aug27 - REEARCH STUDY RESULTS WHO CAN WE BELIEVE TABLE 1.4...

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Unformatted text preview: REEARCH STUDY RESULTS: WHO CAN WE BELIEVE? TABLE 1.4 Acceptable Macronutrient Distribution Ranges (AMDRs) for Healthful Diets Nutrient Carbohydrate 45—6 5% Fat 20—35% Protein 1 0—3 5% *AMDRvalues are expressed as percent oFtotal energy or as percent of total calories. Somme: Institute ofMedicine, Food and Nutrition Board. 2005. Dietary Reference Intakes fizr Energg Carbohydrates, Fiber; For, Fatty Acids, Cholesterol Protein, andAmino Acids (Macronutrients). Washington, DC: National Academies Press. Reprinted by permission. Calculating Your Unique Nutrient Needs The primary goal of dietary planning is to develop a diet or eating plan that is nutri- tionally adequate, meaning that the chances of consuming too little or too much of. any nutrient are very low. By eating foods that give you nutrient intakes that meet the DRI values, you help your body to maintain a healthful weight, support your daily physical activity, prevent nutrient deficiencies and toxicities, and reduce your risk for chronic disease. The DRI values are listed in a table on the inside cover of this book; they are also reviewed with each nutrient as it is introduced throughout this text. Find your life stage group and gender in the left-hand column, then simply look across to see each nutrient’s value for you. Using the DRI values in conjunction with diet-planning tools such as MyPyramid or the Dietary Guidelines for Americans will ensure a healthful and adequate diet. Chapter 2 provides details on how you can use these tools to develop a healthful diet. 'l RE CAP: The Estimated Energy Requirement (EER) is the average daily energy 'l intake that is predicted to maintain energy balance in a healthy adult. The EER ll is defined by a person’s age, gender; weight, height, and physical activity level. ’ The Acceptable Macronutrient Distribution Ranges (AMDRs) define ranges of V intakes for a particular macronutrient that are associated with reduced risk of I in. chronic disease but also provide adequate levels of essential nutrients. The DRI values can be used to plan diets that are nutritionally adequate and healthful. Research Study 9 Results: Who Can We Beheve . “Eat more carbohydrates! Fats cause obesity!” “Eat more protein and fat! Carbohydrates cause obesity!” Do you ever feel overwhelmed by the abundant and often conflicting advice in media reports related to nutrition? If so, you are not alone. In addition to the “high- carb, low-carb” controversy, we’ve been told that calcium supplements are essential to prevent boneless and that calcium supplements have no effect on bone loss; that high fluid intake prevents constipation and that high fluid intake has no effect on constipation. For years, we were told that coffee and tea could be bad for our health; now, it appears that both may actually contain nutrients that are beneficial! How can you navigate this Sea of changing information? What constitutes valid, reliable evi— dence, and how can you determine whether or not research findings apply to you? To become a more educated cansumer and informed critic of nutrition reports in the media, you need to understand the research process and how the results of differ- ent types of studies should be interpreted. Let’s now learn more about research. 17 1 8 CHAPTER 1 THE ROLE OF NUTRITION IN OUR HEALTH Research Involves Applying the Scientific Method When confronted with a claimabout any aspect of our world, fi'om “The Earth is flat” to “Carbohydrates cause obesity,” scientists, including nutritionists, must first con- sider whether or not the claim can be tested. In other words, can evidence be pre— ' s-ented to substantiate the claim, and if so, what data would qualify as evidence? Scientists Worldwide use a standardized method of looking at evidence called the scientific method. This method ensures that certain standards and processes are used in evaluating claims. The scientific method usually includes the following steps, I which are-described in more detail below and summarized in FIGURE 1.11: 0 The researcher makes an observation and desoription of a phenomenon. - The researcher proposes a hypothesis or educated guess. to explain why the phe- nomenon occurs. The researcher develops an experimental design that will test the hypothesis. 