Introduction• Early 1900’s the disease
pellagra was widely spread in southern states.
• Symptoms: – diarrhea– skin rash – mental confusion
• Seen in prisons, orphanages, and mental health institutions
Nutrition-Chapter 2 2
Introduction• Initially people believed it was
an infectious disease. But in 1914 Dr. J Goldberger suggested that diet played a role because all those effected had a diet of:– Corn Bread– Hominy grits– Molasses– Potatoes– Cabbage– Rice
• ***Higher income individuals also ate things like meat, milk, and fresh vegetables!***
Nutrition-Chapter 2 3
Introduction• Tested his hypothesis by adding
missing nutritents to diet and saw complete remission of symptoms…still wasn’t supported.
• Did a “filth party” swabbed nose and throats of sick people and then applied them to healthy people…Result: no disease transfer!...No one believed him!
• Wasn’t until 1937 (8 yrs after Goldberger’s death) that another scientist (Elvehjem) discovered niocin (vitamin) in liver extract.
Nutrition-Chapter 2 4
Introduction• More recent example of a
medical hypothesis involved stomach ulcers
• Warren and Marshall in 1982 hypothesized it was not stress but bacteria that caused ulcers after isolating the bacteria Helicobacter pylori from patients
• No one believed them they believed bland diet and antacids were the only treatment while W&M were suggesting antibiotics!
Nutrition-Chapter 2 5
Helicobacter pylori
• To prove it Marshall actually ingested the bacteria and proved it by developing ulcers.
• They were awarded the Nobel Prize in Medicine in 2005
Nutrition-Chapter 2 6
2.1 Understanding the Scientific Method• In the past, nutrition
facts and dietary practices were based on:
• Intuition• Common sense• “Conventional
wisdom”• Anecdotes
• Today, nutrition experts rely on the scientific method to base nutrition recommendations.
Nutrition-Chapter 2 7
Key Terms related to the Scientific Method
• Hypothesis– Possible explanation about an observation
that guides scientific research
• Anecdote– Reports of personal experiences
• Variable– Personal characteristic or other factor that
changes and can influence an outcome
Nutrition-Chapter 2 9
Laboratory Experiments
• An experiment is a systematic way of testing a hypothesis.
• Experiments are often tested on cells or small animals.
• Experiments may be conducted humans.
Nutrition-Chapter 2 10
Experimentation
Most experiments have two groups:– Treatment group:
receives treatment – Control group: does
not receive treatment; human subjects may receive a placebo
What is a placebo? A fake treatment, such
as a sham pill, injection, or medical procedure
Nutrition-Chapter 2 11
Experiments
• In vitro:– “Test tube”
experimenting on parts derived from living organism, such as cells
• In vivo:– Testing on whole living
organisms, such as lab rodents
Nutrition-Chapter 2 12
Human Research:Epidemiological Studies
• Epidemiology is the study of occurrence, distribution, and causes of health problems in populations.
• Two types of epidemiological studies:
– Experimental (intervention)
– Observational
Nutrition-Chapter 2 13
Experimental (Intervention) Epidemiological Studies
• Experimental epidemiological studies can obtain information about health conditions that may have resulted from specific dietary practices.
• Human subjects divided into two groups:– Experimental (receive
treatment)– Control (no treatment—
typically receive placebo)
Nutrition-Chapter 2 14
What Is the Placebo Effect?
• The placebo effect occurs when a person reports a positive (or negative) reaction to a treatment even though he or she received the placebo.
Nutrition-Chapter 2 15
Observational Epidemiological Studies
• Most human epidemiological research is observational.– Case-control study:
individuals who have a health condition are compared with individuals with similar characteristics who do not have the condition.
– Cohort study: study that measures variables in a group of people over time
Nutrition-Chapter 2 16
Epidemiological studies may be:
1. Prospective◦ Means “to look forward”◦ Follows group of healthy
people into the future and looks for factors that may have contributed to changes in their health
2. Retrospective◦ Means “to look back”◦ Examines people’s past
exposures to explain why some people are affected by a condition and not others
Nutrition-Chapter 2 17
Limitations of Epidemiological Studies
• Cannot establish causation, that is, whether a practice is responsible for an effect.
