Vitamin B12 has critical benefits for the brain and nervous system, yet many are deficient in B12 because they cannot absorb it. Learn how to remedy this.
Vitamin B12 is one of eight essential B vitamins.
It has many benefits for overall health, but plays an especially important role in keeping your brain and nervous system working normally.
Vitamin B12 deficiency, however, affects nearly half of all adults.
Find out what you need to do to overcome this problem and improve your cognitive and mental function.
Benefits of Vitamin B12
Vitamin B12 plays an important role in many physiological functions and protects against a variety of health problems.
It is one of the many nutrients required for building strong bones and warding off osteoporosis. (1)
B12 protects against heart disease by removing the toxic amino acid homocysteine from the bloodstream. (2)
It can reduce the severity and frequency of allergies and asthma attacks. (3)
Vitamin B12 is essential for healthy hair, nails, and skin and is sometimes prescribed topically to treat eczema and psoriasis. (4)
When taken with other B vitamins, it reduces the risk of macular degeneration, an eye disease that eventually leads to blindness. (5)
Mental Health Benefits of B12
But where vitamin B12 is really crucial is in keeping the brain and nervous system healthy and functioning optimally.
B12 is needed for normal capacities in memory, focus, and concentration. (6)
Low B12 levels are associated with depression. (7)
This makes sense when you consider that B12 is required for the formation of the mood-boosting neurotransmitters serotonin and dopamine. (8)
Vitamin B12 can alleviate some of the symptoms of schizophrenia such as apathy, social withdrawal, and emotional inexpressiveness. (9)
Some researchers believe the link between B12 deficiency and dementia and psychiatric disorders is so strong that patients with these conditions should have their B12 levels closely monitored for life. (10)
Learn more —
Key Vitamins for Memory: Deficiencies Are Common
Vitamin B12 Benefits for Neurological Issues
Many seniors diagnosed with dementia or Alzheimer’s are in fact “only” B12-deficient and can make remarkable recoveries when their low B12 levels are addressed. (11)
This misdiagnosis occurs because the symptoms of vitamin B12 deficiency closely mimic that of these diseases.
Both vitamin B12 injections and high doses of oral supplements have proven effective for treating people with these disorders. (12)
There’s exciting evidence that a cocktail of B-complex vitamins may prevent and be useful for treating Alzheimer’s.
An Oxford University study found that taking vitamin B12 along with vitamins B6 and folic acid improved brain function and dramatically reduced brain shrinkage in the area of the brain most affected by Alzheimer’s. (13)
Vitamin B12 Deficiency Symptoms
Vitamin B12 deficiency can have serious consequences, yet up to 40% of American adults are believed to have below normal levels of vitamin B12. (14)
Effects on the brain can manifest as brain fog, memory loss, depression, anxiety, confusion, disorientation, hallucinations, and schizophrenia. (17)
If left untreated, vitamin B12 deficiency can cause a host of neurological problems including gait abnormalities, neuropathy, neuropsychiatric manifestations, and impaired vision, taste and smell. (18)
Learn more —
Brain Vitamins: Essential for a Healthy Brain
Who’s at Risk for Vitamin B12 Deficiency
- are a vegetarian or vegan
- are age 60 or over
- take acid-suppressing drugs
- take metformin for diabetes
- have a chronic digestive disorder such as Crohn’s, celiac disease, or irritable bowel syndrome
- have an eating disorder
- have had weight loss surgery
- have H. pylori, the bacteria that causes ulcers
- abuse alcohol or nitrous oxide
- are HIV-positive
You can try to raise a low B12 level in two ways — with food or with supplements.
Here’s an in-depth look at each.
Vitamin B12 Food Sources
Most people get plenty of vitamin B12 in their diets.
It’s found in animal foods of all kinds — meat, poultry, pork, fish, seafood, dairy, and eggs.
The two best sources of B12 by far are clams and liver which contain 60 times more vitamin B12 than beef and over 100 times more than eggs. (25)
But for those who don’t eat animal products, getting adequate B12 is a very real concern.
