An Overview of Nutrition The Nutrients Energy the capacity to do work o Energy in food is chemical energy o The body can convert this chemical energy to mechanical electrical or heat energy Nutrients chemical substances obtained from food and used in the body to provide energy structural materials and regulating agents to support growth maintenance and repair of the body s tissues Nutrients in Foods and in the Body o Nutrient Composition of Foods Six classes of nutrients Carbohydrates Lipids Proteins Vitamins Minerals Water alcohols and others o Nutrient Composition of the Body Foods also contain fibers phytochemicals pigments additives Body is made of similar materials found in food Mostly water 60 Little carbohydrates proteins vitamins minerals etc Some fat o Chemical Composition of Nutrients Simplest of the nutrients are the minerals Chemical element all atoms are alike Identity never changes Next simplest is water Two elements hydrogen and oxygen Minerals and water are inorganic nutrients They do not contain carbon Carbohydrates lipids proteins vitamins are more complex All contain hydrogen oxygen and carbon Organic compounds Protein Only nutrient that contains Nitrogen o Essential Nutrients The body can make some but not all necessary nutrients The nutrients that foods must supply are essential nutrients The Energy Yielding Nutrients Carbohydrates Fats and Proteins o Energy yielding nutrients the nutrients that break down to yield energy the body can use o Energy Measured in kCalories calories o Energy from Foods The energy released from carbs fat and protein can be measured in Energy is expressed in 1000 calorie metric units known as kilocalories The amount of energy a food provides depends on how much carbohydrate fat and protein it contains Gram of carbs 4 kCals of energy Gram of fat 9 kCals of energy Gram of protein 4 kCals of energy Fat has a greater energy density Foods with a high energy density help with weight gain Alcohol also contributes energy Not considered a nutrient Interferes with growth maintenance and repair of the body Most food contain all 3 energy yielding nutrients Exceptions Sugar pure carb Oil pure fat o Energy in the Body The body uses the energy yielding nutrients to fuel all its activities Energy comes from bonds breaking If its not used for energy its converted to storage compounds o Other Roles of Energy Yielding Nutrients They provide raw materials for building the body s tissues and regulating its many activities o The Vitamins Vitamins are organic but they do not provide energy They facilitate the release of energy from carbs fats and proteins 13 different vitamins each with a specific role to play vulnerable to destruction by heat light and chemical agents The Minerals o Some minerals are put in orderly arrays teeth and bones o Some are found in the fluids of the body o Do not yield energy o Only 16 are known to be essential in human nutrition o Inorganic and therefore do not need to be handled with care Water conducted o Provides the environment in which nearly all the body s activities are o Participates in many metabolic reactions o Supplies the medium for transporting vital materials to cells and carrying waste products away from them The Science of Nutrition The science of nutrition is the study of the nutrients and other substances in foods and the body s handing of them Genome the complete set of genetic material DNA in a organism or a cell o The study of genomes is called genomics Nutritional genomics the science of how nutrients affect the activities of genes and how genes affect the interactions between diet and disease Conducting Research o Researchers use the scientific method to guide their work Scientists make an educated guess hypothesis that they wish to be answered Conduct research studies to collect data that will test hypothesis Manipulate one variable and measure any observed changes All other conditions are held constant o Controls Subjects divided into two groups Experimental group Control group o Sample Size o Placebos Groups must be large Randomization is used so subjects are chosen randomly from the same population by chance Groups must be equal Taking anything believed to be beneficial may hasten recovery Result of expectations is known as the placebo effect Blind experiment subjects do not know whether they are members of the experimental group or the control group When both subjects and the researchers do not known which subjects o Double Blind are in which group Analyzing Research Findings study s limitations o Research findings must be analyzed and interpreted with an awareness of each o As evidence accumulates scientists begin to develop a theory that integrates the various findings and explains the complex relationships o Correlations and Causes Positive correlation increase of x causes increase of y Negative correlation increase of x causes decrease of y Dietary Reference Intakes researchers Correlational evidence proves only that variables are associated not that one is the cause to the other To prove causation scientists have to find evidence of the mechanism o Cautious Conclusions Scientists cannot generalize the findings to all people Must be cautious when research studies using animals are applied to humans Publishing Research review o Findings from a research study are submitted to a board of reviewers peer If the reviewers consider the conclusions to be well supported by the evidence the research has validity They endorse the work for publication in a scientific journal where others can read it o Other scientists need to confirm or disprove new findings through replication Must stand up to rigorous repeated testing done by multiple A set of nutrient intake values for healthy people in the United States and Canada These values are used for planning and assessing diets and include o Estimated Average Requirements EAR Committee must determine the requirement for a nutrient Requirement the lowest continuing intake of a nutrient that will maintain a specified criterion of adequacy The committee selects a different criterion for each nutrient based on its roles in supporting various activities in the body and in reducing disease risks Cluster people into groups based on age and gender EAR is the average amount that appears sufficient for half of the population o Recommended Dietary Allowances RDA Once a nutrient requirement is established the committee must decide what intake to recommend for everybody
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