Vitamin B12, also known as cobalamin, is a water soluble vitamin that can reduce cancer, protect red blood cells and improve energy.
Studies have found vitamin B12 to be one of the most common deficiencies in the world. It is particularly prevalent in “the Indian subcontinent, Mexico, Central and South America, and selected areas of Africa” (1).
It is also common in vegetarians and vegans due to most vitamin B12 coming from animal sources (meat and eggs in particular). Thanks to fortified cereals, vitamin B12 deficiencies are less common in the western world. The foods which provide you with the most vitamin B12 are meat, fish, eggs, shellfish, and milk but you can also take vitamin B12 as a supplement (2).
The supplement is made from a bacterium known as streptomyces griseus which makes it suitable for vegetarians and vegans (3).
A lot of vitamin B12 deficiencies are not caused by a lack of vitamin B12 though, it is from malabsorption. This can be caused by certain medications, or conditions such as atrophic gastritis, pernicious anemia Crohn’s disease, or Celiac disease (4, 5, 6, 7).
When combined with folate and vitamin B6, vitamin B12 may help to reduce cancer risk. The evidence supporting the idea that vitamin B12 can reduce cancer risk is mixed. While some studies found that vitamin B12 is inversely associated with cancer risk, other studies found no such evidence (8, 9.)
A study on Mexican women in 2006 found that high intakes of folate and vitamin B12 led to a decreased risk of breast cancer, particularly in postmenopausal women (10).
It seems that there is some evidence that vitamin B12 does have some effect on certain cancers, but there isn’t enough evidence to say definitively either way. In fact, as we will explore in the side effects section, vitamin B12 may even increase the risk of certain cancers.
Vitamin B12 can help reduce birth defect risk when taken by pregnant women. A lot of studies in India (where vitamin B12 deficiency is common) have found that low vitamin B12 levels during pregnancy can lead to birth defects (11).
It can also contribute to early birth. This can be caused by raised Homocysteine levels, which can lead to lower birth rate and a increased risk of type II diabetes in the child (12.)
Taking a vitamin B12 supplement can help to reduce the risk of birth defects, low birth rate, or premature births by reducing Homocysteine levels in the blood (13).
Vitamin B12 also creates nucleic acid which is used to form DNA (14).
Vitamin B12 can reduce inflammation. High levels of homocysteine can lead to inflammation of the blood vessels which can lead to coronary heart disease. A 2013 study on elderly people with poor vitamin B12 levels found that vitamin B12 supplementation could reduce homocysteine levels and “normalize biomarkers of deficiency” (15).
Vitamin B12 can increase red blood cell production. Vitamin B12 can combine with folic acid (also known as folate or vitamin B9) to help produce red blood cells and it can also improve the function of iron in the body (16, 17.)
This can have many benefits, particularly in athletes. Exercise can actually decrease red blood cell mass through “mechanical rupture when red blood cells pass through the capillaries in contracting muscles” (18.)
Increasing red blood cell count can help to fight this, and can also help to improve cardiovascular performance by increasing the amount of oxygen that can be transported throughout the body. Increased red blood cell production will also help combat anemia.
Vitamin B12 injections are used to treat chronic fatigue syndrome. Studies have shown that vitamin B12 can treat chronic fatigue syndrome by functioning as a nitric oxide scavenger (19.) This can also be attributed to the effect it has on Homocysteine.
Another study found that patients with fibromyalgia and chronic fatigue syndrome had increased concentrations of Homocysteine in their blood (20.) By reducing Homocysteine levels in the blood, vitamin B12 may help to reduce fatigue.
Your digestion can be improved by vitamin B12. Studies have shown that vitamin B12 can help improve digestion by contributing to the “structure and function of human gut microbial communities” (21.)
In other words, vitamin B12 can help with healthy gut bacteria production which improves digestion. The study describes it as “a precious resource in the gut”.
Vitamin B12 may help to improve cognition, but more research is required. While some studies have demonstrated an improvement in cognition in people taking vitamin B12 as a supplement, others have found no evidence linking the two.