• When two events or observations occur simultaneously within a population, it is not necessarily an indication that one is related to each other.
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Correlations
What is a correlation? A relationship between variables Occurs when two variables change over
the same period◦ Important to understand that some changes
could be coincidences and not the result of “cause and effect” relationships
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Elements of an Experimental Epidemiological Study
1. Reviewing scientific literature
2. Developing a hypothesis
3. Designing the study – Double-blind studies– Reviewing human subjects research designs
4. Conducting human research
5. Analyzing data, drawing conclusions, and reporting findings– Research bias
6. Spreading the news
7. Following up with more research
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Confusion and Conflict
The science of nutrition is constantly evolving.
Old beliefs are discarded and advice changes as nutrition scientists conduct more research and gain greater understanding.
23Nutrition-Chapter 2
Nutrition Information: Fact or Fiction
Be wary of ads for nutrition-related products
that rely on testimonials and anecdotes.
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Be Skeptical of Claims
• Do not assume that information in popular media is reliable.
• First Amendment to U.S. Constitution guarantees freedom of speech.
• Consumers are responsible for questioning and researching accuracy of nutrition information.
25Nutrition-Chapter 2
Ask Questions
What motivates the authors, promoters, or sponsors to provide the information?
Is the source scientific, such as an article in a peer-reviewed nutrition journal?
If a study is cited, how was the research conducted?
Does source cite respected nutrition or medical journals or mention reliable experts?
26Nutrition-Chapter 2
What Is Quackery?
Quackery is promoting useless medical treatments.
Practicing medicine without proper training is illegal.
BUT, providing nutrition information and advice without proper training is legal.
27Nutrition-Chapter 2
Look for Red Flags (Signs of Unreliable Nutrition Information)
Promises of quick and easy remediesPromises of quick and easy remedies
Claims that sound too good to be trueClaims that sound too good to be true
Scare tacticsScare tactics
Personal attacks on registered Personal attacks on registered dietitians or conventional scientistsdietitians or conventional scientists
Statements about the superiority of Statements about the superiority of natural dietary supplementsnatural dietary supplements
28Nutrition-Chapter 2
Look for Red Flags (cont.)
Testimonials and anecdotesTestimonials and anecdotes
Information that promotes a product’s Information that promotes a product’s benefits while overlooking its risksbenefits while overlooking its risks
Vague, meaningless, or scientific-Vague, meaningless, or scientific-sounding termssounding terms
Sensational statements without citing Sensational statements without citing references or sourcesreferences or sources
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Look for Red Flags (cont.)
Recommendations based on a single Recommendations based on a single studystudyInformation concerning nutrients or Information concerning nutrients or human physiology that are not human physiology that are not supported by reliable scientific supported by reliable scientific evidenceevidenceDramatic generalizationsDramatic generalizationsDisclaimers, usually in small or Disclaimers, usually in small or difficult-to-read printdifficult-to-read print
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Using the Internet Wisely
Be careful and consider sources of Internet information
Consider:◦Who or what organization sponsors site?◦ Is information intended to promote a product’s
sales?◦ Is there a comprehensive disclaimer such as
“not responsible or obligated to verify statements?”
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Tips for Searching Nutrition Information on the Internet
1. Use multiple web sites, especially government sites.
2. Be wary of survey sites. 3. Rely on sites reviewed
or managed by health professionals.
4. Look for Health on the Net symbol.
5. Do not trust a site that does not indicate valid sources.
6. Do not trust a site that attacks medical or scientific establishment.7. Avoid sites that provide online diagnoses or treatments.8. Be wary of commercial sites (*.com) even those with links to reliable sites.9. Avoid providing your personal information.
32Nutrition-Chapter 2
Reliable Nutrition Experts
Where do you find factual answers about food or nutrition?◦ There is no standard legal definition for
“nutritionist” or “nutritionalist.”◦ Physicians generally do not have extensive
education in nutrition. Reliable sources of information: college or
university nutrition instructors or registered dietitians.
33Nutrition-Chapter 2
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