Vitamin B12: Benefits, Sources & Deficiency Symptoms

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Vitamin B12 is a water-soluble vitamin and nutrient that plays several essential roles in the human body. This includes making DNA and supporting the nerve and blood cells.It does not exist naturally in the body and must be derived from food.

In this article, we’ll look at all aspects of Vitamin B12 including its health benefits, recommended daily allowance, safety, side effects and deficiency, and biological functioning.

If you’re considering supplementing with this vitamin, this information should help you decide if it’s right for you.

Overview: B Vitamins

The 8 B vitamins have potent antioxidant properties, meaning they kill damaging free radicals in the body and reduce oxidative stress. This greatly enhances the immune system (1).

The B vitamins assist the body’s enzymes to perform essential cellular functions.

They help metabolize fats and carbohydrates, produce energy, repair and synthesize DNA and RNA, support brain health, synthesize key neurochemicals, and break down amino acids (2).

What is Vitamin B12?

Vitamin B12 contains the mineral cobalt, so it’s sometimes called cyanocobalamin. You can get it from a number of different food sources, such as beef, milk, clams, cheese, ham, eggs, chicken, yogurt, tuna, trout, liver, salmon, and fortified breakfast cereals (3).

This vitamin plays an essential role in the formation of red blood cells, supporting neurological function, and synthesizing DNA.

This is why it’s so important that you consume enough foods that contain Vitamin B12.

Vitamin B12 can also be taken in supplement form, as well as derived from food. It’s fairly common to develop a deficiency as you age if you don’t take in the correct amount (4).

How Does Vitamin B12 Work?

Vitamin B12 enters the body attached to protein. Our stomachs contain hydrochloric acid, which is able to detach the vitamin from the protein (5).

In the next stage, Vitamin B12 combines with a protein called intrinsic factor, which is produced in the stomach. This mix is absorbed by the body, and the vitamin goes to where it’s needed (5).

Is It Safe?

Vitamin B12 is very unlikely to lead to many negative effects if you take too much of it, in fact, there’s been no tolerable upper intake level established by the Institute of Medicine for that reason (3).

Therefore you don’t have to be concerned about taking excess Vitamin B12. Health issues like megaloblastic anemia, weakness, constipation, and loss of appetite, and others may occur if you get too little Vitamin B12 (5).

Vitamin B12 Health Benefits

Vitamin b12 Health Benefits

1. Treat Cardiovascular Disease

One of the risks of developing heart disease and stroke is high levels of homocysteine in the blood. This is an amino acid that is rich in sulfur (3).

Vitamin B12, Vitamin B6, and folate play an important role in lowering the amount of homocysteine in the blood.

Studies have indicated that supplements of Vitamin B12 and folate may significantly lessen levels of homocysteine (3).

What the Science Says

Although research does show that Vitamin B12 will lower the amount of homocysteine in the body, the results do not always indicate that this lessens the risk of developing heart disease (3).

A study in The BMJ that took place in Western Australia found that levels of Vitamin B12 and folate were not correlated with death from coronary heart disease or cardiovascular disease.

However, research published in the Journal of Cardiology found that low levels of Vitamin B12 were linked with cardiovascular risk factors in participants.

One study in the American Journal of Preventive Medicine looked at the association between low Vitamin B12 levels in vegetarians and their risk of developing cardiovascular disease.

They discovered that the benefits of a vegetarian diet in lessening the risk of cardiovascular disease are negated by low levels of Vitamin B12.

2. Treat Dementia

Low levels of Vitamin B12 in the body increase the amount of homocysteine in the blood. This may lessen the levels of substances that are required to produce key neurotransmitters in the brain (3).

In turn, this could increase the chances of developing Alzheimer’s disease and dementia and has also been linked to cognitive decline (3).

What the Science Says

A study published in the New England Journal of Medicine concluded that a high level of homocysteine is a strong independent risk factor for developing dementia.

Another study in the American Journal of Clinical Nutrition found that low levels of Vitamin B12 are a risk factor for cognitive decline in older adults.

It’s important to note that B12 has not been found to elevate cognition generally. For example, a study in the American Journal of Clinical Nutrition looked at people with no or moderate cognitive impairment.

Researchers gave the subjects Vitamin B12 for 24 weeks and found no improvement in cognition.

3. Treat Megaloblastic Anemia

This disease leads to the formation of red blood cell precursors called megaloblasts in the bone marrow. It occurs due to impaired DNA synthesis, which is often caused by a deficiency in Vitamin B12 and folate (6).

For this reason, the most effective treatment for this condition is the supplementation of B12 and folate.

What the Science Says

A review article in Revista Médica Del Hospital General De México cited that deficiency in Vitamin B12 is one of the most common reasons people develop megaloblastic anemia, which can lead to neurological symptoms.

Similarly, an article in the Journal of General and Family Medicine stated that the treatment for megaloblastic anemia is a lifelong administration of Vitamin B12.

The Annals of Internal Medicine did a review of studies on the treatment of megaloblastic anemia with Vitamin B12 and found it to be very effective overall.

4. Improve Athletic Performance

Vitamin B12 is considered by many people to be a supplement that can increase your energy level and enhance athletic performance.

The reasoning behind this, first of all, is the important role this vitamin plays in energy metabolism  (3).

In addition, because B12 is an effective treatment for megaloblastic anemia and its symptoms of tiredness and weakness, it’s thought to be an energy enhancer for healthy people as well. However, the evidence for this premise is quite weak (3).

What the Science Says

A study published in the Journal of Clinical Nutrition looked at the effect of Vitamin B12 on physical performance and found no difference with the placebo group.