0 The researcher collects and analyzes data that will either support or reject the hypothesis. Ifthe data are rejected, then an alternative hypothesis is proposed and tested. If the data support the original hypothesis, then a conclusion is drawn. m Observations I m Hypothesis I ' Experiment l‘ Modified hypothesisl Observations I M Data do not silppcirt hypothesis l Repeatexperim'ent l Reject hypothesis I Modify hypothesis Accept hypothesis I Theory I FIGURE 1.11 The scientific method, which Forms the framework For scientific research. Step 1: Observations are made regarding some phenomenon, which lead the I researcher to ask a question. Step 2: A hypothesis is generated to explain the observa- tions. Step 3: An experiment is conducted to test the hypothesis. Observations are made during the experiment, and data are generated and documented. Step 4: The n data may either support or refute the hypothesis. If the data support the hypothesis, "‘ more experiments are conducted to test and confirm support For the hypothesis. A hypothesis that is supported after repeated testing may be called a theory. It the data do not support the hypothesis, the hypothesis is either rejected or modified and then i retested. Data-support hypothesis RESEARCH STUDY RESULTS: WHO CAN WE BELIEVE? 19 0 The experiment must be repeatable, so other researchers can obtain similar results. 0 Finally, a theory is proposed offering a conclusion drawn from repeated experi- ments that have supported the hypothesis time and time again. {)hservation of a Phenomenon Initiates the Research Process The first step in the scientific method is the observation and description of a phe- nomenon. As an example, let’s say you are working in a healthcare office that caters to mostly elderly clients. You have observed that many of the elderly have high blood pressure, but there are some who have normal blood pressure. After talking with a large number of elderly clients, you notice a pattern developing in that the clients who report being more physically active are also those having lower blood pressure readings. This observation leads you to question the relationship that might exist between physical activity and blood pressure. Your next step is to develop a hypothesis, or possible explanation for your observation. A Hypothesis Is a Possible Explanation for an Observation A hypothesis is also referred to as a research question. In this example, your hypothesis would be, “If elderly people exercise regularly, then their blood pressure will decrease.” Your hypothesis must be written in a way so that it can be evaluated as either true or false. To evaluate a hypothesis you must collect data and use a reli- able method of analyzing that data. When determining whether a hypothesis is cor- rect or not, three criteria must be met: the hypothesis is testable, unbiased, and repeatable. Determining whether a hypothesis is valid requires a well—thought-out experimental design. An Experiment Is Designed to Test the Hypothesis An experiment is a scientific study that is conducted to test a hypothesis. A well— designed experiment should include several key elements: 0 The sample size or the number of people being studied should be adequate to ' ensure that the results obtained are not due to chance alone. For example, would you be more likely to believe a study that tested five people or five hundred? 0 Having a control group is essential for comparing treated and untreated individu- als. A control group is a group of people who are as much like the treated group as possible except with respect to the variable being tested, for instance, elderly people who do not exercise. Using a control group helps a researcher to judge Whether a particular treatment has worked or not. One way scientists compare data between the experimental and control groups is by plotting variables on a graph. The independent variable is controlled or manipulated by the experi- menter, for example, 45 minutes of aerobic exercise a day. The dependent variable is not manipulated, but simply observed or measured by the experimenter. In the case of your study, this would be the participants’ blood pressure readings. The independent variable is plotted on the horizontal axis {or x-axis) and the depend— ent variable on the vertical axis (or y-axis). - A good experimental design also attempts to control for other variables that may coincidentally influence the results. For example, what if someone in your study was on a diet, smoked, or took blood pressure—lowering medication? Since any of these factors could affect the results, researchers try to design experiments that have as many constants as possible. In doing so, they increase the chance that their results will be valid. To use an old saying, you can think of validity as “Comparing apples to apples.” Data Is Collected and Analyzed to Determine Whether it Supports or Rejects the Hypothesis As part of the design of the experiment, the researcher must determine what kind of data is to be collected and how it will be collected. For example, in your study the data being collected are the blood pressures of various elderly individuals. These val- hypothesis An educated guess as to why a phenomenon occurs. 