HNES 250: Nutrition Midterm Exam Study Guide – Structured Study Notes

Nutrition: Linking Food and Health

Definition and Importance of Nutrition

• Nutrition is the science that studies the interactions between living organisms and the substances they consume for sustenance, growth, reproduction, and health.

• Nutrition is crucial for maintaining health, preventing disease, supporting growth and development, and optimizing bodily functions.

Types and Classes of Nutrients

• Essential nutrients are nutrients that the body cannot synthesize in sufficient quantities and must be obtained from the diet (e.g., vitamins, minerals, essential fatty acids, essential amino acids).

• Nonessential nutrients can be synthesized by the body and are not required in the diet.

• The six classes of essential nutrients are:

  1. Carbohydrates

  2. Fats (Lipids)

  3. Proteins

  4. Vitamins

  5. Minerals

  6. Water

Dietary Reference Intakes (DRIs)

• DRIs are a set of reference values used to plan and assess nutrient intakes of healthy people. They include:

  • Recommended Dietary Allowance (RDA)

  • Estimated Average Requirement (EAR)

  • Adequate Intake (AI)

  • Tolerable Upper Intake Level (UL)

Assessing Nutritional Status

• Assessment can be done at the individual or population level using:

  • Dietary surveys

  • Biochemical tests

  • Clinical evaluations

  • Anthropometric measurements (e.g., height, weight, BMI)

• Nutrition deficiencies occur when nutrient intake does not meet the body's needs, leading to health problems.

The Scientific Method in Nutrition

• The four steps are:

  1. Observation

  2. Hypothesis

  3. Experimentation

  4. Conclusion

Reliable Sources of Nutrition Information

• Peer-reviewed scientific journals

• Registered dietitians (RDs)

• Government agencies (e.g., USDA, NIH)

• Professional organizations (e.g., Academy of Nutrition and Dietetics)

Designing a Healthful Diet

Components and Principles of a Healthful Diet

• A healthful diet is adequate, moderate, balanced, and varied.

• Diet planning principles include nutrient density, energy balance, and moderation.

Food Labels and Nutrition Facts Panel

• Food labels provide information on serving size, calories, macronutrients, micronutrients, and % Daily Values.

• The Nutrition Facts Panel helps consumers assess the nutritional adequacy of foods.

Types of Label Claims

• Nutrient content claims (e.g., "low fat") describe the level of a nutrient.

• Health claims link a food or nutrient to a reduced risk of disease.

• Structure/function claims describe the effect of a nutrient on normal body structure or function (e.g., "calcium builds strong bones").

Dietary Guidelines for Americans and USDA MyPlate

• The Dietary Guidelines for Americans provide science-based advice for healthy eating patterns.

• USDA MyPlate divides foods into groups and recommends servings and serving sizes for each group.

• Discretionary calories are calories remaining after meeting nutrient needs; they can be used for added sugars, fats, or alcohol.

Moderation and Eating Out

• Practice moderation by controlling portion sizes, choosing nutrient-dense foods, limiting added sugars and fats, and being mindful of frequency of eating out.

The Human Body: Are We Really What We Eat?

Appetite vs. Hunger

• Appetite is the psychological desire to eat, influenced by sensory input, emotions, and environment.

• Hunger is the physiological need for food, regulated by internal cues such as hormones and nutrient levels.

Gastrointestinal System and Digestion

• Major organs: mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.

• Accessory organs: salivary glands, liver, gallbladder, pancreas.

• Each organ contributes to digestion, absorption, and elimination of food.

Key Enzymes and Hormones

• Enzymes: amylase, protease, lipase, lactase, sucrase, maltase.

• Hormones: gastrin, secretin, cholecystokinin (CCK), gastric inhibitory peptide.

Roles of Gallbladder, Pancreas, and Liver

• Gallbladder: stores and releases bile for fat digestion.

• Pancreas: secretes digestive enzymes and bicarbonate.

• Liver: produces bile, processes nutrients, detoxifies substances.

Types of Absorption in the Small Intestine

• Passive diffusion

• Facilitated diffusion

• Active transport

• Endocytosis

Common Digestive Disorders

• Gastroesophageal reflux disease (GERD)

• Ulcers

• Food allergies

• Celiac disease

• Diarrhea

• Constipation

• Irritable bowel syndrome (IBS)

Carbohydrates: Plant-Derived Energy Nutrients

Types of Carbohydrates

• Simple carbohydrates: monosaccharides (glucose, fructose, galactose) and disaccharides (sucrose, lactose, maltose).

