Dietary Fat Composition

Another promising area of study involves the effect of dietary fat composition on the risk of Alzheimer's disease. The composition of fat in the diet is known to affect blood cholesterol levels. In metabolic studies, diets with a high ratio of saturated fat to polyunsaturated or monounsaturated fats resulted in a poor blood cholesterol profile, characterized by high levels of low-density lipoprotein and low levels of high-density lipoprotein cholesterol.[12] Consumption of transunsaturated fat, obtained from partially hydrogenated vegetable oils in commercially baked products, is particularly hypercholesterolemic.[13]

Although the biochemical mechanism is not yet identified, cholesterol appears to be an important component in Alzheimer's disease and is involved in both the generation and deposition of A-beta.[14] One of the more important genetic risk factors for Alzheimer's disease, the apolipoprotein E-ε4 allele (APOE-ε4), is the principal cholesterol transport in the brain.

Several lines of evidence support the theory that an elevated blood cholesterol level is related to the development of Alzheimer's disease. In experimental models, animals fed high-fat and high-cholesterol diets exhibited impaired learning and memory performance compared with animals on control diets and also demonstrated more A-beta deposition in the brain, greater loss of neurons, and other Alzheimer's disease-related neuropathology.[15,16] One study of 444 Finnish men found that an elevated blood cholesterol level (> 6.5 mmol/L) in midlife was associated with 3 times the risk of developing Alzheimer's disease in late life.[17]

Two recent studies of patients who had been prescribed statin drugs found a significantly lower risk of Alzheimer's disease compared with similar patients who were not prescribed these medications.[18,19] Whether the observed reduction in Alzheimer's disease resulted from cholesterol lowering or some other property of these medications remains to be seen as the findings of related studies emerge.

The 3 prospective dietary studies conducted in Chicago,[20] New York,[21] and Rotterdam[22] also examined the relation of dietary fat intake to the development of Alzheimer's disease. The Chicago study reported the strongest evidence of an association. High intake of saturated fat doubled the risk of Alzheimer's disease, and even moderate intake of trans fat increased the risk by 2 to 3 times.[20] By contrast, higher intake of both polyunsaturated and monounsaturated fats was associated with lower risk of developing Alzheimer's disease.

The New York study found evidence of a greater 4-year risk of Alzheimer's disease for those with higher intakes of total fat and saturated fat but no evidence of an association with the intake of polyunsaturated fat.[21] Investigators for the Rotterdam study also found an increased risk of disease with higher intakes of total fat, saturated fat, and cholesterol after 2 years of follow-up,[22] but none of the dietary fats was associated with Alzheimer's disease after 6 years of follow-up.[23] Further study will be required to understand the inconsistent findings across studies and to determine whether the composition of fat in the diet is causally related to risk of Alzheimer's disease.


http://www.medscape.com/viewarticle/466037_2
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I sent this to the Weston Price folks for comment...any researchers here care to critique this? At face value, it is a bit of a worry...

Val

One of the things that comes to my mind is wondering if people who eat a lot of saturated fat also eat more starch with it, and vice versa for the folks who ate more vegetable oils...so the meat and butter eaters would have potatoes and bread, and the olive oil eaters would perhaps have more salads....There is no indication that the researcher controlled for other aspects of diet. One would need to read the original studies, rather than just the abstracts to see what was done.

It would also be interesting to learn about the population demographics of Alzheimer's..do countries and populations who naturally eat a lot of sat fats have higher incidence of Alzheimers? The Inuit for example?

Val

If they were looking might they also find that those who ate the most brussel sprouts also had higher levels of Alzheimer's?

If you look for an association of people who eat a particular thing and people who have a disease, I can't help but think some of the time you're going to be just completely wrong.

Maybe its not what they're eating, but what they aren't eating or genetic?

What about people that eat lots of saturated fats and have good cholesterol readings?

I think that the researchers did not look at whether the sat fat came along wiith trans fat. Also, they usually get what people eat from a questionaire which is not very accurate. I think these results are very wrong.

