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Transcript
Nutrition “Leave your drugs at the chemist’s pot if you can heal your patient with food.” Hippocrates Introduction to Nutrition Nourishment: • Provision of energy and building materials essential for growth and survival Nutrition: • Study of food and nutrients, their actions, interactions and balance in relation to health and disease • Overall role of nutrition is to supply appropriate substrates to cells of various tissues for moment to moment function Introduction to Nutrition Nutrient: • • • a substance that nourishes macronutrients ( protein, carbohydrate, fats) micronutrients (vitamins, minerals, trace elements) Essential nutrient: • a nutrient required for survival (species specific) Conditionally essential nutrient • one that may become essential under certain conditions Nutrients in question include, among other things: • oxidizable energy sources used for production of useful chemical energy carriers such as ATP • amino acids required for protein synthesis, as precursors for purines & pyrimidines and other specialized molecules • vitamins required for a variety of specific cell functions • inorganic compounds such as calcium, phosphorus, iron, etc. Nutrient Functions • Structural • Muscle, bone, cytoskeletal • Functional • enzymatic reactions, transport, synthesis, degradation, energy metabolism… LIFE! • Chemical • toxicity, pharmacologic properties- includes phytochemicals, “functional foods” Nutrition and Health and Disease: Evolution of Guidelines _ _ _ Historically, dietary restrictions were related to religious practices and law. Late 1800’s: Germ theory of disease: contaminated foods could act as vectors. Early 1900’s: Vitamin theory of disease: substances missing from diet contributing to disease. Nutrition and Health and Disease: Evolution of Guidelines _ Post WW2: Framingham, Twin Cities, 7 Country studies: evaluated diet and life style risks for development of cardiac disease: – Link between dietary excess and development of chronic disease Nutrition and Disease • • • • • • • • • • • Obesity Type II diabetes Atherosclerotic cardiovascular disease Hypertension Cancer Dental carries Osteoporosis Anemia Infection Pregnancy outcomes Pediatric growth and development Nutrition and Disease • Chronic diseases: Diabetes, Cardiovascular disease, Hypertension, Stroke and Cancer _ Prevalent: 7 out of 10 who die each year die from chronic disease- more than 1.7 million. _ _ Costly: 75% of the nation’s $1.4 trillion medical care costs. Preventable Dietary Reference Intakes Dietary Reference Intakes (DRI) • Reference values for meeting needs for essential nutrients and energy • Determined by Food and Nutrition Board of the National Academy of Sciences • Firmly established on basis of experimental evidence • Designed to prevent impairment of health from nutritional inadequacy which is directly related to diet and to which susceptibility is universal RDA - DRI • Defined as the amounts of nutrients considered sufficient to meet the physiological needs of practically all healthy persons in a specific group (age and gender based) and the amount of food sources of energy needed by members of that group • Designed to prevent nutritional deficiencies which lead to specific pathological conditions • Focus now on indicators of nutritional sufficiency and on levels which may prevent chronic disease RDA/ DRI’s • deal mainly with quantities of micronutrients and protein needed daily • do not deal with non-nutrients and nutrients that are not essential • specific values are given for different age-sex groups • serve as standards for establishing health policy • Terminology - Dietary Reference Intake (DRI) has “replaced” the term RDA in United States & Canada DRI includes • Estimated Average Requirement (EAR) - intake at which risk of inadequacy is 50% (EAR is evidence-based) • Recommended Dietary Allowance (RDA) - intake at which risk of inadequacy is 2 - 3% • RDA set relative to EAR: RDA = EAR + 2SDEAR • Tolerable Upper Limit (UL) - highest level of daily intake likely to pose no risks of adverse effect to almost all persons in general population • Adequate Intake (AI) - set for those nutrients without enough evidence to develop RDA, no consistent relationship to EAR or RDA DRI Example: Calcium _ _ _ _ _ _ _ _ _ Infant 0-6 months: Infant 6-12 months: Child 1-3 y: Child 4-8 y: Males/Females 9-13, 14-18 Males/Females 19-30, 31-50 Males/Females 51-70, >70 Pregnancy Lactation 210 mg 210 mg 500 mg 800 mg 1300 mg 1000 mg 1200 mg same as age group same as age group New Macronutrient Guidelines and DRI’s announced recently (Sept. 2002) For ages >19 years old (% of total calories) • Carbohydrates: 45 - 65% • Fats: 25 - 35% • Protein: 10 - 35% • Fiber: 25-38 g per day • Essential fatty acids: w-3’s new • Increased exercise recommended: • 60 minutes per day of moderate activity for children and adults DRI’s and Food Labels _ _ _ Daily Values for nutrients listed on food labels as required by FDA Reference Daily Intake for vitamins and minerals Uses RDA’s for 18 y/o male (highest RDA) except for iron (19-30 y/o female) Dietary Guidelines Dietary Guidelines • Differ from DRI in several aspects • Much more general than DRI • Primarily deal with quantities of certain foods and nonessenteial dietary components (e.g., fiber, cholesterol, saturated fat, etc.) and proportions and types of energy sources judged desirable in healthful diets Dietary Guidelines • advice on selecting foods to achieve nutritionally adequate diet • deal mainly with proportions of energyyielding nutrients in diet • include advice on consumption of such nonnutrients as fiber and cholesterol • recommendations are general, without specification for different segments of the population Dietary Guidelines • are health policy proposals • directed toward prevention of chronic diseases for which diet is a potential modifying factor and to which susceptibility is highly variable • evidence mainly indirect from