Chapter 1: Nutrition Basics Factors that influence food choices Food choices are affected by:

Chapter 1: Nutrition Basics

Factors that influence food choices

Food choices are affected by:

• Taste and personal preference: Flavor, texture, smell, appearance, and cravings.

• Habit and culture: Family traditions, religion, cultural foods, and learned eating patterns.

• Availability and convenience: What foods are accessible, how easy they are to prepare, and time constraints.

• Cost: Food prices, income, and a person’s food budget.

• Nutrition and health goals: Weight management, disease prevention, athletic performance, allergies, and medical conditions.

• Emotions: Stress, boredom, sadness, celebration, or using food as comfort.

• Social influences: Friends, family, advertisements, influencers, and social events.

• Knowledge and beliefs: Nutrition education, personal values, food philosophies, and beliefs about diet.

• Environmental influences: Food marketing, portion sizes, restaurants, school or workplace food availability.

• Physiological needs: Hunger, fullness, thirst, age, pregnancy, activity level, and sleep.

Whole, processed, and ultra-processed foods

• Whole food: A food close to its natural form with little or no processing. Examples: apples, eggs, beans, plain oats, vegetables, and fresh fish.

• Processed food: A whole food that has been altered through cooking, freezing, drying, canning, pasteurizing, or adding ingredients such as salt or sugar. Examples: canned beans, frozen vegetables, whole-grain bread, cheese, and canned tuna.

• Ultra-processed food: An industrially formulated product made mostly from refined ingredients, additives, and substances extracted from foods. It is often highly convenient and packaged. Examples: soda, candy, many packaged snack cakes, instant noodles, and some frozen meals.

Processing is not automatically unhealthy. Frozen vegetables, canned beans, and fortified foods can still provide valuable nutrients; however, a healthy pattern generally emphasizes whole or minimally processed foods.

Six classes of nutrients

1. Carbohydrates

2. Lipids, or fats

3. Proteins

4. Vitamins

5. Minerals

6. Water

Macronutrients and micronutrients

Macronutrients:

• Carbohydrates.

• Fats.

• Proteins.

Macronutrients are needed in relatively large amounts. Carbohydrates, fats, and proteins can provide energy.

Micronutrients:

• Vitamins.

• Minerals.

Micronutrients are required in smaller amounts but are essential for metabolism, growth, immunity, and body regulation.

Calories per gram

Water, vitamins, and minerals do not provide calories.

Calculating calories from macronutrients

Formula:

Calories=grams of nutrient×calories per gramCalories=grams of nutrient×calories per gram

Example:

A food contains:

• 30 grams carbohydrate.

• 10 grams protein.

• 5 grams fat.

Calculation:

• Carbohydrate: 30×4=120

• Protein: 10×4=40

• Fat: 5×9=45

• Total: 120+40+45=205

Calculating the percentage of calories from each macronutrient

Formula:

Percentage from nutrient=calories from nutrienttotal calories×100Percentage from nutrient=total caloriescalories from nutrient​×100

Using the example above:

• Carbohydrate: 120÷205×100=58.5%120÷205×100=58.5%.

• Protein: 40÷205×100=19.5%40÷205×100=19.5%.

• Fat: 45÷205×100=22.0%45÷205×100=22.0%.

The percentages add to approximately 100%.

Dietary Reference Intakes

The Dietary Reference Intakes, or DRIs, are nutrient reference values used to plan and evaluate diets for healthy people.

• RDA — Recommended Dietary Allowance: The average daily intake level that meets the nutrient needs of approximately 97–98% of healthy people in a particular age and sex group.

• EAR — Estimated Average Requirement: The intake level estimated to meet the needs of 50% of healthy people in a specific age and sex group.

• AI — Adequate Intake: A recommended intake used when there is not enough evidence to establish an RDA. It is based on observed or experimentally determined intake levels.

• UL — Tolerable Upper Intake Level: The highest average daily intake unlikely to cause harmful effects for most healthy people. The UL is not a recommended amount to consume.

Nutrition assessment examples

Acceptable Macronutrient Distribution Ranges

The AMDR is the recommended percentage of total daily calories from each energy-yielding macronutrient:

Leading causes of death linked with diet

Diet can contribute to or increase the risk of several major causes of death, especially through high blood pressure, obesity, high cholesterol, diabetes, and chronic inflammation.

Five commonly identified diet-related causes are:

1. Heart disease

2. Cancer

3. Stroke

4. Type 2 diabetes

5. Chronic kidney disease

Heart disease and cancer are currently the two leading overall causes of death in the United States, while stroke, diabetes, and kidney disease are also major conditions influenced by dietary patterns.

