Chapter 1: What Is Nutrition? – Foundations of Nutritional Science

What Is Nutrition?

Definition and Scope

Nutrition is the science of food and how it affects the body. It encompasses the study of nutrients in food, how the body uses them, and the relationship between diet, health, and disease. Nutrients are compounds in foods that serve as building blocks for body components and sustain body processes.

• Nutrition: The science of food and its relationship to health and disease.

• Nutrients: Essential compounds in food required for growth, maintenance, and regulation of body processes.

Factors Influencing Food Choices

Determinants of Dietary Habits

• Taste (salty/sweet), texture, and enjoyment

• Culture and environment

• Social life (eating with others, trends)

• Nutrition knowledge

• Advertising

• Time, convenience, and cost

• Habits, routine, and emotions

Example: People may choose foods based on cultural traditions during holidays or special occasions.

Categories of Nutrients

Six Essential Nutrient Classes

• Carbohydrates

• Lipids (fats)

• Proteins

• Vitamins

• Minerals

• Water

These nutrients are required for various physiological functions and must be obtained from the diet.

Non-nutrient Compounds

• Nondigestible fiber

• Phytochemicals (plant-derived) and zoochemicals (animal-derived): Compounds that may provide health benefits but are not classified as nutrients.

• Chemicals added by food manufacturers

Example: Phytochemicals in colorful fruits and vegetables may help prevent cell damage.

Functional Foods

Table: Functional Food Compounds and Benefits

This Compound	Found in This/These Functional Food(s)	May Have This Health Benefit
Beta-carotene	Carrots, pumpkin, cantaloupe, broccoli	Functions as an antioxidant in the body
Lycopene	Tomatoes, tomato sauce	May lower risk of prostate cancer
Soy protein	Tofu, soy milk	Lowers risk of heart disease
Beta-glucan	Oatmeal, oats, oat bran	Lowers blood cholesterol
Plant sterol and stanol esters	Fortified margarines	Lowers blood cholesterol
Omega-3 fatty acids	Salmon, sardines, tuna	May reduce the risk of heart disease
Whole grains	Whole-wheat bread, brown rice, popcorn	May reduce the risk of some cancers and heart disease
Flavanols	Dark chocolate, green apples, cherries	May contribute to heart health
Anthocyanins	Berries, red grapes, cherries	Act as antioxidants, may contribute to brain function
Probiotics	Active cultures in fermented dairy products such as yogurt	Support intestinal health

Chemical Composition of Nutrients

Organic vs. Inorganic Nutrients

• Organic nutrients contain carbon (carbohydrates, lipids, proteins, vitamins).

• Inorganic nutrients do not contain carbon (minerals, water).

Some nutrients also contain hydrogen, oxygen, and nitrogen.

Essential vs. Nonessential Nutrients

Definitions

• Essential nutrients: Must be consumed from food; cannot be synthesized in sufficient quantities by the body.

• Nonessential nutrients: Can be synthesized by the body in adequate amounts.

• Conditionally essential nutrients: Normally nonessential, but become essential under certain conditions (e.g., vitamin D if not exposed to sunlight).

Energy-Yielding Nutrients

Energy and Measurement

• Energy is the capacity to do work, measured in kilocalories (kcal).

• 1 kcal = energy required to raise 1 kg of water by 1°C.

• On nutrition labels, 'Calorie' (uppercase C) refers to kilocalories.

Energy Provided by Nutrients

• Carbohydrate: 4 kcal/gram

• Protein: 4 kcal/gram

• Fat (lipid): 9 kcal/gram

• Alcohol (not a nutrient): 7 kcal/gram

Example Calculation: If an apple contains 25g of carbohydrates: $4 \times 25 = 100$ kilocalories from carbohydrates.

Macronutrients and Micronutrients

Definitions

• Macronutrients: Needed in large amounts (carbohydrates, fats, proteins, water).

• Micronutrients: Needed in small amounts (vitamins, minerals).

