[Neuroscience] Re: Carotenoid Transport into the RPE

John H. via neur-sci%40net.bio.net (by johnh from goawayplease.com)
Thu Dec 6 03:40:35 EST 2007


"A.G.McDowell" <nospam from nospam.co.uk> wrote in message
news:iafCiJAmQvVHFw7T from mcdowella.demon.co.uk...
> In article <4755969a$0$25349$ed362ca5 from nr2.newsreader.com>, Glen M.
> Sizemore <gmsizemore2 from yahoo.com> writes
>>
> (trim)
>>>
> Confidence intervals are only a little further into the statistics books
> than p-values and are a good deal more illuminating. If the p-value
> would reject the null hypothesis then the confidence interval gives you
> a measure of how far away from the null hypothesis you can plausibly be.
> If the p-value would not reject the null hypothesis you get a measure of
> how big an effect there might be hiding under the noise.
>
> One useful application of confidence intervals is to run an experiment
> with the intention of dismissing some proposed effect - you can't prove
> a negative, but you could come up with a small confidence interval
> around zero and say that any possible effect must be negligible. This
> would be a reason for doing experiments on folk wisdom preventative
> measures for eyesight even if you didn't believe them; you could advance
> the state of knowledge by running a statistically rigorous experiment to
> dismiss them once and for all.


snip

Thanks for your input. The statistical anomalies are one problem but during
the the course of this rushed analysis I have come to despair of what
typically passes as health news. Infuriartingly there are mountains of
websites citing a study or two and then claiming the same proves that
substance A or B is the way to go re this or that health related matter.
Health reports are clear evidence of sick minds. I have developed an
approach which helps address this issue but it is very taxing and beyond
most people. I would have to spend the rest of my life studying health
related issues re nutrition and still only cover a small proportion. My
approach is simply(!) to address the relevant issue at multiple levels of
analysis. So I look for synergy between epidemiological(try to avoid
retrospective studies but cannot always be done), physiological studies,
cellular studies, and to a much lesser extent biochemistry studies. It is
the only way I can think of that allows me any reasonable degree of
confidence in these investigations. Obviously this is a far cry from a
typical gold standard of clinical practice, The Cochrane Reviews. I'm even
more cynical about meta analyses ...

There is a clear antagonism between conventional and alternative medicine
which is another bugabear confounder. Obviously there are "folk wisdom"
remedies that can have considerable value, I've used some myself and to very
good effect. Unfortunately I intuit a bias against the same in US studies, a
bias towards the same in some European studies, and in China they just love
Chinese traditional medicine ... . This is a real shit, it just makes it all
that much harder. Fortunately there are sources around that make strenuous
efforts to be objective. In general though I regard much of what passes as
"health new" as deepy misleading and hopelessly simplistic. A few examples:

Selenium.

One doctor said to me that I had fallen for the selenium myth. This dumb
dick obviously had read a paper in over 20 years. The RDA in Australia for
Se is 65 ug, yet longitudinal studies indicate that 200ug supplementation
halved the rates of many major cancers, and some say the upper safe limit is
400ug. Australia has very low Se in the soils, so much so that when cattle
were first introduced here Se had to be added to their feed. However if the
cattle are feeding near coal power stations, which can release lots of Se,
they can experience Se toxicity. Only recently has Se been added back into
multi vits and the reason for this is that when the value of Se was first
established the dumbass anal health nuts took too much and so had Se
toxicity. So the conventional recommendation for Se is way too low and needs
to be country, perhaps even geographic region specific.

Macular Degeneration

The typical advice is to eat lots of carotenoids. Generally okay except
these are stored in the liver, fat soluble, and the true protective value is
found in two specific carotenoids, lutein and zeaxanthin. Pro vitamin A
carotenoids go directly into the vision cycle and can be reprocessed through
the RPE, generally it is extremely difficult to have a deficiency of pro
vitamin A but macular protection, which is very important for anyone
intending to live past 70, is more contingent on lutein and zeaxanthin
intake than beta carotene. Some studies even demonstrate that too much beta
carotene increases the risk of Age related macular degeneration and this
does have concordance with some cellular and biochemical studies. It may
even have concordance at a physiological level because the gut transporters
for carotenoids may prefer pro vitamin A's over L and Z, hence it is wise to
try focus on those foods which specifically increase the intake of the
latter, rather than just pumping up on vitamin A in general. Only last night
I found a few studies indicating that lutein and zeaxanthin are often
transported by HDL and vLDL. This may be misleading though, it could be that
being fat soluble the L and Z were bound to the fats being transported, not
HDL and vLDL specifically. In relation to Stargardts there is even strong
evidence to suggest that keeping pro vitamin A carotenoid intake low is a
good idea. My friends took their daughter off to a naturopath who
immediately prescribed massive Vit A dosing(perhaps even high enough to
cause liver toxicity). Naturally I hit the roof and wanted to tear down that
naturopaths shingle.

RDAs in general

RDAs are a joke, individual nutrition requirements can vary many fold and
even vary depending on overall health. RDAs are at best a broad guide but
RDAs are really about preventing deficiency related pathologies not
optimising health. Typically, even for lipid soluble nutrients, one can take
many times the RDA without ill effect, though I'd be cautious in pushing
that barrow too far. Mega dosing of vitamin C can be dangerous, it may even
induce extensive oxidation. Yet the megadosing C idea was originally
promulgated by Linus Pauling, the only person to win the Nobel Twice. Meg
dosing of Vit A, if sustained, may not only be a risk factor for macular
degeneration, there is emerging evidence it may induce osteoporosis.
Excessive iron intake is just plain dumb, if you have any inflammatory
condition reducing iron intake, even phlebotomy, can reduce
inflammation(there are also a number of studies that offer support for
this). That's why you rarely see iron in multi vits these days, or at least
very low levels of the same. Yet I can remember 20 years ago ... . Calcium
from milk? That is also problematic.
--------------
I'll stop here ... it just goes on and on and on. It's a real shit. The
irony being that the single best thing we do for our health is learn to stay
little hungry. Caloric restriction(still problems here), weekly fasting,
alternative dietary regimes, all ideas you won't find in the health shops or
the doctors'surgeries or the naturopaths, are far wiser approaches than
salivating over the latest "health news". Hmmm, maybe I should write a book
about all the bullshit that passes as Health News.

So thanks for your input. As you can see that statistical issue is just the
tip of an incredibly deceptive ice berg.

Now that I'm home from work and got that off my chest, I can start working 
again ...

John.







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