A 2003 study in the Cochrane Database of Systematic Reviews found no evidence that “folic acid, with or without vitamin B12, has a beneficial effect on cognitive function or mood or health of cognitively impaired older people” (22.)
But the study conceded that much more research is required.
In 2011 a cross-sectional examination of vitamin B12, cognition, and brain MRI measures found that Methylmalonate (a marker of vitamin B12 deficiency) could negatively affect cognition (23.) This means that vitamin B12 supplementation may improve cognition, but only in people who are already deficient.
Taking vitamin B12 supplementation without a deficiency should have no effect on cognition.
Lots of studies have found that vitamin B12 deficiency is a possible cause of dementia and cognitive decline in the elderly. A 2000 study concluded that anyone suffering with cognitive impairment should be checked for vitamin B12 deficiency (24.)
This suggests that vitamin B12 supplementation could help to treat these conditions.
Low vitamin B12 levels have been linked to depression. A study in 2000 found that a “metabolically significant vitamin B12 deficiency” was associated with a large increase in the risk of severe depression (25.)
This demonstrates that taking vitamin B12 to treat a deficiency could also help treat depression, provided that the depression was caused by a vitamin B12 deficiency.
This does not mean that vitamin B12 supplementation is a cure for depression though, and it is important to make that distinction. But studies still indicate that it is worth increasing folate and vitamin B12 intake in people who are suffering from depression (26.)
Another study found that increasing folate and vitamin B12 levels may help to treat people suffering from depression who have not responded to antidepressant treatment (27.)
Most studies link the effectiveness of vitamin B12 supplementation to the effect it has on homocysteine which seems to be a potential cause of depression.
Increased vitamin B12 levels may help Lacunar stroke patients recover. A study into the effects of vitamin B12 supplementation on patients with lacunar stroke found that high doses of vitamin B12 led to an improvement in verbal learning (28.)
It seems that the main benefits of vitamin B12 supplementation are reserved for people who are deficient in it, or are suffering from malabsorption due to other conditions. People who have sufficient vitamin B12 through diet will see no additional benefits. Almost all of these benefits can be attributed to the effect of vitamin B12 on Homocysteine levels in the blood.
Reducing this seems to lead to improved mood and cognition, as well as a reduction in birthing problems, chronic fatigue, and cancer risk. Getting vitamin B12 through diet seems to be the most effective way to remove the risk of deficiency, but for vegetarians and vegans this is not always possible.
The avoidance of animal products can easily lead to a deficiency, which explains why large parts of India (where vegetarianism is common) suffer from vitamin B12 deficiency.
On the whole vitamin B12 is considered non-toxic and is therefore safe to consume, provided that you don’t massively overdose on it. There are still some side effects and possible risks to taking it though.
Increased prostate cancer risk. A 2004 study was designed to investigate the effectiveness of folate and vitamin B12 at protecting the body against prostate cancer. Instead of finding any evidence to support this, the researchers actually found a three-fold increase in risk associated with vitamin B12 intake.
They even suspected that vitamin B12 could stimulate prostate cancer development (29.)
A study in Norway that looked into cancer incidence and folate acid and vitamin B12 supplementation in patients with ischemic heart disease (30.)
The study found that combining folic acid and vitamin B12 “was associated with increased cancer outcomes and all-cause mortality”. At the time of writing this had not been noticed in similar studies, and therefore should be questioned.
Vitamin B12 may have an adverse effect on people with abnormal levels of red blood cells. According to the University of Maryland Medical Centre “people with abnormal levels of red blood cells or abnormalities in their red blood cells” should be cautious about vitamin B12 (31.)
This is because it can actually be harmful for people with certain conditions that arise from abnormalities in their red blood cells.
They give an example of people suffering from Leber’s disease, which is a disease of the eye. Apparently, vitamin B12 supplementation can cause serious damage to the optic nerve in sufferers of this disease.
The only other real issue with vitamin B12 is the way that it can interact with other medications. But the list of medications is very small, according to the University of Maryland article these are: Anti-seizure medications, chemotherapy medications, gout medications, and some medications for diabetes. If you are on medications it is best to consult with your doctor first, before increasing your B12 intake.
