Chapter 1: Food for Health PDF

Chapter 1: Food for Health  Learning Objectives By the end of this chapter you should be able to: ✓ Define the terms nutrition, essential nutrient, macronutrient, and micronutrient ✓ List the six classes of nutrients and describe the three general functions of nutrients ✓ Describe the diff...

Chapter 1: Food for Health  Learning Objectives By the end of this chapter you should be able to: ✓ Define the terms nutrition, essential nutrient, macronutrient, and micronutrient ✓ List the six classes of nutrients and describe the three general functions of nutrients ✓ Describe the different types of malnutrition and how diet-gene interaction affects our health ✓ Identify the factors other than nutrition that affect food choices and the importance of variety, balance, and moderation in maintaining a healthy diet ✓ List the steps of the scientific method and identify different types of nutrition studies 2 Definitions and Concepts Nutrition is a science that studies the interactions between living organisms and the food they consume (textbook definition). “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.” (from The Council on Food and Nutrition of the American Medical Association) Nutrients (chemical substances in foods that provide energy and structure and help regulate body processes) and energy are provided by food. 3 Nutrition and the Canadian Diet In the past, people spent most of their day obtaining food ingredients and preparing meals. Consider modern lifestyle – food preparation takes time Cultural changes – less time spent eating as a family, changes in portion sizes Today convenience has taken over decisions about food choices Estimated 25% of Canadians eat food prepared at a fast-food restaurant at least once a day. Fewer meals at home, less time preparing food and portion sizes have increased enormously More people eat processed foods. Convenience (faster vs. takes more time), cost (affordability), availability (seasonal vs. year-round) 4 Characteristics of the Canadian Diet Consider… Not only have our food portions increased, but plate, bowl and cup sizes have as well. In the 1960's the standard dinner plate size was 9 inches, and today the average dinner plate is 14 inches! Research shows that deciding how much food we eat is, in part, perceptually driven by environmental or contextual cues - that is, if you decide to eat half a bowl of cereal, the size of the bowl will largely influence how much you serve yourself, and subsequently, how much you eat. For example, a study in the British Medical Journal (2005) showed teenagers at weight-loss camps poured 77% more juice into short, wide glasses than into tall narrow glasses 6 Your Choice: Convenience Has Its Costs Financial costs and kilocalorie costs Home food preparation vs. “eating on the run” Examples: Morning coffee and muffin Home: 8-oz coffee (with whole milk and sugar) and English muffin with butter = $0.50, 200 kilocalories “On the run”: 16-oz mocha and bran muffin = $5.00, 850 kilocalories 7 How Healthy Is the Canadian Diet? The Canadian Community Health Survey (CCHS) shows that the Canadian diet is not as healthy as it could be. Approximately 50% of Canadian adults do not meet the recommended servings for vegetables and fruit. Canadians need to eat more veggies and fruits, whole grains and plant-based protein foods. With the consumption of more processed and convenience foods, the Canadian population is consuming more sodium, saturated fats, and sugar, and fewer nutrients. 8 Leading Causes of Death 9 Food Provides Nutrients To date – 45 nutrients have been determined to be essential to human life. Essential nutrients – nutrients that must be provided by the diet to support life ones we cannot make or not in sufficient quantities to satisfy needs intake is determined by our food choices Fortified foods – foods to which nutrients have been added replace nutrients lost during processing or to prevent known/common inadequacies (often vitamins and minerals) Natural health products – occupy a middle-ground between foods and drugs include vitamins, minerals and supplements, amino acids, fatty acids, probiotics, herbal and homeopathic remedies, and traditional medicines Phytochemicals and zoochemicals – non-essential but helpful(?) 10 Classes of Nutrients: Macronutrients Six classes of nutrients: carbohydrates, proteins, lipids, water, vitamins and minerals Different ideas about how to group these categories (e.g. energy provided, quantity needed, chemical structure) Energy-yielding nutrients include carbohydrates, proteins, and fats. are also called macronutrients. Macronutrients are needed in the body in large amounts each day (on a scale of kg or g per day) Micronutrients are needed in smaller amounts (milligrams or micrograms) Organic molecules (carbon bonded to hydrogen) = carbohydrates, proteins, lipids and vitamins Inorganic molecules (no carbon-hydrogen bonds) = water and minerals 11 Energy-Yielding Nutrients Macronutrients provide energy to the body. Units of measure for the energy provided by carbohydrates, lipids and proteins kilocalories (kcalories or kcals) – unit of heat to express amount of energy provided by food kilojoules (kjoule or kJ) – unit of work to express energy intake and output 1 kcal = 4.18 kJ OR 4.18 kJ = 1 kcal calories – 1/1000 of a kcal BUT if using a ”C” means kcal *but some food labels use calorie and Calorie as interchangeable (and meaning kcal 12 Carbohydrates, Lipids, and Proteins Energy Provided by Macronutrients Kcalories/Gram Kjoules/Gram Carbohydrate 4 16.7 Lipid 9 37.6 Protein 4 16.7 Alcohol 7 29.3 TABLE 1.1 Energy Provided by Macronutrients and Alcohol ”Not all calories are equal” – think carefully Measurements do not change – one gram of one macro vs. another is still one gram Energy and how our bodies use the nutrient changes the ways in which intake of those macros impact our bodies 14 Macronutrients: Carbohydrates Carbohydrates are one type of macronutrient. Provide readily available energy. Carbohydrates include: sugars – mono and disaccharides – table sugar, in fruits and milk starches – polysaccharide in plants – vegetables and grains Fibre (cellulose) belongs to the carbohydrates category but does not provide energy. Carbohydrates contain 4 kcalories/gram. Storage in the body is limited - glycogen 15 Classes of Macronutrients: Lipids Lipids are commonly called “fats” or “oils” (dependent on state at room temperature) Lipids are a concentrated form of energy (more per equivalent unit of weight compared to carbohydrates and proteins). High efficiency storage Triglyceride is a type of fat that is found in abundance in the body. Storage is limitless Foods high in saturated fatty acids may promote certain diseases. Foods high in unsaturated fatty acids may help prevent certain diseases. Lipids contain 9 kcalories/gram. 16 Categories of Macronutrients: Proteins Proteins are required for growth, maintenance, and repair of the body. Most heterogeneous type of molecule in the body Proteins can also supply energy. Meat, fish, poultry, milk, legumes, vegetables, and grains can provide protein. Proteins are made up of different combinations of amino acids (subunits). Proportions of different amino acids vary from one protein to another Proteins provide 4 kcalories/gram. 17 Classes of Nutrients: Water Water is a macronutrient, meaning that it is required in large amounts. Water does not provide kcalories. Water makes up approximately 60% of the healthy human body. Many functions within the human body Transport medium, lubricant, body temperature regulation From foods and beverages (small amounts of water are “produced” by the body but not sufficient to meet needs) 18 Classes of Nutrients: Micronutrients Micronutrients (vitamins and minerals) provide no energy for the body but are necessary for proper functioning of the body. Micronutrients have unique structures therefore unique roles Micronutrients are very important for good health but are required in small amounts. Many assist in a variety of body processes how our body uses energy from macros, bone growth, blood clotting, oxygen transport and tissue growth, development and repair Micronutrients can be found in most foods. Fresh foods are a good natural source of micronutrients. Fortified processed foods also supply vitamins and minerals. 19 Composition of the Human Body 20 Functions of Nutrients: Providing Energy Working together, macronutrients and micronutrients help the body to stay healthy. Biochemical reactions in the body help to release the energy contained in carbohydrates, fats, and proteins. Energy is used to synthesize new compounds, maintain body functions and fuel physical work. Excess energy consumed is stored – primarily as fat – to be used when immediate dietary sources are not available If more energy is consumed than is needed, over time body weight will increase. 21 Functions of Nutrients: Forming Structures Most of the weight of the body is due to water, fat, and protein. Nutrients help to form and maintain the shape and structure of the body. Proteins form ligaments and tendons (that hold bones together and attach muscles to bones) and overall structure of muscles. Also framework of bones and teeth (mineral deposits that harden) At the cellular level, lipids and proteins make up the membranes that surround cells. 22 Regulating Body Processes Sum of all the reactions that occur in the body are called metabolism. The proper regulation of metabolism is called homeostasis. Each class of nutrient plays a role in helping to maintain homeostasis. Protein (enzymes) help to speed up or slow down metabolic reactions. Often along with vitamins and minerals Water acts as a solvent and forms the basis of the solution in which all chemical reactions take place Helps to regulate temperature. 