Vitamin B12 (Cobalamin): Sources, Health Benefits, Deficiency, Side effects, RDA
Vitamin B12 is one of the most important Vitamins for our bodies that is mostly received from food sources of animal origin. In this article we explore What is Vitamin B12, the best food sources, it’s health benefits and deficiency problems that might occur from poor absorption.
What is Vitamin B12
Vitamin B12 or cobalamin is of paramount importance to the body. In the body of an adult there are 2 to 5μg and with the largest percentage (80%) found in the liver.
It was discovered relatively recently, only in 1948 when it was isolated from the liver. It acquired the name cobalamin as it contains a cobalt molecule in its composition.
Vitamin B12, also called cobalamin, is a water-soluble vitamin involved in the metabolism of every cell in the human body. It is particularly important in the normal functioning of the nervous system through its role in myelin synthesis and in the maturation of red blood cells in the bone marrow.
Vitamin B12, one of the eight water-soluble B vitamins of the B complex, is the largest and most structurally complex vitamin. It exists as a complex in animal proteins and its main source is the microorganisms of the intestinal tract of vegetarian animals.
Most people in developed countries get enough vitamin B12 from eating animal products, including meat, milk, eggs and fish. There are also foods that are fortified with vitamin B12. Vitamin B12 supplements are available in either single-agent or multivitamin tablets, while pharmaceutical formulations can be administered by intramuscular injection.
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Generally, a deficiency is rarely observed. There are, however, some groups, which should place special emphasis on its adequate intake.
Vitamin B12 Health Benefits
Our body needs vitamin B12 because:
Vitamin B12 Recommended Daily Intake
Like many vitamins, vitamin B12 is not made in the body. For this reason, it must be taken either through food or supplementation.
For people over 14 years of age, the recommended daily dose is 2.4 μg per day. For pregnant women it is 2.6μg/day and for breastfeeding women it is 2.8μg/day.
Research has shown that specific amounts of cobalamin/B12 can improve some conditions, such as:
- Mental disorders e.g. depression, mental and physical stress: 100-500μg
- Anemia due to vitamin B12 deficiency: 250-500μg.
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Vitamin B12 Food Sources
Vitamin B12 is found mainly in animal products and rarely in plant products. That is why strict vegetarians should take a supplement or choose cereals that are enriched with B12. The main sources of B12 are the following:
| Food (100g) | B12 | RDA (%) |
|---|---|---|
| Beef liver | 100 μg | 4200% |
| Lamb liver | 84 μg | 3500% |
| Bird livers | 56 μg | 2300% |
| Calf kidneys | 31 μg | 1300% |
| Canned sardines | 28 μg | 1150% |
| Shelled mussels | 22 μg | 900% |
| Oysters | 18 μg | 750% |
| Mackerel | 10 μg | 400% |
| Brewer’s yeast powder | 5 μg | 200% |
| Fresh salmon | 5 μg | 200% |
| Tuna | 4,3μg | 180% |
| Shiitake mushrooms | 4,8 μg | 200% |
| Eggs | 1,1μg | 45% |
TIPS
– Cooking up to 100°C has little effect on vitamin B12, but at higher temperatures losses can be as high as 20%.
– Vitamin B12 is water-soluble, i.e. it dissolves in water. The amounts that are not used are stored by the body in the liver and other tissues.
– However, vitamin B12 deficiency is quite common. Deficiency is either due to not getting enough vitamin B12 from food, or not being able to absorb it properly.
Vitamin B12 Deficiency
Vitamin B12 deficiency is perceived in four stages:
- first we have a decrease in blood levels (stage 1),
- then there is a low concentration of the vitamin at the cellular level (stage 2),
- then we have an increase in homocysteine, a harmful amino acid, in the blood and a decrease in DNA synthesis (stage 3)
- and finally macrocytic anemia, with symptoms of fatigue, weakness, lethargy, memory loss and neurological disorders (stage 4).
Severe deficiency in this vitamin can be a risk factor for depression, paranoia and hallucinations, and irreversible damage to nerves can be caused.
Many of the things that characterize the third age (difficulty walking, numbness and tingling sensations in hands and feet, yellowing, joint pains, shortness of breath, impaired memory, loss of taste and smell, incontinence, etc.) are partly due to vitamin B12 deficiency.
Vitamin B12 appears to help prevent Alzheimer’s disease and improves memory levels according to the American Academy of Neurology.
In particular, research reported in the American Journal of Clinical Nutrition shows that in people aged 60 to 78 in Scotland, those with high levels of cobalamin and folic acid in the blood also performed better on intelligence tests!
Vitamin B12 deficiency is usually seen in vegetarians, the elderly, people with digestive disorders and those who have had weight loss surgery, as the procedure interferes with the body’s ability to extract it from food.
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Its deficiency is also observed in those who consume increased amounts of alcohol, as the absorption of B12 by the body is reduced.
Finally, in people with diseases that cause malabsorption in the intestine, such as celiac disease, ulcerative colitis, Crohn’s disease, irritable bowel syndrome.
People taking antacids or ulcer medications often have a vitamin B12 deficiency and should take a daily supplement.
Blood levels of B12 would also be good to test patients taking metformin – a diabetes drug – amino salicylic acid for tuberculosis or inflammatory bowel disease (IBD), as well as the antiepileptic drugs primidone, phenobarbital and phenytoin.
