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Alzheimer's disease prevention: What you need to know *****

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Low foltae high homocysteine linked to high risk of Alzheimer's disease

Saturday Oct 26, 2013 (foodconsumer.org) -- Alzheimer's disease risk may be lowered by simply eating high amounts of green leafy vegetables or taking folate supplements, according to a study released in Osong Public Health and Research Perspectives.  

Alzheimer's disease is a major form of dementia and doctors say there is no cure for this disease. But evidence suggests that the disease can be prevented in the first place.

The study led by J.H. Song and colleagues from National Institute of Health, Korea Centers for Disease Control and Prevention in Seoul, Korea shows that low serum folate was linked to high risk of Alzheimer's disease.  Folate or folic acid is found high in green leafy vegetables.

On the other hand, the study also revealed that high serum homocysteine was associated with high risk for Alzheimer's disease, compared with those who had lower levels.

For the study, researchers compared 424 controls who had normal cognitive function, with 382 with mild cognitive impairment and 56 dementia patients for the concentrations of total homocysteine, folate, and vitamin B12 in their blood samples.

Compared with controls, dementia or Alzheimer's patients had higher serum homocysteine concentrations, but lower serum folate concentrations.  And an inverse association was found between homocysteine levels and serum folate or vitamin B12 concentrations.
 
Those who had moderate hyperhomocysteinemia were five times as likely as those who had low levels of homoncysteine to acquire dementia or Alzheimer's disease.

Additionally, those who had low serum folate were nearly 4 times as likely as those who had high serum folate concentrations to suffer dementia.

The researchers concluded "Elevated serum Hcy (homocysteine) and decreased serum folate concentrations are associated with the risk of dementia in Korean elders."

It's believed that Alzheimer's disease, which is a major form of dementia, has something to do with oxidative stress or inflammation and antioxidants can help relieve the oxidative stress and thus reduce the risk of Alzheimer's disease.  

Folate or folic acid is only found in plant-based foods particularly in green leafy vegetables, which have also high levels of natural antioxidants.  Food manufacturers fortify folate in processed foods to promote sales so many processed foods including flour have been fortified with folate.  (Note:  too much supplemental folate has been linked to some diseases like cancer.).  Therefore, low folate levels mean low intake of green leafy vegetables, which also means low intake of antioxidants.  So it is uncertain whether low serum folate is a cause for Alzheimer's disease.

More studies on the link between low folate, high homocysteine and high risk of Alzheimer's disease

Early this year, Chinese scientists published a study in  Zhongguo Ying Yong Sheng Li Xue Za Zhi revealing a similar conclusion.  They found that high serum homocysteine or hyperhomocysteinemia is associated with low folate, and both high homocysteine and low folate are linked to high Alzheimer's disease risk.

Homocysteine, a non-protein amino acid that is biosynthesized from methionine, an amino acid used in protein synthesis, is not necessarily the cause for increased risk of Alzheimer's disease, many studies have shown.  Homocysteine can be converted back into cysteine with the help of B-vitamins such as folate, which are found high only in vegetables.

There may be two reasons for a person to get high levels of homocysteine, high intake of eggs, which have high levels of methionine and other high methionine foods, and low serum B-vitamins or low intake of green leafy vegetables.

Early studies show serum homocysteine can be lowered with medications, but the risk of diseases a heart disease, heart attack and stroke cannot be lowered, which means that homocysteine may only be a niomarker, but not a cause for the risk of Alzheimer's disease.

Such evidence suggests high risk of Alzheimer's disease may have something to do with a person's dietary pattern, that is, high intake of eggs or other high methionine foods and low intake of green leafy vegetables may increase the risk of Alzheimer's disease.  Eggs have not only high methionine, but also very high cholesterol, which has been associated with elevated Alzheimer's disease.  So what increases the risk may be cholesterol but not high methionine nor homoncysteine.

Excess cholesterol boosts risk of Alzheimer's disease

Luigi Puglielli from Massachusetts General Hospital, Harvard Medical School in Charlestown, Massachusetts  and colleagues published a paper in 2003 in the prestigious medical journal called Nature Neuroscience that explains why high cholesterol increases the risk of Alzheimer's disease.

According to that report, cholesterol participates in the regulation of both the generation and clearance of the beta-amyloid protein (Abeta) in specific brain regions.  A hallmark of Alzheimer's disease is an abnormal accumulation of A beta.  And high cholesterol levels increase the level of A beta as shown in laboratory and animal studies.  And it has been demonstrated that cholesterol lowering drugs can also lower A beta as well.

