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