Re: What does the latest "study" really tell us about eating fish?
- From: "Sbharris[atsign]ix.netcom.com" <sbharris@xxxxxxxxxxxxx>
- Date: 12 Oct 2005 19:16:41 -0700
montygram wrote:
> I read a report of this study in Newsday newspaper, page A5, 10/11/2005
> - that is the source of my information. Let's review it:
>
> 1. It is from the good people at Rush, who would not even answer a
> basic question I put to them about a previous "study" of theirs
> that concluded that "saturated fat," but not "animal fat" was
> "associated" with Alzheimer's disease (AD) among a group of
> people who did not consume any appreciable amount of coconut oil or
> palm kernel oil. How is this possible? They would not answer when I
> asked. After thinking it over, I realized what they had done, which
> was to note that items like pork and beef were less healthy than
> chicken and fish (in general). Why didn't they just say that, as
> other researchers have? I don't know, but I doubt you will get an
> answer if you ask them. I couldn't.
COMMENT:
They probably figured you were unable to understand a logistic
regression on variables of food composition. Yes, it's always possible
in logistic regressions to get a variable that is a proxy variable
(marker variable) for the true causal agent. In this case, it's always
possible saturated fat is a proxy for something else unhealthy. And for
that matter, it's possible that fish-eating is a proxy for some other
really healthy activity. Just unlikely.
> 2. It appears that they are mining the same sources they did for the
> other study. They give simple tests to old people and also ask them to
> fill out questionnaires about what they ate. Many of them went on to
> develop AD within a few years. Were their memories failing before
> obvious signs of AD were present, and can we trust their memories at
> that point? Unless there is a way to control for this, it cannot be
> considered "science."
COMMENT:
It is controlled by means of the other recalled foods of the same
eating frequency. Why would the start of Alzheimer's disease cause a
person to differentially forget that they ate (say) fish once a week,
vs. porkchops once a week? I don't know if there were controls for
poverty of recall (to correct for people who couldn't recall ANY low
frequency items) but good studies usually do this. For just the reasons
we're discussing.
> 3. The conclusion was "eating fish at least once a week is good for
> the brain, slowing age-related mental decline." Now I agree that
> this makes sense, if the people ate fish low in fat as a substitute for
> beef and pork (and fried chicken, as well as a few other nasty things
> they would have eaten instead). But what about those great omega 3
> PUFAs, you ask? On to the next item:
>
> 4. "The researchers looked for, but failed to find, a link between
> omega-3 fatty acids and protection from brain decline."
COMMENT:
Yes, but they did find a link between long chain omega-3's and brain
decline. It's DHA that is in brains. If you dilute out that effect by
looking at ALL omega-3's in the diet (including ALA from plants which
isn't converted well to DHA) you may not find any effect. Which they
did not.
> Just as I
> have said here many times, it is not that fish is so good, but that
> beef and pork (especially they way they are processed, prepared,
> cooked, etc.) are so bad.
COMMENT
No, you're mis-reading the study. If you improperly lump in non-fish
omega-3, you don't find brain protection. But you wouldn't expect to.
It's not the plant omega-3's the normal human brain is made of. It's
the fish omega-3's.
> I've eaten canned tuna which had a label
> that said 0 grams of fat, so the fat is not the issue.
COMMENT:
That just means they picked their serving size to get the fat below 1
gram, meaning they can legally put down "0". It doesn't mean it really
is zero. That doesn't mean tuna doesn't have a lot of w-3 per calorie.
Is has hundreds of times more than your coconut oil, and more than any
other meat you can name.
> Basically,
> canned tuna with 0 grams of fat is a good source of protein, though a
> bit serotogenic (so eating a lot would be unhealthy, though that was
> not the case among these old folks) and the mercury levels could be a
> concern to some. In other words, compared to a fried steak, high in
> iron, oxidized cholesterol, arachidonic acid and other PUFAs, etc.,
> something like canned tuna is much better.
COMMENT:
No. Again, it is true that fish is relatively low in fat (10% of
calories typically, and almost never more than 15%), but if you look at
it as grams w-3 per calorie, your tuna still beats your other meats by
a mile. Sorry for your hypothesis. Guess you'll have to stop eating it.
SBH
.
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