Background: Dietary fat intake is a compelling focus for prevention of late-life cognitive decline; it is readily modifiable and may have significant impact on both general health and cognitive function.They found that monounsaturated fat was related to less decline than saturated fat. When people think "monounsaturated fat" they think olive oil. Unfortunately, olive oil contains saturated fat. Two tablespoons of olive oil contain the same amount of saturated fat as 2 eggs or a cubic inch of cheddar cheese.
Methods: We examined prospectively the relations of major dietary fatty acids (FAs) (saturated [SFA], mono-unsaturated [MUFA], total poly-unsaturated [PUFA], trans-unsaturated); n-6 and n-3 (omega-3) FAs; and the n-6:n-3 FA ratio to late-life cognition. Among 6,183 Women's Health Study participants aged 65-95 years, we measured baseline fat intake using a validated semi-quantitative food frequency questionnaire and assessed cognition 3 times over 5 years.
Conclusions: Higher saturated fat intake is associated with worse 5-year cognitive decline, while higher MUFA intake is related to less decline. Higher omega-3 intake is associated with better episodic memory over time, while higher n-6:n-3 ratio is associated with decline. These results strongly support the hypothesis that the balance of different fat types is relevant to cognitive aging.
Foods that are naturally high in monounsaturated fat and also low in saturated fat include vegetable greens, rice, corn, chickpeas - foods that are naturally low in fat.
Update: Here's another study, except in women with type 2 diabetes. Women, by the way, have a higher prevalence of both type 2 diabetes and cognitive decline than men. Same finding, saturated fat leads to cognitive decline:
Dietary Fat Intake and Cognitive Decline in Women With Type 2 Diabetes, Diabetes Care, 2009
We evaluated cognitive function in 1,486 Nurses' Health Study participants, aged ≥70 years, with type 2 diabetes.You can't say that their diabetes led to their cognitive decline because the researchers analyzed diet before and after diabetes diagnosis and found the same link. (You might say that it contributed though.) You might also say, as they did, that the same processes that caused the diabetes also caused the mental decline:
Conclusions: In women with type 2 diabetes, we found that higher intakes of saturated and trans fat were related to substantially worse cognitive decline. ... The magnitude of these results was considerable, and the associations we observed were equivalent to the cognitive effects we find for 6–7 years of aging in these women.
Importantly, these relations were similar before and after diabetes diagnosis.
To our knowledge, this is the first large-scale prospective study to examine dietary fat intake in relation to cognitive decline among type 2 diabetic subjects.
"Higher intakes of saturated and trans fat and lower intakes of mono- and polyunsaturated fat can contribute to insulin resistance and an atherogenic lipid profile. Moreover, insulin resistance, high insulin levels, and cholesterol are all implicated in β-amyloid accumulation in the brain—the pathologic hallmark of Alzheimer's disease."
Lately, I have be working hard to reduce fat from my diet. It is not easy. Fat seems to be everywhere. No wonder we have cognitive decline as we get older. However, I am having success if the reduction in my cholesterol numbers is an indication.
The big things are greatly reducing meat and dairy consumption plus eliminating all fried foods. Salad dressings are a no-no since they are mostly fat. One must also avoid added cooking oils. Of course, processed foods and junk foods are also a good source of too much fat. This leaves mostly a plant based diet. However, some plants based foods contain high levels of fat so ones needs to be careful not to eat too much of them. These high fat plant based foods include dark chocolate (my favorite), avocados (guacamole), nuts and seeds (even flax seed is over 60% fat). So good luck with getting the fat out.
There is fat in everything. Ok, not everything. I'm exaggerating. Very little fat in celery. Still, it's near impossible to go out to eat and avoid fat. And the fat you do get is crap fat, especially, as you say, in processed foods. Cheap soybean and corn and cottonseed oils that have been solvent-bathed, hydrogenated, bleached, and heated to an inch of their genetically-modified life, if they had any life. Full of omega-6 fatty acids which this study found led to memory loss.
Boiling has been my go-to method of cooking these days. When it doubt, boil.
I'm looking at another study. I'll add it to the bottom of this one. Same finding ... saturated fat intake leads to cognitive decline. Animal foods and dairy products supply a lot of saturated fat.
Bix, I know we can't eliminate all fat from our diets. And we need a little fat in out diets. As you pointed out, almost all foods have some fat. Even beans and apples have about 3% by calories. The "Fork over Knives" guys say we should only get 10% of our calories from fat. You need a completely plant based diet to do that. 10% may be excessive for people without cardio-vascular disease but we certainly we need less than the 30 to 35% the USDA has in its guidelines. I do know that lowering my fat intake will lower my cholesterol. I am aiming for about 20% fat in my diet. I think I can do that without completely eliminating all high-fat plants I like and I can enjoy a little meat and cheese once in a while.
By the way I forgot to mention olives (green or black)on my previous comment. They have a lot of fat too ( >75% by calories)
It's really the carbohydrate content of the diet that is the problem. Check out "Why We Get Fat" by Gary Taubes.
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