino acids, lactate) to maintain levels during fasting or prolonged exercise
- : A metabolic state where the body uses fat for energy instead of carbohydrates, often occurring during prolonged fasting or very low-carbohydrate diets
Simple vs complex carbohydrates
- include monosaccharides (glucose, fructose, galactose) and (, , )
- Found in fruits, vegetables, milk, and refined sugars (table sugar, syrup)
- Rapidly digested and absorbed, causing a quick rise in blood glucose levels
- Have a high , meaning they rapidly increase blood sugar
- include (, fiber)
- Found in whole grains (oats, brown rice), legumes (beans, lentils), and vegetables
- Slowly digested and absorbed, leading to a gradual rise in blood glucose levels
- Have a low to moderate , promoting more stable blood sugar
- Blood glucose effects differ between simple and
- Simple carbohydrates cause rapid spikes and drops in blood glucose, which can lead to energy crashes and cravings
- Complex carbohydrates promote more stable blood glucose levels, providing sustained energy and reducing the risk of diabetes and other metabolic disorders
- Fiber helps slow glucose absorption, reducing blood glucose spikes and improving insulin sensitivity
- : A measure that takes into account both the quantity and quality of carbohydrates consumed, providing a more accurate representation of a food's impact on blood sugar levels
Fiber's role in nutrition
- (pectins, gums, mucilages) dissolves in water, forming a gel-like substance
- Found in fruits (apples, citrus), vegetables (carrots, peas), oats, and legumes
- Promotes digestive health by softening stool and preventing constipation
- Feeds beneficial gut bacteria (), supporting a healthy and immune function
- (, hemicellulose, lignin) does not dissolve in water
- Found in whole grains (wheat bran), nuts, and vegetables (cauliflower, green beans)
- Adds bulk to stool and promotes regular bowel movements, preventing constipation and diverticular disease
- Fiber aids in blood glucose control by slowing glucose absorption, helping to maintain stable blood sugar levels, which is particularly beneficial for individuals with diabetes
- Soluble fiber binds to bile acids in the intestine, reducing cholesterol reabsorption and helping lower LDL (bad) cholesterol levels, thus decreasing the risk of cardiovascular disease
- Fiber increases feelings of fullness (satiety) and reduces overall calorie intake, aiding in weight management and obesity prevention
- Adequate fiber intake lowers the risk of certain cancers, particularly colorectal cancer, by promoting healthy bowel function and reducing exposure to carcinogens in the digestive tract
Key Terms to Review (71)
American Diabetes Association: The American Diabetes Association (ADA) is a non-profit organization focused on the prevention, education, and research of diabetes. It provides guidelines for managing diabetes and advocates for policies to improve the lives of those affected by the disease.
Athletes: Athletes are individuals who engage in regular, rigorous physical activity or sports, often with the goal of improving performance and achieving competitive success. Their nutritional needs are unique and tailored to support intense training and recovery.
ATP: ATP, or adenosine triphosphate, is the primary energy currency of living cells. It is a high-energy molecule that stores and transports chemical energy within the body, powering a wide variety of cellular processes essential for life.
Blood glucose: Blood glucose is the concentration of glucose present in the blood, essential for providing energy to body cells. It is tightly regulated by hormones such as insulin and glucagon to maintain homeostasis.
Blood sugar: Blood sugar, also known as blood glucose, is the concentration of glucose present in the bloodstream. It is a critical source of energy for the body's cells and is tightly regulated to maintain metabolic homeostasis.
Carbohydrate loading: Carbohydrate loading is a dietary strategy used to maximize the storage of glycogen in muscles and liver before endurance events. It involves increasing carbohydrate intake while tapering exercise over several days.
Carbohydrate Metabolism: Carbohydrate metabolism is the series of chemical reactions and processes that the body uses to convert carbohydrates from food into energy that can be used by cells throughout the body. It is a crucial aspect of overall energy production and regulation within the human body.
Carbohydrates: Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen that serve as a primary energy source for the body. They are categorized into simple sugars and complex carbohydrates, impacting blood sugar levels differently.
Cellulose: Cellulose is a complex carbohydrate and a major component of plant cell walls. It is indigestible by humans but plays a crucial role in digestive health as dietary fiber.
Complex carbohydrates: Complex carbohydrates are polysaccharides composed of long chains of sugar molecules. They are found in foods like grains, legumes, and vegetables and provide sustained energy due to their slow digestion.