20 CHAPTER‘] THE ROLE OF NUTRITION IN OUR HEALTH theory A conclusion drawn from repeated experiments. ues could be collected by a person or a machine. An automatic blood pressure gauge would provide the most reliable and consistent data as opposed to blood pressure measurements taken by an individual or several individuals. Consider that the data you’re collecting is evidence that will be closely scrutinized by other scientists. Once the data or evidence has been collected, it must be interpreted or analyzed. Often, the data will begin to make sense only after it has been organized and put into different forms such as tables or graphs that reveal patterns that at first Were not obvious. Most scientific results must have a quantitative aspect to them; in other words, the results have to be measurements that can be compared. In the case of your study you can compare blood pressure readings from both your study participants and the control group to see whether there is a significant difference between the two groups. ReSults must show a certain confidence level or statistical significance. Most scientists insist on a significance level of 95%, which means that the result obtained has a 95% chance of being true. So if you found that the blood pressure numbers in your experimental group and your control group were significantly dif- ferent at the 95% level you could be fairly certain that exercising regularly can lower blood pressure. Most Hypotheses Need to Be Refined Remember that a hypothesis is basically a guesa as to what causes a particular phe- nomenon. Rarely do scientists get it right the first time. The original hypothesis is often refined after the initial results are obtained, usually because the answer to the question is not clear and leads to more questions. When this happens an alternative hypothesis is proposed, a new experiment is designed, and the new hypothesis is tested. It is important to emphasize that one research study does not prove or dis- prove a hypothesis. Ideally, multiple experiments are conducted over many years to thoroughly examine a hypothesis. Science exists to allow us to continue to challenge existing hypotheses and expand what we currently know. .. An Experiment Must Be Repeatable As we just said, one research study does not prove or disprove a hypothesis. Unfortu- nately, media reports on the findings of a research study that has just been pub- lished rarely include a thorough review of the other studies conducted on that topic. Thus, one article in a newspaper or magazine should never be taken as absolute fact on any topic. Repeatability is a cornerstone of scientific investigation. Scientists and skeptics alike must be able to replicate an experiment and arrive at similar conclu- sions or the hypothesis becomes invalid. The experimental design plays a key role in repeatability. Other inveStigators must follow the design of the experiment as closely as possible, using sample sizes and subjects as well as equipment and control measures similar to those used by the initial investigators. Have you ever wondered why the measurements used in scientific textbooks are always in the metric system? The answer is repeatabil- ity. Scientists use the metric system because it is a universal system. It is this ele- . ment of the scientific methodarepeatability—that allows scientists to form : theories. A Theory May Be Developed Following Extensive Research If the results of multiple experiments consistently support a hypothesis, then it is possible to develop a theory. A theory represents a hypothesis or group of related hypotheses that has been confirmed through repeated scientific experiments. Theo- ries are strongly accepted principles, but they can be challenged and changed as a result of applying the scientific method. Remember that, centuries ago, it was theo- rized that the Earth was flat. People were so convinced of this that they refused to sail beyond known boundaries because they believed they Would fall off the edge of the Earth. Only after multiple explorers challenged this theory was it discovered that the Earth is round. We continue to apply the scientific method today to test hypotheses and challenge theories. rejected, then. an alternative hyp port the original hypothesis, then at conclusion is drawn. A hypothesis that is supported afler repeated experiments may be called a theory. ,.;.,al“_iOuS Types of Research Studies Tell Us lilifferent Stories rly peeple. These results do not indicate that reg- EpldémIOIPg'cal studies mdlcate - - - - reiatlonshlps between Factors, such as bemeenlexercise and blood pressure in older adults, but cannot prove cause and effect. 22 CHAPTER 1 THE ROLE OF NUTRITION IN OUR HEALTH These findings would indicate that other factors in addition to physical activity may play a role in affecting the blood pressure levels of elderly people. Clinical trials are tightly controlled experiments in which an intervention is given to determine its effect on a certain disease or health condition. Interventions may include medications, nutritional supplements, controlled diets, or exercise pro— grams. Clinical trials include the experimental group, who are given the interven- tion, and the control group, who are not given the intervention. The responses of the intervention group are compared to those of the control group. In the case of your experiment, you could assign one group of elderly people with high blood pressure to an exercise program and