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What You Eat and Why
PowerPoint Presentation adapted from
Dana Wu Wassmer, MS, RD
What is nutrition?
Nutrition is
“the science of food, the nutrients and the substances therein, their action, interaction, and balance in relation to health and disease, and the process by which the organism ingests, absorbs, transport, utilizes, and excretes food substances”----The Council on Food and Nutrition of the American Medical Association
Nutrition is the study of
Nutrients in food
Nutrients in the body
Science of Nutrition includes
Anatomy
Physiology
Biochemistry
Medicine
Exercise
Nutrient
Chemical substances in foods that contribute to health, many of which are essential parts of the dietEssential nutrients: substances that, when left out of the diet, lead to poor healthBody can’t make themBody can’t make enough
Body Uses Nutrients for
Energy
Growth
Maintenance
Repair
Regulating body processes
Nutrition is a Young Science
First vitamins were isolated in the 1930s
Most recent vitamin (B12) in 1948
Information is constantly changing and growing based on scientific evidence
Focus of Nutrition is Changing
In the past, the emphasis was on preventing deficiencies
Current Focus
Diet related to disease
Using nutrients to prevent diseasesHeart diseaseHigh blood pressureSome cancersObesityDiabetes
Current Focus
Using nutrients to prevent Problems of agingOsteoporosisMacular degeneration (disease of the
eyes)
Birth defectsSpina bifidaCretinism
Why is nutrition important?
Nutrition and Health
Poor diet and sedentary lifestyle are risk factors for chronic diseases:
Disease of the heart (31% of all deaths)
Cancer (23%)
Cerebrovascular disease (~7%)
Diabetes (3%)
Account for ~2/3 of all death
Prevention
Adequate nutrition
Excess nutrition and obesity
“Affliction of affluence”
Inactivity
Many diseases are preventable
Your choice
Classes of Nutrients
Essential nutrients
Nonessential nutrients
Energy-yielding nutrients
Nutrients for growth, development, and maintenance
Nutrients that regulate body processes
The Six Classes of Nutrients
Carbohydrates
Fats
Proteins
Vitamins
Minerals
Water
The first 3 categories provide Calories
Carbohydrates
Sugars
Starches
Fibers
Carbohydrates
Composed of C, H, O
Provide a major source of fuel for the body
Basic unit is monosaccharide (glucose)
Simple and Complex CHO
Energy yielding (4 kcal /gm)
Carbohydrate Structure
LipidsComposed of C, H and fewer Os
Basic unit is fatty acid
Triglyceride is the major form of lipid
Fats and oils
Lipid Structure
Role of Lipids
Unsaturated Fatty Acids
Saturated Fatty Acids
Essential Fatty Acids
Energy yielding (9 kcal /gm)
ProteinsComposed of C, O, H, NBasic unit is amino acidMake up bones, muscles, other tissues, and components(9) Essential amino acids (11) Nonessential amino acidsEnergy yielding (4 kcal /gm)
Protein Structure
VitaminsComposed of various elements
Organic (contain carbon atoms bound to hydrogen atoms)
Fat soluble
Water soluble
Yield no energy
Role of Vitamins
Vital to life
Regulate body processes
Needed in tiny amounts (micrograms and milligrams)
MineralsInorganic substances (no carbon bound to hydrogen)
Needed in tiny amounts
Not destroyed in cooking
Trace minerals (need <100 mg)
Major minerals (need >100 mg)
Yields no energy
Role of Minerals
Structure
Calcium: bones and teeth
Blood
Iron, copper
Fluid Balance
Sodium, potassium, chloride
WaterComposed of H, OVital to lifeRequire about 8 cups/dayIs a solvent, lubricant, medium for transport, chemical processes, and temperature regulatorMakes up majority of our bodyYields no energy
Phytochemicals
Not nutrients, meaning they aren’t required for life
Reduce disease riskCancerHeart attackAge related blindness
Come only from plants
Phytochemicals Food Sources
Composition
Nutrients French Fries Adult Male
CHO 37% <1%
Protein 4% 16%
Fat 17% 16%
Minerals 1% 6%
Water 41% 62%
Transformation of Energy
1,000 calories = 1 kcal = 1(food) Calorie
CHO PROTEIN FAT ALCOHOL
ENERGY SOURCES
What is a Calorie?