23 Functions of Nutrients Summary Function Nutrient Example Energy Carbohydrate Glucose is a carbohydrate that provides energy to body cells. Lipid Fat is the most plentiful source of stored fuel in the body. Protein Protein consumed in excess of protein needs will be used for energy. Structure Lipid Lipids are the principal component of the membranes that surround each cell. Protein Protein in connective tissue holds bones together and holds muscles to bones. Protein in muscles defines their shape. Minerals Calcium and phosphorus are minerals that harden teeth and bones. Regulation Lipid Estrogen is a lipid hormone that helps regulate the female reproductive cycle. Protein Leptin is a protein that helps regulate the size of body fat stores. Carbohydrate Sugar chains attached to proteins circulating in the blood signal whether the protein should remain in the blood or be removed by the liver. Water Water in sweat helps cool the body to regulate body temperature. Vitamins B vitamins regulate the use of macronutrients for energy. Minerals Sodium is a mineral that helps regulate blood volume. 24  Nutrition and Health How we eat has a huge impact on how much we weigh, how healthy we are and how likely we are to develop chronic disease Malnutrition can mean eating too little or too much of one or more nutrients. Impact is immediate but also can have serious long-term consequences Undernutrition is malnutrition caused by eating insufficient amounts of energy-providing foods or nutrients. Deficiency in energy (weight loss), poor growth, inability to reproduce and in severe cases disruptions to homeostasis can cause death Consequences of individual nutrient deficiencies and length of time to respond to treatment – vitamins A, B12, and C, calcium and water25 Nutrition and Health Overnutrition is also malnutrition caused by eating an excess of energy-providing foods. Excess of certain nutrients can have adverse or toxic effects Most often is from supplements not usually enough in the foods we eat to cause toxicity Often are not immediate consequences – most common in Canada are effects that contribute to development of chronic diseases (heart disease, type 2 diabetes, some types of cancer, high blood pressure) In Canada, over 60% of adults are overweight or obese because of overnutrition 26 Diet and Genes 27 Food Choices for a Healthy Diet Food choices we make are usually only partly influenced by how “healthy” that food is for us (or the nutrient composition of that food) Food availability has changed significantly as foods can be transported of greater distances, foods are kept fresher (or preserved) so that there are more food choices available all year round Food availability depends on: Geography Transportation and mobility Available income Food storage and preparation equipment Health status – e.g. allergies, disease 28 Food Choices for a Healthy Diet Cultural and personal/family background also can influence food choices, and therefore also the nutrients we take in Health is impacted by cultural and personal variables such as: 1. Culturally specific foods – foods that are more/less common in particular cultures cooking 2. Family practices – holidays/traditions what you are familiar with/have been exposed to/know how to prepare 3. Religious dietary laws – foods associated with certain holidays/practices 4. Ethnic menu preferences 29 Food Choices for a Healthy Diet Health is impacted by cultural and personal variables such as: 5. Social acceptability – peer pressure, politeness 6. Personal preference – foods that are more or less appealing (not always based on nutrient composition or how “healthy” they are) personal ethic or motivations 7. Psychological and emotional factors – comfort foods 8. Health concerns – individual perceptions or beliefs about what might make them ”healthier” (reduce risk of disease) or meet a particular goal (e.g. “weight loss”) 9. Media 30 Nutrient Density Adequate diet = rich in nutrient dense foods enough energy to keep weight in a desired range proper types and amounts of macros and water sufficient but not excessive vitamins and minerals Nutrient density is a measure of the nutrient a food provides compared to its energy content. more foods that are less dense usually means it is harder to meet your nutrient needs more nutrient dense foods mean less to meet needs and have option for other foods (??) For example, broccoli is more nutrient-dense than French fries. 31 Nutrient Density 32  Choices to Boost Nutrient Density Lower Nutrient Density Choice Instead of Higher Nutrient Density Choice Have this... this... Soft drink Low-fat milk Chocolate candies Fruit and nut trail mix Apple pie Fresh apple Potato chips and sour cream dip Baked tortilla chips and salsa Triple fudge brownie Oatmeal raisin cookie Fried chicken Roasted chicken without skin French fries Oven-baked potato wedges 33 Eat a Variety of Foods No one food provides all necessary nutrients. Selecting a variety of foods helps the body to obtain all necessary nutrients (i.e. adequate nutrient intake). Try to select a variety of different foods within each food group not all vegetables or proteins are the same in terms of the nutrients they provide There are many interactions between foods. Select a variety of foods –> provides the fuel the body needs, even if some of the food interactions are not positive. (e.g. one counters or enhances the absorption of another) 34 Balance Your Choices Mixing and matching foods in proportion. Reduces the chance