The recommended dosage of vitamin B12 varies depending on your age, the National Institute of Health has different measurements in micrograms (mcg) starting from 0.4mcg for a baby, then small increases until the child reaches 9-13 years old where their intake should be 1.8mcg (32.)
From 14 years and up, people should consume 2.4mcg per day, but increase this to 2.6mcg when pregnant, or 2.8mcg while breastfeeding.
If you are at risk of a vitamin B12 deficiency, or you are elderly or vegan your recommended dosage is 1,000mg or 1mg (33.)
This is obviously a lot higher because the amount of vitamin B12 already present in the diet is very low.
Q: What foods are high in b12?
A: The best sources of Vitamin B12include: eggs, milk, cheese, milk products, meat, fish, shellfish and poultry. Some soy and rice beverages as well as soy based meat substitutes are fortified with vitamin B12.
Q: What is the normal range of B12?
A: Values of less than 200 pg/mL are a possible sign of a vitamin B12 deficiency. People with this deficiency are likely to have or develop symptoms. Older adults with vitamin B12 levels between 200 and 500 pg/mL may also have symptoms.
Q: Can you overdose on B12?
A: No you can’t. However the federal government advises not to take more than 100 milligrams a day.
Q: Can you take B12 at night?
A: Although there is no difference in the way you should take a B12 supplement at night as opposed to during the day, some people have trouble sleeping when they take B12 at night. If you have trouble sleeping, you may prefer to take your B12supplement early in the day.
Q: What is the best absorbed form of B12?
A: Methylcobalamin and adenosylcobalamin are the two natural, active forms of vitamin B-12. Methylcobalamin specifically absorbs easily since it is the principal circulating form of B-12.
Q: Whats the difference between vitamin B complex and a B12 supplement?
A: Vitamin B complex supplements usually have all the B Vitamins including vitamin B-12. Other B vitamins consist of vitamin B1, B2, B3, B5, B6, B12, B13, B15. Vitamin B12 is found in animal products and it is quite a common vitamin for Vegans to take as they may become deficient in this vitamin.
Q: Does B12 cause constipation?
A: No, but a lack of it can.
Q: Does B12 help with depression?
A: Yes, b12 can help with depression as low levels of B-12 and other B vitamins such as vitamin B-6 and folate may be linked to depression.
Supplementation with vitamin B12 is for the most part unnecessary provided that you have a healthy diet which includes lots of meat, and dairy. Most of the benefits of supplementation with vitamin B12 appear to only affect people who are deficient, or are suffering from malabsorption.
But considering that there are large percentages of the population who are deficient, the benefits of vitamin B12 are not to be ignored.
A reduction in certain cancer risks is a definite benefit, but this has to be weighed against the possible increase in the risk of other cancers (such as prostate cancer). The benefits of vitamin B12 supplementation when pregnant are harder to ignore.
Not only is the evidence stronger, but provided that you stay within a moderate dose there are no real downsides. Taking vitamin B12 with folate seems to increase the effectiveness of both ingredients.
Most of the benefits that are caused by increased vitamin B12 can be attributed to the effect that it has on Homocysteine. By lowering Homocysteine, vitamin B12 can help treat chronic fatigue syndrome, reduce birth defect risk, possibly reduce depressive symptoms.
The potential increase in the risk of certain cancers is of course a concern, but there is definitely not anywhere near enough evidence at this moment in time. Both studies that we looked at pointed out that the results were unexpected and that more research was required in future.
The effect on people with abnormal levels of red blood cells, or with abnormally shaped red blood cells is a much more evidence based issue.
When it comes to this it is recommended to discuss the issue with your doctor first, in fact if you have any medical issues or take any medications it is best to talk to your doctor – in case vitamin B12 supplementation interacts with it.
If you are a vegetarian or vegan, you are elderly, or have a condition that affects absorption of vitamin B12 then supplementation is definitely recommended.
If you do not fit into these categories, then keeping your levels naturally high through diet is a better strategy. Ensure that you are consuming meat or dairy products as these are the best sources of vitamin B12.