A measurement of energy
“the amount of heat it takes to raise the temperature of 1 gram of water by 1 degree Celsius”
Energy Yielding Nutrients
CHO: 4 kcal/gm
Protein: 4 kcal/gm
Fat: 9 kcal/gm
(Alcohol: 7 kcal/gm)
Adjusted for digestibility
Account for substances (in food) not available for energy use
Contribution to Total Kcals
One day’s intake (1980 kcal)
290 gm of CHO (x 4 kcal/gm)
60 gm of fat (x 9 kcal/gm)
70 gm of protein (x 4 kcal/gm)
% of kcal as CHO= (290 x 4)/1980 = 0.59 or 59%
% of kcal as Fat= (60 x 9)/1980 = 0.27 or 27%
% of kcal as PRO= (70 x 4)/1980 = 0.14 or 14%
Desire to eat
HungerPhysical biological drive
AppetitePsychological drive
Satiety
Regulated by the hypothalamus
Feeding centers
Meal size and composition
Hormones
Influences of Food Choices
Goals of Good Nutrition
Prevent malnutritionDeficiency diseasesOsteoporosis/calciumAnemia/iron, B vitaminsScurvy/vitamin C
Goals of Good Nutrition
Prevent overnutritionExcess intakesCaloriesSaturated FatCholesterolSodium
Nutrition-Related Problems
Obesity
Increasing in all age groups
Excess Calories
Heart disease and strokes
Calories
Saturated fat
Cholesterol
Sodium
Nutrition-Related Problems
Cancer
Excess calories
Excess Fat
Too few fruits/vegetables
Diabetes
Excess calories
How are Nutrition Questions Answered?
Questions askedHypothesis generatedResearch experiments conductedFindings evaluated by investigatorsFindings evaluated by other scientists and publishedFollow-up experiments conducted to confirm or extend the findings
The Scientific Method at Work
Epidemiologial Studies
The study of how disease rates vary among different populationsFor example: How does the rate of stomach cancer in Japan compare with that in Germany?Does not prove cause and effect, but can suggest a relationshipOften a starting point for research
Animal Studies
Animal studies are often a first step in testing a hypothesisAlso, sometimes humans cannot be ethically used as subjects in researchMust find a good “animal model”: a disease in animals that is similar to that in humansFor example, Vitamin C is an essential nutrient in the guinea pig, but not in most other animals
Case Control Study
Individuals who have the condition in question are compared with those who are similar in most respects, but don’t have the disease
For example, middle aged men with lung cancer might be compared with middle aged men who don’t, in order to identify risk factors
Double-Blind Study
Subjects are randomly divided into an experimental group, who receive a given treatment, and a control group, who do not
Sometimes subjects serve as their own control
Neither the subject nor the researcher knows which group the subject belongs to or when they are receiving the active treatment
Example of Hypothesis Testing in Blind Studies
Epidemiological studies revealed that smokers who eat fruits and vegetables had a lower risk of lung cancer
Hypothesis: beta carotene in the fruits and vegetables reduces the damage to the lungs caused by smoke
Hypothesis Testing in Blind Studies
In a double blind study, smokers were given either beta-carotene supplements or placebo
The risk of lung cancer was actually found to be higher in those treated with the beta carotene
Association does not mean causation
Reporting Experimental Results
Peer-reviewed journals
American Journal of Clinical Nutrition
Journal of the American Dietetic Association
New England Journal of Medicine
Evaluating Nutrition Advice
Who said it?CredentialsEducation
Nutrition ExpertsRegistered dietitianBS nutritionADA approved coursesInternshipNational ADA examOhio Licensed dietitian
Where Was it Published?
Scientific journal
Popular magazines
Newspapers
Disreputable source
Evidence
Testimonial
Anecdotal
Poorly-designed experimentSingle studySmall groupShort time framePoorly controlled
Warning Signs
Unaccepted principles
No disadvantages
Claims “cure”
Too good to be true
Bias against medical science
“New” or “secret”
Profit motive