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chapter 1 revised 2005

chapter 1 revised 2005 - Glovsky/Richman Northeastern...

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Unformatted text preview: Glovsky/Richman Northeastern University Nutrition BHS U105 1 2 What factors influence our choice of foods? Sensory Influences Taste, Texture, Smell Studies on infants reveal humans have an innate desire for sweets. The sight or smell of food can often trigger the desire to eat even when we are not hungry! 3 What Factors Influence Our Choice of Foods? Cognitive Influences Advertising and Promotion (commercials for target audiences ) Social Factors Nutrition and Health Beliefs Day to Day: Habits Comfort/Discomfort Foods Food Cravings (chocolate, ? Deficiency cravings) Availability, convenience, economy Body weight and image 4 What factors influence our choice of foods? Cultural Influences: Eating is a primary way of "connecting" with others! Cultural Beliefs and Traditions Cultural cuisine Religion 5 So, What is "The American Diet"? Cultural diversity in the U.S. American diets are Professionals are delivering the message about a "Heavy" in meat and potatoes "Light" in fruits and whole grains "Super sizing" of America "healthy" diet, but are Americans "getting it"? 50% of Americans are overweight Less than half exercise vigorously Health messages compete with advertising 6 Nutrition: A Definition "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, transports, utilizes, and excretes food substances"The Council on Food and Nutrition of the American Medical Association 7 Nutrition: Nutrition: More Definitions What is a "nutrient"? Focus on Focus on function of nutrients Essential chemicals in food that support Essential chemicals in food that support human life Must come from diet Must come from diet Defined in terms of their absence in the Defined in terms of their absence in the body What happens to the body when that What happens to the body when that chemical is not present in adequate amounts. 8 6 Categories of nutrients Nutrients Serve 3 general functions: Carbohydrate, Protein, Fat (organic or contain carbon) Vitamins (organic), Minerals (inorganic) Water (inorganic) Provide fuel or energy (calories) Regulate body processes (blood pressure, energy production, temperature regulation) Contribute to body structures (bones, muscles, all cells) 9 Nutrients No foods contain just one nutrient Energy providing nutrients: 3 Macronutrients: Needed in the largest quantities Carbohydrate: Starches and Sugars Protein: Mainly found in meats and dairy Lipid: Fats, oils, cholesterol, phospholipids 10 Nutrients Micronutrients: smaller quantities Water: the most important! Vitamins: regulate bodily processes such as blood clotting, calcium balance, energy metabolism Minerals: body structures and regulate processes such as fluid balance Our bodies are ~60% water 11 Nutrients Macronutrients Micronutrients Water** CHO* Fat* Protein* vitamins Minerals** *Provides energy for the body **Inorganic nutrients 12 Carbohydrates (CHO) Composed of carbon, hydrogen, oxygen Major source of fuel for the body Starches and sugars Found in largest proportion in grains, vegetables, legumes (dry beans and peas), fruits, dairy products Body converts dietary CHO to blood sugar or glucose 13 Lipids Composed of carbon, hydrogen, oxygen Provide structure for body cells, Carry fatsoluble vitamins A, D, E, K Provide starting material for many hormones Food Sources: fats and oils added to foods, meats and other animal proteins, dairy foods, some vegetable sources such as coconut, olives, avocado 14 Proteins Composed of smaller building blocks called amino acids Contain carbon, hydrogen, and oxygen in addition to nitrogen Some are essential, can't be made in the body, so much be in the diet Build and maintain body structures Found in foods from animals, dairy foods, vegetables, grains 15 Vitamins Regulate body processes, keep organs and tissues functioning Do not contribute energy, but have vital roles in extraction of energy from macronutrients. Fatsoluble and watersoluble in the body Found in a wide variety of foods 16 Minerals and Water Minerals: Inorganic substances; 16 are essential to health Found in a wide variety of foods Deficiencies are uncommon, except calcium and iron Chemically simplest nutrient, most important Can survive longer without any other nutrient than we can without water Temperature control, lubrication of joints, transport of nutrients and wastes Body is ~60% water Water: (Inorganic) 17 Energy in foods: CHO, protein and fat broken Nutrients and Energy down yielding NRG usable by cells Kilocalorie: a measure of potential energy in foods The arithmetic: Amount of energy it takes to raise the temperature of 1 kilogram of water by 10 Celsius CHO yields 4 kcal/gram, Protein yields 4 kcal/gram Fat yields 9 kcal/gram Alcohol yields 7 kcal/gram 18 Calculations Total Calories in any food is equal to: Calculating %age of Macronutrients Grams CHO x 4 + Grams Protein x 4 + Grams Fat x 9 Total diet calculation See page 17 of Text 25 gm CHO x 4 = 100 kcals If food has 400 calories, then CHO contributes 25% of those calories 19 20 Nutrition and the Scientific Process Scientific method: Hypotheses formed from observations and are then tested by experiments 4 Types 1) Epidemiological Studies Compares disease rates among population groups May ID conditions related to diseases, such as diet or smoking Examples Some nutrient deficiencies first thought to be caused by infectious agents (Scurvy and sailors in 18th century) Breast cancer and soy, smoking and lung cancer, high fat diets 21 and heart disease Scientific Process Epidemiological Studies, cont. Provide info about relationships but do not clarify cause and effect Show correlations between 2 factors Provide clues and insights leading to further study disease relationships Animal and human studies can further clarify diet and 22 2) Animal Studies Scientific Process Can provide preliminary data that may lead to hypotheses Study hypotheses that can not be tested on humans May not be directly applicable to humans Need to follow animal studies with cell culture studies or human clinical studies to determine specific effects in humans 23 Scientific Process 3) Cell Culture Studies Can isolate cells and grow in lab Study effects of nutrients or other components of food on metabolic processes of cells Used in study of chemical compounds on gene expression May lead to design of diets based on individual genetic profile 24 Scientific Process 4) Human Studies: 2 types of study design A) Case Control Small scale epidemiologic studies One group who have a condition compared to a similar group who do not 2 groups matched as closely as possible Examine effects of one aspect of difference No intervention 25 Scientific Process Human Studies (cont) B) Clinical Trials: the Gold Standard Experimental group given the intervention Controlled studies including intervention Experimental group and control group compared Important elements of study design Random assignment to study groups: reduces risk of bias Use of placebos Blinding of subjects and researchers Double blind study: both researchers and subjects unaware of the subjects group assignments 26 Scientific Process Human Clinical Trials (cont) Placebo Effect Powerful influence (1/3 subjects show effect) Expectations of effect are powerful!! Clinical Trials can show clear cause and effect relationships but require large numbers of subjects and are expensive and time consuming to conduct 27 Scientific Process Human Clinical Trials (cont) Peer Review of Experimental Results Communicate with other scientists Critical review Ensures highest quality & objectivity are published Experts in same field can assure results of research are not influenced by the funding agency 28 Nutrition Research Intervention Studies Observational studies Or Epidemiologic studies Animal Human Metabolic Or Clinical In vitro (within and Between cells Intervention Studies: change conditions and measure results. These studies give evidence on cause and effect. Observational: strictly observe. Show associations w/o identifying causality. Statistical Correlations Fall, 2005 Does Not prove Causation 29 9 Laboratory Research 1. Select potential agents 2. Evaluate efficacy, pharmacology, toxicity An Example: The N ational Cancer Institute Chemoprevention Program Epidemiologic Research 1. Identify agents and natural experiments 2. Refine and test hypotheses 1. Evaluate clinical, lab, epidemiological findings 2. Conduct human trials for efficacy, safety 3. Implement demonstration programs Human Intervention Research Population D issemination Fall, 2005 10 30 So.... How Good is the Evidence that Diet Causes Cancer? w eak In vitro studies (e.g. cellular carcinogenesis) Animal studies (Does it apply across species?) Human Studies Descriptive epidemiology Population comparisons, time trends, migrant studies It depends! st ronger Analytic observational epidemiology Casecontrol studies, cohort studies st rongest Experiments or trials (very limited opportunities) Fall, 2005 11 31 32 Fall, 2005 12 From Research to Headline Be careful and critical of what you read/hear Media may overemphasize or sensationalize facts, sound bites One study does not provide all answers! Some degree of opinion is introduced into report Often summarized in nontechnical terms and chosen and written to attract an audience Science is constantly changing and evolving 33 Red Flags of Junk Science Offers of a quick fix, especially for problems that no other authority can solve Claims that sound too good to be true Simplistic conclusions from single study or those not peer reviewed Dramatic statements refuted by reputable scientific organization 34 Red Flags of Junk Science List of "good/bad" foods Diets that eliminate any food group Recommendations to sell a product What are the credentials of the "expert" associated with the company? THINK CRITICALLY!!! 35 ...
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