Sunday, June 4, 2023

Are dementias and B–vitamins deficiency related?

Losing memory in old age is a scary thought. Currently, there is no cure for Alzheimer’s disease, a type of memory loss. Are there simple nutritional ways that can possibly help prevent such memory loss? And can some nutrients help slow down the progression of these diseases?

First things first. All types of memory loss are not necessarily medical disorders. Sometimes, the forgetfulness is due to old age. It could also be due to lifestyle reasons, such as stress, lack of sleep, or alcohol consumption.

So, it is important to confirm with your doctor that the memory loss is due to Alzheimer’s or vascular dementia. Read a comprehensive article on this website: Early warning signs of dementias.

B-vitamins and vascular integrity

There are hundreds of research papers highlighting the role of B–vitamins (primarily, B–2, B–6, B–9, and B–12) in keeping our blood vessels healthy.

There are many vitamin B’s, which have similar structures, food sources, and actions. So, the convention is to refer to the group, as a whole, as B–vitamins.


We get proteins from many food sources, such as meats, fish, eggs, dairy products, nuts, and some vegetables. Many of these proteins contain an amino acid called Methionine.

In our blood, Methionine undergoes a very important process called Methylation. During this process, an intermediate substance, called Homocysteine, is formed. Homocysteine is a very harmful substance, and it is not present in the body unless produced as above.

How does homocysteine cause problem?

A high level of homocysteine in the blood causes damage to the inner lining of the arteries. This causes inflammation in those places. Such damaged arteries harden and develop blockages.

Homocysteine interferes with the way cells use oxygen. This causes free radicals to build up. These can oxidize LDL–cholesterol, which is then deposited in the arterial walls. This is how blood vessel blockages happen.

Homocysteine stimulates the growth of, something called, smooth muscle cells. This leads to deposits of collagen into the walls of the arteries. This is how blood vessel hardening happens.

Once various blood vessels harden and develop blockages, various medical disorders arise depending on the location of the damaged blood vessels.

High levels of homocysteine in the blood have been linked to Alzheimer’s, vascular dementia, poor concentration and judgment, and lowered mood. It is also linked to heart disease, congestive heart failure, stroke, migraine, cancer, macular degeneration, and hearing loss. It affects fertility levels in women and can lead to miscarriages.

Homocysteine in normal people

Luckily, in a normal person, homocysteine survives in the blood for a very short duration. Vitamins B–9 and B–12 immediately convert them back into methionine. About 50% of the homocysteine is, thus, re–methylated back to methionine.

The remaining 50% is converted to another amino acid, called Cysteine, in the presence of vitamin B–6. Cysteine is used by the body to make a substance called Glutathione. Glutathione is an extremely powerful antioxidant, which protects our body’s cells from oxidative damage.

The two processes above also require vitamin B–2 and magnesium. Once converted, homocysteine does not have any toxic effects. Thus, vitamins B–2, B–6, B–9, B–12, and magnesium are essential in keeping homocysteine levels low.

Normal levels of homocysteine

Blood homocysteine levels generally rise as we age. Men have higher levels than women, in general. The observed levels in most individuals are:

For men:
19 — 60 years: 4 to 10 µmol/L
Above 60 years: 6 to 15 µmol/L
Elevated: 11 µmol/L

For women:
19 — 60 years: 3 to 7 µmol/L
Above 60 years: 6 to 15 µmol/L
Elevated: 10 µmol/L

The normal levels of homocysteine are considered to be 5 to 15 µmol/L. However, the risk of diseases starts rising above 6.3 µmol/L. Also, for each 5 µmol/L rise in homocysteine levels, the risk of coronary heart disease events rises by 20%.

Hence, one is advised to keep the homocysteine levels below 6.3 µmol/L.

Causes of increased homocysteine

  • Deficiencies of vitamin B–2, B–6, B–9, B–12, and magnesium
  • Smoking
  • High coffee intake
  • High alcohol intake
  • Medications, such as corticosteroids, and proton pump inhibitors (taken for acidity, or heartburn)
  • Diabetes
  • Osteoporosis (fragile bones)
  • Rheumatoid arthritis
  • Thyroid problems

Read more about homocysteine and the science behind it.

Interpretation and guesses

From this discussion on homocysteine, we can say that homocysteine damages blood vessels in the body. Depending on the location of the damaged blood vessels, we should get a different medical condition:

  • If the damage is in the heart arteries, we can get heart attacks.
  • If the damage is in the small blood vessels in the eye, we can get eye degeneration.
  • If the damage is in the blood vessels that reach the brain, we can get a stroke.

If we hypothesize that Alzheimer’s disease and vascular dementias involve some kind of vascular damage in the brain, such dementias also could be caused by high homocysteine. And if that is true, that risk can be lowered by B–vitamins.

Is there any such relation? Let us take a look at some research in the last 20 years about dementias and B–vitamins.

Published scientific papers

Let us look at what research papers, published over the years, say.

Paper 1

A paper in Alternative Medicine Review journal in 2003 said that the deficiencies of Vitamin B–6, B–9 and B–12 lead to high levels of homocysteine in the blood. This leads to reduced brain function, with the death of vascular structures and neurons in the brain. High homocysteine is a strong, independent risk factor for stroke.

Paper 2

A paper in the Current Molecular Medicine journal in 2009 said that a deficiency of folic acid (vitamin B–9) causes DNA damage, reactive oxidative species (free radicals), mitochondrial dysfunction, and cell death. There is a strong correlation between low vitamin B–levels with medical conditions such as stroke, Alzheimer’s disease, and depression.