A review of the research in Nutrients looked at people without nutritional deficits to see if supplementation with Vitamin B12 would increase energy level and physical performance. They found no support for this theory.

5. Fix Nerve Damage

Vitamin B12 plays a key role in supporting nerve functioning. There’s evidence that it can heal nerve damage and improve functional recovery after traumatic brain injury (7).

It’s able to do this by enhancing the axon growth of neuronal cells in the traumatized area. For this reason, it’s used frequently in treatment with patients who have nerve disorders (7).

What the Science Says

A study published in Frontiers in Pharmacology examined the effect of Vitamin B12 on mice with traumatic brain injury. They concluded that the vitamin decreased motor neuron loss, leading to normal neural functioning.

Other research supports this finding. A study in the American Journal of Pathology found that Vitamin B12 is a superoxide scavenger that protects retinal ganglion cells.

Vitamin B12 Deficiency and Side Effects

If you have too high a dose of Vitamin B12 in your system, you may have mild side effects including anxiety, headache, dizziness, nausea, vomiting, and headache (5).

A deficiency in Vitamin B12 can lead to a number of problems, so it’s important to resolve it right away.

It could lead to nerve damage, megaloblastic anemia, depression, confusion, dementia, poor memory, balance problems, and a sore mouth or tongue (5).

Less serious symptoms that may occur include weakness, constipation, weight loss, and tiredness.

Babies can also become B12 deficient, which may cause failure to thrive, megaloblastic anemia, and problems with normal development and movement (5).

There are certain people who have trouble getting enough Vitamin B12. This is often an issue with vegetarians and especially vegans because meat is the best way to naturally absorb this vitamin (5).

In addition, people over the age of 50 have trouble absorbing B12 because they don’t have enough hydrochloric acid in their stomachs.

Some conditions can cause a deficiency, including pernicious anemia, digestive disorders, celiac disease, and Crohn’s disease (5).

Recommended Daily Allowance

Vitamin b12 Sources

The recommended daily allowance for adults and teens from 14-18 is 2.4 mcg. The levels for children, pregnant, and breastfeeding women are as follows (5):

  • Up to 6 months – 0.4 mcg
  • 7-12 months – 0.5 mcg
  • 1-3 years – 0.9 mcg
  • 4-8 years – 1.2 mcg
  • 9-13 years – 1.8 mcg
  • Pregnant women – 2.6 mcg
  • Breastfeeding women – 2.8 mcg

Drug Interactions

There are several medications which disrupt the absorption of Vitamin B12 and may lead to low levels in the body.

If you’re taking any of the following drugs, talk to your doctor about supplementing with extra Vitamin B12 (5).

  • Metformin is a medication which is used to treat diabetes. It can interfere with Vitamin B12 levels in the body.
  • The antibiotic chloramphenicol can lower the amount of Vitamin B12 in the body.
  • Histamine H2 receptor agonists are used as treatment for peptic ulcer disease. They may also disrupt levels of B12 in your system.
  • Medication which treats peptic ulcer disease and acid reflux called proton pump inhibitors may alter levels of Vitamin B12.


Are There Any Fruits And Vegetables Rich In Vitamin B12?

There are no fruits and vegetables which contain Vitamin B12.

However, they are rich in other vitamins, minerals, and antioxidants which are very important for the body and the immune system. Your diet should include a good amount of fruits and vegetables.

Does Vitamin B12 Help You Sleep?

There is some evidence to indicate that Vitamin B12 could help you sleep, and maybe an effective treatment from sleep-wake rhythm disorders.

A case study of 2 patients who had such disorders published in Sleep concluded that Vitamin B12 was an effective treatment for sleep dysfunction.

Should I Take Vitamin B12 in the Morning or in the Evening?

It’s always best to take any vitamin, including B12, in the morning.

Taking it before you go to bed is not as effective because your digestion is slower at night and your body will have difficulty absorbing the vitamin.

Can Vitamin B12 Cause Weight Gain?

No, Vitamin B12 will not cause you to gain weight. In fact, there’s been a lot of speculation that it could be part of a weight loss program.

Some people believe that it gives you energy and helps speed up your metabolism, leading to fat-burning and weight loss.

According to the Mayo Clinic, there’s no real evidence that Vitamin B12 can help you shed your unwanted pounds (8).

Should I Take B12 Every Day?

As long as you follow the recommended daily intake we provided, there is no reason why you can’t take this vitamin on a daily basis.

In fact, taking a daily B vitamin or multivitamin which includes B vitamins is very healthy for your body.

Can I Take Vitamin B12 and Vitamin D Together?

Yes, you certainly can. You can take a multivitamin that includes both of these, or separate D and B12 vitamins with no negative consequences at all.


Vitamin B12 is a nutrient that is crucial for various bodily processes, including making red blood cells, the synthesis of DNA, and supporting neurological function.

It’s crucial that you keep your levels of this vitamin up, as having a deficiency can lead to a number of health problems.

In order to do this, eat foods like beef, salmon, liver, cheese, clams, chicken, and trout. In addition, you may consider taking a supplement in the form of either a multivitamin or a B vitamin complex.

Making sure you have the appropriate levels of Vitamin B12 can also help with several health problems, including nerve damage, cardiovascular disease, dementia, and megaloblastic anemia.

There’s no evidence that it can raise energy levels or increase your athletic performance.

Taking vitamin B12 supplements should be one part of an overall healthy lifestyle, including a diet rich in vitamins and minerals and physical exercise several times a week.


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