EXAM1 Flashcards
Epidemiological (observational) study
Generate hypothesis and establish complex associations/correlations
Explore or test correlations between exposures and outcomes by diet
Can explore complex relationships but cannot prove a causal relationship
Interventional (Experimental)
Test hypothesis and establish causality
Manipulate one or more factors (ind variables) and measure outcomes (dept variables) in subjects
Distinguish 3 major type of epidemiological studies
Cross-sectional
Measure various exposures and outcomes simultaneously
I.e. The National Health and Nutrition Examination Survey (NHANES)
Distinguish 3 major type of epidemiological studies
Retrospective
Assess outcomes before potential causes
Weakest. Compare those with condition to similar people w/o condition
Case-control: compare people who do and don’t have a condition or disease, closely matching them in age, gender, and other variables so that differences in other factors will stand out. These differences may account for the condition in the group that has it
Distinguish 3 major type of epidemiological studies
Prospective Cohort
Follow a group of people sharing certain characteristics over a long period of time
Framingham Heart Study: smoking and high cholesterol affect heart health
Temporality in establishing causal relationships
potential causes (exposures) must appear before outcomes
Necessary
if cause is not there, outcome won’t occur
Essential nutrients are necessary for health but not sufficient
Essential nutrients
Required for physiological functions but can’t be produced - not at all or not in sufficient quantity - by our body; thus, they must be obtained from diet
Operational definition: When they are removed from diet, health declines; when they are added back into diet, health improves
Sufficient
if the cause is there, the outcome will be to
I.e. Vitamin C is sufficient to cure scurvy
Contributory
the cause is necessary and/or sufficient (and thus has effects) only under certain circumstances
I.e. Niacin is necessary for preventing pellagra only when protein consumption is insufficient
Assessment of exposures challenges
- Lack of reliable measurements
- Potential confounding factors and biases
Assessment of health outcomes of interest
- Indexes/biomarkers of disease are used
- Nutritional Assessments are often not specific
24 hr recall
food and drink recorded over 24 hours
May not represent usual intake
Challenges:
* Recall bias
* Retrospective study
Food frequency questionnaire
Food intake patterns
Limited in accuracy and completeness
Observational study
Food Record (Food Diary)
Recorded when person consumes food
Challenges
* Portion sizes estimated
* Most accurate method of dietary assessment
* May not be representative
* Observer effect
Observational study
ABCD of Nutritional Assessment
Anthropometric measurements
* Weight
Biochemical testing (laboratory tests)
* Best method for detecting nutrient deficiency (ie. iron)
Clinical assessment (physical exam)
* Paleness to access anemia
Dietary assessment (diet and health history)
Primary deficiency caused by inadequate diet.
Secondary deficiency caused by problem inside the body (i.e. crohn’s disease)
Interventional studies:
Randomized human clinical trial limitations
Medrn. diet sufficient in preventing cardiovascular events in high-risk
Clinical trial recruiting those at high risk for cardiovascular disease (smoking, hypertension, high LDL, low HDL, overweight/obese, family history) and applying mediterranean diet (provided olive oil or nuts)
Costly and time consuming
* Provide foods for 5 years
Difficult to control for all confounding factors
* Low subject compliance
Ethics
* Chose to use low fat diet as control over high fat diet
Subjects may not be representative: “Generalizability”?
* Applicable conclusions for general population
Reproducibility?
