This summary is based on knowledge clips and modules available for student who follow(ed) the course
Food Components and Health (HNH-32206 – NUTR101x) and was made in December 2018. The
information provided via other learning material (lectures and assignments) has not been implemented
in this summary.
Module 1 – Basic Principles of Nutritional Science
1.2 – Overview of Study Designs
Research forms the basics of nutritional science. Experimental studies (interventions/trial). Particular
factor is changed, e.g. diet. Most powerful research design in nutritional science only this study can
show a causal relationship. Standard: subjects are randomly divided in two or more groups. Placebo
for the control group. Treatment can also involve an entire diet or an advice. Ideally, interventions
should be double-blind (participants and researchers do not know). In the most powerful study
designs: half of participants first get A followed by B, other group first B followed by A (crossover
design). Usually, study not performed for risk factors. Most often only for short period. Take people
who have had a heart attack since the chance for a second one is big.
In observational studies, the researches don’t change anything, but record the dietary habits of a large
number of people. Do not provide information on whether a relation between a dietary component
and an outcome for certain diseases is causal. Cannot lead to the conclusion. Rather they can conclude
that something is associated. Study relies on natural variation between groups, thus hard to get
meaningful data. To make a link between dietary intake and risk of disease, solid information about
the composition of the diet is needed (dietary assessment). When the participant does this
themselves, it’s called self-reported dietary assessment. Most common way to do this is via the Food
Frequency Questionnaire (FFQ), which needs to be adapted for each country. Another way is to ask
people to recall the foods they ate over the past 24 hours, also diaries can be used. This can be quite
accurate, but people tend to change their food consumption, also expensive and time-consuming.
Food composition tables helps researches to determine the nutrient intake. Conclusion cannot be
drawn, only stated that it has an association or correlation. Observational studies have been really
important to prove that smoking increases the risk for lung cancer. Study can be really powerful when
the effect is very large. Harder for food studies since the effect are smaller and many confounding
factors. Types of observational studies:
- Ecological study. Population based studies. Units of analysis are not individuals but
populations or groups of people. Example: relation between consumption of olive oil and risk
of heart disease. Disadvantages: wrong conclusions (alcohol-traffic: other factors such as road,
seatbelt etc.).
- Cross-sectional study. Dietary intake and outcome are assessed at the same time, ‘snapshot’.
Example: diet soda related to BMI. Disadvantages: exposure could be the consequence of the
outcome, in stead of other way around (high BMI people drink diet soda to lose weight),
reverse causality. Main limitation: inability to determine which comes first, exposure or
outcome. When people don’t know about the parameter (blood pressure etc.), the direction
is often fixed. Prone to confounding: third factor which is related to both determinant and
outcome. Example: meat consumption has relation to colon cancer but actually meat
consumption is related to BMI which is related to the disease. Adjustment for confounding by
applying computational tools.
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, - Case-control study. Retrospective; they look back. Group of people with disease (cases) and
group without disease (control). Dietary assessment tool is used (FFQ), determine difference
in intake of nutrients or foods. Advantage: allow to study link between diet and rare diseases.
Disadvantage: prone to different types of bias; selection bias (e.g. different economic groups,
different diet), use same hospital to use this. Or recall bias: systematic differences between
cases and controls in the way they remember or report dietary intake. Due to different
recollection of the past than healthy people. Minimize this by use a control group with
different disease. Prone to confounding.
- Cohort study. Prospective; people are followed over time. Key point is that the participants
report their dietary habits at the beginning of the study and sometimes again every couple
years. Asked if they develop a certain disease. Very powerful and form the basis for many of
our dietary recommendations. Limitations: 1) relies on self-reported dietary assessments, not
very accurate, 2) confounding, can be partly removed during data analysis.
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,1.3 – Designing Research Studies
Experimental study: add 75 grams of almonds to the diet and give iso-caloric product to other test
group. Throat cancer: institutional review board needs to approve the study. Case-control would be a
better option. Vegetables on heart disease: experimental cannot be done since it will be obvious in
which group a participant will be. Cohort study will be better, but needs to include many people. Can
only establish correlation, not conclusion. In nutrition, effects can be low, increasing the risk of not
being causal. Meta studies: findings of several independent studies are combined and re-analysed,
best method of analysis.
