Chapter 1: Food Choices – Nutrients and Nourishment

Chapter 1 Notes: Food Choices, Nutrients and Nourishment

• The Science of Nutrition

  • Identifies the amount of food we need
  • Recommends best food sources
  • Identifies components in food that are helpful or harmful
  • Helps us make better choices
  • Improves our health
  • Reduces our risk of diseases
  • Increases our longevity

• Why Do We Eat the Way We Do?

  • Personal Preferences
  • Enjoyment
  • Nourishment
  • Age
  • Sensory Influences: Taste, Texture, and Smell
  • Flavor
  • Classic tastes: Sweet, sour, bitter, salty, and umami
  • Emotional and Cognitive Influences
  • Habits
  • Comfort/discomfort foods
  • Food advertising and promotion
  • Eating away from home
  • Food and diet trends
  • Social factors
  • Knowledge of health and nutrition
  • Environmental Influences
  • Economics
  • Food availability
  • Cultural influences
  • Religion

• The Social Ecological Model (Figure 1.8)

  • A framework for nutrition and physical activity decisions
  • Adapted from: CDC NPAO Manual (2008), Institute of Medicine (2005), Story et al. (2008)
  • Emphasizes multiple levels of influence on eating and activity

• The Standard American Diet

  • Healthful aspects: Too few nutrient-dense foods (fruits, vegetables, low-fat dairy, whole grains)
  • Harmful aspects: Too much sodium, solid fat, saturated fat, added sugars

• TABLE 1.1: Average U.S. Consumption vs Recommendations, 2013

  • Based on a 2,000-calorie diet
  • Categories include Meat, eggs, Grains, Vegetables, Dairy, Fruit and nuts
  • Note: Rice data were discontinued; sources: USDA Loss-adjusted Food Availability Data

• Introducing the Nutrients: Definitions and Functions

  • Nutrients – Functions
  • Support normal growth and development
  • Maintain cells and tissues
  • Provide fuel to do physical and metabolic work
  • Regulate body processes
  • Six classes of nutrients
  • Carbohydrates
  • Lipids (fats and oils)
  • Proteins
  • Vitamins
  • Minerals
  • Water

• Figure 1.9: The Six Classes of Nutrients

  • Water is the most important nutrient; essential for survival
  • Macronutrients: carbohydrates, proteins, and fats are needed in larger amounts
  • Micronutrients: vitamins and minerals needed in smaller amounts

• Introducing the Nutrients: Definitions and Examples

  • Definition of nutrients
  • Absence from the diet leads to a specific health change
  • Reintroducing the chemical restores health change
  • Not only chemicals in food: phytochemicals, antioxidants
  • Three general functions (Figure 1.10)
  • (1) Micronutrients, some lipids and proteins, and water regulate body processes (e.g., blood pressure, energy production, temperature)
  • (2) Lipids, proteins, minerals, and water provide structure to bone, muscle, and other cells
  • (3) Macronutrients supply energy to power muscle contractions and cellular functions

• Classifications of Nutrients

  • Macronutrients: carbohydrates, lipids, and proteins
  • Micronutrients: vitamins and minerals
  • Organic (contain carbon): carbohydrates, lipids, proteins, and vitamins
  • Inorganic: minerals and water

• Carbohydrates

  • Energy: ~4 kilocalories per gram
  • Functions: energy source
  • Food sources: grains, vegetables, legumes, fruits, dairy products
  • Notes: includes sugars and starches

• Lipids (fats and oils)

  • Energy: ~9 kilocalories per gram
  • Types: triglycerides (fats and oils), cholesterol, phospholipids
  • Functions: energy source, structure, regulation
  • Food sources: fats and oils, meats, dairy, some plant sources

• Proteins

  • Energy: ~4 kilocalories per gram
  • Made of amino acids
  • Functions: energy source, structure, regulation
  • Food sources: meats, dairy, grains, legumes, vegetables

• Vitamins

  • Total: 13 vitamins
  • Functions: regulate body processes; vital for extracting energy
  • Fat-soluble vitamins: A, D, E, K
  • Water-soluble vitamins: eight B vitamins and vitamin C
  • Food sources: all food groups

• Minerals

  • Macrominerals and microminerals (trace minerals)
  • Functions: structure and regulation
  • Food sources: all food groups