Nutritional status
the health of a person related to how well his/her diet meets the person’s individual nutrient requirements
Both under and overnutrition represent states of malnutrition or poor nutritional status (overnutrition/ toxicity)
Nutrition
The process by which a living organism obtains, assimilates, and uses nutrients or other food components for growth, maintenance of tissues, and reproduction
Human nutrition
science of how dietary intakes affect development, health, and risk of developing diseases later in life
Diet
the foods and beverages a person eats or drinks
Nutrients
Chemical compounds in diet (foods and drinks) that organisms need to sustain life
At an organismal level, nutrients:
Promote growth
Maintain tissues
Regulate physiological processes
* Including reproduction
At a cellular level, nutrients serve as:
Energy substrates
Structural materials
Regulatory agents
Macro vs. micronutrients
Quantity in diet
Macronutrients: carbs, proteins, lipids, water, alcohol
Micronutrients: minerals, vitamins
Organic vs. inorganic nutrients
Organic: compounds containing carbon links
Inorganic: water and minerals
Organic: Vitamins, carbs, proteins, lipids, alcohol
Energy-yielding vs. non-energy-yielding nutrients
Energy-yielding: Carbs (4 kcal/g), proteins (4 kcal/g), lipids (9 kcal/g), alcohol (ethanol)
Non-energy yielding: water, vitamins, minerals
Essential vs. non-essential nutrients vs. conditionally essential nutrients
Operational definition through experiments
I.e. choline depletion/repletion study that established essentiality
Nutrient requirement: lowest intake level of a nutrient that maintains basic physiological functions and supports optimal health
Nutrient requirements differ among individuals
Energy density
a measure of the energy a food provides relative to the weight if the food (kcal per gram)
Nutrient density
the amount of micronutrients and protein of a food item relative to its energy content
Nutrient dense foods- high in nutrients but relatively low in calories
Nutrient-dense foods contain vitamins, minerals, complex carbohydrates, lean protein, and healthy fats
DRI
a set of nutrient intake values for healthy people in the US and Canada. These values are used for planning and assessing diets and include: Estimated Average Requirements (EAR), Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL)
Apply to healthy individuals within a specific gender/life stage group
Established when scientific data are sufficient
EAR
the average dietary energy intake that maintains energy balance and good health in a person of a given age, gender, height, and level of physical activity
Amount that covers half of the population
RDA
the average daily amount of a nutrient considered to meet the known nutrient needs of practically all healthy people; a goal for dietary intake by individuals
Derived from EAR
RDA = EAR + 2 Standard Deviations
AI
the average daily amount of a nutrient that appears sufficient to maintain a specified criterion; a value used as a guide for nutrient intake when an RDA cannot be determined
Established when scientific data are insufficient to establish EAR/RDA
Choline has AI data
UL
the maximum daily amount of a nutrient that appears safe for most healthy people and beyond which there is an increased risk of adverse health effects
Monosaccharides
gluctose, fructose, galactose
Disaccharides
Maltose, sucrose, lactose
Polysaccharides
Amylose, amylopectin, glycogen
Glucose
in starch and blood
aldehyde C=O on terminal end
Fructose
sweetest of nutritionally relevant sugars. I.e. fruit
Ketone C=O on internal carbon
Galactose
in dairy products and milk
Aldehyde C=O on terminal end
Structual forms
Have open (Fischer) and closed ring (Hawthorth projection)
* Both glucose and fructose can form a 5-membered (furanose) or 6-membered (pyranose) ring, although one typically predominates
Fructose often depicted as furanose
Anomeric Carbons
- Anomeric carbon is the C=O (carbonyl) is attached to
- Anomeric on second carbon for fructose and first for glucose and galactose
Glycosidic linkage
Formation: condensation (water is released)
* One sugar loses hydrogen and one loses hydroxyl
Breaking: hydrolysis (digestion- water is a reactant)
Maltose
glucose-glucose
Alpha-1,4 glycosidic linkage
Partial digestion
Sucrose
glucose-fructose
Alpha-1-beta-2 glycosidic linkage
* Unique because glycosidic bond between both anomeric Cs; therefore both trapped in cyclic form, and entirely non-reducing because both anomeric Cs used in glycosidic bond
Lactose
galactose-glucose
Beta-1,4 glycosidic bond
* Difficult to digest (i.e. cellulose)
Sweetness ranking
Fructose, sucrose, glucose, maltose, galactose, lactose
Most to least sweet
Amylose
linear chain of alpha-1,4 glucose molecules
Reducing and nonreducing ends
Amylopectin
branching chain of alpha-1,4 glucose, with alpha-1,6 branches
One reducing end
Glycogen
Branching chain of alpha-1,4 glucose with alpha-1,6 branches (but generally more branches than amylopectin)
* Storage form of glucose in your body- found in muscle and liver
* Liver is blood glucose buffer system: helps maintain blood glucose (thus, glycogen in liver can be mobilized and pushed out into circulation)
Muscle uses it for energy reserve (it cannot contribute to maintenance of blood glucose)
Several nonreducing and one reducing end
Non-digestible or incompletely digestible polysaccharides
Oligosaccharides (3-10 monosaccharides): typically have both alpha and beta glycosidic bonds
Cellulose
Insoluble carbohydrate
beta-1,4 glycosidic bonds which can’t be hydrolyzed
Hemicellulose
Soluble or insoluble, depending on type/structure
Adds bulk to fecal matter and decreases intestinal transit time