Chapter 2: Healthy Eating and Food Labels

Six diet-planning principles

Many introductory nutrition courses identify these six principles:

1. Adequacy: The diet provides enough energy, nutrients, vitamins, minerals, and water to meet the body’s needs.

2. Balance: The diet contains appropriate proportions of different foods and nutrients without overemphasizing one food or nutrient.

3. Variety: The diet includes many different foods from all major food groups.

4. Moderation: Foods high in added sugar, saturated fat, sodium, and calories are consumed in limited amounts.

5. Nutrient density: A food provides a large amount of nutrients compared with the number of calories it contains.

6. Energy control: Energy intake is balanced with energy expenditure to help maintain a healthy body weight.

Food label interpretation

When reading a Nutrition Facts label, check:

1. Serving size: The amount used for all the nutrition information listed below it.

2. Servings per container: The number of servings in the package.

3. Calories: Calories listed are usually for one serving, not necessarily the entire package.

4. Total fat: Also examine saturated fat and trans fat.

5. Cholesterol and sodium: Nutrients many people need to limit.

6. Total carbohydrate: Includes dietary fiber and total sugars.

7. Added sugars: Sugars added during processing or preparation.

8. Protein: Grams of protein per serving.

9. Vitamins and minerals: Pay attention to nutrients such as vitamin D, calcium, iron, and potassium.

10. Percent Daily Value: Shows how much one serving contributes to a general daily reference diet.

Serving size calculations

If a package contains multiple servings:

Total calories=calories per serving×number of servings eatenTotal calories=calories per serving×number of servings eaten

Example:

• One serving = 150 calories.

• You eat 2.5 servings.

150×2.5=375 calories150×2.5=375 calories

The same calculation applies to fat, carbohydrate, protein, sodium, and other nutrients.

Ingredient list

• Ingredients are listed in descending order by weight.

• The first ingredient is present in the greatest amount.

• Look for whole grains, fruits, vegetables, beans, nuts, and recognizable ingredients near the beginning.

• Added sugars may appear under names such as sugar, syrup, honey, dextrose, maltose, or high-fructose corn syrup.

• A product can contain multiple forms of sugar even if sugar is not the first ingredient.

• The ingredient list and Nutrition Facts label should be considered together.

Nutrients to limit

When following a healthy eating pattern, limit:

• Added sugars: Generally less than 10% of daily calories.

• Saturated fat: Generally less than 10% of daily calories.

• Trans fat: Keep intake as low as possible.

• Sodium: Excess sodium can increase blood pressure.

• Excess calories: Especially from foods low in nutrients.

• Alcohol: If consumed, it should be limited.

The FDA’s updated “healthy” labeling criteria also emphasize limits for added sugars, saturated fat, and sodium.

Why follow a healthy diet?

A healthy diet can:

• Provide energy for daily activities and exercise.

• Supply nutrients needed for growth, repair, and body functions.

• Support a healthy immune system.

• Help maintain a healthy body weight.

• Reduce the risk of heart disease, stroke, type 2 diabetes, some cancers, and other chronic diseases.

• Support brain health, digestion, and bone health.

• Improve athletic performance and recovery.

• Help prevent nutrient deficiencies.

Food-label claims

A health claim must involve both a substance and a disease or health-related condition. A nutrient content claim describes the amount of a nutrient, while a structure-function claim describes normal body structure or function.

Chapter 3: The Digestive System

Main route through the GI tract

Food travels through the following route:

Mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus

Accessory organs that help digestion include:

• Salivary glands.

• Liver.

• Gallbladder.

• Pancreas.

Mouth

• Receives food and begins mechanical digestion through chewing.

• Saliva moistens food.

• Salivary amylase begins carbohydrate digestion.

• Lingual lipase begins limited fat digestion.

• The tongue forms food into a bolus for swallowing.

Esophagus

• Moves the swallowed bolus from the mouth to the stomach.

• Uses peristalsis, which is a series of involuntary, wave-like muscular contractions.

Stomach

• Stores and mixes food.

• Produces hydrochloric acid, which helps denature proteins and destroy many microorganisms.

• Begins significant protein digestion with pepsin.

• Produces intrinsic factor, which is needed for vitamin B12 absorption later in the small intestine.

• Converts the bolus into a semifluid mixture called chyme.

• Absorbs small amounts of water, alcohol, and some medications.

Small intestine

The small intestine includes:

1. Duodenum

2. Jejunum

3. Ileum

Its functions include:

• Completing most chemical digestion.