Paper 3

A paper published in Fortschritte der Neurologie-Psychiatrie journal (in German) in 2003 said that high homocysteine levels cause damage to the large and small blood vessels in the brain. It said that high levels of homocysteine with memory loss may indicate deficiency of vitamins B–6, B–9 and B–12.

Paper 4

A paper in the Journal of Alzheimer’s Disease in 2013 showed that low blood levels of folate (vitamin B–9), vitamin B–12, and homocysteine are associated with brain function in cognitively impaired elderly patients. The association was stronger in those patients with Alzheimer’s disease than in those with mild cognitive impairment.

Paper 5

A paper published in the Chinese Journal of Applied Physiology in 2013 showed that there is a significant negative correlation between blood homocysteine levels and cognitive levels in Alzheimer’s patients. High blood homocysteine levels are one of the risk factors for the onset of Alzheimer’s. Folate (vitamin B–9) deficiency is an important reason to cause elevated homocysteine levels in Alzheimer’s.

Vitamin B–9 is also called folic acid or folate. Folate is a naturally occurring form in foods. Folic acid is the synthetic form of vitamin B–9. The body does not handle folic acid well and finds it difficult to convert it into an active form.

Paper 6

A paper in the New England Journal of Medicine in 2002 showed that blood homocysteine level is a strong, independent risk factor for the development of dementia and Alzheimer’s disease.

16% of people above the age of 70 years develop mild cognitive impairment (MCI, mild memory loss), and half of these (8% of the total) develop further into Alzheimer’s disease. The researchers found a graded increase in the risk of Alzheimer’s as well as MCI with rising blood levels of homocysteine.

Accelerated brain atrophy, or decay, is seen in patients who convert to Alzheimer’s from MCI. So anything that slows down brain decay may help in preventing, or delaying, Alzheimer’s.

Paper 7

A paper in the journal Nutrition in Clinical Care in 2002 said that low levels of vitamin B–9 cause both stroke and Alzheimer’s.

Paper 8

A paper published in the journal Lancet Neurology in 2003 said that high blood levels of homocysteine and Alzheimer’s disease could be linked through stroke or other disorders of blood vessels.

High blood homocysteine is an independent risk for stroke and another independent risk factor for Alzheimer’s disease. In 25% of the cases, Alzheimer’s disease and other dementias are attributed to stroke.

Memory loss in Alzheimer’s disease is associated with some evidence of brain infarcts on autopsy. Infarcts are small areas of dead tissue cells due to insufficient blood supply. The blood flow restriction may be caused by blood vessel rupture or blockages.

Paper 9

A paper published in PLOS One in 2010 showed that by increasing supplementation with B–vitamins (B–6, B–9, and B–12) slowed the rate of brain degeneration in patients with mild memory loss.


Research is still ongoing about whether supplementation with B–vitamins will prevent, reverse, or slow down the progression of dementias. And if yes, what dosage, source, and duration are to be used? In the interim, it is a good idea to play safe and load up on B–vitamins.

B–vitamins are water–soluble vitamins. So if you consume them in excess, they are excreted out of your body. As a result, their levels will rarely get toxic in your body.

Your body cannot store B–vitamins, except vitamin B–12, for long periods of time. So, you need to regularly consume B–vitamins through foods.

Since there is a comprehensive article on this website on B–vitamins, I am not repeating that matter here. Read on this website: Everything you want to know about B–vitamins.

Testing for deficiencies

To check for B–vitamin deficiencies, people get their blood vitamin B–12 levels tests. There are three limitations of blood vitamin B–12 checking:

  • It does not tell you about vitamins B–6 and B–9 levels in the blood. Deficiencies of either can cause trouble, as mentioned above, even if vitamin B–12 levels are fine.
  • Blood homocysteine levels may go up, even before vitamins B–6, B–9, or B–12 levels dip low enough to be flagged abnormal.
  • Homocysteine levels can go high in kidney disease, underactive thyroid (hypothyroidism), or alcoholism. In such patients, levels of vitamins B–6, B–9, or B–12 may be normal.

So, it is better to get a serum homocysteine test done. It is a common and relatively inexpensive test.

Of course, if your doctor has advised you vitamin B–12 test, talk to him first. For example, your doctor may have advised you blood vitamin B–12 test to rule out pernicious anemia. That is a different disease category than what high homocysteine levels lead to.

However, if it is allowed in your country, and so, if you are going to check your vitamin B–12 levels for your own satisfaction, do consider a blood homocysteine test, instead.

Blood homocysteine is not a screening test. So, there is no need to keep doing it routinely.

If the blood homocysteine levels are higher than 6.3 µmol/L, increase your dietary B–vitamins intake and supplementation. Seek medical advice, if the levels are even higher. I would not give a cutoff number for that since it can become a medico–legal issue.

In conclusion

Multiple papers show a very strong relationship between B–vitamin deficiency and Alzheimer’s disease and vascular dementias, as well as their progression.

As one ages, one gets Vitamin B–6, B–9, B–12 deficiencies.

Vegetarian and vegan people are often found to be severely deficient in B–vitamins.

Check your blood homocysteine level. Try to keep it below 6.3 µmol/L.

Supplementation with B–vitamins helps in mild memory loss.

Perhaps, supplementation with B–vitamins may also help in preventing memory loss. Since there is no harm, consider increasing your intake of B–vitamins through food or supplements.

First published on: 18th September 2013
Image credit: NastyaSensei Sens on
Last Updated on: 30th April 2023


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