• Complex carbohydrates: oligosaccharides and polysaccharides (starch, glycogen, fiber).

Soluble vs. Insoluble Fiber

• Soluble fiber dissolves in water, forms gels, and can help lower blood cholesterol (e.g., oats, beans, apples).

• Insoluble fiber does not dissolve in water and promotes bowel regularity (e.g., whole grains, vegetables).

Digestion and Absorption of Carbohydrates

• Carbohydrates are broken down by enzymes (amylase, maltase, sucrase, lactase) into monosaccharides for absorption.

Role and Recommendations for Carbohydrates

• Primary energy source for the body, especially the brain and red blood cells.

• Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates: 45–65% of total calories.

• Adequate Intake (AI) for fiber: varies by age and gender (e.g., 25–38 g/day for adults).

• Recommended intake of added sugars: less than 10% of total calories.

Health Risks and Food Sources

• Diets high in simple sugars may increase risk of obesity, type 2 diabetes, and dental caries.

• Good sources of carbohydrates: whole grains, fruits, vegetables, legumes, dairy.

• Alternative sweeteners: aspartame, sucralose, stevia.

Diabetes and Alcohol

• Type 1 diabetes: autoimmune destruction of insulin-producing cells.

• Type 2 diabetes: insulin resistance and relative insulin deficiency.

• Hypoglycemia: abnormally low blood glucose.

• Moderate alcohol consumption may have some benefits but also risks; alcohol is metabolized primarily in the liver.

• Alcohol abuse can cause physiological, behavioral, and teratogenic effects (e.g., fetal alcohol syndrome).

Fats: Essential Energy-Supplying Nutrients

Types of Fatty Acids

• Saturated fatty acids: no double bonds; solid at room temperature (e.g., butter).

• Monounsaturated fatty acids: one double bond (e.g., olive oil).

• Polyunsaturated fatty acids: two or more double bonds (e.g., corn oil).

Saturation and Fatty Acid Structure

• Saturation affects the shape and physical state of fatty acids.

• Cis fatty acids: hydrogens on the same side of the double bond; trans fatty acids: hydrogens on opposite sides, often produced by hydrogenation.

Essential Fatty Acids

• Linoleic acid (omega-6) and alpha-linolenic acid (omega-3) are essential for health.

Digestion, Absorption, and Transport of Fats

• Fats are emulsified by bile, digested by lipases, absorbed as fatty acids and monoglycerides, and transported in chylomicrons.

Functions and Recommendations

• Fats provide energy, support cell structure, and aid in absorption of fat-soluble vitamins.

• Recommended intake: total fat 20–35% of calories, saturated fat less than 10%, essential fatty acids as per DRIs.

• Sources of omega-3 fatty acids: fatty fish, flaxseed, walnuts.

Fats and Cardiovascular Disease

• High intake of saturated and trans fats increases risk; unsaturated fats may be protective.

• Lifestyle recommendations: reduce saturated/trans fats, increase physical activity, consume more fruits and vegetables.

Proteins: Crucial Components of All Body Tissues

Types of Amino Acids

• Essential amino acids: must be obtained from the diet.

• Nonessential amino acids: can be synthesized by the body.

• Conditionally essential amino acids: required in the diet only under certain conditions (e.g., illness).

Protein Digestion, Absorption, and Synthesis

• Proteins are digested by proteases into amino acids, absorbed in the small intestine, and used for protein synthesis.

Roles of Amino Acids and Proteins

• Proteins are involved in structure, enzymes, hormones, immune function, and transport.

Protein Quality and Dietary Allowance

• Protein quality depends on amino acid composition and digestibility.

• Limiting amino acid: the essential amino acid in shortest supply in a food protein.

• Complete proteins: contain all essential amino acids (e.g., animal proteins).

• Complementary proteins: combinations of foods that together provide all essential amino acids (e.g., rice and beans).

• Recommended Dietary Allowance (RDA) for protein: $0.8\ \mathrm{g/kg}$ body weight for adults.

Health Risks and Sources

• High-protein diets may stress kidneys and increase risk of dehydration.

• Good protein sources: meat, dairy, legumes, nuts, grains, soy products.

Protein-Related Disorders

• Inadequate intake: kwashiorkor, marasmus.

• Genetic abnormalities: phenylketonuria (PKU), sickle cell anemia.