Memory and Vitamin B12
Of the B vitamins, vitamin B12 and folic acid are the most important for enhancing memory and preventing cognitive decline. Given the importance of vitamin B12, it is most likely that its deficiency will lead to memory loss. However, up until recently, most studies have found no improvement in memory with vitamin B12 supplementation. What changed? What were the researchers doing wrong? Read on to find out.
by Brad Chase
Vitamin B12 is also known as cobalamin and one of the 8 B vitamins.
Vitamin B12 is the most structurally complex of all vitamins. It is found in all human cells where its functions range from DNA synthesis and regulation to blood formation and energy production. But just as importantly, vitamin B12 is absolutely essential for the normal functioning of the nervous system including the brain.
There are 4 known forms of this vitamin: cyanocobalamin, hydroxocobalamin, adenosylcobalamin and methylcobalamin. Of these vitamers, cyanocobalamin does not exist in nature. Instead, it is produced when hydroxycobalamin is purified over activated charcoal (it picks up trace amounts of cyanide).
Methylcobalamin and adenosylcobalamin are produced in the human body where they serve as cofactors of certain enzymes.
Hydroxocobalamin, on the other hand, is produced by bacteria.
Only bacteria produce the basic form of vitamin B12. Therefore, dietary sources of vitamin B12 include plants and animals in which vitamin B12-producing bacteria grow symbiotically.
Animals are, however, a better source of the vitamin than plants. This is because these bacteria usually live in the roots of plants and are mostly was removed during food preparation.
Animals, on the other hand, have these bacteria in their guts or store the vitamin in their livers.
Therefore, animal liver is an excellent sources of vitamin B12. Other good sources include meat, poultry, eggs, milk, dairy products, fish and shell fish.
Vitamin B12 is also commonly added to fortified foods including breakfast cereals, energy bars and soy products.
Other sources of vitamin B12 include supplements which are available in different dosage forms from pills to liquids, injections, patches and nasal sprays.
The recommended dietary intake of vitamin B12 ranges from 2 to 3 microgram per day for adults. Pregnant and lactating women are advised to go near the upper limit.
The major cause of vitamin B12 deficiency is pernicious anemia.
Vitamin B12 deficiency is a rather delicate state. Even at levels slightly below the normal range, vitamin B12 deficiency can start to show clear symptoms such as depression, fatigue and memory loss.
Chronic vitamin B12 deficiency can serious and permanent damage especially to the brain. When vitamin B12 deficiency gets rather serious, it can cause mania and psychosis.
Vitamin B12 Deficiency and Those at Risk
Vitamin B12 deficiency usually affects old people more than any age group. Care should also be taken by pregnant women and nursing mothers as they need for vitamin B12 is higher.
It is believed that the main reason vitamin B12 deficiency is more common in the elderly than any other age group is the reduction in stomach acid levels as we grow older.
Vitamin B12 obtained from dietary sources is often combined with certain proteins. It takes the action of stomach acid to release the bound vitamin B12 for absorption in the gut. However, it has been shown that about 30% of elderly people do not produce sufficient stomach acids to release adequate amounts of vitamin B12 for absorption.
Another group of people who are at a high risk of vitamin B12 deficiency due to low stomach acid production are those who regularly use acid-suppressing drugs such as antacids and anti-ulcer drugs.
For the people who are at a great risk of vitamin B12 deficiency due to insufficient acid production in the stomach, regular consumption of vitamin B12 supplements or fortified foods is necessary to meet their recommended daily intake of the vitamin.
Unlike vitamin B12 obtained from dietary sources, supplemental vitamin B12 is supplied unbound to proteins, and therefore, do not need stomach acid for absorption.
However, both natural and synthetic forms of vitamin B12 need to combine with an intrinsic factor in the stomach before they can be absorbed. This factor is lacking in people suffering from pernicious anemia, an autoimmune disease. Therefore, vitamin B12 injections may be necessary to address this deficiency to help bypass the need for gastrointestinal absorption.
Vegetarians (all vegans and strict vegetarians) are yet another group of people who need regular vitamin B12 supplementation.
The effect of vitamin B12 deficiency is most pronounced in old people. One of the main presentations of this deficiency is cognitive decline.
Cognitive decline is often believed to be one of the signs of aging in old people but more often than not, it is due to vitamin B12 deficiency. Clear signs of cognitive decline in the elderly include poor memory and confusion while performing simple, everyday tasks.
