Effect of different animal and vegetable fats

miles

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http://cancerres.aacrjournals.org/conte ... 7.abstract

Hello, I found this study on the Comparative effects of different animal and vegetable fats on tumours in rats.
Can anyone explain to me why the study seems to show that that a 20 per cent corn oil diet seems to have been better than 20 per cent beef fat in terms of not facilitating tumours?
Thanks.
 

4peatssake

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miles said:
http://cancerres.aacrjournals.org/content/46/2/757.abstract

Hello, I found this study on the Comparative effects of different animal and vegetable fats on tumours in rats.
Can anyone explain to me why the study seems to show that that a 20 per cent corn oil diet seems to have been better than 20 per cent beef fat in terms of not facilitating tumours?
Thanks.
I just had a very quick glance but perhaps the answer is as simple as - because "This work was supported by Grants CA-33240 and CA-24538 from the National Cancer Institute, NIH."
 

Mittir

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Few quotes from the study
Rats fed a 20% beef tallow diet during the same period also demonstrated
enhanced tumor development as compared to rats fed the 5% corn oil diet for the entire experiment, although these increases barely missed statistical significance.

If beef tallow does not cause statistically significant change then leave it
out of conclusion.It is more reasonable to say that Lard increased
tumor development than just saying animal fat did it.
They did not do their analysis on fatty acid composition for any of the
fat they used. They relied on the food supplier. The PUFA content
of lard is almost identical to USDA data.It has been shown
that fatty acid composition of non ruminant like pig
depends largely on dietary fatty acid composition.
Corn and grain fed pig can have upto 30 percent PUFA.
Beef tallow also reflects it dietary intake of fatty acids. RP mentioned how so many
studies use high PUFA lard and blame the results on saturated fat.

They mentioned that estrogen in animal fat could have been a cause. Then
they rule out that possibility based on some tests. I do not know if these authors
are expert in endocrinology. The lead author has a PhD in physiology and specialization
in Pharmacology. It is a possibility that they made a mistake in measuring estrogen's
role in tumor development.They clearly do not know the mechanism ..
The mechanism(s) by which animal fat diets bring about this stimulated tumor development is unknown; however, it does not appear to result from exogenous or endogenous endocrine stimulation.

They discussed that their results differ from other previous studies particularly
on PUFA rich oil and beef tallow.

dietary fat intake stimulates murine mammary tumorigenesis. In
general high fat diets containing primarily polyunsaturated fatty
acids enhance mammary tumor growth to a greater extent than
do diets containing saturated fatty acids, and fats with the
highest concentrations of C18:2 fatty acids (linoleic) are the most
potent (18-20). Thus high corn oil (60% linoleic) diets have been
shown to stimulate mammary tumorigenesis to a greater extent
than do equally high lard (10% linoleic), palm oil (10% linoleic),
beef tallow (3% linoleic), or coconut oil (2% linoleic) diets, when
fed to rats during the promotional phase of carcinogenesis
(19,
21-24).
Rogers ef al. (8) have reported similar
findings in rats fed high lard diets. However, the current study
suggests that this stimulation may not be unique to lard or is an
effect which can be induced by all high saturated fat diets.
(Based on statistically insignificant association between beef tallow and tumor)
 

4peatssake

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Mittir said:
RP mentioned how so many studies use high PUFA lard and blame the results on saturated fat.
^This.

Thanks for taking your time to break this down Mittir.
 

jyb

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Mittir said:
They did not do their analysis on fatty acid composition for any of the
fat they used. They relied on the food supplier. The PUFA content
of lard is almost identical to USDA data.It has been shown
that fatty acid composition of non ruminant like pig
depends largely on dietary fatty acid composition.

It's actually a pretty serious scientific flaw. In terms of scientific rigour, medical research is really closer to psychology (whose top journals famously publish articles with dodgy statistical work because that makes more spectacular findings possible) than science.
 

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