• Water

  • Most important nutrient
  • Functions: temperature control, lubrication of joints, transportation of nutrients and wastes
  • Food sources: beverages and foods

• Nutrients and Energy

  • Energy: the capacity to do work
  • Energy sources: carbohydrates, lipids, protein
  • Measurement: kilocalorie (kcal) – 1,000 calories = 1 kilocalorie
  • Energy-per-gram values (Figure 1.11):
  • Carbohydrate: 4\ \text{kcal/g}
  • Lipids: 9\ \text{kcal/g}
  • Protein: 4\ \text{kcal/g}
  • Alcohol: 7\ \text{kcal/g}
  • Also: energy associated with heating water: 1\ \text{kcal} \text{ raises } 1\ \text{kg water by } 1^{\circ}\text{C}

• Energy in Foods

  • When is a kilocalorie a calorie?
  • Calorie vs Kilocalorie
  • General term for energy in food
  • Typical energy values per gram: Carbohydrate 4 kcal/g, Fat 9 kcal/g, Protein 4 kcal/g, Alcohol 7 kcal/g
  • Visual: energy density per gram (Figure 1.11)

• CALCULATING THE ENERGY AVAILABLE FROM FOODS

  • General formula
  • ext{Total kcal} = (g{carb} \times 4) + (g{protein} \times 4) + (g_{fat} \times 9)
  • Example 1 (Page 25):
  • 275\ g\ \text{carbohydrate} \times 4\ \text{kcal/g} = 1100\ \text{kcal}
  • 75\ g\ \text{protein} \times 4\ \text{kcal/g} = 300\ \text{kcal}
  • 67\ g\ fat \times 9\ \text{kcal/g} = 600\ \text{kcal} \ ( ext{rounded from }603)
  • Total = 2000\ \text{kcal}
  • Example 2 (Page 26):
  • 39\ g\ carb \times 4\ \text{kcal/g} = 156\ \text{kcal}
  • 10\ g\ protein \times 4\ \text{kcal/g} = 40\ \text{kcal}
  • 16\ g\ fat \times 9\ \text{kcal/g} = 144\ \text{kcal}
  • Total = 340\ \text{kcal}

• CALCULATING THE PERCENTAGE OF KILOCALORIES FROM NUTRIENTS

  • Example:
  • g_{carb} \times 4 = \text{carbohydrate kcal}
  • g_{protein} \times 4 = \text{protein kcal}
  • g_{fat} \times 9 = \text{fat kcal}
  • \text{Total kcal} = \text{sum of above}
  • \%\ carbo\ kcal = \frac{\text{carbohydrate kcal}}{\text{Total kcal}} \times 100
  • \%\ protein\ kcal = \frac{\text{protein kcal}}{\text{Total kcal}} \times 100
  • \%\ fat\ kcal = \frac{\text{fat kcal}}{\text{Total kcal}} \times 100
  • Example values (275 g carb, 75 g protein, 67 g fat; Total 2000 kcal):
  • Carbohydrate: 275 \times 4 = 1100\ \text{kcal} \quad \Rightarrow\quad \frac{1100}{2000} \times 100 = 55\%
  • Protein: 75 \times 4 = 300\ \text{kcal} \quad \Rightarrow\quad \frac{300}{2000} \times 100 = 15\%
  • Fat: 67 \times 9 = 603(\approx 600) \ \text{kcal} \quad \Rightarrow\quad \frac{600}{2000} \times 100 = 30\%
  • Be Food Smart: Calculate percentages of calories in food
  • Exercise example: If you need to consume 2,000 kilocalories daily with 35 percent from fat, how many grams of fat are needed per day?