Complex Carbohydrates: Complex carbohydrates, also known as polysaccharides, are large, branched molecules composed of many simple sugar units (monosaccharides) linked together. They serve as important energy storage and structural components in the body and various food sources.
DASH diet: The DASH diet (Dietary Approaches to Stop Hypertension) is an eating plan designed to reduce blood pressure. It emphasizes the consumption of fruits, vegetables, whole grains, and lean proteins while limiting salt, red meat, and added sugars.
Dietary Approaches to Stop Hypertension diet (DASH): The Dietary Approaches to Stop Hypertension (DASH) diet is a nutritional plan focused on reducing blood pressure through balanced intake of nutrients. It emphasizes consumption of fruits, vegetables, whole grains, lean proteins, and low-fat dairy while limiting sodium and saturated fats.
Disaccharides: Disaccharides are carbohydrates composed of two monosaccharide molecules linked together. Common examples include sucrose, lactose, and maltose.
Disaccharides: Disaccharides are a type of carbohydrate composed of two monosaccharide units joined together through a condensation reaction. They serve as an important source of energy and are commonly found in many foods.
Electron Transport Chain: The electron transport chain is a series of protein complexes and electron carriers located in the inner membrane of mitochondria. It is a crucial component of cellular respiration, responsible for the final stage of ATP production through the process of oxidative phosphorylation.
Energy supply: Energy supply refers to the provision of energy that the body requires to perform biological functions. In nutrition, it primarily comes from macronutrients like carbohydrates, fats, and proteins.
Enzymes: Enzymes are biological catalysts that accelerate chemical reactions in the body without being consumed. They play a crucial role in digestion and metabolism.
Fermented foods: Fermented foods are foods and beverages produced through controlled microbial growth and the conversion of food components through enzymatic action. Common examples include yogurt, sauerkraut, kimchi, and kefir.
Fiber: Fiber is a type of carbohydrate that the body cannot digest. It helps regulate the body's use of sugars, keeping hunger and blood sugar in check.
Fiber: Fiber refers to the indigestible parts of plant-based foods that pass through the human digestive system without being broken down. It plays a crucial role in maintaining gut health, managing chronic conditions, and promoting overall wellness.
Fructose: Fructose is a simple sugar, or monosaccharide, that is naturally found in fruits, vegetables, and honey. It is one of the three main dietary sugars, along with glucose and sucrose, and is known for its role in carbohydrate metabolism and potential impacts on the gastrointestinal system.
Galactose: Galactose is a simple sugar (monosaccharide) that is part of the carbohydrate family. It is commonly found in milk and dairy products, often bonded with glucose to form lactose.
Galactose: Galactose is a monosaccharide, a simple sugar that is a C-4 epimer of glucose. It is an important carbohydrate that plays a role in the body's metabolism and gastrointestinal system.
Gluconeogenesis: Gluconeogenesis is the metabolic process by which the body synthesizes glucose from non-carbohydrate precursors, such as amino acids, lactate, and glycerol. This process is essential for maintaining blood glucose levels, especially during periods of fasting or starvation, when the body needs to generate glucose from alternative sources to meet its energy demands.
Glucose: Glucose is a simple sugar and an essential carbohydrate that serves as the primary source of energy for the body's cells. It is crucial in metabolic processes and is regulated by insulin to maintain blood sugar levels.
Glucose Transporter Proteins: Glucose transporter proteins, also known as GLUTs, are a family of membrane-bound proteins responsible for facilitating the transport of glucose across cell membranes. They play a crucial role in regulating glucose homeostasis and energy metabolism within the body.
GLUT4: GLUT4 is a glucose transporter protein that plays a crucial role in the uptake and utilization of glucose by cells, particularly in skeletal muscle and adipose tissue. It is responsible for insulin-stimulated glucose transport, a key process in maintaining blood glucose homeostasis and energy metabolism.
Glycemic index: Glycemic Index (GI) measures how quickly a carbohydrate-containing food raises blood glucose levels. Foods with high GI are rapidly digested and absorbed, causing a swift rise in blood sugar, while low GI foods are absorbed more slowly.
Glycemic Index: The glycemic index is a measure of how quickly a food containing carbohydrates raises blood sugar levels. It provides a numerical value that ranks carbohydrate-containing foods based on their effect on blood glucose levels. This concept is particularly relevant in the context of carbohydrate metabolism, endocrine wellness, and the impact of nutrition on chronic endocrine illnesses.
