Human Nutrition Lecture Notes
Foundations of Human Nutrition and Dietary Guidelines
Food directly affects the physical body and influences overall health outcomes.
The body metabolizes food to produce energy necessary for life.
Adequate nutrition is essential to maintaining wellness, whereas inadequate nutrition is a primary contributor to disease.
United States Department of Agriculture (USDA) Dietary Guidelines: - The USDA is the primary source of health information for nutrition educators, policy makers, and healthcare providers. - These standards and guides provide recommendations intended for healthy individuals. - They are not specific to the unique needs of people with metabolic disorders or other medical conditions.
Dietary Guidelines 2020-2025: - Adopt a balanced eating pattern. - Limit the intake of fats. - Include fat-free or low-fat dairy products. - Consume a variety of fresh fruits and vegetables. - Prioritize whole grains and nutrient-dense foods and beverages. - Maintain physical activity. - Limit sodium intake to less than per day, except for African Americans, who should limit intake to less than per day. - Consume alcohol only in moderation. - Practice safe food handling.
Nutrition Facts Label: - Labeling is required and must include: - Serving size and the number of servings per package. - Total calories and calories from fat per serving. - A list of key nutrients present. - Percent Daily Values ().
MyPlate (2011): - Guidelines found at www.choosemyplate.gov providing suggestions for: - Food variety. - Portion size control. - Physical activity. - Tools for successful nutritional lifestyle changes.
Understanding Nutrients and Metabolism
Nutrients: Defined as the building blocks for cells and tissues, they supply energy and help manufacture, maintain, and repair cells.
Macronutrients: Nutrients that supply the body with energy, categorized as carbohydrates, proteins, and lipids.
Micronutrients: Vitamins and minerals that help manufacture, repair, and maintain cells through metabolic processes.
Metabolism: The process by which the body changes and uses nutrients for vital processes and bodily functions. Metabolic reactions are triggered by enzymes and include: - Anabolism: A process that requires energy to build up tissues. - Catabolism: A process that releases energy by breaking down substances.
Carbohydrates: The Primary Energy Source
Carbohydrates provide nearly all the energy for the brain and are the primary energy source for the body.
Simple Carbohydrates: Monosaccharides and disaccharides that are easily and quickly digested to supply energy. - Sources: Corn syrup, honey, milk, table sugar, molasses, sugar cane, sugar beets, and fruits.
Complex Carbohydrates: Polysaccharides that take longer to digest. - Sources: Vegetables, breads, cereals, pasta, grains, and legumes.
Fiber: A type of complex carbohydrate that is not digestible by humans. It provides no usable glucose but aids in the passage of bowel movements.
Metabolic Processes and Storage: - Glucose is stored as glycogen in the liver and muscle tissue. - Glycogenolysis: The conversion of stored glycogen back into glucose for energy when needed. - Gluconeogenesis: The conversion of stored protein and lipids into fuel (ketones) for energy when carbohydrates are unavailable. - Ketones: An alternative fuel source used when glucose is not available.
Functions: - Enhance insulin secretion. - Increase a sense of fullness and satisfaction (satiety). - Supply energy for muscle and organ function.
Proteins: The Building Blocks
Proteins are made up of amino acids, which are the building blocks of most proteins in the body.
Protein Synthesis: Requires all necessary amino acids to be present simultaneously.
Essential Amino Acids: Cannot be synthesized by the body and must be obtained through the diet.
Non-Essential Amino Acids: Can be synthesized by the body.
Classification of Proteins: - Complete Proteins: Foods containing all essential amino acids for protein synthesis. - Incomplete Proteins: Foods that do not provide all essential amino acids (typically non-animal sources). Combining two incomplete proteins (e.g., peanut butter on a whole grain roll) can create a complete protein, which is vital for vegetarian diets.
Functions of Proteins: - Tissue building, growth, maintenance, and repair of cells. - Precursors to digestive enzymes and hormones. - Combine with iron to form hemoglobin. - Immune function: Lymphocytes and antibodies are proteins. - Regulate fluid and acid-base balance. - Serve as a secondary energy source.
Lipids: Fats and Oils
Lipids are insoluble in water. Fats are solid at room temperature, while oils are liquid.