• Diet and Health

  • What does it mean to be healthy?
  • WHO defines health as “a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.”
  • Disease definition and nutrition impact
  • Disease: “an impairment of the normal state of the living animal … that interrupts or modifies the performance of the vital functions.”
  • Food choices are most likely to affect our risk for developing chronic diseases

• Leading Causes of Death in the United States (TABLE 1.3)

  • Rank 1: Heart disease
  • Rank 2: Cancer
  • Rank 3: Chronic lower respiratory diseases
  • Rank 4: Accidents (unintentional injuries)
  • Rank 5: Stroke
  • Rank 6: Alzheimer's disease
  • Rank 7: Diabetes mellitus
  • Rank 8: Influenza and pneumonia
  • Rank 9: Kidney disease
  • Rank 10: Intentional self-harm (suicide)
  • Note: Some causes are conditions for which nutrition is important in prevention or treatment
  • Source: CDC/NCHS Leading Causes of Death (2015)

• Diet and Health: Physical Activity

  • Sedentary lifestyle is a risk factor for chronic disease
  • Role in long-term weight management

• Physical Activity Guidelines (Current)

  • Children and adolescents: at least 60 minutes daily (should be mostly aerobic)
  • Adults: 150 minutes of moderate-intensity aerobic activity per week with muscle-strengthening activity on ≥ 2 days/week OR 75 minutes of vigorous-intensity aerobic activity per week with muscle-strengthening on ≥ 2 days/week

• Applying the Scientific Process to Nutrition

  • The Scientific Process enables researchers to test the validity of hypotheses
  • Hypothesis: proposed explanation based on limited evidence as a starting point for further investigation
  • Used to expand nutrition knowledge

• Figure 1.12: The Scientific Process (steps)

  • (1) Make observations
  • (2) Formulate a hypothesis
  • (3) Test the hypothesis
  • (4) Analyze data
  • (5) Communicate results

• Common Study Designs in Nutrition Research (Table 1.4)

  • Human studies include:
  • Epidemiological studies: compare disease rates among population groups; identify related conditions or behaviors (e.g., diet, smoking); can show correlations but not causation; provide clues for further studies
  • Case-control studies: compare individuals with a condition to those without; identify differing factors that may influence disease
  • Clinical trials (randomized, double-blind, placebo-controlled): controlled interventions to determine impact on health parameters; include experimental and control groups
  • Animal studies: provide preliminary data or study hypotheses not testable in humans; results cannot be directly extrapolated to humans; require follow-up with human studies
  • Cell culture studies: isolate cells and study effects of nutrients on metabolic processes in vitro; nutrigenomics explores how nutrients affect gene expression; may explain individual differences in disease risk

• From Research Study to Headline

  • Publishing results in scientific journals; peer review helps ensure quality
  • Transition from journals to public media can lead to sound bites that omit details and mislead

• From Journals to the Public (Media Representation)

  • In-depth research articles become thirty-second sound bites in the media
  • Sorting facts from fallacies in media: popular media may distort facts via omission of details

• Figure 1.14: Sifting facts and fallacies

  • At each step from original research to media, biases can be introduced
  • Best consumer information cites sources for reported facts

• Evaluating Information on the Internet

  • There are no universal rules for posting on the Internet
  • Consider the source
  • Keep the scientific method in mind
  • Be on the lookout for “junk science”

• References and Notes

  • The content includes notes and figures from CDC, Institute of Medicine, and Story et al. regarding the social-ecological model and environmental approaches to healthy eating
  • All material is from the Sixth Edition of Discovering Nutrition by Insel, Ross, McMahon, and Bernstein

• Quick reference formulas and numbers

  • Energy per gram (approximate):
  • Carbohydrates: 4\ \text{kcal/g}
  • Lipids: 9\ \text{kcal/g}
  • Proteins: 4\ \text{kcal/g}
  • Alcohol: 7\ \text{kcal/g}
  • 1 kcal relation to water heating: 1\ \text{kcal} \rightarrow 1\ \text{kg of water by } 1^\circ\text{C}
  • Energy calculations example: combining macronutrient grams to Total kcal via
  • \text{Total kcal} = (g{carb} \times 4) + (g{protein} \times 4) + (g_{fat} \times 9)
  • Percentage calculations example (for a 2,000 kcal diet):
  • \%\ carbo = \dfrac{g_{carb} \times 4}{\text{Total kcal}} \times 100
  • \%\ protein = \dfrac{g_{protein} \times 4}{\text{Total kcal}} \times 100
  • \%\ fat = \dfrac{g_{fat} \times 9}{\text{Total kcal}} \times 100

• Key takeaways

  • Nutrition science blends biology, chemistry, health, and behavior
  • Food choices are influenced by biology, psychology, society, and environment
  • Understanding energy balance and nutrient functions helps make informed dietary choices
  • Critical thinking is essential when interpreting nutrition information in media or online