Saturday, August 24, 2019
ABS 394
Subtopic 1C!
•Can descriptive and correlational studies give us information about
causation, that is, whether one factor is the cause of another? Why or
why not?
No, because we cannot say with certainty that there is not another
variable driving any conclusions.
•What type of studies would we have to perform to collect evidence that
one factor is the cause of a specific outcome?
Experimental studies because they give a cause and effect by
manipulating one variable and keeping the others to remain the same.
• Why are systematic reviews necessary for determining cause-effect
relationships better?
"It is a method for systematically combining pertinent qualitative and quantitative ""
"study data from several selected studies to develop a single conclusion that has
"greater statistical power.!
•Greater statistical power!
•Confirmatory data analysis!
•Greater ability to extrapolate to general population affected!
•Considered an evidence-based resource!
"In order to establish cause and effect relationships, we need to do experimental ""
"studies, but they are not easy to do. We are very limited in the choices of "" "
"treatments we can use on humans due to ethical reasons. We usually gather " "
"multiple studies similar in design and do systematic reviews or meta-analyses, " "
"but often times the conclusions we reach are still not as concrete as we desire.!
• Why are meta-analyses statistically stronger than the analysis of any
individual study?
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Saturday, August 24, 2019
This conclusion is statistically stronger than the analysis of any single
study, due to increased numbers of subjects, greater diversity among
subjects, or accumulated effects and results.
•What observations formed the basis of the initial idea that high fat
consumption caused heart disease?
It was under the bases that working Neapolitans had less heart disease
than their neighbors. The more affluent ate a lot of meat and fat while the
working class had a lot of pasta and fresh fruits/veggies, lacking the high
intake of fat as the affluent. The connection was not fat but cholesterol.
•Why did scientists around mid 1950s think that eating a particular kind
of fat, saturated fat, caused cholesterol buildup in the arteries which lead
to heart attacks?
Scientists found that your blood level went up the more you ate a
particular kind of fat. The more animal fat consumed the more heart
disease was shown. The data showed correlation between fat and heart
disease, although it wasn’t causation.
•Was there enough scientific evidence for the initial recommendation for
eating less fat to reduce heart disease?
No, because there was no other data to show causality.
•What are the consequences of consuming foods that are low-fat or fat-
free but have high amounts of refined carbohydrates?
There is more sugar and calories. Obesity and type 2 diabetes grows
dramatically.
•Were the conclusions drawn for high fat or saturated fat intake causing
heart disease based on correlational or experimental studies? Can we
obtain cause and effect relationships simply from correlations or
associations?
The conclusions were based on correlational studies. You cannot obtain
cause and effect relationships from correlations.
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Saturday, August 24, 2019
•What is a fat molecule (triglyceride) made of?
A 3 carbon chain that act as a backbone, & 3 long carbon chains that are
called fatty acids
•What part of the fat molecule determines whether
the fat is solid or liquid at room temperature?
fatty acids
•What is the chemical difference between a saturated and an unsaturated
fatty acid?
fatty acids with one single bond are saturated, those with one or more
double bonds are unsaturated and are rigid which means there are
different ways to arrange those double bonds. The chemical difference is
in the shape.
•What is a trans-fat? How is it made? Where do we find trans-fats?
It is a stable, unsaturated fatty acid. It has the same building blocks as an
unsaturated fat. You can find them in foods with the labeling “partially
hydrogenated”.
•What are the major conclusions from this meta- analysis regarding total
amount of fat consumption and serum cholesterol levels and heart
disease?
Associations between dietary fat intake and risk of CHD is surprisingly
small and the results are not consistent. It failed to account for trans
isomers of unsaturated fats and lack of control for intakes of other types
of fat and other components of diet than total amount of fat in
determining the risk of CHD. Controlled clinical trials have also shown
that replacing saturated fat with polyunsaturated fat is more effective in
lowering serum cholesterol and reducing risk of CHD than simply
reducing total fat consumption.
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Saturday, August 24, 2019
•Which types of fats have been shown to lower the risk of heart disease most
effectively? %
saturated fat, olive oil. Partial replacement of dietary saturated fat with
unsaturated fats seems to reduce the risk of CHD. They also conclude that
increasing intakes of polyunsaturated fats are likely of greater benefit for
cardiovascular health than further reducing saturated fat intakes. Not all
polyunsaturated fats seem to be beneficial.!
•Is there any scientific basis for the low-fat campaign that was promoted
for the last several decades?
No
•Is there any strong evidence for a link between egg consumption and risk
of heart disease?
No
•Which types of changes in the diet did they find to be most effective in
improving blood sugar control?
Similar to the studies on heart disease above, they found that replacing either
carbohydrates or saturated fats with polyunsaturated fats is beneficial for improving
blood sugar control. Substituting carbohydrate and saturated fat with a diet rich in
unsaturated fat, particularly polyunsaturated fat, was beneficial for the regulation of
blood sugar. Sole emphasis on lowering consumption of carbohydrates or saturated
fats would not be optimal.!
• What are some recommended food sources for improving blood sugar
control?
Translated to foods, these findings support benefits of increasing consumption of vegetable oils
and spreads, nuts, fish, and vegetables rich in unsaturated fats (e.g., avocado), in place of either
animal fats or refined grains, starches, and sugars.
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