A review conducted by Leila A Shobab from University of British Columbia in Vancouver,  Canada and colleagues and published in The Lancet Neurology also explains how cholesterol increases risk of Alzheimer's disease.

Statins lower the risk of Alzheimer's disease

Another study published in Oct 2013 in Atherosclerosis shows that long-term use of statins decreases the risk of hospitalization for dementia.

The study conducted by Giovanni Corrao from University of Milano-Bicocca in Milan, Italy and colleagues involved 152,729 patients aged 40 years or older who were newly treated with statins from 2003 through 2004 and 1380 patients were hospitalized for dementia including Alzheimer's disease during a follow-up that ended in 2010.
 
The researchers found that compared with those had less than six months of statin treatment, those who had 7 to 24 months of treatment were at 15% reduced risk of Alzheimer's disease.  Long term treatment (more than 4 years) reduced the risk by more than 25%.

But not all statins are effective in helping Alzheimer's disease patients.  As the study by Corrao et al. shows, simvastatin and atorvastatin worked well, but not fluvastatin and pravastatin.

Corrao et al. are not the first to discover that statins can help dementia patients.  In September, 2013, K. Steenland from School of Public Health in Atlanta, Georgia reported in Journal of American Geriatrics Society that statin use can slow cognitive decline in older men and women with normal cognition or mild cognitive impairment.

Food consumers need to be alerted to misinformation circulated over the internet that claims that cholesterol is important for the brain, which is only partially correct and that people need to eat foods that contain high cholesterol or promote the synthesis of cholesterol.  People do not need to eat cholesterol for the brain.  Humans can make it in vivo.

Food consumers need also to remember too much cholesterol can not only increase the cardiovascular risk, but also Alzheimer's disease risk.  Those who advocate the eating of foods that promote the production of cholesterol forget one thing, that is, cholesterol is not an essential nutrient and people do not have to eat high cholesterol foods such as eggs and meat to get cholesterol.  Humans can synthesize as much cholesterol as they need.

Evidence seems to suggest that eating high amounts of green leafy vegetables and eating no little or no foods that contain high cholesterol or promote the synthesis of cholesterol may cut the risk of dementia like Alzheimer's disease.

As for statins, food consumers need to know that using statins for a long term can cause adverse effects such as muscle pain.  Those who eat too much food that promotes the cholesterol production may want to consider using alternative medicines or dietary supplements to lower their serum cholesterol levels.   Red yeast rice, a food that is used in Asia to brew rice wine, has been found as effective as statins, but no side effects are found associated with use of this dietary supplement.

Drinking fruit and vegetable juices prevents Alzheimer's disease

Also it has been found that drinking fruit and vegetable juices often can also significantly reduce the risk of Alzheimer's disease.  A study published in Sept. 2006 in the American Journal of Medicine found evidence suggesting that fruit and vegetable juices delays the onset of Alzheimer's disease.

Qi Dai, MD, PhD from Vanderbilt School of Medicine in Virginia and colleagues conducted the study and found men and women drinking fruit and or vegetable juice at least three times per week can reduce the risk of Alzheimer's disease by 76%, compared with those drinking less than 3 times per week.
 
The researchers pointed out that oxidative damage caused by the β-amyloid peptide plays an important role in the pathogenesis of Alzheimer’s disease and many polyphenols are more protective against hydrogen peroxide than antioxidant vitamins.

The protective effect was even more significant among those with an apolipoprotein Eε-4 allele and those who were physically inactive.  

Diets linked to lower risk of Alzheimer's disease

A review published in 2013 in BioMed Research International indicates some dietary components are beneficial to Alzheimer's disease including antioxidants, B-vitamins, polyphenols and polyunsaturated fatty acids.  The review by N. Hu et al from Qingdao University in Qingdao, China also reveals that consumption of fish, fruit, vegetables, and coffee reduces the risk of Alzheimer's disease.  Some dietary patterns like the Japanese diet, and the Mediterranean diet compared with other dietary patterns may also help lower the risk of Alzheimer's disease.

(David Liu)

Keywords: Folate, homocysteine, B-vitamins, cholesterol, statins, red yeast rice, green leafy vegetables, eggs, and meat.

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