PCC BIO 127IN - Tutorial 1B The Science of Nutrition

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Tt il1BTutorial 1BThe Science of Nutrition1The goals of this tutorial are to describe the fll ifollowing:1) the difference between an anecdote and scientific evidence.2) the difference between a clinical indicator from negative clinical outcomes.3) the different types of dietary studies.4) the difference between a correlation and a causal factor.5) What questions to ask when a nutritional study is mentioned in the news5) What questions to ask when a nutritional study is mentioned in the news.6) The role of statistics.27) The Six points of causality.“Anecdotal Evidence”versus ScientificAnecdotal Evidence versus Scientific EvidenceAn “anecdote” is a story, so not surprisingly, “anecdotal Evidence” is based on a story or incident.The following is a true example of a nutritional anecdote.My dad who is in his mid 70s will often get leg cramps atNight, which is annoying because it’s a kind of a rudeNight, which is annoying because it s a kind of a rude Awakening. Well, someone told him to drink orange juiceWhen that happens because it works for him (this other guy).3Anecdotal evidence is really no evidence at all.ecdota e de ce s ea y o e de ce at aThe major reason it isn’t evidence is that it’s not a jproperly controlled evaluation of what’s in question. Scientific evidence, on the other hand is based on the design and execution of an experiment andthe design and execution of an experiment and evaluation of the results.I suggest that if you are not familiar with the scientific method, you read pages 11 -15 in your 4textbook. It’ll make the rest of this tutorial more “palatable”.Negative Clinical Outcomes Versus Clinical IndicatorsI’d like to make a distinction between what you might call “Negative Clinical Outcomes” and “Clinical Indicators”. Either or both of these may be evaluated in a nutritional studyWe can define a negative clinical outcome as a condition that when it occurs has an immediate and significant effect on the individual. The be evaluated in a nutritional study.gmost dramatic of these would be death. This are innumberable negative clinical outcomes but a few of themThis are innumberable negative clinical outcomes but a few of them include a heart attack, stroke, hip fracture, and blindness. I think you get the idea (obviously, there are many many others.)A clinical indicator, on the other hand, is usually a measurement that when it reaches a particular value may indicate that the individual, or lti fidiid l i tik fd l i thi i5population of individuals, is at risk of developing something very serious –that is, some negative clinical outcome .An example of a negative clinical outcome is stroke This is an extremelyAn example of a negative clinical outcome is stroke. This is an extremely serious condition that results in loss of functional brain tissue and often leads to major disability. In fact, more people in the U.S. suffer from disability due to stroke than to Alzheimer’s Diseasedisability due to stroke than to Alzheimer s Disease.A clinical indicator that suggests someone is at risk of getting a stroke isA clinical indicator that suggests someone is at risk of getting a stroke is having consistently high blood pressure – which is of course a measured value.If you are alive, you have blood pressure. And your blood pressure may go up considerably, for example, while exercising. This means that blood pressure is a good thing and even high blood pressure under situations is p essu e s a good t g a d e e g b ood p essu e u de s tuat o s snormal.However, if your blood pressure is consistently high when you are at rest, then this is a clinical indicator that you are at risk of developing a stroke6then this is a clinical indicator that you are at risk of developing a stroke. (We’ll discuss hypertension later in the course in more detail.)Some nutritional studies look at clinical indicators, some at negative clinical outcomes and some look at both It entirely depends on theclinical outcomes , and some look at both. It entirely depends on the study design and goals of the investigators.For example, the oldest longitudinal/epidemiological study (we’ll define what that is shortly) in the U.S. is the one conducted in the town of Framingham Massachusetts. In this study, they are looking at multiple negative clinical outcomes and clinical indicators What’s more they are even looking at this in theclinical indicators. What s more, they are even looking at this in the offspring now of the original study participants in hopes of evaluating genetic influences. In this study investigators are evaluating cause of death, diet, blood pressure, blood cholesterol levels, and various other deat , d et, b ood p essu e, b ood c o este o e e s, a d a ous ot eblood constituents in hopes of establishing links to a number of negative clinical outcomes, such as heart attack, stroke and so on.7The following slide provides a simple illustration that indicates the relationship between a few negative clinical outcomes and clinical indicators.DEATHStrokeHigh Blood CholesterolHigh Blood PressureNegative ClinicalKidney FailureHeart AttackNegative ClinicalOutcomesLfVii(Myocardial Infarction)Loss of VisionBone FractureLow Bone Mineral DensityConsistently High BloodGlucose (in diabetes)8Negative clinical outcome are in red, while clinical indicators are in blue.The following are different types of Nutritional StudiesCase Study (or Case Report)Epidemiological StudyLongitudinal StudyProspective Study (or Follow-up Study)Prospective Study (or Follow-up Study)Dietary Intervention Trial (or clinical trial)Animal Studyy()9The next few slides describe each of these.Case StudiesCase Stud esA case study is one that is based only one individual. That is, all the data comes fromyy,just one person and not a group of subjects.Often the data descriptive, sometimes quantitative, or may even be just a photograph.An example of a case study is given in the following slide. It’s a simple report (published in the New England Journal of Medicine) that presents a radiograph as its dataradiograph as its data.1011Case studies might serve a couple of functions.For one, they might serve to illustrate what can happen under rare unusual or extreme situationshappen under rare, unusual ,or extreme situations.Secondly, they might stimulate ideas (hypothesis) for further experimental studies. Nonetheless, one needs to appreciate their limitation.12Nonetheless, one


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