assign a second group of elderly people with high blood pressure to a program in which no exercise is done. After the intervention phase was completed, you could compare the blood pressure of the elderly people who exercised to that of those who did not. lfthe blood pressure of the intervention group decreased and the blood pressure of the control group did not, and if the amount of the decrease was statistically significant, than you could prepose that the exercise program caused a decrease in blood pressure. There are other important things to consider when conducting a quality clinical trial. Ideally, it is best to randomly asaign research participants to intervention and control groups. Randomizing participants is like flipping a coin or drawing names from a hat; doing this reduces prejudice or bias to the assignment of each group. If possible, it is also important to “blind” both researchers and participants to the treat- ment being given. A double-blind experiment is one in which neither researchers nor participants know which group is really getting the treatment. Blinding helps pre- vent the researcher from seeing only the results he or she wants to see. In testing the effectiveness of a medication or nutritional supplement, the blind- ing process can be assisted by the use of a placebo. A placebo is an imitation treat— ment that has no scientifically recognized therapeutic value, for instance, a sugar pill that looks, feels, smells, and tastes identical to the medication being tested. In this case, neither the researcher giving the medication nor the study participant receiv~ ing it knows whether the pill being administered is the medication being tested or a placebo. Another important. variable that cannot be overlooked in clinical trials is the effect of participation in the study on the participant’s state of mind. This is known as the psychosomatic efi'ect or placebo effect. Sometimes, just knowing they’re in a study will cause participants to experience physiological changes that they may interpret as therapeutic. For example, since the elderly people in your study know they are part of a study concerning high blood pressure, they may subconsciously be more relaxed and content because they feel validated and important. They may therefore show a decrease in blood pressure. Use Your Knowledge of Research to Help You Evaluate Media Reports How can all of this research information assist you in becoming a better consumer and critic of media reports? By having a better understanding of the research process and types of research conducted, you are more capable of discerning the truth or fal- lacy within media reports. Keep the following points in mind when examining any media report: 0 Who is reporting the information? Is it an article in a newspaper, in a magazine, or on the Internet? If the report is made by a person or group who may finan— cially benefit from you buying their products, you should be skeptical of the reported results. Also, many people who write for popular magazines and news- papers are not trained in science and are capable of misinterpreting research results. ' Who conducted the research, and who paid for it? Was the study funded by a company that stands to profit from certain results? Are the researchers receiving goods, personal travel funds, speaking fees, or other perks from the research -.==- _ _. sponsor, or do they have investments in companies or products related to their study? If the answer to these questions is yes, there exists a conflict of interest between the researchers and the funding agency. If a conflict of interest does exist, it may seriously compromise the researchers’ ability to conduct unbiased research and report the results in an accurate and responsible manner. . Is the report based on reputable research studies? Did the research follow the scientific method, and Were the results reported in a reputable scientific journal? Ideally, the journal is peer-reviewed; that is, the articles are critiqued by other specialists working in thesame scientific field. A reputable report should include the reference, or source of the information, and should identify researchers by name. This allows the reader to investigate the original study and determine its merit. Reputable _ ._ _ _ ,, journals include the American Journal of Clinical To become a more educated consumer and informed critic of ' Nutrition, Journal of Nutrition, Journal of the American Dietetic Association, the New England Journal of Medicine, and the Journal of the Ameri- can Medical Assoeiation (JAM). 0 Is the report based on testimonials about personal experiences? Are sweeping conclusions made from only one study? Be aware of personal testimonials, as they are fraught with bias. In addition, one study cannot answer all of our ques— tions or prove any hypothesis, and the findings from individual studies should be placed in their proper perspective. nutrition reports in the media, you need to understand th...
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