observations between diet and disease incidence Consensus Dietary Guidelines Circulation 100:450 (1999) _ The Unified Dietary Guidelines: American Cancer Society, American Dietetic Association, American Academy of Pediatrics, National Institutes of Health and American Heart Association. Consensus Dietary Guidelines Circulation 100:450 (1999) • Saturated fat < 10% of calories • Total fat < 30% of calories • Polyunsaturated fat < 10% of calories • Monounsaturated fat < 15% of calories • Cholesterol < 300 mg/day • Carbohydrates > 55% of calories • Total calories to achieve and maintain desirable weight • Salt intake limited to < 6 g/day Consensus Dietary Guidelines Circulation 100:450 (1999) _ The consensus panel concluded that for many individuals the recommendations could best be achieved by following U. S. Dietary Guidelines and Food Guide Pyramid USDA Food Guide Pyramid USDA Food Pyramid (1992) Fats, Oils & S weets US E S PARINGLY Milk, Yogurt & Cheese Group 2-3 S ERVINGS Vegetable Group 3-5 S ERVINGS Meats, Poultry, Fish, Dry Beans, Eggs & Nuts 2-3 S ERVINGS Fruit Group 3-5 S ERVINGS Bread, Cereal, Rice & Pasta Group 6-11 S ERVINGS Nutrition and Your Health: Dietary Guidelines for Americans USDA & USDHHS 5th ed., May 2000 Aim for Fitness • Aim for a healthy weight • Be physically active Build a Healthy Base • Let the Pyramid guide your food choices • Choose a variety of grains daily, especially whole grains • Choose a variety of fruits and vegetables daily • Keep food safe to eat Choose Sensibly • Choose a diet that is low in saturated fat and cholesterol and moderate in total fat • Choose beverages and foods to moderate your intake of sugars • Choose and prepare foods with less salts • If you drink alcoholic beverages, do so in moderation Criticism of USDA Food Guide Pyramid USDA Food Pyramid as annotated by W. C Willet in Science 264 : 532 - 537 (1994) Low-fat products are preferable. Calcium supplements are effective substitutesfor preventing fractures Importance is well documented. Greens and dark orange vegetables should be included. Even more frequent servings may be beneficial. Ignores critical differences in types of fat. Saturated and trans fatty acids should be minimized, but monosaturated and polyunsaturated fats may be beneficial Misleading. Two or three servings of meat per day may be unhealthy Benefits are well documented Whole grain & minimally processed products should be emphasized Willet Food Guide Pyramid From Willett, Walter C., Eat, Drink, and Be Healthy , Fireside, New York (2001) Revision of Food Guide Pyramid _ _ Currently underway, expected 2005 Areas expected to be addressed – Portion sizes: are currently not consistent with portion sizes typically consumed or stated on food labels as required by FDA » Most problematic with grains/starches » Pyramid suggests 6-11 servings per day, counting 1 serving as 1/2 small bagel How are we eating? Percent of People Meeting Recommendations for: Total Fat ( 30% Kcal ); Saturated Fat ( < 10% Kcal); and Fruits and Vegetables ( • 5 servings a day). (1989-91) A few comments on Obesity and Comorbidities A few comments on obesity • The most serious nutritional problem in the United States and the industrialized world is the marked increase in obesity • The problem is extending to less developed countries. • It is growing at epidemic rates in adult populations • Also occurring at alarming rates in children * ¶ Notes: *For adults Overweight includes Obese & Extremely obese ¶All values for children are for Overweight For 1976 - 1980, 47% of adults were overweight (15% were obese) Obesity and comorbidity risk Table 2. Increased Risk of Obesity Related Diseases with Higher BMI BMI of BMI between BMI between BMI of Disease 25 or less 25 and 30 30 and 35 35 or more Arthritis 1.00 1.56 1.87 2.39 Heart Disease 1.00 1.39 1.86 1.67 Diabetes (Type 2) 1.00 2.42 3.35 6.16 Gallstones 1.00 1.97 3.30 5.48 Hypertension 1.00 1.92 2.82 3.77 Stroke 1.00 1.53 1.59 1.75 Source: Centers for Disease Control. Third National Health and Nutrition Examination Survey. Analysis by The Lewin Group, 1999. U.S. NIH revised weight guidelines: 1994 and 1998 • Guidelines apply equally to men & women • Guidelines do NOT allow for weight gain in middle age • Revisions made in response to mounting evidence that increases in weight associated with increased risk of premature death from heart disease, diabetes, and certain cancers • At each height, proposed guidelines recommend weights that translate to a Body Mass Index (BMI) of 18.9 - 24.9 • In medical literature, BMI is calculated by BMI = Weight(kg)/[Height(m)]2 • Current research suggests that obesityrelated health problems begin to mount at BMIs above 25 U. S. National Institutes of Health obesity guidelines (June, 1998) BMI • Underweight < 18.5 • Normal 18.5 - 24.9 • Overweight 25 - 29.9 • Obese (Class I) 30 - 34.9 • Obese (Class II) 35 - 39.9 • Obese (Class III) > 40 In this unisex version: • weights at lower end of range recommended for persons with low ratio of bone to fat • weights at upper end of range advised for those with more muscular physiques • most of us fall into the 1st category, thus DHHSNIH suggest that we aim for lower end of range Conversion factors: • Weight (lb) x 0.454 kg/lb = Weight (kg) • Height (in)/39.4 = Height (m) Conflicting Nutritional Advice Nutrition Recommendations _ _ _ Nutrition science is a rapidly growing field of study, many new and sometimes conflicting findings and advice reported in popular press. “Guidelines” often influenced by special interest groups. Consumer behavior is greatly influenced by multi-billion dollar food industry. Recent info on consumer confusion and negativism about nutritional advice J. Am. Dietitics Assoc (01/01/01) Reported survey results on conflicting advice about “healthy diet” • >40% were tired of hearing about foods they should or should not eat • ~40% thought that dietary guidelines be taken with “a grain of salt” • 70% said government shouldn’t tell people what to eat •