Alzheimer’s & Cholesterol

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Alzheimer’s disease (AD) currently afflicts at least 4 million Americans and is the leading cause of dementia. The incidence of AD increases with age. Unless something is done to prevent the development of this disease, we can expect the number of Americans with AD to double or triple in the next 20-30 years as the “Baby Boomers” grow older. Medical doctors have little to offer people at risk for AD. Currently there are no FDA approved drugs that can slow the progression of this devastating disease. Prescription drugs currently approved for AD may temporarily reduce the symptoms but do not slow the progression of the underlying disease process.

Blood flow to brain is important

The number two cause of dementia in the US results from disease of the blood vessels. Hypertension, diabetes and high levels of LDL and homocysteine all promote atherosclerosis. In the brain, atherosclerosis and damage to the arterioles can reduce the amount of blood and oxygen reaching the brain. The reduced flow of blood can impair the function of brain cells and this leads to a loss of mental function over time. Controlling risk factors for cardiovascular disease (CVD) can slow, stop or even reverse the damage to these blood vessels. Therefore, controlling CVD risk factors with diet and/or drugs not only greatly reduces the risk of a stroke but can also improve blood flow to the brain, slow the loss of mental function and reduce the risk of senility.

Growing scientific evidence is now suggesting that the same high saturated fat and cholesterol diet that promotes atherosclerosis may also impair brain function by promoting AD. When most people think of high LDL levels in the blood, they associate it with clogged arteries and an increased risk of cardiovascular disease. However, new research is now suggesting that higher levels of LDL in the blood may not only promote the growth of atherosclerotic plaques in the arteries but may also be contributing to the build-up of beta-amyloid plaques in the brain.1 These beta-amyloid plaques are believed to be what kills off brain cells and leads to the loss of brain function in people with AD.

Two recent studies have shown that lowering serum cholesterol levels with statin drugs significantly decreased the prevalence of AD.

• In one study of 60,000 medical records from 3 hospitals, Dr. Wolozin and colleagues found those who took statin drugs to lower their serum cholesterol had a prevalence of probable AD that was 60-73% lower than among those not on statins.2

• The second study identified more than 24,000 people with high cholesterol levels who had taken statins to lower LDL. They were compared with 2 groups:

- 11,000 similar patients who took other cholesterol lowering drugs, which are much less effective at lowering LDL

- 25,000 people with cholesterol levels not high enough to justify cholesterol-lowering medications

Those patients taking the statin drugs were less than 1/3 as likely to have developed dementia.3

Some researchers believe that statin drugs may have some property other than their cholesterol-lowering effects that could impact the development of AD. Other researchers believe the statin drugs reduce AD simply because they reduce LDL. No one as yet is sure how high LDL promotes AD.

The first hint

The first hint that blood lipids and AD were related was the observation that people with a genetic predisposition to develop atherosclerosis because they inherit a certain protein associated with the transport of cholesterol in the blood (Apo E4) were also much more likely to develop AD.4 People who have 2 genes for Apo E4 experience a greater rise in LDL on a typical high-fat American diet than people with genes for Apo E 2 or 3.5

About 15 years ago, Dr. Sparks observed that the atherosclerotic plaque and beta-amyloid plaques tended to occur together when he autopsied brains. About 9 years ago he showed that rabbits fed a cholesterol-rich diet developed both types of plaques. Remarkably, he also showed that the beta-amyloid plaques believed to cause AD actually shrank when the animals were placed on a low-fat, cholesterol-free diet. A study of people in Rotterdam found that those who ate the most omega-3 rich fish had a 70% reduction in the incidence of AD compared to those who ate the least fish. The authors of this study suggested, “that a high saturated fat and cholesterol diet increases the risk of dementia, whereas, fish consumption may decrease this risk.6

Research in animals has shown that fruits and vegetables rich in anti-oxidant nutrients and phytochemicals may also improve mental function in older animals. Others researchers have found that people who consume moderate amounts of alcohol for many years tend to score better on cognitive function tests compared to abstainers or heavy drinkers.7 The regular use of aspirin appears to reduce both the risk of CVD and also AD. It certainly seems like more than a coincidence that so many things that decrease the risk of CVD also decrease the risk of AD.

Bottom Line:

It is too soon to draw any firm conclusion about diet and AD. However, a more vegetarian diet that is low in salt, fat, and cholesterol with modest amounts of nonfat dairy and omega-3 rich fish (salmon, tuna, mackerel, sardines) can be expected to help maintain normal brain function. It is comforting to know that the same type of diet that can prevent or reverse atherosclerosis is likely to help prevent the development of AD and dementia. By Dr. James J. Kenney, PhD, RD, FACN.

References:

1. Haley RW. Arch Intern Med 2000;57:1410-2

2. Wolozin B, et al. Arch Neurol 2000;57:1439-43

3. Jick H, et al. Lancet 2000;356:1627-31

4. Saunders A, et al. Neurology 1993;43:1467-72

5. Tikkanen MJ, et al. Arteriosclerosis 1990;10:285-8

6. Kalmijn S, et al. Ann Neurol 1997;42:776-82

7. Elias PK, et al. Am J Epidemiol 1999;150:580-0

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