EDIT: Arrgh, I'm an idiot and linked to the wrong study. Here's the correct one: http://onlinelibrary.wiley.com/doi/10.1002/ana.23593/abstract
(Incorrect but very similar study: http://www.ncbi.nlm.nih.gov/pubmed/21568955)
Briefly, this was a prospective observational questionnaire-based study which tracked fat intake of "older" women. The women who reported eating the most saturated fat had the most cognitive decline over 4 years. Those who ate the most monounsaturated fat had the least cognitive decline.
I know, I know, corrolation does not equal causation and questionnaires are notoriously unreliable. But I feel nervous when I see studies suggesting that saturated fat is bad for you, and I see a fair number of them. I find it hard to point others to studies such as the Krauss 2010 meta-analysis (which found no increased cardiac risk associated with saturated fat) when there are plenty of other ones which reach the oppsite conclusion.
Reassure me, please?
asked byAnnika (1356)
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on May 24, 2012
at 11:28 AM
Annika, my guess would be that there is a correlation because the women who eat more saturated fat are the least healthy, eat more junk food, exercise less and generally care less about their health. This is what observational studies such as this normally show. They also normally show a correlation with sat fat intake and smoking and drinking.
On the other hand, women who eat more mono fats are more likely to be health conscious, look after themselves and exercise.
Based on these correlations I have mentioned, it is safe to assume that mono-unsaturated fats make women exercise more. And that saturated fat make women smoke and drink. Both these statements are equally ridiculous.
Obervsational studies such as this, can not show that sat fat does anything, it is nearly impossible for an observational study to prove anything.
on May 23, 2012
at 07:49 PM
First -- This study didn't find sat fat correlated with cognitive decline:
There were no associations between degree of cognitive decline and intake of SFA (P=.69), TFA (P=.54), or DC (P=.64) ...
Greater intake of SFA, TFA, and DC was not associated with cognitive decline, whereas greater MUFA intake was associated with less cognitive decline.
SFA = Saturated fat; TFA = trans fat; MUFA = MONOunsaturated fat (olive oil, canola oil, refined safflower oil, etc).
Seconda -- This is a population-based study and the dietary data was gathered using food frequency questionnaires (FFQs). FFQs are NOTORIOUSLY unreliable -- they're highly subjective and inaccurate. They ask individuals to report how often they eat certain food stuffs (ie, "How many times per week do you eat _" etc). The user's answer is, at best, a guestimate. Also, FFQs often aren't terribly specific -- ie, no differentiation between different types of margarine, despite the fact that fats vary considerably across brands.
These types of studies can be helpful for forming a hypothesis to base further study on, but not so useful for making dietary recommendations.
Keep eating butter.
on May 24, 2012
at 02:41 AM
Here is another good answer..
on May 24, 2012
at 10:53 AM
Interesting. Two studies saying very similar things: MUFA seems protective. PUFA and total fat seem neutral. Saturated seems to be neutral to damaging. There's most likely more than fat in play here, so I think broader studies looking at cognitive decline with the entire diet are really necessary. Is there a comfounding dietary variable associated with satruated fat and cognitive decline? Perhaps.
But it would be silly to write off one or the other by cherry-picking which studies you agree with.