Lecture 19- Human nutrition Flashcards
What are the important principle in human nutrition?
- Adequacy: enough of all essential nutrients, fiber and energy
- Balance: don’t rely on one type of food for everything
- Energy Control: don’t overeat
- Moderation: not too much or too little of anything.
- Variety: the spice of life; include a large number of different foods in your diet.
What are the USDA dietary guidelines?
- Designed to promote population-wide dietary changes to reduce nutrition-related chronic disease.
- Updated every 5 years (started in 1980)
- Designed to answer question “What should I eat?” • 3 basic messages…
What is the aim for fitness in humans?
- Aim for a healthy weight
* Be physically active each day (at least 30 minutes/day)
How do you build a healthy base with nutrition?
- Let the Pyramid guide your food choices (to be discussed next) • Choose a variety of grains daily, especially whole grains
- Choose a variety of fruits and vegetables daily
- Keep food safe to eat
How to 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 salt
- If you drink alcoholic beverages, do so in moderation
What is the food guide pyramid?
- Concept first published in 1916: focused on increasing sugar and fat intake!
- 1950-1970: “Basic Four Food Groups” implied that we should consume equal amounts from each
- 1992: first “pyramid” published; revised in 1996 and 2000; visual representation of USDA Dietary Guidelines
What is the foods vs nutrients debate?
- Guidelines suggesting types of foods that we should eat
- USDA Dietary Guidelines
- USDA Food Guide Pyramid
- Guidelines suggesting what and how much nutrients we should consume
- Recommended Dietary Allowances (RDA)-”old”
- Dietary Reference Intakes (DRI)- ”new”
What is a nutrient requirement?
- How much of each nutrient the body requires to maintain physiologic functions and internal reserves.
- This definition is evolving.
What are the recommended dietary allowances? (RDAs)
- Values represent best estimates of how much of a nutrient intake is required to meet the requirements of practically all healthy individuals.
- First published in 1941 by the Food and Nutrition Board of the National Academy of Sciences; now in 10th edition.
- Being phased out as most important nutrient reference and replaced by the DRIs.
What are the dietary reference intakes? (DRI)
- Set of reference values for nutrient intakes to be used in assessing and planning diets for healthy people.
- Estimated Average Requirement (EAR).
- Recommended Dietary Allowance (RDA). • Adequate Intakes (AI).
- Tolerable Upper Intake Levels (UL).
What is the estimates average requirements? (EAR)
- Nutrient intake level estimated to meet the needs of 50% of a particular population.
- Recognizes possible health benefits beyond basic physiologic function.
What is an important point to remember with the guidelines?
- Note that many factors (environmental and genetic) interact to determine one’s true requirements.
- Biochemical tests are required to determine true requirements.
- Thus, DRIs still represent estimates of requirements for individuals.
What are the ‘new’ recommended dietary allowances (RDA)?
- EAR now required in order to set RDA.
- Thus, some nutrients do not have “new RDAs.”
- Still not always an accurate measure of individual requirements. • Very often overestimates requirements.
What is adequate intake (AI)?
- Used when there isn’t enough scientific data to determine EARs.
- Often determined by documenting normal intakes of healthy people. • All DRI values for infants are AI levels; based on intake of breast milk.
- When AIs are used, this reflects lack of knowledge and need for more research.
What are the tolerable upper intake levels (UI)?
• Maximal intakes that are thought to be safe.
• Recognition of increasing use of dietary supplements and applies to
nutrient intake from supplements alone!
• More is not always better!
• Not to be used as a target intake for any population.
What is the daily reference values? (DRV)
• Daily Reference Values (DRV).
• Established to help consumers follow recommendations for health and
disease prevention (Dietary Guidelines).
• Based on 2000 kcal diet (average).
• Suggest maximal levels of intake for fat, saturated fat, cholesterol and sodium.
• Suggest intake levels for protein, carbohydrate and fiber.
• Note that some are controversial.
What are the references daily intakes?
- Reference Daily Intakes (RDI).
- Highest amount of each nutrient recommended for any adult age group.
- May overestimate, but never underestimate, need. • Based on “old” RDAs.
- Will probably be revised using new DRIs.
What is the appropriate various standards?
• Know your target group: population (EAR) or individual (RDA or AI). • Public health programs tend to rely on RDAs (thus, almost all
individuals’ needs are met).
• Use as comparison values for assessing individual diets.
How to choose foods to get nutrients?
• Food Labels
• Regulated by the Food and Drug Administration (FDA), except for meat
products.
• 1990-Nutrition Labeling and Education Act passed by Congress requiring labeling of foods.
• 1994-”Nutrition facts” labels appeared
What are the mandatory components of a food label?
- Statement of identity
- Net contents of package
- Manufacturer
- List of ingredients (in descending order, by weight)
- Nutrition information
- This includes added water (unless
What are the nutrition facts on labels?