Glycemic load: Glycemic load (GL) measures the impact of carbohydrate consumption on blood sugar levels, taking into account both the quality (glycemic index) and quantity of carbohydrates. It provides a more comprehensive assessment compared to glycemic index alone.
Glycemic Load: Glycemic load is a measure of the impact of a food on blood sugar levels. It takes into account both the quality and quantity of carbohydrates in a food, providing a more comprehensive assessment of a food's effect on blood glucose compared to the glycemic index alone.
Glycogen: Glycogen is a multi-branched polysaccharide of glucose that serves as a form of energy storage in animals and humans. It is primarily stored in the liver and muscles.
Glycogen: Glycogen is a complex polysaccharide that serves as the primary storage form of glucose in the human body. It is found primarily in the liver and skeletal muscles, where it can be rapidly broken down to provide energy when needed.
Glycogenesis: Glycogenesis is the metabolic process by which glucose molecules are converted and stored as glycogen, the primary carbohydrate storage form in the body. This process is crucial for maintaining blood glucose levels and providing a readily available energy source for the body.
Glycogenolysis: Glycogenolysis is the metabolic process by which glycogen, the storage form of glucose in the body, is broken down to release glucose. This process occurs primarily in the liver and skeletal muscles to provide a readily available source of energy when the body's demand for glucose increases.
Glycolysis: Glycolysis is the metabolic pathway that converts glucose, a six-carbon sugar, into two three-carbon molecules called pyruvate. This process is the first step in cellular respiration and occurs in the cytoplasm of cells, providing a rapid source of energy in the form of ATP.
Insoluble Fiber: Insoluble fiber is a type of dietary fiber that cannot be dissolved in water. It passes through the gastrointestinal tract largely intact, adding bulk to stool and promoting regular bowel movements. This fiber type is an essential component of a healthy diet, with implications across carbohydrate metabolism, gastrointestinal wellness, and overall nutritional strategies.
Insulin: Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels and facilitating the body's use of glucose for energy. It is a key player in carbohydrate metabolism, the function of digestive organs, and the overall health and wellness of the endocrine system.
Ketosis: Ketosis is a metabolic state in which the body primarily uses fat and ketone bodies, rather than glucose, as its main source of energy. This occurs when carbohydrate intake is significantly reduced, forcing the body to shift its fuel source to fat and ketones produced by the liver.
Krebs Cycle: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is a key part of cellular respiration, where the energy stored in glucose and other organic molecules is released and used to produce ATP, the primary energy currency of the cell.
Lactase: Lactase is an enzyme produced in the small intestine that breaks down lactose, a sugar found in milk and dairy products. It is essential for proper digestion of dairy foods.
Lactose: Lactose is a disaccharide sugar found in milk and dairy products. It consists of glucose and galactose molecules linked together.
Lactose: Lactose is a disaccharide sugar found in milk and dairy products. It is composed of two monosaccharides, glucose and galactose, and is a key component of the carbohydrate profile in dairy-based foods.
Lactose intolerance: Lactose intolerance is the inability to digest lactose, a sugar found in milk and dairy products, due to a deficiency of the enzyme lactase. Symptoms commonly include bloating, diarrhea, and abdominal pain after consuming dairy.
Maltose: Maltose is a disaccharide composed of two glucose molecules linked by an α(1→4) bond. It is commonly found in foods like malted grains and is produced during the digestion of starch.
Maltose: Maltose, also known as malt sugar, is a disaccharide composed of two glucose molecules linked together. It is a key intermediate in the digestion and metabolism of carbohydrates, particularly in the breakdown of starch and glycogen.
Mediterranean diet: The Mediterranean diet is a nutritional plan inspired by the traditional eating habits of countries bordering the Mediterranean Sea. It emphasizes whole foods, healthy fats, lean proteins, and abundant fruits and vegetables to promote overall health and well-being.
Metabolism: Metabolism is the set of life-sustaining chemical reactions in organisms that convert food into energy, build and repair tissues, and manage waste. It encompasses catabolic pathways that break down molecules to produce energy, and anabolic pathways that utilize this energy to construct components of cells such as proteins and nucleic acids.
Microbiome: The microbiome refers to the diverse community of microorganisms, including bacteria, viruses, fungi, and protozoa, that reside within the human body, particularly in the gastrointestinal tract. These microorganisms play a crucial role in various aspects of human health and nutrition.