that you will have too much of one thing or not enough of another Balanced diet: Whole grains Vegetables and fruit Vitamins and minerals Protein, carbohydrates, fat, water Energy balance 35 Everything in Moderation Moderation means all types of foods and beverages are okay, as long as they are taken in moderation. Moderation means not consuming too much energy, fat, sugar, sodium, or alcohol. Need to consider the portions and proportions of each type of food you are consuming Larger portions of certain foods relative to small portions of others can lead to excess kcal and therefore weight gain Idea that by limiting portions you can enjoy more different foods (including those you like but that might be less nutrient dense) Complication of “portion distortion” – what a “portion” looks like has changed expectations for size of foods has changed packaging now has been implemented to help with this 36 Understanding Science Helps Us Understand Nutrition Nutrition is a science. Developing an understanding of the process of science will help us to understand the relationship between nutrition and health. Understanding nutritional processes will help us to make wise (informed) nutrition decisions. Decision-making in terms of nutrition and diet strategies should be supported by evidence-based research Remain open to taken-for-granted beliefs and concepts giving way to new ideas and recommendations for change that are supported through a rigorous process of study and review 37 The Scientific Method Advances in nutrition are made using the scientific method. The scientific method uses a systematic, unbiased approach to examine the interaction of food, nutrients, and health. The steps in the scientific method are: o Observation o Hypothesis o Theory Following these steps when conducting research is essential and must be clearly documented. one criteria of a credible study is that it is replicable 38 Steps in the Scientific Method 39 What Makes a Good Study? A well-conducted experiment requires: Quantifiable data: Can we measure the information in a scientific manner? Appropriate experimental population: Is the population large enough and pertinent to the study? Appropriate sample size: sufficient number of participants to ensure desired effects. Suitable study duration: study is long enough to see a desired effect. Qualitative vs. Quantitative approaches Analysis (usually statistical) and publication 40 Statistical Analysis 41 Types of Nutrition Research Studies Treatment group: A group of participants in an experiment who are receiving an experimental treatment. Control group: A group of participants identical to the experimental group that does not receive the experimental treatment. *Ideally, randomization places participants in the treatment or control groups Placebos are identical in appearance to the actual treatment but are of no therapeutic value. 42 Types of Nutrition Research Studies Observational studies can include epidemiology, the study of diet, health and disease patterns, and correlation. Correlation (association) studies do not provide causation. Correlation can be direct (positive) or inverse (negative). Prospective cohort study: the dietary intake of a healthy population is recorded and their health is followed for years. Randomization: participants in an intervention trial are assigned to a treatment or control group entirely by chance. Confounding factors: something that is related to the outcome being investigated (e.g. disease) or might influence the outcome (e.g. dietary intake) 43 Types of Nutrition Research Studies Single-blind study: subjects do not know which treatment they are receiving. Double-blind study: neither the subjects nor the investigators know which treatment is being received. The peer review system allows for scientific interpretation of experimental results. Review of the process, methods and statistical analyses that were performed 44 Types of Nutrition Research Studies 45  Table 1.4 Understanding Relative Risk Critical Thinking: Doing Nutrition Research Nutrition research depends on both prospective cohort studies and randomized controlled trials for evidence. Think about the kinds of questions researchers want to ask and what is most appropriate to answer those questions Consistent results between different study types strengthens the evidence for a specific hypothesis. More than one study comes up with similar results = stronger likelihood of result Results countering another study is not necessarily saying that either study is wrong Example: two studies testing the hypothesis that intake of dairy products reduces colon cancer risk. 47 Critical Thinking: Doing Nutrition Research Study 1 Cohort study with almost 480,000 participants, 70% female, average age of 52 years at beginning of study. Participants completed food intake survey and information on dairy intake was used. Information on potential confounders also collected. Participants followed for 11 years, and number of cases of colon cancer recorded. Results: Total Dairy Intake (g/day) Hazard Ratio Quantile 1 (400g/day) 0.77 (0.70 − 0.86) P trend