Types of Lipids: - Glycerides: Triglycerides are the main glycerides found in food ( of lipids). - Sterols: Cholesterol is the main type of animal sterol, found in animal proteins and synthesized in the liver. It is necessary for cell membranes, Vitamin D, estrogen, and testosterone, but excess contributes to atherosclerosis. - Phospholipids: Consist of two hydrophobic tails and one hydrophilic head. They are a key component of lipoproteins and transport lipids in the bloodstream.
Lipoproteins: - Low-Density Lipoproteins (LDL): Transport cholesterol to body cells. - High-Density Lipoproteins (HDL): Remove cholesterol from the bloodstream and return it to the liver to produce bile.
Fatty Acids: - Saturated Fatty Acids. - Monosaturated Fatty Acids. - Polyunsaturated Fatty Acids.
Functions of Lipids: - Supply essential nutrients and fatty acids. - Aid in the absorption of fat-soluble vitamins. - Provide energy (body burns fat as needed). - Provide flavor and satiety (creamy taste and texture). - Insulation, protection of vital organs, and thermoregulation. - Enable accurate nerve impulse transmission. - Essential to cell metabolism; critical for brain and nerve function.
Vitamins: Vital Micronutrients
Vitamins cannot be made by the body but are necessary for metabolism and tissue maintenance.
Fat-Soluble Vitamins (A, D, E, K): - Stored primarily in the liver and adipose tissue. - Deficiencies occur in diseases affecting fat digestion or in inadequate diets. - Toxicity is possible because they are not readily excreted. - Vitamin A (Retinol): - Function: Night and color vision, cellular growth, skin/mucous membrane health, skeletal/soft tissue growth, reproduction. - Source: Fish liver oil, liver, butter, cream, egg yolk, yellow fruit, green leafy vegetables, fortified milk. - Vitamin D: - Function: Regulates blood calcium levels and bone resorption/deposit. - Source: Fish liver oil, fish, fortified milk, sunlight exposure. - Vitamin E: - Function: Antioxidant, protects RBCs and muscle tissue, brain health, immune function. - Source: Vegetable oils, nuts, milk, eggs, muscle meats, fish, wheat/rice germs, green leafy vegetables. - Vitamin K: - Function: Synthesis of clotting factors, bone development. - Source: Green leafy vegetables, liver.
Water-Soluble Vitamins (B-Complex and C): - Must be consumed daily as they are not stored; excess is excreted by kidneys. - Vitamin B1 (Thiamin): Energy from glucose, nervous/GI/cardiovascular function. Sources: Whole grains, beef, pork, beans. - Vitamin B2 (Riboflavin): Metabolism, antioxidant, tissue/brain health. Sources: Milk, cheese, eggs, green vegetables. - Vitamin B3 (Niacin): Energy production, cholesterol control. Sources: Chicken, tuna, peanuts, dairy. - Vitamin B5 (Pantothenic Acid): Fat/cholesterol metabolism, heme formation. Sources: Meats, whole grains, legumes. - Vitamin B6 (Pyridoxine): Protein metabolism, RBC production, neurotransmitter synthesis. Sources: Meats, poultry, fish, beans. - Vitamin B9 (Folacin/Folic Acid): DNA synthesis, hemoglobin formation, prevents neural tube defects. Sources: Green leafy vegetables, liver, eggs. - Vitamin B12 (Cyanobalamin): Metabolic reactions, myelin sheath maintenance, DNA formation. Sources: Dairy, meat, poultry, fish. - Vitamin C (Ascorbic Acid): Collagen synthesis, capillary support, antioxidant, iron absorption, immune function. Sources: Citrus fruits, tomatoes, potatoes.
Minerals and Water
Macro Minerals (>100 mg/day): Calcium, Magnesium, Phosphorus, Potassium, Sodium.
Trace Minerals: Essential but in lower concentrations: Copper, Fluoride, Iodine, Iron, Zinc.
Absorption: Mostly in the small intestine; the body self-regulates absorption and excretion.
Functions: Fluid regulation, nerve transmission, energy production, bone/blood health, metabolic waste removal.
Deficiencies and Excesses: - Calcium deficiency: Osteoporosis. - Iron deficiency: Anemia. - Magnesium deficiency: Hypertension and coronary artery disease. - Sodium excess: Hypertension, Myocardial Infarction (MI), Cerebrovascular Accident (CVA).
