Nutrition Lecture Notes Flashcards

Nutrition Overview

Definition:

Nutrition is the science studying how the body utilizes nutrients to sustain various physiological functions and maintain overall health. This field encompasses the processes of ingestion, digestion, absorption, metabolism, and excretion of nutrients.

Functions of Nutrition:

• Energy Production: Provides the necessary energy for bodily functions, physical activity, and metabolic processes, approximately 45-65% of total energy should come from carbohydrates.

• Tissue Growth Promotion: Supports the growth and development of tissues, particularly during critical growth phases such as childhood, pregnancy, and post-operative recovery. Proteins play a vital role in this process.

• Regulation: Ensures homeostasis and proper regulation of the body at cellular, tissue, and whole-body levels, including hormone levels and metabolic pathways that regulate factors like blood sugar levels, hydration, and energy use.

• Comprehensive Study: Covers food composition, ingestion, digestion, absorption, transportation of nutrients, and waste disposal, which is crucial for understanding factors that enhance or diminish overall health.

Importance of Human Nutrition

• Supports:

  • Brain Function: Nutrients like omega-3 fatty acids, antioxidants, and B-vitamins are crucial for cognitive development, mood regulation, and memory consolidation.

  • Growth and Development: Critical during periods of rapid growth such as childhood and adolescence, where nutrients support physical, mental, and emotional health.

  • Immune Function Regulation: Adequate nutrition enhances immune responses, with vitamins A, C, D, and minerals like zinc playing significant roles.

  • Homeostasis: Maintains the balance of bodily systems such as temperature regulation, hydration, and pH levels optimizing performance and health.

  • Tissue Repair and Regeneration: Supplies amino acids, vitamins, and minerals necessary for recovery from injuries and during surgical healing.

• Focus: Emphasizes evidence-based science integrating anatomy, physiology, biochemistry, and epidemiology, fostering an understanding of individual nutritional needs, including personalized dietary approaches.

• Caution: The variability in individual responses to food signifies that dietary interventions must acknowledge personalized factors such as genetics, lifestyle, health conditions, and cultural preferences;

• Current Trends: Nutritional science is continuously evolving, with current studies challenging established nutritional guidelines based on outdated or weak methodologies. Emerging research often emphasizes the benefits of whole foods such as fruits, vegetables, whole grains, and limited processed options.

• Research Limitations: Epidemiological studies often rely on self-reported dietary data, posing risks for inaccuracies. Furthermore, industry biases can cloud objectivity in nutritional research interpretations, affecting dietary guidelines.

Scientific Methodology in Nutrition

• Randomized Clinical Trials (RCTs):

  • Considered the gold standard for establishing causality since they effectively control for various confounding factors. RCTs can help illustrate the effects of particular dietary changes over time.

  • Limitations include high costs, ethical concerns when withholding treatment, and logistical challenges, making them less frequent in nutrition research compared to observational studies.

• Epidemiological Data:

  • While useful for identifying trends and associations between diet and disease outcomes, these data often suffer from misinterpretations when setting public health guidelines despite inherent reliability issues.

  • These studies may also overlook underlying biases such as socio-economic factors that affect dietary habits.

• Health Concerns:

  • Alarmingly noting the deterioration in population health linked to poor dietary habits, misinformation, and lack of nutritional education resulting in rising rates of obesity, diabetes, and other non-communicable diseases across many demographics.

Composition of the Human Body

• Elements: The human body comprises 27 of the 100 known elements, with six elements (oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur) being the primary building blocks of biomolecules, reflecting complex biochemical processes.

• Major Elements:

  • Oxygen (63%): Essential element for cellular respiration and energy production.

  • Carbon (18%): The backbone of all biological molecules, including carbohydrates, proteins, and lipids.

  • Hydrogen (9%): A crucial component of water and compounds such as carbohydrates and proteins.

  • Nitrogen (3%): Essential for amino acids, which form proteins and nucleic acids such as DNA and RNA, critical for protein synthesis.

• Body Composition: Roughly 55-65% water, with proteins and lipids together making up 30-40%, and minerals accounting for about 5% of body mass. Water plays a key role in metabolic processes and thermoregulation.

• Nutrient Categories:

  • Macronutrients: Carbohydrates, lipids, and proteins that are needed in larger amounts to provide energy and structural functions. Carbohydrates account for the primary energy source, while proteins are mainly for growth and repair tasks.

  • Micronutrients: Vitamins and minerals required in smaller quantities yet critical for numerous bodily functions such as metabolism, immunity, and bone health. Examples include vitamin C (for immune function) and calcium (for bone health).

  • Essential vs Non-essential Nutrients: Essential nutrients (e.g., omega-3 fatty acids, certain amino acids, vitamins) must be obtained through dietary intake because the body cannot synthesize them. In contrast, non-essential nutrients can be produced internally.

Carbohydrates

• Composition: Carbohydrates are composed of carbon, hydrogen, and oxygen in roughly a 1:1:1 ratio; they represent a primary energy source for the body often referred to as "starches and sugars".

