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Saturated Fat Linked to Alzheimer’s Disease

Saturated fat (from animal source) has been implicated as associated with increased cholesterol (bad and total), high blood pressure, atherosclerosis, and other forms of cardiovascular disease, and is now linked with Alzheimer's disease as well.
Saturated fat (from animal source) has been implicated as associated with increased cholesterol (bad and total), high blood pressure, atherosclerosis, and other forms of cardiovascular disease, and is now linked with Alzheimer's disease as well.

Saturated fat (from animal source) has been implicated as associated with increased cholesterol (bad and total), high blood pressure, atherosclerosis, and other forms of cardiovascular disease, and is now linked with Alzheimer’s disease as well.

The Winnipeg Free Press released this article today:  Saturated Fat May Make Brain Vulnerable to Alzheimer’s Disease

bacon

The article talks about a small study released by the Journal of American Medical Association, which found that increased intake of saturated fats decreased a chemical called ApoE (Apolipoprotein E) which helps chaperone amyloid beta proteins out of the brain.

In Alzheimer’s disease, abnormal clumps of amyloid beta peptide and neurofibrillary tangles reside in the brain leading to increasing neurodegeneration, causing the forgetfulness and dementia that we associate with the disease.  The amyloid beta peptides cause plaques to form on the brain.

Apolipoprotein E might sound familiar, lipoproteins are what are commonly referred to as “cholesterol,” as the fats and cholesterols actually travel through the body in a vessel which is encased in phospholipids (which have a fat-soluble phase towards the inside of the vessel, where the cholesterols and fats reside, and water-soluble phase (the protein) on the outside which allows the vessel to travel through the body via the bloodstream).  Good cholesterol vs bad cholesterol is merely the type and size of the vessel, and demarks it’s main constituents, for instance VLDL and LDL are larger and contain more cholesterol and fat and less protein, whereas HDL (good) cholesterol is smaller, denser, and contains more protein. Although these “standard” lipoproteins are within general body transport, and the brain has it’s own transport system.

lipoprotein diagram - chylomicrons, VLDL, LDL, HDL have this basic form

lipoprotein diagram – chylomicrons, VLDL, LDL, HDL have this basic form

lipoproteins

In the study, it was found that people who consumed a high-saturated fat diet had higher levels of the amyloid beta protein circulating within spinal fluids.  It was also found that people who consumed a low-saturated fat diet were able to reduce the levels of amyloid beta protein circulating.   These changes were detectable after only a month of diet changes.

Apolipoprotein is a protein involved specifically in the transport of cholesterol. Apo-E is a component of VLDL, HDL, chylomicrons, and chylomicron remnants, and the most important physiological form is that involved with LDL cholesterol and it’s LDL receptor-related protein and the LDL receptor. In this system, it helps deliver cholesterol back to the liver for processing and removal.  The cholesterol cycle itself however, is ridiculously complicated so I will leave you with this image to just ponder that thought for a moment.

the cholesterol cycle, from my class notes

the cholesterol cycle, from my class notes

 

This isn’t the first study to look at this, not nearly.  Nor is it the only deleterious effect of saturated fat that has been found.  

In this 2003 study of 815 subjects who were followed for 4 years, it was found that intake of saturated and trans fat were positively associated with the development of Alzheimer’s in 131 subjects.  Where those within the highest 20% of saturated fat intake were found to have a 2.2X increased risk of onset of the disease.  An inverse relationship was found between vegetable oils/fats and Alzheimer’s disease.

Similarly, in another study analyzing the risk of Alzheimer’s disease in New York over a four year period, the risk was found to be greater for those with high intake of total and saturated fats.  And in another study analyzing the association between dietary fat intake and dementia, it was found that high intakes of saturated fat and cholesterol increased the risk of dementia, while high intake of fish oils (omega-3) decreased this risk.

And, the Australian study published in 2009 in the British Journal of Nutrition, demonstrated that a diet high in saturated fats causes damage to the selective blood-brain-barrier that exists on all brain blood vessels that protects the brain from toxins and chemicals that shouldn’t cross.  In this animal study it was shown that a 2-month long high-saturated fat diet caused significant change to blood vessels and substantial deterioration to blood vessel structures. The brains that were studied were remarkably similar to human Alzheimer’s patients and had very high levels of amyloid, AND there were high levels of fat found in those amyloid deposits on the brain.

Ok, enough scientific evidence.  What’s a saturated fat?  Well the very simple definition is that it is a fat that is saturated in Hydrogen atoms and therefore contains no double bonds.  The chemical structure as a result is very linear.

Sat-Unsat-Fat

 

fatacids

 

Saturated fats are generally from animal sources, such as full fat dairy, beef, bacon, and you know, probably everything you love and hold dear.

19513

 

 

fatty sandwich fresh meat plate burger fat bacon

So what can you do?  Well, the recommendation in Canada (based on all the available scientific evidence) is for no more than 10% of caloric intake to come from saturated fats.  So, for instance, if you have a 2200 calorie diet, then no more than 220 calories should come from saturated fats (daily, on average).  Since fats provide 9 kcal per gram then that is equal to 24.4 grams, which still gives you lots of room since:

  • 1 cup of 2% milk provides ~ 3 grams of saturated fat
  • 1 oz of cheddar cheese is ~ 6 grams of saturated fat
  • 1 oz of bacon is ~ 4 grams of saturated fat

The answer my friends, is therefore moderation & a mindful diet.

 

References

Morris MCEvans DABienias JLTangney CCBennett DAAggarwal NSchneider JWilson RS. (2003). Dietary fats and the risk of incident Alzheimer disease. Archives of Neurology, 60(8), 1072.

Gropper SS, Smith JL, Groff JL. (2009). Advanced Nutrition and Human Metabolism, 5th Eds. Belmont, CA: Wadsworth.

Mahan LK, Escott-Stump S, Raymond JL. (2012). Krause’s Food and the Nutrition Care Process, 13th Eds. St Louis, MO: Elsevier.

Luchsinger JA, Min-Xing T, Shea S, Mayeux R. (2002) Caloric intake and the risk of Alzheimer disease. Arch Neurol. 2002;59:1258-1263.

Kalmijn S, Launer LJ, Ott A, Witteman JC, Hofman A, Breteler MM. (1997). Dietary fat intake and the risk of incident dementia in the Rotterdam Study. Ann Neurol. ;42:776-782

Morris, MC (2004). Diet and Alzheimer’s disease: what the evidence shows. Medscape General Medicine, 6(1),e8. Retrieved from http://www.medscape.com/viewarticle/466037_2

Zukerman, W (2009). Saturated fats linked to Alzheimer’s disease. ABC Science. Retrieved from http://www.abc.net.au/science/articles/2009/09/08/2679589.htm#.Ub-fS-e1GSo

 

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