Plant Sources of B12: A Dangerous Myth
Almost half of lacto-ovo vegetarians and over 90% of vegans are B12-deficient. (26)
And unfortunately, there’s a persistent dietary myth that’s causing a lot of these people real harm.
Green algae like spirulina, fermented soy products, and brewer’s yeast are purported to be plant sources of vitamin B12. (27)
But, in reality, these plant foods contain B12 analogs which are similar to, but not the same as, vitamin B12.
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By binding with B12 receptors, these pseudovitamins block the intake of true B12. (28)
So consuming these B12 analog-containing foods can make a B12 deficiency even worse!
The only substantial vegetable source of true vitamin B12 is the sea vegetable nori (Porphyra umbilicalis). (29)
Some vegetarians, and especially vegans, take brewer’s yeast or yeast-based products like Marmite or Red Star Nutritional Yeast believing them to be a good food source of B12.
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This makes it no different than taking a supplement.
If you’re a vegan, there’s no way around it. You need supplemental B12.
I urge you to visit VeganHealth.org to find a wealth of evidence-based information on vitamin B12.
Additionally, you may want to read Vegan for Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet.
In this book, registered dietitians and long-time vegans Jack Norris and Virginia Messina debunk enduring myths about vegan nutrition, including that of vitamin B12.
Unfortunately, simply eating plenty of vitamin B12-rich foods is not always the answer since many people have problems with vitamin B12 absorption.
Here’s why …
Vitamin B12 occurs in animal foods bound to protein and gets released when hydrochloric acid and gastric protease in the stomach break this bond.
But many factors can inhibit this process. (33)
The first is age.
An estimated 10-30% of adults over the age of 50 have difficulty absorbing vitamin B12 from food.
There are several classes of medications that interfere with vitamin B12 absorption.
Proton pump inhibitors (PPIs) like Nexium, Prevacid and Prilosec and histamine-2 receptor antagonists (H2RAs) like Pepcid, Tagamet and Zantac are popular for acid indigestion, acid reflux, GERD, heartburn, and ulcers.
Metformin is a very popular drug for treating type 2 diabetes.
Forty percent of patients using metformin have a vitamin B12 deficiency or are in the low-normal range. (42)
Seventy-seven percent of metformin users develop peripheral neuropathy, a common form of nerve damage associated with type 2 diabetes.
Other medications that affect B12 levels include anti-seizure medications and chemotherapy drugs. (43)
Lack of Intrinsic Factor
In a very small portion of the population, vitamin B12 deficiency is caused by a lack of intrinsic factor, a protein secreted by the stomach lining that binds to vitamin B12 and enables its absorption. (44, 45)
Lack of intrinsic factor can be caused by weakened stomach lining or certain autoimmune diseases. (46)
This can lead to pernicious anemia, a decrease in red blood cells that occurs when the intestines cannot properly absorb vitamin B12.
If left untreated, it ultimately leads to serious neurological damage.
Treatment usually involves mega-doses of oral B12 or regular B12 injections.
Choosing the Best Vitamin B12 Supplement
It’s almost always preferable to get your nutrition from food rather than supplements, but vitamin B12 might be an exception.
For those with compromised digestive systems, supplemental B12 is better absorbed than it is from food where it’s bound to protein. (47)
And for some, the ability to absorb vitamin B12 from dietary supplements is limited by how much intrinsic factor is present.
There are a lot of options when choosing a B12 supplement.
Besides being available in the usual tablets, capsules, and liquid drops, it is also available in sublingual tablets, sprays, or lozenges.
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You’ll also find several forms of B12 in supplements.
Cyanocobalamin is a cheap and common synthetic form of B12.
It is not well absorbed and actually produces a small amount of cyanide in the body, so it should be avoided. (50)
Higher quality supplements contain methylcobalamin or adenosylcobalamin. (51)
Another form to consider is hydroxocobalamin which is the recommended form of B12 for anyone with the MTHFR genetic mutation.