• Receiving bile from the liver and gallbladder.

• Receiving digestive enzymes from the pancreas.

• Absorbing most nutrients.

• Using villi and microvilli to create a large absorptive surface area.

The majority of nutrient absorption occurs in the small intestine, especially the jejunum.

Large intestine

• Absorbs water and electrolytes.

• Houses bacteria that ferment some undigested carbohydrates and produce certain compounds, including vitamin K.

• Forms and stores feces.

• Includes the cecum, colon, and rectum.

Rectum and anus

• The rectum stores feces temporarily.

• The anus controls elimination of feces through the anal sphincters.

Digestive hormones

Where macronutrient digestion occurs

The pancreas supplies enzymes that digest carbohydrates, proteins, and fats.

Peristalsis

Peristalsis is the involuntary, rhythmic contraction and relaxation of smooth muscles that pushes food and waste through the GI tract.

• It occurs in the esophagus, stomach, small intestine, and large intestine.

• It is different from segmentation, which mixes intestinal contents back and forth.

Absorption in the intestines

Absorption is the movement of digested nutrients from the GI tract into the blood or lymph.

The intestinal lining contains:

• Villi: Fingerlike projections.

• Microvilli: Tiny projections on the cells of the villi.

• Capillaries: Small blood vessels that absorb water-soluble nutrients.

• Lacteals: Lymph vessels that absorb most dietary fats.

Three basic absorption mechanisms

1. Simple diffusion

   • Molecules move from an area of higher concentration to an area of lower concentration.

   • No energy is required.

   • Example: Some fatty acids and fat-soluble substances.

2. Facilitated transport

   • Molecules move down their concentration gradient through a transport protein.

   • No direct energy is required.

   • Example: Some forms of fructose transport.

3. Active transport

   • Molecules move against their concentration gradient.

   • Requires energy and a transport protein.

   • Example: Glucose, galactose, amino acids, and some minerals.

Bloodstream route for absorbed nutrients

Most water-soluble nutrients enter the blood capillaries in the intestinal villi.

Route:

Intestinal capillaries → hepatic portal vein → liver → hepatic vein → inferior vena cava → heart → general circulation

Nutrients transported this way include:

• Glucose and other monosaccharides.

• Amino acids.

• Water-soluble vitamins.

• Minerals.

• Short-chain fatty acids.

• Water.

The liver can store, modify, detoxify, or release nutrients into the circulation.

Lymphatic route for absorbed nutrients

Most dietary fats are packaged into chylomicrons inside intestinal cells.

Route:

Intestinal cells → lacteals → lymphatic vessels → thoracic duct → bloodstream near the left subclavian vein → heart → general circulation

This route is used mainly for:

• Long-chain fatty acids.

• Monoglycerides reassembled into triglycerides.

• Cholesterol.

• Fat-soluble vitamins A, D, E, and K.

Chapter 4: Carbohydrates

Monosaccharides

Monosaccharides are single sugar units.

• Glucose: Main blood sugar and major energy source.

• Fructose: Found in fruit, honey, and some sweeteners.

• Galactose: Found as part of lactose in milk.

Disaccharides

Disaccharides contain two monosaccharides.

Digestive enzymes break disaccharides into monosaccharides before absorption.

Polysaccharides

Polysaccharides are long chains of sugar units.

Examples include:

• Starch: Plant storage carbohydrate.

• Glycogen: Animal storage carbohydrate.

• Fiber: Nondigestible carbohydrate from plant foods.

Glycogen

• Glycogen is the storage form of glucose in animals.

• It is stored mainly in the liver and skeletal muscles.

• Liver glycogen helps maintain blood glucose between meals.

• Muscle glycogen is used primarily by the muscle during activity.

• Glycogen stores are limited and are replenished by eating carbohydrates.

Starch and plant storage forms

Plants store glucose as starch.

The two main forms of starch are:

• Amylose: Mostly straight chains of glucose.

• Amylopectin: Branched chains of glucose.

Starch is stored in foods such as:

• Potatoes.

• Corn.

• Rice.

• Wheat.

• Oats.

• Beans.

• Peas.

Simple versus complex carbohydrates

The terms “simple” and “complex” describe chemical structure, not automatically whether a food is healthy. A piece of fruit contains simple sugar but also provides fiber, vitamins, minerals, and water.

Carbohydrate digestion and enzymes

1. Mouth

   • Salivary amylase begins breaking starch into smaller carbohydrate fragments.

2. Stomach

   • Little carbohydrate digestion occurs because stomach acid inactivates salivary amylase.