Module 2 – Carbohydrates
2.2 – Chemistry of Carbohydrates
Simple carbohydrates: mono- and disaccharides. Monosaccharides: glucose, fructose and galactose
(not present in our diets as monosaccharide). Monosaccharides can be absorbed directly into the
bloodstream, don’t require digestion, and can be used as energy source. Disaccharides: maltose (glu-
glu), sucrose (glu-fruc) and lactose (glu-gala, milk sugar). Galactose not as monosaccharide in diet,
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, maltose only little. Need to be broken down into monosaccharides, hydrolysis supported by enzymes
(sucrase, etc.). Table-sugar is sucrose, blood sugar is glucose. Inverted sugar: mixture of equal amounts
of glucose and fructose, produced by enzymatic cleavage, sweeter than sucrose. Used to retard sugar
crystallization and to retain moisture in packaged food. High-fructose corn syrup: HFCS number
(percentage fructose), ratio of fructose and glucose differ.
Complex carbohydrates: polysaccharides: glycogen, starch and fibres. Glycogen: resembles
amylopectin, present in small amounts in animal foods. Starch: polymer of glucose in the form of
amylopectin (branched) and amylose (linear). Non-digestible: dietary fibres are dietary carbohydrates
that are not subject to digestion by endogenous enzymes, but may be digested by bacteria in the colon.
Common classification: viscous fibres (soluble) and non-viscous fibres (insoluble). Or in three
categories: fibres naturally from food, obtained from raw material or synthetic. Support proper
function of the GI tract, prevents constipation and contributes to several other health effects. Soluble
fibre: pectin, some hemicelluloses (xylans, mannans, guar gum) and fructans (polymers of fructose,
inulin). Insoluble fibres: cellulose, lignins (not a polysaccharide), many hemicelluloses and resistant
starches. RS1: physically inaccessible starch, RS2: granular starch (e.g. unripe banana), RS3:
retrograded starch (cooked and cooled starchy foods) and RS4: chemically modified.
Bran: concentrated source of fibre, germ: not that rich in fibre but high in vitamins and minerals,
endosperm: starch-rich.
2.3 – Carbohydrate Content of Foods
Predominant sources of carbohydrate in most people’s diet are starchy foods such as wheat, corn, rice,
cassava and potatoes. The raw forms of these foods (e.g. whole wheat, brown rice etc) also contain
substantial amounts of fibre, which is mostly lost during processing. Many foods are rich in
carbohydrates due to their high sugar content, which is present naturally (as in fruits) or added during
processing. Plant foods in their natural form usually contain substantial amounts of fibre. Glycogen
(carbohydrate) in meat. Fibre sources: fruits, vegetables, nuts and seeds, legumes, whole grains.
2.4 – Carbohydrate Digestion and Absorption
Digestible carbohydrates: mouth: saliva contains amylase which can break down starch to some
degree. As soon as the food is swallowed and enters the stomach, salivary amylase becomes
inactivated by the acidity. Duodenum: pancreatic amylase, polymer of glucose is broken down to
maltose (glu-glu) and glucose subunits. Body has appropriate enzymes to break down disaccharides to
monosaccharides (disaccharidases: lactase, sucrase and maltase). Uptake by enterocytes, which have
specific transporters. Then they go from the cell interior to the bloodstream and immediately go
through the portal vein to the liver. Fructose is cleared so no fructose reaches the tissue outside the
liver. Glucose continues to go through the body.
Non-digestible carbohydrates. Not subject to digestion by digestive enzymes. Depending on the type
of fibre, some digestion takes place in the large intestine, which happens through the microbiota (colon
bacteria), known as fermentation. Products: depends on the microbiota, short chain fatty acids (SCFA):
acetate, propionate and butyrate. These are believed to contribute to the positive health effect of
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