Mineral Details: - Calcium (Ca): Bone/teeth formation, blood clotting, nerve conduction, heart action. Sources: Dairy, sardines, broccoli. - Potassium (K): Intracellular fluid control, acid-base balance, BP regulation. Sources: Unprocessed foods, avocados, dates. - Sodium (Na): Water balance, acid-base balance, muscle/nerve action. Sources: Table salt, baking soda, celery, spinach. - Fluoride: Resists dental caries. Sources: Fluorinated water, toothpaste, tea. - Iron: Hemoglobin synthesis, drug detoxification in liver. Sources: Meats, spinach, seafood, enriched cereals.
Water: Makes up a large percentage of body weight. It is the site for chemical processes, transports substances, maintains temperature, lubricates joints, and acts as a metabolic catalyst. Intake needs are approximately per day.
Energy Balance and Nutritional Needs Throughout Life
Energy in nutrients is measured in calories.
Energy Balance: Calories in must equal calories burned. Too few leads to undernourishment; too many leads to obesity.
Basal Metabolic Rate (BMR): Energy required at rest for major organ function. Affected by composition, growth, temperature, disease, and physical exertion.
Total Energy Needs: Calories for BMR plus calories for physical activity.
Nutrition in Adults: - Critical nutrients: Protein, Vitamin D, Calcium, Folic Acid, and Iron. - Women of childbearing age should take Folic Acid. - Middle adults face decreased BMR and potential weight gain.
Nutrition in Older Adults: - Need fewer calories but the same nutrient density. - Physical changes: Decreased thirst, taste, and smell. - Barriers: Tooth loss, depression, GERD, decreased gastric secretions, and glucose intolerance.
Vegetarianism Forms: Lacto-ovo, Lacto-vegetarian, Ovo-vegetarian, and Vegan. Risks include being protein, vitamin, or mineral deprived.
Weight Management and Health Assessment
Weight Status: Determined by Body Mass Index (BMI). - Normal: to . - Overweight: BMI but . - Obesity: BMI .
Weight Loss Recommendations (AHA): Calorie restriction, behavior modification, varied nutrient-balanced diet, activity, sleep, and stress reduction.
Physical Assessment: - Clinical signs of poor nutrition: Poor skin turgor, poor wound healing, changes in hair/nails, brittle lips/tongue, concave abdomen, ascites, and edema.
Dietary History Methods: - 24-Hour Recall: Client names all food eaten in one day. - Food Frequency Questionnaire: Identifies how often food groups are eaten over a timeframe. - Food Record (Diary): Most accurate; records quantity and type over time.
Laboratory Values: - Blood Glucose: Normal range fuel. Hyperglycemia () triggers insulin; Hypoglycemia () triggers glucagon. - Albumin: Low levels indicate malnutrition or liver disease; affected by fluid status. - Prealbumin: Fluctuates daily based on protein intake. - Transferrin: Measures protein depletion and iron deficiency. - BUN (Urea): High in kidney impairment or dehydration; low in protein deficiency. - Creatinine: End product of muscle metabolism; high levels indicate kidney impairment.
Nutritional Support and Special Diets
Modified Consistency Diets: Clear liquids, full liquids, mechanical soft, and pureed.
Impaired Swallowing (Dysphagia): Caused by tumors, stroke, or anatomical defects. Interventions include: - High-Fowler’s position during meals. - Chin tuck method. - Avoiding straws. - Using thickening agents. - Checking for food pocketing.
Enteral Nutrition (Tube Feeding): - Delivery of liquid nutrition into the upper intestinal tract via tube. - Risks: Aspiration, infection/pneumonia, diarrhea, and metabolic disturbances. - Tube Types: - Short-term (<6 weeks): Nasogastric (NG), Oropharyngeal, Nasoenteric. - Long-term (>6 weeks): Gastrostomy (G-tube), PEG, Jejunostomy (J-tube). - Feeding Schedules: Continuous (24 hours), Cyclic (night feedings), Intermittent (30-60 mins), and Bolus (5-10 mins via syringe). - Systems: Open system (high contamination risk, 4-hour limit) vs. Closed system (prefilled, 24-48 hour use).
Parenteral Nutrition (IV): - Used when the GI tract is non-functional. - Solutions are hypertonic and administered via a large central vein (e.g., Subclavian or PICC). - TPN: Contains dextrose, amino acids, vitamins, and minerals. - Lipid Emulsions: Provide essential fatty acids and supplemental calories.