Functions of the Major Nutrients

Table: Functions of the Major Nutrients by Type

Nutrient	Provides Energy	Growth, Maintenance, Support, Structure	Regulates Body Processes
Carbohydrates	Yes	No	No
Protein	Yes	Yes	Yes
Fats	Yes	Yes	Yes
Water	No	Yes	Yes
Vitamins	No	No	Yes
Minerals	No	Yes	Yes

Roles of Each Nutrient Class

Carbohydrates

• Composed of carbon, hydrogen, and oxygen.

• Primary function: Supply glucose, the main energy source for body cells, especially red blood cells and the brain.

• Food sources: Breads, cereals, legumes, nuts, fruits, vegetables, and dairy products (the only animal source).

Lipids (Fats)

• Composed of carbon, hydrogen, and oxygen.

• Categories: Triglycerides, phospholipids, sterols.

• Functions: Provide energy, structural component of cell membranes, hormone backbone.

• Food sources: Margarine, butter, oils, animal products.

Proteins

• Composed of carbon, hydrogen, oxygen, and nitrogen.

• Functions: Build and maintain tissues, act as enzymes, neurotransmitters, and immune molecules; secondary energy source.

• Food sources: Meat, poultry, fish, dairy, legumes, soy, nuts, seeds, whole grains, vegetables, some fruits.

Vitamins

• Composed of carbon, hydrogen, and oxygen.

• Function as coenzymes in metabolic reactions.

• Classifications: Water-soluble (B-complex, C; not stored, need daily) and Fat-soluble (A, D, E, K; stored in body).

Minerals

• Inorganic elements essential for body processes and structure (e.g., bone, red blood cells).

• Major minerals: Need at least 100 mg/day; found in amounts ≥5 grams in the body.

• Trace minerals: Need less than 20 mg/day; found in amounts <5 grams in the body.

Water

• Makes up the majority of body fluids and cells.

• Functions: Metabolism, digestion, absorption, nutrient transport, temperature regulation, lubrication, organ cushioning.

• Cannot be stored; must be replenished daily.

Balanced Diet and Supplements

Dietary Recommendations

• Eat a variety of whole foods: whole grains, fruits, vegetables, lean meats, low-fat dairy.

• Functional foods may provide additional health benefits (e.g., phytochemicals, zoochemicals, fiber).

• Supplements are only necessary for those unable to meet nutrient needs through food (e.g., lactose intolerance).

• The supplement industry is not regulated; food sources are preferred.

Diet and Health

Impact of Diet on Disease

• A healthy diet reduces the risk of chronic diseases (heart disease, cancer, stroke, diabetes).

• Maintaining a healthy weight through diet decreases chronic disease risk.

Table: Leading Causes of Death in the United States

Cause	Nutrition Related
Heart disease	X
Cancer	X
Stroke	X
Diabetes	X
Liver disease/cirrhosis	X (alcohol)

Assessing Nutritional Status

Definitions

• Healthy

• Malnourished

• Undernourished

• Overnourished

A Registered Dietitian Nutritionist (RDN) can assess nutritional status using standardized methods.

Table: The ABCDs of Nutrition Assessment

Type of Assessment	Measurements	What They Determine
Anthropometric	Height, weight, BMI, waist-to-hip ratio, waist circumference	Growth, obesity, changes in weight, risk of chronic diseases
Biochemical	Blood, urine, feces	Protein, mineral, vitamin status, disease
Clinical	Physical exam (skin, lips, mouth, muscles, joints, appearance)	Signs of deficiencies/excesses
Dietary Intake	Diet history, diet record, food frequency questionnaire, 24-hour recall	Usual nutrient intake, deficiencies/excesses

Current State of the American Diet

Areas for Improvement

• Excess intake: Added sugar, sodium, saturated fat

• Too little intake: Fiber, some vitamins (D), calcium, potassium, iron (especially in women)

• Poor dietary practices are often linked to eating location and habits (e.g., eating in the car, prepared meals, eating in front of screens).

Evaluating Nutrition Information

Reliable Sources and Misinformation

• Sound nutrition advice is based on consensus from multiple peer-reviewed studies.

• Be cautious of single reports or trends from social media.

Additional info: Peer-reviewed journals and registered dietitians are reliable sources for nutrition information.