It is also the form usually used in B12 injections for treating deficiency. (52)
Strange But True: No plants or animals can synthesize vitamin B12. It can be made only by microorganisms like bacteria and fungi. Even synthetic vitamin B12 supplements require bacteria for production.
Vitamin B12 Supplement Dosage
The Recommended Dietary Allowance of vitamin B12 for adults is 2.4 micrograms (mcg). (53)
If you’ve ever read B12 supplement labels, you’ve noticed that supplements often contain much more than this.
For example, here’s the label of one that contains a whopping 83,330% of the RDA.
This high number seems more reasonable when you understand that only about 2% of the B12 in supplements is absorbed. (54)
If your level is very low, your doctor may want to give you injectable vitamin B12 to increase it quickly, especially if you have pernicious anemia, permanent nerve damage, or ongoing digestive problems.
However, research has found that taking an oral supplement is as effective at raising blood levels of B12 as injections, so you may want to discuss trying mega-doses of oral B12 first. (55)
An intriguing alternative for overcoming malabsorption is the use of a transdermal vitamin B12 patch.
I’ve not found any studies on the effectiveness of the B12 patch, but anecdotal evidence seems promising.
Vitamin B12 supplements are considered very safe and no tolerable upper intake level (UL) has been determined.
Doses as high as 2 mg per day do not cause any side effects. (56)
Vitamin B12 Testing
If you suspect that your vitamin B12 level is low, you can try taking a supplement to see if it helps your symptoms.
If supplementation will be effective, you should feel results fairly quickly, within a week or so.
But there’s only one way to know your B12 status for sure — get tested.
This is particularly advisable if you fall into one of the at-risk groups.
You can have your doctor run a B12 test or you can order one yourself from one of the many online labs.
Overhyped Benefits of Vitamin B12: Memory, Energy, and Weight Loss
Lastly, here’s a look at some supposed benefits of B12 that are more hype than reality.
Billions of dollars are spent every year on supplements and energy drinks that claim to improve memory, boost energy, or aid weight loss due, at least in part, to their vitamin B12 content.
The idea that B12 can increase energy originated from the observation that it works quite remarkably to increase energy in people who are B12-deficient.
But if you aren’t deficient, taking more won’t increase your energy level a bit.
According to the International Society of Sports Nutrition, the energy boost received from energy drinks has been clearly proven to come from caffeine and sugar — not from any other ingredients, including vitamin B12. (57)
There’s also no credible evidence that taking extra vitamin B12 can help you lose weight. (58)
Low levels can definitely adversely affect your memory and other cognitive functions.
If you have experienced memory loss, you should certainly make sure you’re getting adequate amounts of vitamin B12 from either your diet or supplements, or both.
But that does not make B12 a miracle memory nutrient that works for everyone.
Even mega-doses of vitamin B12 do not benefit healthy adults with normal B12 levels.
Dr. Susan Shurin of the National Institutes of Health gave this testimony to Congress in the Vitamin B12–State of the Science Report about vitamin B12 being marketed for enhancing energy, memory, and mood:
“Claims are made that vitamin B12 administration will improve energy levels, memory, concentration, and mood.
All of these are true when persons deficient in vitamin B12 are treated; however, there is no evidence at all of those clinical benefits when the vitamin is given to persons who are not deficient.
Administration of vitamin B12 does not enhance the physical or cognitive function of persons who are not Vitamin B12 deficient.”
Vitamin B12 Benefits: The Bottom Line
Vitamin B12 is essential for a healthy brain and nervous system.
It’s also protective for a range of mental and physical health conditions.
Though readily found in animal food sources, there are many factors that can interfere with its absorption including age, medications, and your gastrointestinal health.
The impact of a vitamin B12 deficiency can be very serious.
If you have any doubt that you’re deficient, have your vitamin B12 level tested.
If your level is below normal, take steps to increase your intake of B12.
Eat more foods rich in vitamin B12, take a high-quality vitamin B12 supplement, and discuss whether you could benefit from oral B12 mega-doses or B12 injections with your doctor.