However, cognitive decline should not be taken as a compulsory presentation of aging.
Vitamin B12 supplementation may help reverse cognitive decline especially when it is taken for long time. However, vitamin B12 can only improve aspects of cognition (learning, reasoning, memory etc.) in people who are deficiency of the vitamin. Those who do not have vitamin B12 deficiency rarely benefit from taking more of the vitamin.
It is still unclear how vitamin B12 affects memory and other cognitive function but the most popular theory is the effect of the vitamin on a compound called homocysteine.
Vitamin B12 is required for the conversion of homocysteine to methionine. This conversion is necessary because the resulting methionine is further converted to an intermediate that is needed for the formation of myelin (the sheath around nerves), different neurotransmitters and phospholipids used in making the membranes of nerve cells.
Neurotransmitters, myelin and membrane phospholipids are the core of the nervous system.
Neurotransmitters are the chemical messengers that carry all transmissions in the brain while myelin and phospholipids maintain the integrity of the nerves.
When vitamin B12 deficiency occurs, the conversion of homocysteine to methionine proceeds poorly. Therefore, homocysteine accumulates in the body. When homocysteine accumulates in nerve cells, it kills them off. In the cardiovascular system, homocysteine accumulation can increase the risk of stroke and heart disease.
It has been confirmed that the accumulation of homocysteine in the brain is linked to dementia and Alzheimer’s disease. However, most studies have found that lowering homocysteine levels through vitamin B12 supplementation did not improve cognitive function.
Not all studies done on the effect of vitamin B12 on memory and/or cognitive function has been positive. In fact, most of them conclude that vitamin B12 provides no benefits. However, they all seem to share the same flaw that is addressed by the last study described in this section.
A 1994 study published in the Journal of the American Geriatrics Society described a long-term study designed to access the link between low serum levels of vitamin B12 on diseases that causes dementia.
In this study, 410 subjects between aged 75 to 85 years who were never diagnosed with dementia were recruited. Over the course of 5 years, the vitamin B12 levels of the subjects were determined and tests for dementia and associated diseases such as Alzheimer’s were administered.
The results showed that there was no way to predict the subjects who developed dementia from their vitamin B12 levels. In addition, those who had low vitamin B12 levels and did develop dementia did not respond to vitamin B12 given monthly.
A 1970 study published in the journal, Biological Psychiatry, arrived at the same conclusions but with vitamin B12 and folic acid deficiencies.
A 2008 intervention review of the major, available studies up to that point was done by the Cochrane Dementia and Cognitive Impairment Group. The review found no evidence that folic acid, whether combined with vitamin B12 or not, improved cognitive function.
The review however agrees that both B vitamins were able to reduce homocysteine levels in patients suffering from cognitive impairment but that it is uncertain what benefits this effect has.
However, the Cochrane review recognized the need for more randomized, controlled studies to determine the roles of folic acid and vitamin B12 in dementia. Another advice given was that such studies should take longer to fully access the benefits of the B vitamins on cognition.
In fact, both recommendations turned out to be what was needed to get a clearer picture of the link between vitamin B12 (and folic acid) and cognitive function in the elderly.
A 2011 study published in The American Journal of Clinical Nutrition was both large and long.
900 adults aged between 60 and 74 years were recruited for this 2-year study. Each of the study subjects either received placebo or a combination of 400 microgram folic acid plus 100 microgram vitamin B12 daily.
Assessments of memory and cognition were done after 12 months and then after 24 months of supplementation. These tests accessed memory, attention and speed of performing mental tasks.
The results of this study showed exactly what was wrong with previous studies done on the subject and proved right the intuition of the Cochrane reviewers.
Just like the studies before this one, there was no difference in the test scores of the vitamin group and the placebo group after 12 months of supplementation.
However, after 24 months, there was a marked and statistically significant improvement in the vitamin group over the placebo group especially in memory tasks. For example, in the short-term memory test, the vitamin group came from behind the placebo group to place higher on the score charts.
The last study showed that vitamin B12 can indeed improve memory especially in the elderly who have vitamin B12 deficiency.
In addition, combining vitamin B12 with folic acid can help improve the result. Both B vitamins can help cure anemia as well as protect the nervous system.
However, more importantly, the benefits of vitamin B12 supplementation on memory takes a while and an excellent result requires long-term therapy. The benefits of vitamin B12 supplements for people suffering from memory loss and general dementia kicks in after the first year and can gradually improve the longer supplementation is continued.
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