I think this is the crux of the matter. The abstract starts out saying that high cholesterol readings are implicated in Alzheimer's, and the usual pattern in industrialized countries (who have the higher incidences of Alzheimers) is that of high saturated fat AND high carbs. There are other studies that show the alleged poor effects of saturated fats are exclusively found along with high carb consumption. Take away the carbs, and saturated fat has protective effects regarding stroke, for instance.

I'm going to have my blood levels checked in a few months, and I expect them to be good, judging from the fact that I've lost weight, have great blood pressure, and the wonderful way I feel. I'll go from there.

Also, I feel there is enough evidence of high carb consumption being bad for you that other things are incidental. Some people may have to watch their saturated fat intake, but if my blood profiles look good, I'm not going to worry about Alzheimers.

On a personal note, my maternal grandmother suffered from it for a decade, and I know her diet was high in noodles, biscuits, and the like. She also had high blood pressure for many years. It makes me feel better to avoid these aspects of her life.

The article also starts out with the asumption:

We all know that one isn't true -- except possibly for trans fats. As soon as I read that sentence, the credence of the report was lost for me. Researchers, in my opinion, should not assume anything. And they should do their research before they start a new one.

Yes, but the next sentence, which fleshes out the quoted sentence above, is followed by a reference to some study which the authors believe will back up their assertion. So these authors believe they are basing their assertion on somthing more than assumption. Are the references valid?? I need to get onto MedLine to check out the authors' footnotes to see what information they are using.

I think it is important with this article to treat it with more respect *initially* because they do provide references. I don't want to bash the article until I check those references to see how valid the studies are that the authors are using. It is entirely possible, of course, that the studies are great but may not actually demonstrate the conclusions these authors are drawing (or maybe they do). Articles that just give bald statements without providing backup references are the real problems.

It's also important that we check these references because since they may be used by the anti-saturated fat people to back up their statements. We need to know what these studies/references say specifically so we can refute them specifically or acknowledge them if they bring up valid points.

Just my 2 cents

Grendeldog, that is just what I think as well..unfortunately I don't have access to the facilities to look up original articles where I live. I did send the URL to the Weston Price folks and hope they will do this, or perhaps already have. I suspect that the overal carb consumption may be significantly different between the sat fats vs non sat fats people, and so what would be needed in due course is a study that controls for carbs...if they kept track of these peoples' total diets, they should be able to reanalyze the data and partial out the effect of carbs. However it is likely that they only kept track of fats consumption, so the results could be confounded.

Val

Daninmidmo,

Yes, they did differentiate between trans fats and sat fats.

It is also true that they only quoted one study showing an increase in LDL and decrease in HDL with sat fats...again, once
carbs are controlled for, as in more recent studies that we all are familiar with, the reverse is true it seems, as as much anecdotal evidence here also shows.

ADKPam, be sure to tell us your latest blood results.

Val

Haven't had a chance to look up too much yet, but here is an abstract of 'Reference #13' from MedScape. (Reference#12 didn't have an abstract on line, but here is the reference (it is a meta-study rather than a 'new' study): Mensink RP, Katan MB. Effect of dietary fatty acids on serum lipids and lipoproteins: a meta-analysis of 27 trials. Arterioscler Thromb. 1991;12:911-912. )