Monosaccharide: A monosaccharide is the simplest form of carbohydrate and consists of a single sugar molecule. Examples include glucose, fructose, and galactose.
Monosaccharides: Monosaccharides are the simplest and most basic units of carbohydrates, serving as the building blocks for more complex carbohydrate structures. They are the primary source of energy for the body and play crucial roles in digestion and the overall functioning of the gastrointestinal system.
Oligosaccharides: Oligosaccharides are short chains of three to ten monosaccharide units. They play a crucial role in gut health by serving as prebiotics and aiding in digestion.
Pancreatic amylase: Pancreatic amylase is an enzyme produced by the pancreas that helps in the digestion of carbohydrates. It breaks down starches into simple sugars which can be absorbed by the body.
Pancreatic Amylase: Pancreatic amylase is an enzyme produced by the pancreas that plays a crucial role in the digestion of carbohydrates. It is responsible for breaking down large, complex carbohydrate molecules into smaller, more easily absorbable sugars.
Plant-forward meal plan: A plant-forward meal plan emphasizes the consumption of plant-based foods while not necessarily excluding animal products. It focuses on incorporating more vegetables, fruits, whole grains, legumes, nuts, and seeds into daily meals to enhance nutritional intake and health benefits.
Polysaccharides: Polysaccharides are complex carbohydrates composed of long chains of monosaccharide units bound together. They play crucial roles in energy storage and structural integrity in living organisms.
Polysaccharides: Polysaccharides are large, complex carbohydrate molecules composed of long chains of monosaccharide units. They serve as important structural and energy-storage compounds in living organisms.
Probiotics: Probiotics are live microorganisms, primarily bacteria, that when consumed in adequate amounts, provide health benefits to the host. They are often referred to as the 'good' or 'friendly' bacteria that reside in the human gastrointestinal tract and play a crucial role in maintaining gut health and overall well-being.
Processed foods: Processed foods are foods that have been altered from their natural state for safety reasons or convenience. These alterations can include canning, freezing, refrigeration, dehydration, and aseptic processing.
Pyruvate: Pyruvate is a key intermediate in carbohydrate metabolism, serving as the final product of glycolysis and the entry point for the citric acid cycle. It is a versatile molecule that plays a central role in energy production within the cell.
Salivary amylase: Salivary amylase is an enzyme produced by the salivary glands that initiates the digestion of carbohydrates in the mouth. It breaks down starches into simpler sugars, aiding in the initial phase of carbohydrate digestion.
Salivary Amylase: Salivary amylase is an enzyme produced in the salivary glands that initiates the breakdown of complex carbohydrates, such as starch, into simpler sugars. It plays a crucial role in the digestion process and is closely connected to the topics of carbohydrate metabolism and the function of the digestive organs.
Simple Carbohydrates: Simple carbohydrates, also known as simple sugars or monosaccharides, are the most basic units of carbohydrates. They are easily digested and absorbed by the body, providing a quick source of energy.
Soluble Fiber: Soluble fiber is a type of dietary fiber that dissolves in water, forming a gel-like substance in the digestive tract. This fiber plays a crucial role in carbohydrate metabolism, gastrointestinal health, and the implementation of nutritional strategies to promote overall wellness.
Starch: Starch is a complex carbohydrate that serves as the primary storage form of glucose in plants. It is a polysaccharide composed of long chains of glucose units and is a major component of many staple foods, providing a significant source of energy for the human diet.
Starches: Starches are complex carbohydrates composed of numerous glucose units linked together. They are a major source of energy found in foods like potatoes, rice, and corn.
Sucrose: Sucrose is a disaccharide composed of glucose and fructose. It is commonly known as table sugar and is widely used in various foods and beverages.
Sucrose: Sucrose is a disaccharide composed of glucose and fructose. It is commonly known as table sugar and is widely used as a sweetener in food and beverages. Sucrose is an important carbohydrate that plays a significant role in the context of carbohydrate metabolism and energy production within the body.
Ultraprocessed foods: Ultraprocessed foods are industrially manufactured foods that contain ingredients not typically used in home cooking, such as additives, preservatives, and artificial flavors. These foods often undergo multiple processing steps and are designed to be convenient and palatable.
Whole foods: Whole foods are minimally processed or unprocessed foods that are as close to their natural state as possible. They include fruits, vegetables, whole grains, nuts, seeds, and legumes.