Nutrition, Food and Health

Background

• Nutrition
  • AMA – “the science of food, the nutrients and substances therein, their action, interaction, and balance in relation to health and disease, and the process by which the organism ingests, digests, absorbs, transports, utilizes, and excretes food substances”
  • Why study nutrition? What is the importance of nutrition in our lives?
• Food
  • Derived from plants and animals
  • Contains essential and nonessential nutrients
  • Nutrients
    • Chemical substances obtained from food used to provided energy, building materials, and regulators to support growth, maintenance, and repair of the body’s cells and tissues
    • Two main classes: macronutrients and micronutrients (vitamins and trace minerals)
      
• Health
  • Develop and maintain a state of health that is optimal
    • What is optimal?
      
    • Health status is affected by
    • Food choices (diet planning principles, emotional, physical, cultural, etc...)
    • Exercise
  • Poor health and disease states
    • Inadequate or excessive amounts of nutrients cause disease
    • Malnutrition may arise due to poor diets, existing disease states, genetic factors, food availability, etc….
    • Overnutrition occurs as a result of consumption of nutrients beyond need
    • Undernutrition occurs as a result of decreased consumption of nutrients needed

Classes of Nutrients

• Six classes: carbohydrates, lipids, proteins, vitamins, minerals, and water
• Provide energy: Carbohydrates, proteins, lipids
• Promote Growth and Development: Proteins, lipids, vitamins, minerals, water
• Regulate Body Processes: Proteins, lipids, vitamins, minerals, water
• Nutrients
• Organic (carbohydrates, lipids, proteins, vitamins)
• Inorganic (minerals and water)

• Carbohydrates

• Composed of carbon, hydrogen, and oxygen
• Provide major source of fuel (4 kcal per gram)
• Classes: simple sugars (e.g. glucose) and complex sugars
• Lipids

• Composed of carbon, hydrogen, and few oxygen
• Provide more energy than carbohydrates (9 kcal per gram)
• Insoluble in water
• Triglycerides – composed of glycerol and three fatty acids – major source of energy for the body and major form of lipid in foods
• Saturated and unsaturated lipids

• Proteins

• Composed of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur
• Used in construction of the body such as bone and muscle
• Can provide energy (4 kcal per gram)
• Proteins are composed of units called amino acids
• 20 amino acids exist and 9 are essential for adults 10 for infants

• Vitamins

• Enable many reactions to occur in the body
• They themselves don’t provide usable energy
• Thirteen vitamins

• Fat soluble (A, D, E, K)
• Water soluble (B and C)
• Minerals

• Major Minerals
• Trace Minerals

• Water

• Composed of hydrogen and oxygen
• Acts as a solvent and lubricant, medium for transporting nutrients and waste, and a medium for temperature regulation and chemical processes
• Body composed of 60% water – we require 2 liters daily

Nutrient Composition of Diets

• Quantities of various nutrients that people consume vary widely
• Daily intake of protein, lipids, and carbohydrates is around 500 grams
• Daily intake of minerals is around 20 grams
  
• Daily intake of vitamins is around 300 milligrams
• Nutrient composition of the body differs from one person to another
  
• Nutritional profiles of foods we eat determine contribution to nutrient composition of body (...you are what you eat?...)
  
• Thus need guidelines: Daily Values and DRIs
• What about nutrient suppliments? How do they affect diet and health? What are some examples? Are they safe?
  

Energy Sources

• The body's ability to maintain optimal physiology is based on available energy
  
• Food source of energy: carbohydrates, lipids, and proteins
• Foods may provide more than one of these sources of energy
• Alcohol may provide energy (7 kcal per gram) but is not considered a nutrient
• Body transforms the energy trapped in carbohydrate, lipid, and protein into other forms of energy in order to perform many different physiological processes
• Calorie versus Kilocalorie
  • Specific heat (calorie) – energy to raise one gram of water one degree Celsius
  • Dietary Calorie – one kilocalorie (kcal) – 1000 calories
• How do we calculate the energy content of a food item?
  
• 4-9-4 estimates can be used to determine energy content of foods
  • Hamburg:
    • Carbohydrates 39 grams x 4 kcal/gram
    • Fat                               32 grams x 9 kcal/gram
    • Protein                         30 grams x 4 kcal/gram
    • Total                                        564 kcals
  • To determine what portion of total energy intake is contributed by the various energy-yielding nutrients
    • If 1980 kcal consumed in one day
      • % of kcal as carbohydrates = (290 x 4)/1980 = 0.586 or 59%
      • % of kcal as lipids = (60 x 9)/1980 = 0.273 or 27%
      • % of kcal as protein = (70 x 4)/1980 = 0.141 or 14%

North American Diet

• To maintain one's health status, indiciduals need to be able to properly assess their diet
  

  • Assess all aspects of food choices and how they affect the body!

• What influences food choice and behavior?

  • Flavor, texture, and appearance

  • Early exposure to certain foods

  • Routines and habit

  • Our concept of "nutritional" or "healthy"

  • Advertising

  • Restaurants and vending machines

  • Social changes

  • Economics

  • Genetics (cardiovascular disease, obesity, hypertension, diabetes, cancers, osteoporosis, etc...)

  • Cultural influences

• Health promotion and disease prevention: U.S. govenment http://www.healthypeople.gov/

Field of Nutrition

• Science of nutrition developed many years ago
• Many scientists were able to correlate disease states with the lack of certain foods/nutrients
• Thus DRIs were developed to inform people of dietary needs
• Example of major DRI used: RDAs (Recommended Dietary Allowances) for nutrients was published (1943) in recognition of poor nutritional health of many Americans
  • Enables a person to plan and assess intakes
  • Levels are considered adequate to meet needs of healthy people

Scientific Research

• How were the DRI developed?
  
• Scientific research is used to determine amount of nutrients needed by the human body
• Scientific method
  • Observation of a natural phenomenon
  • Suggest explanations (hypothesis)
  • Test hypothesis by performing controlled experiments
  • If many experiments support hypothesis, the hypothesis becomes a theory
  • Nutritional hypotheses established by studying dietary and disease  patterns among various populations
  • Epidemiology (study of disease rates) supports nutritional studies
  • Exam of human experiments performed:
    • Case controlled
    • Double-blind study