- Must be on most food labels • Serving size (standardized)
- # Servings/container
- % “Daily Values”
- Represents needs of “average” person
- Based on Reference Daily Intakes (RDIs) and Daily Reference Values (DRVs)
- Required: fat, saturated fat, cholesterol, fiber, sugar, protein, vitamins A and C, calcium and iron. Trans fatty acids (added in 2006)
- Daily values for lower and higher calorie requirements
What are the examples of descriptive terms?
• Examples: sugar free, low fat, light, healthy • Tightly regulated
What is the continuum of nutritional status?
- Under-nutrition: associated with nutritional deficiency diseases and protein/energy malnutrition
- Common in 1800s and early 1900s
- Now only associated with extreme poverty, alcoholism, illness and eating disorders
- Over-nutrition: consumption of more than is necessary for health
- Highly associated with many chronic diseases (heart disease, stroke, cancer)
- Good health lies between these extremes
What are the ABCDs of nutritional assessment?
- Anthropometric data
- Biochemical tests (blood, urine or feces samples)
- Clinical observations: signs and symptoms of nutritional deficiencies • Dietary intake
What is the anthropometric assessment?
- Physical measurements of the body
* Body Dimensions (weight, height, and circumferences) • Body Composition (fat, muscle, water)
Why do we care about height and weight?
- Used to assess risk for certain diseases
- Used to help monitor progression and severity of certain diseases • Assess growth and development of babies and children
- Assess health and progress of pregnancy
What other dimensions to consider?
- Circumferences of head (infants), waist and hips can be measured. • Increased waist to hip ratio has been “linked” to disease risk.
- Head circumference can indicate brain development in infants.
Why do we care about body composition?
- Body fat is a risk factor for chronic diseases (heart disease, some cancers)
- Assessment of fitness of athletes and others
How do you measure body composition?
- Skinfold calipers used to estimate body fatness.
* Others: underwater weighing, x-ray methodologies (DXA).
How to use RDAs for dietary assessment?
- RDA group: Female 19-24
- RDA Calcium: 1200 mg
- Dietary Assessment Estimates intake of: 1000 mg • 1000 mg / 1200 mg x 100 = 83% of RDA
- Should you be concerned?
What is the rule of thumb with intake? (if you should be concerned when getting lower or higher percentage of intake)
- Intake > 75% RDA: lower risk
* Intake
What are the basics of body weight management?
- The “Energy Balance Equation”
- Energy In = Energy Out + Energy to Stores
- Remember that energy can be neither created nor destroyed. • If you eat it, it has to either be used or stored.
- This is not rocket science…
How do you estimate body fat?
- Body Mass Index (BMI)
- Wt (kg) / ht2 (m2)
- NIH guidelines (1998)
- Normal:19-24.9kg/m2
- Overweight: 25-29.9 kg/m2
- Obese: >30 kg/m2
- Controversial
What are the issues with obesity and health?
- 55% of American adults overweight or obese
- Related to higher risk for
- High blood pressure • Heart disease/stroke • Diabetes
- Cancer
What are the issues with weight regulation?
- Current theories recognize the many environmental and genetic interactions
- Genetics (molecular biology) thought to explain 50-90% of variation in body fat.
- Sociocultural influences
- Perception of ideal weight
- Availability of food
- Social aspect of eating
- Age and Lifestyle • Exercise!
What are some of the current theories regarding weight of humans?
- Race/ethnicity (nature or nurture?) • Socioeconomic status
- Poverty is associated with higher rates of obesity.
- Employment
- Employed women are thinner… • Chicken or egg?
- Psychological factors
- “restrained eaters”
- “binge eaters”
- “yo-yo” dieting (weight cycling)
What are the components of weight management?
• Components
• Diet composition (energy in)
• Positive or negative energy balance?
• Is a particular macronutrient to blame?
• 1950-1960: carbohydrates were blamed
• These diets “successfully” help people lose weight because caloric intakes are low.
• 1970-1990: “pyramid power” suggested that proteins (or fats) were to blame!
• 1990-2003: carbohydrates bad again.
• Variety and moderation the key (again).
-• Physical Activity (energy out)
• Also decreases caloric intake by • Decreasing stress
• Produces feelings of self-worth
• Provides socialization
• Doesn’t need to be strenuous to work!
• Behavioral changes that focus on identifying cues that cause
unhealthy eating
• Where does fat go when you lose weight?
How do you burn fat?
• The act of metabolising triglycerides stored in adipose tissues • Average fatty acid’s: • Oleate C18 H34O2 • Palmiate C16H32O2 • Linoleate C18H32O2 • All esterify to C55H104O6 • Oxidation → 55CO2 + 52H2O + energy • Complete oxidation of 10kg human fat requires 29kg of inhaled O2 -you breathe out the fat when burning
What are some examples of changes in knowledge about diet?
- Key examples:
- Cholesterol and fats
- Eggs
- Dairy
- Low fat • Etc.
- This is difficult for the general public to comprehend and follow
