glossary in SPOCs!
basic principles nutritional science
ecological study
-
- looking at existing data
- advantage: large number of individuals
- disadvantage: expensive, no info on individual level and can easily lead to wrong
conclusions (correlation isn't causation)
cross-sectional study
-
- snapshot
- advantage: relatively easy and inexpensive
- disadvantage: reverse causality (exposure could be consequence of outcome) and
prone to confounding
case-control study
-
- only difference between groups: colon cancer
- advantage: allows for studying link between diet and rare diseases
, - disadvantage: selection bias, recall bias (different accuracy of memory between
groups) and confounding
cohort study
-
- over time
- advantage: prospective (followed over time) and large number of individuals
- disadvantage: expensive, confounding and self-reported dietary assessments aren’t
always accurate
intervention study (experimental)
-
- random assigning groups
- crossover design
-
- advantage: reveal causal relations and the randomization
- disadvantage: observer bias (solution: ‘blinding’ researcher), ethical considerations
and difficult to study the effect of intervention on disease risk
observational study: only correlation relations
experimental study: causal relations
,carbohydrates
simple carbohydrates: glucose, maltose, lactose
complex carbohydrates: glycogen, starch and fiber
invert sugar: enzymatic cleavage of sucrose → glucose + fructose
high fructose corn syrup (HFCS): corn > starch > glucose > fructose
- variable ratio fructose/glucose
added sugars: added during processing of foods
dietary (fiber) carbohydrates not subject to digestion by endogenous enzymes
- may be partially digested by bacteria in colon
soluble (viscous) fibers: pectins, fructans
insoluble (nonviscous) fibers: cellulose, lignins, resistant starch (RS)
good fiber sources: fruits, vegetables, nuts, seeds, legumes, whole grains
poor sources: milk (products), meat, most processed foods (white bread/rice)
carbohydrate digestion is roughly 1-2 hours
vili increase intestine surface
absorptive cells: enterocytes
absorbed nutrients converge into portal vein > liver
no digestion of dietary fiber in mouth, stomach or small intestine
, digestion/fermentation of dietary fiber in colon by bacteria of gut microbiome
factors affecting composition of gut microbiome: diet, DNA, lifestyle, age, weight, medicine
fermentation of fiber > SCFAs (short-chain fatty acids) & gas
- acetate, propionate, butyrate
blood glucose control: insulin (uptake and storage) and glucagon (breakdown)
- glucose is stored as glycogen
brain uses (in rest) a quarter of your glucose energy (not enough glucose > faint)
fasting;
pancreas: exocrine and endocrine cells
- exocrine cells secrete proteases, lipase, and amylase into the small intestine (via
ducts)
- endocrine cells (islets of Langerhans) secrete their substance directly into the
bloodstream
incretins: set of hormones (in intestine) which stimulate decrease of blood glucose through
insulin
- GLP-1, GIP
- delay gastric emptying (fullness)
- suppresses glucagon secretion
- enhances glucose-dependent insulin secretion
- enhances beta-cell proliferation
- possibly improves insulin sensitivity
basic principles nutritional science
ecological study
-
- looking at existing data
- advantage: large number of individuals
- disadvantage: expensive, no info on individual level and can easily lead to wrong
conclusions (correlation isn't causation)
cross-sectional study
-
- snapshot
- advantage: relatively easy and inexpensive
- disadvantage: reverse causality (exposure could be consequence of outcome) and
prone to confounding
case-control study
-
- only difference between groups: colon cancer
- advantage: allows for studying link between diet and rare diseases
, - disadvantage: selection bias, recall bias (different accuracy of memory between
groups) and confounding
cohort study
-
- over time
- advantage: prospective (followed over time) and large number of individuals
- disadvantage: expensive, confounding and self-reported dietary assessments aren’t
always accurate
intervention study (experimental)
-
- random assigning groups
- crossover design
-
- advantage: reveal causal relations and the randomization
- disadvantage: observer bias (solution: ‘blinding’ researcher), ethical considerations
and difficult to study the effect of intervention on disease risk
observational study: only correlation relations
experimental study: causal relations
,carbohydrates
simple carbohydrates: glucose, maltose, lactose
complex carbohydrates: glycogen, starch and fiber
invert sugar: enzymatic cleavage of sucrose → glucose + fructose
high fructose corn syrup (HFCS): corn > starch > glucose > fructose
- variable ratio fructose/glucose
added sugars: added during processing of foods
dietary (fiber) carbohydrates not subject to digestion by endogenous enzymes
- may be partially digested by bacteria in colon
soluble (viscous) fibers: pectins, fructans
insoluble (nonviscous) fibers: cellulose, lignins, resistant starch (RS)
good fiber sources: fruits, vegetables, nuts, seeds, legumes, whole grains
poor sources: milk (products), meat, most processed foods (white bread/rice)
carbohydrate digestion is roughly 1-2 hours
vili increase intestine surface
absorptive cells: enterocytes
absorbed nutrients converge into portal vein > liver
no digestion of dietary fiber in mouth, stomach or small intestine
, digestion/fermentation of dietary fiber in colon by bacteria of gut microbiome
factors affecting composition of gut microbiome: diet, DNA, lifestyle, age, weight, medicine
fermentation of fiber > SCFAs (short-chain fatty acids) & gas
- acetate, propionate, butyrate
blood glucose control: insulin (uptake and storage) and glucagon (breakdown)
- glucose is stored as glycogen
brain uses (in rest) a quarter of your glucose energy (not enough glucose > faint)
fasting;
pancreas: exocrine and endocrine cells
- exocrine cells secrete proteases, lipase, and amylase into the small intestine (via
ducts)
- endocrine cells (islets of Langerhans) secrete their substance directly into the
bloodstream
incretins: set of hormones (in intestine) which stimulate decrease of blood glucose through
insulin
- GLP-1, GIP
- delay gastric emptying (fullness)
- suppresses glucagon secretion
- enhances glucose-dependent insulin secretion
- enhances beta-cell proliferation
- possibly improves insulin sensitivity