3. Small intestine

   • Pancreatic amylase continues starch digestion.

   • Brush-border enzymes complete digestion:

     • Maltase breaks maltose into glucose and glucose.

     • Sucrase breaks sucrose into glucose and fructose.

     • Lactase breaks lactose into glucose and galactose.

     • Isomaltase helps digest branched starch fragments.

4. Absorption

   • Monosaccharides are absorbed into intestinal cells and then enter the bloodstream.

Carbohydrate foods

Examples of foods that contain carbohydrates:

• Fruit.

• Milk and yogurt.

• Bread and pasta.

• Rice and grains.

• Potatoes and corn.

• Beans and peas.

• Sugary foods and beverages.

Complex-carbohydrate foods

Nutrient-dense complex-carbohydrate foods include:

• Oatmeal.

• Brown rice.

• Whole-wheat bread.

• Quinoa.

• Barley.

• Beans.

• Lentils.

• Potatoes with the skin.

• Sweet potatoes.

• Vegetables.

• Whole-grain cereals.

Condensation versus hydrolysis

Condensation reaction

• Joins smaller molecules together to form a larger molecule.

• Removes water.

• Example: Joining monosaccharides to form a disaccharide.

Hydrolysis reaction

• Breaks a larger molecule into smaller molecules.

• Adds water.

• Digestive enzymes use hydrolysis to break down carbohydrates, proteins, and fats.

Memory clue:

• Condensation constructs.

• Hydrolysis hydrates and breaks apart.

Glucose balance

The body maintains blood glucose mainly through the hormones insulin and glucagon.

Insulin

• Released by the pancreas when blood glucose rises, such as after a meal.

• Helps body cells take in glucose.

• Promotes storage of glucose as glycogen.

• Lowers blood glucose.

Glucagon

• Released by the pancreas when blood glucose falls between meals.

• Stimulates glycogen breakdown.

• Stimulates glucose production by the liver.

• Raises blood glucose.

Other hormones that can raise blood glucose include:

• Epinephrine: Helps provide rapid energy during stress or exercise.

• Cortisol: Supports glucose production during prolonged stress.

• Growth hormone: Reduces glucose uptake by some cells and supports blood glucose maintenance.

Alternatives to glucose

When glucose is unavailable or carbohydrate intake is very low, the body can use:

• Stored glycogen: Short-term glucose reserve.

• Fatty acids: Used by many tissues for energy.

• Ketone bodies: Produced by the liver from fat and used by the brain and other tissues when carbohydrate availability is low.

• Amino acids: Can be used to make glucose, although using body protein excessively can lead to loss of muscle tissue.

The brain normally depends heavily on glucose, but during prolonged fasting or very low carbohydrate intake it can use more ketone bodies.

Gluconeogenesis

Gluconeogenesis means “making new glucose.”

• It is the production of glucose from non-carbohydrate substances.

• It occurs primarily in the liver and, to a lesser extent, the kidneys.

• Substrates include amino acids, glycerol from fat, and lactate.

• It helps maintain blood glucose during fasting or carbohydrate restriction.

• If carbohydrate intake remains very low, the body can break down body proteins into amino acids for glucose production. This is one reason severe or prolonged restriction can threaten muscle tissue.

Benefits of starch

Nutrient-rich starches can:

• Provide glucose for energy.

• Replenish muscle glycogen after exercise.

• Provide B vitamins, minerals, and fiber when found in whole grains, beans, and vegetables.

• Support steady energy when eaten as part of a balanced meal.

Choose minimally processed starches more often, such as oats, brown rice, beans, potatoes, and whole-grain bread.

Benefits of fiber

Fiber is a nondigestible carbohydrate found mainly in plants.

Soluble fiber

• Dissolves or swells in water.

• Can help lower blood cholesterol.

• Slows digestion and glucose absorption.

• Supports fullness.

• Sources include oats, beans, apples, citrus fruits, and barley.

Insoluble fiber

• Adds bulk to stool.

• Helps promote regular bowel movements.

• Supports normal movement through the digestive tract.

• Sources include whole grains, wheat bran, vegetables, and the skins of many fruits.

Overall fiber benefits

• Helps prevent constipation.

• Supports a healthy gut microbiome.

• May improve blood glucose control.

• May help regulate cholesterol.

• Can support healthy weight management by increasing fullness.

• Helps replace lower-nutrient foods when obtained from vegetables, fruits, beans, and whole grains.

Important distinction: Fiber can be fermented or partially broken down by gut bacteria, but human digestive enzymes cannot fully digest it.

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