N Engl J Med 1990 Aug 16;323(7):439-45 (ISSN: 0028-4793)
Mensink RP; Katan MB
Department of Human Nutrition, Agricultural University, Wageningen, The Netherlands.
BACKGROUND. Fatty acids that contain a trans double bond are consumed in large amounts as hydrogenated oils, but their effects on serum lipoprotein levels are unknown. METHODS. We placed 34 women (mean age, 26 years) and 25 men (mean age, 25 years) on three mixed natural diets of identical nutrient composition, except that 10 percent of the daily energy intake was provided as oleic acid (which contains one cis double bond), trans isomers of oleic acid, or saturated fatty acids. The three diets were consumed for three weeks each, in random order. RESULTS. On the oleic acid diet, the mean (+/- SD) serum values for the entire group for total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol were 4.46 +/- 0.66. 2.67 +/- 0.54, and 1.42 +/- 0.32 mmol per liter (172 +/- 26, 103 +/- 21, and 55 +/- 12 mg per deciliter), respectively. On the trans-fatty-acid diet, the subjects' mean HDL cholesterol level was 0.17 mmol per liter (7 mg per deciliter) lower than the mean value on the diet high in oleic acid (P less than 0.0001; 95 percent confidence interval, 0.13 to 0.20 mmol per liter). The HDL cholesterol level on the saturated-fat diet was the same as on the oleic acid diet. The LDL cholesterol level was 0.37 mmol per liter (14 mg per deciliter) higher on the trans-fatty-acid diet than on the oleic acid diet (P less than 0.0001; 95 percent confidence interval, 0.28 to 0.45 mmol per liter) and 0.47 mmol per liter (18 mg per deciliter) higher on the saturated-fat diet (P less than 0.001; 95 percent confidence interval, 0.39 to 0.55 mmol per liter) than on the oleic acid diet. The effects on lipoprotein levels did not differ between women and men. CONCLUSIONS. The effect of trans fatty acids on the serum lipoprotein profile is at least as unfavorable as that of the cholesterol-raising saturated fatty acids, because they not only raise LDL cholesterol levels but also lower HDL cholesterol levels.

So it looks like they controlled for diet by making carbs equal across all three groups.
So this means that there is no way to check for a significant sat fatsxcarbs interaction vs sat fats in the absence of carbs.

Val

Val

I wouldn't worry about the Mensink study (reference 12). The same authors updated their study in 2003 analysing 60 controlled trials, and give a more favourable view of saturated fat. They looked at the ratio of total to HDL cholesterol, which they say is a more specific (better) marker of coronary artery disease. They found that unsaturated fats lowered the ratio (good thing) and saturated fats did not change it (neither good nor bad).

Then they looked at individual saturated fatty acids: lauric acid increased HDL and lowered the ratio (good); myristic and palmitic acid had no effect (neither good nor bad, neutral); stearic acid slightly lowered the ratio ( slightly good).

This does NOT show that saturated fat worsens blood lipid profiles, but to be more or less neutral. They end by saying that the findings should be confirmed by prospective observational studies. Just such a study by Walter Willett and his Harvard team does indeed confirm these results.

If the alzheimers article is up to date (why does no one ever date their articles?), I wonder why they used the old study? Fishy.

EvelynS, Thanks so much for updating us...I thought it was all a bit fishy too. And yesterday I saw a couple of abstracts of articles re the Rotterdam study, both of which stated that the study showed NO connection between dietary fat and Alzheimer's.
It is disturbing that the article tht kicked off this thread came via Medscape, which is read by zillions of doctors.

Val

Read the actual studies. The differences they talk about are tiny, and barely measurable.

Without going into too much math here, most studies like this report the data as Relative Risk, or Odds Ratios. (Such as RR or 1.98 2.2.)

Note that in the most 'compelling' study, saturated fat intake showed a RR of 2.2.

By most standards, that's barely significant. In fact, MOST studies about diet and such show piddly RR's.

(A good primer on this RR business: http://www.junkscience.com/JSJ_Cour...docourse/14.htm)

Anyway, to quote from one of the studies cited:

"Intakes of total fat, animal fat, and dietary cholesterol were not associated with Alzheimer disease." Arch Neurol 2003 Feb;60(2):194-200~~~~(ISSN: 0003-9942) Morris MC; Evans DA; Bienias JL; Tangney CC; Bennett DA; Aggarwal N; Schneider J; Wilson RS


They've made a mountain out of a molehill, just to get headlines.

KWalt wrote:The real problem is that most people, including me sometimes, just read the headlines and don't bother to check their references, if they give any, to see what the real scoop is and most of them believe what they read too. I'm to the point where I have so little time, that instead of doing my own research, I read what people here, like you-all who did the research, have to say and take everything with a heavy dose of cynicism.