• Types:

  • Monosaccharides: Simple sugars, including glucose (a primary energy source for cells), fructose (found in fruits), and galactose (part of lactose).

  • Disaccharides: Formed by two linked monosaccharides, such as sucrose (table sugar), lactose (milk sugar), and maltose (found in malted foods).

  • Polysaccharides: Complex carbohydrates include starches (energy storage in plants), glycogen (energy storage in animals), and dietary fibers (indigestible components that support gut health).

• Roles: Carbohydrates play a key role in providing energy for metabolic processes and are vital for brain function due to glucose dependency.

• Fiber: An essential component for gastrointestinal function, promoting regularity, and gut health, fiber does not provide energy but aids in nutrient absorption by maintaining digestive health through bulk formation.

Lipids

• Definition: Lipids include a diverse group of naturally occurring organic molecules that are generally insoluble in water but soluble in organic solvents. They include fats, oils, cholesterol, and phospholipids.

• Functions:

  • Energy Storage: Fats provide a concentrated source of energy, more than double that of carbohydrates or proteins, and are crucial for maintaining body heat.

  • Cell Membrane Structure: Lipids are major components of cell membranes, providing structural integrity and fluidity, thanks to phospholipids.

  • Hormone Synthesis: Lipids serve as precursors for steroid hormones and other signaling molecules essential for various physiological processes.

  • Nutrient Absorption: They aid in the absorption of fat-soluble vitamins (A, D, E, K), critical for numerous biochemical functions.

Digestive System Overview

• Stomach Function:

  • The stomach secretes gastric juice, comprising hydrochloric acid (HCl) and digestive enzymes, with a pH ranging from 1.5 to 2.5, which activates pepsinogen into pepsin for efficient protein digestion, thus breaking down food into chyme.

  • The Three phases of gastric secretion: Cephalic (anticipatory), Gastric (stimulated by food), and Intestinal (further digestion and nutrient absorption), each playing a distinct role in the overall digestion process.

• Small Intestine:

  • Serving as the primary site for nutrient digestion and absorption, pre-digested chyme is neutralized by bicarbonate upon entering from the stomach, allowing enzymes to function effectively.

  • The absorptive surface area is significantly increased by structures such as villi and microvilli, facilitating maximal nutrient uptake through active transport and diffusion.

Accessory Organs in Digestion

• Liver: Produces bile, which is essential for the emulsification and digestion of fats, effectively breaking down large lipid globules into smaller droplets, allowing for improved enzyme action; additionally, the liver detoxifies substances and modifies nutrients absorbed by the digestive tract.

• Gallbladder: Stores and concentrates bile produced by the liver until it is needed for digestion, releasing it in response to the hormone cholecystokinin (CCK) when fats enter the small intestine. Gallstones can form when the bile becomes supersaturated with cholesterol or bilirubin, posing potential digestive issues.

• Pancreas: The pancreas produces pancreatic juice containing a wide range of digestive enzymes (amylase, lipase, and proteases) crucial for the final steps of breaking down carbohydrates, fats, and proteins occurring in the small intestine. The hormone secretin stimulates pancreatic enzyme release, helping balance the pH levels in the intestine.

Large Intestine

• Functions: Absorbs leftover water and electrolytes from undigested food; serves as temporary storage for fecal matter while housing beneficial gut flora that aids in nutrient production, synthesizing vitamin K, and maintaining gut health.

• Composition of Feces: Approximately 30% bacteria (gut microbiota), 10-20% fat, and significant undigested fibers contribute to overall digestive health and play a role in preventing conditions such as constipation and colon cancer.

Dietary Fiber and Its Benefits

• Types:

  • Soluble Fiber: Fermentable, health-promoting fiber found in oats, barley, and legumes, effective in lowering cholesterol levels and stabilizing blood glucose levels.

  • Insoluble Fiber: Non-fermentable fiber found in whole grains, nuts, and vegetables; provides bulk to stool and aids with regular bowel movements, preventing constipation.

• Health Effects:

  • Regulates digestion by promoting bowel regularity, enhancing gut health, and reducing the risk of gastrointestinal diseases.

  • Lowers cholesterol levels and produces short-chain fatty acids (SCFAs) beneficial for colonic health and maintaining metabolic processes.

Recommendations for Carbohydrate and Fiber Intake

• Carbohydrates: It is recommended that carbohydrates make up 45% to 65% of total energy intake, predominantly from whole food sources rich in nutrients like fruits, vegetables, and whole grains to maximize their health benefits.

• Added Sugars: Should not exceed 25% of total energy intake; health organizations suggest that intake be as low as 5-10% to foster better health outcomes and prevent associated health issues such as obesity and diabetes.

• Fiber Intake: Daily references suggest a target of 25 grams for women and 38 grams for men to support optimal gastrointestinal health and function.

  • Examples: Consuming whole grains (e.g., brown rice, quinoa), fruits (e.g., apples, bananas), vegetables (e.g., broccoli, carrots), legumes (e.g., beans, lentils), and seeds (e.g., chia, flaxseed) can help meet these recommendations.