Nutrition 225 Midterm 1 Study Guide: Key Concepts and Mechanisms

Science of Nutrition

Factors Influencing Food Choice

Food choices are influenced by a variety of factors, with taste being one of the most significant. Other influences include cultural preferences, health concerns, availability, and social factors.

• Taste: Primary determinant for most individuals.

• Additional info: Other factors may include cost, convenience, and advertising.

Tools for Healthful Eating

Experimental vs. Observational Research

Nutrition science relies on both experimental and observational research to understand dietary impacts.

• Experimental Research: Researcher assigns interventions (e.g., diet, supplement) to participants.

• Observational Research: Researcher observes existing behaviors and looks for associations.

• Key Difference: Experimental research can establish causation; observational research identifies correlations.

Dietary Reference Intakes (DRIs)

DRIs are a set of reference values used to assess and plan nutrient intakes.

• EAR (Estimated Average Requirement): Meets needs of 50% of a specific group.

• RDA (Recommended Dietary Allowance): Meets needs of 97–98% of a group.

• UL (Tolerable Upper Intake Level): Highest daily intake unlikely to cause harm.

Acceptable Macronutrient Distribution Ranges (AMDR)

AMDRs provide recommended ranges for macronutrient intake as a percentage of total calories.

• Carbohydrates: 45–65%

• Fat: 20–35%

• Protein: 10–35%

Label Claims

Food labels may include several types of claims, each regulated differently.

• Nutrient Content Claim: Describes amount of nutrient (e.g., "low sodium").

• Structure/Function Claim: Describes role of nutrient in normal body function (e.g., "Calcium builds strong bones").

• Authorized Health Claim: Links food to reduced disease risk (e.g., "Diets low in saturated fat may reduce heart disease risk").

Mindful Eating S's

Mindful eating encourages awareness and enjoyment of food.

• Smile

• Slow

• Savor

2020 Nutrition Label Updates

Americans are encouraged to consume more of certain nutrients, as reflected in updated nutrition labels.

• Vitamin D

• Iron

• Potassium

• Calcium

Nutrient Density

Nutrient density refers to the amount of nutrients per calorie in a food.

• High Nutrient Density: Spinach, berries, salmon

• Low Nutrient Density: Donuts, soda, candy

The Human Body & Digestion

Enzymes in Digestion and Location of Action

Digestive enzymes break down macromolecules into absorbable subunits. Each enzyme has a specific site of production and action, targeting particular nutrients.

• Salivary Amylase: Produced in salivary glands; acts in mouth; targets carbohydrates.

• Pepsin: Produced in stomach glands; acts in stomach; targets proteins.

• Gastric Lipase: Produced in stomach glands; acts in stomach; targets lipids.

• Pancreatic Amylase: Produced in pancreas; acts in small intestine; targets carbohydrates.

• Trypsin/Chymotrypsin: Produced in pancreas; acts in small intestine; targets proteins.

• Pancreatic Lipase: Produced in pancreas; acts in small intestine; targets lipids.

• Brush Border Enzymes: Produced in small intestine; act in small intestine; target final breakdown of carbohydrates and proteins.

Hormones in Digestion

Digestive hormones regulate the process of digestion by controlling enzyme release, motility, and nutrient absorption.

• Insulin: Signals cells to store glucose; released after eating.

• Glucagon: Signals release of stored glucose; released when blood glucose drops.

• Additional info: Other hormones include gastrin, secretin, and cholecystokinin (CCK).

Transportation of Nutrients

Nutrients are absorbed from the small intestine and transported via two main routes.

• Blood (Portal Vein): Water-soluble nutrients go directly to the liver.

• Lymph: Fat-soluble nutrients enter the lymphatic system before reaching the bloodstream.

Types of Absorption

Absorption mechanisms include passive and active transport.

• Passive Absorption: Nutrients move from high to low concentration without energy.

• Additional info: Active absorption requires energy and carrier proteins.

Carbohydrates

Types of Carbohydrates

Carbohydrates are classified based on their chemical structure.

• Monosaccharides: Single sugar units (e.g., glucose, fructose).

• Disaccharides: Two sugar units (e.g., sucrose).

Parts of a Whole Grain

Whole grains contain three main components, each with unique nutritional benefits.

• Endosperm: Starch-rich center.

• Bran: Fiber-rich outer layer.

• Germ: Nutrient-rich core.

Hormones Insulin and Glucagon

Insulin and glucagon are key hormones in carbohydrate metabolism.

• Insulin: Promotes storage of glucose.

• Glucagon: Promotes release of glucose from storage.

Purpose of Glycogen

Glycogen serves as the body's stored carbohydrate, providing quick access to glucose when needed.

• Stored in: Liver and muscles.

• Function: Maintains blood glucose during fasting or intense activity.

4-4-9 Rule for Calculating Calories

The 4-4-9 rule helps determine the caloric value of macronutrients.

• Protein: 4 kcal/gram

• Carbohydrate: 4 kcal/gram

• Fat: 9 kcal/gram

Example Calculation:

• 10g protein x 4 = 40 kcal

• 15g carbs x 4 = 60 kcal

• 5g fat x 9 = 45 kcal

• Total = 145 kcal

$\text{Total Calories} = (\text{Protein grams} \times 4) + (\text{Carbohydrate grams} \times 4) + (\text{Fat grams} \times 9)$

Proteins, Lipids, and Other Nutrients

6 Essential Nutrients

The body requires six essential nutrients for health and function.

• Carbohydrates

• Lipids

• Proteins

• Vitamins

• Minerals

• Water

Nutrition & Genetics

Nutrigenetics

Nutrigenetics studies how individual genetic differences affect responses to nutrients and diet.

• Application: Personalized nutrition recommendations based on genetic profile.

Functional Foods & Phytochemicals

Phytonutrients, Zoochemicals, Functional Foods

Functional foods contain bioactive compounds that provide health benefits beyond basic nutrition.

• Phytonutrients: Natural chemicals made by plants (e.g., flavonoids).

• Zoochemicals: Compounds found in animal-derived foods (e.g., omega-3 fatty acids).

• Functional Foods: Foods with added health benefits (e.g., fortified cereals).

Gut Health

Prebiotics vs. Probiotics

Gut health is supported by both prebiotics and probiotics.

• Probiotics: Live beneficial microbes (bacteria or yeast) that support gut health.

• Prebiotics: Foods that feed beneficial microbes (e.g., fiber).

• Mnemonic: Pro = the bugs; Pre = the food for bugs.

Additional Carbohydrate Terms

Glycogen, Glucagon, Gluconeogenesis, Glycogenolysis, Insulin, Sucrose

These terms describe key processes and molecules in carbohydrate metabolism.

• Glycogen: Stored form of glucose in liver and muscles.

• Glucagon: Hormone released when blood glucose drops; stimulates glycogen breakdown.

• Gluconeogenesis: Formation of glucose from non-carbohydrate sources.

• Glycogenolysis: Breakdown of glycogen to release glucose.

• Insulin: Hormone that promotes glucose uptake and storage.

• Sucrose: Disaccharide composed of glucose and fructose.