The most common signs of vitamin B12 deficiency are:
- difficulty in walking and balance
- numbness in the hands, feet and legs
- anemia
- swollen tongue
- yellow skin
- tiredness
More detailed symptoms and health effects are as follows:
- reduction of white blood cells
- unexplained fatigue/exhaustion and drowsiness especially in the evening hours
- muscular weakness
- numbness and muscle cramps
- reduced memory and inability to concentrate
- low mood
- changes in the texture and color of the tongue
- reduced vision
- frequent headaches
- nausea and dizziness
- colorless / dull skin
- stomach ulcer
- diarrhea
- instability
- increase in homocysteine
Prolonged vitamin b12 deficiency causes severe, irreversible damage to the nervous system. It is no coincidence that Alzheimer’s patients have low levels of vitamin B12 in blood tests.
☝ Vitamin B12 deficiency can occur in between 40% and 80% of the vegetarian population.
Vitamin B12 Absorption
The key to sufficiency or deficiency is absorption.
The Endogenous factor is a glycoprotein produced by cells in the stomach walls and is essential for the absorption of vitamin b12 from the diet.
During digestion, gastric acids separate vitamin b12 from the food and endogenous factor binds to vitamin b12 and allows it to be absorbed in the small intestine.
Unfortunately, problems of Vitamin B12 absorption start after 50, along with bowel problems.
People who are on strong medication or have severe digestive damage such as inflammation in the gut, irritable bowel syndrome, celiac disease, etc. are likely to develop vitamin b12 deficiency.
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The deficiency arises as there are limited foods that these individuals can consume.
The most common reason that creates a problem in the absorption of b12 is malignant anemia where our body cannot produce enough of the endogenous factor glycoprotein.
☝ Malignant anemia is the most common reason for deficiency in developed countries.
Another reason why vitamin b12 deficiency can occur is poor junk food diets common in developed countries and also in young ages.
The amount of Vitamin B12 that our body absorbs is used for its daily needs and the excess is stored in the liver for future use or excreted in the urine.
Vitamin B12 is found primarily in animal foods. It is present in a few plant sources, such as spirulina, nutritional yeast and fortified cereals, and is not present in fruit.
Vitamin B12 Toxicity
Hypervitaminosis from Vitamin B12 is relatively rare. You need to understand that Vitamin B12 is water soluble. Therefore excess Vitamin B12 is excreted in the urine.
However, in case of over-supplementation or hypervitaminosis, numbness of the skin, irritability or even possible allergic reactions are observed.
Elevated values (not due to excessive intake from supplements) are likely to be diagnosed in people with liver problems (such as acute hepatitis etc.), problems related to diabetes mellitus, or even in cases of leukemia and stomach malignancy.
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Vitamin B12 Supplements
Vitamin B12 supplements can be found in various forms.
Supplements containing one of its two activated forms: methyl-cobalamin or adenosine-cobalamin, seem to be more effective.
For better absorption they should be taken before eating. Hydroxocobalamin is used in injectable form.
| Brand | Amount | Mg/Serving | |
|---|---|---|---|
| 1️⃣ | Solgar | 60 nuggets | 1000 mcg |
| 2️⃣ | Nutricost | 240 capsules | 2000mcg |
| 3️⃣ | Jarrow Formulas | 100 Chewable Tablets | 2500 mcg |
| 4️⃣ | Thorne | 60 capsules | 1000 mcg |
| 5️⃣ | VitBoost | 60 drops | 5000 mcg |
B12 And Brain Ageing
A new study has shown that vitamin B12 can prevent memory loss associated with advanced age.
Scientists at the Karolinska Institutet in Sweden followed more than 500 people over the age of 50.
Participants underwent annual brain MRIs, cognitive ability and brain function tests and blood levels of vitamin b12 for 9 years.
The researchers found that people with normal levels of B12 in the body experienced fewer problems with memory loss and brain shrinkage than those who were deficient.
Specifically, people who had the highest levels of vitamin B12 in the body had the best memory test scores. The results of the study were published in the Journal of the American Medical Association.
Professor Rajaprabhakaran Rajarethinam is a psychiatrist at Wayne State University School of Medicine in the state of Indiana, USA. He studied the effect of vitamin b12 on the brain for the National Institutes of Health.
Dr. Rajarethinam says his research confirms previous results regarding the benefits of B12 on brain functions.
“Depression, senile dementia, brain dysfunction are often associated with vitamin b12 deficiency,” he said.
“Vitamin b12 deficiency is responsible for cognitive dysfunction much more often than we thought”
As we age we produce less gastric fluids which makes it difficult to absorb b12 from food. So it’s no coincidence that researchers estimate that 10 to 20% of the population over 50 are potentially deficient in vitamin b12.
Other people who are likely to be vitamin b12 deficient are vegetarians and vegans as their diets do not include animal products that are predominantly high in b12.
Other individuals likely to have a B12 deficiency are those taking antacid medications or treatments. Antacids block the production of gastric fluids needed for b12 absorption.
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Final Take
Vitamin B12, also known as cobalamin, plays a special role in various functions of the body. We often do not associate the various symptoms and discomforts we have with its deficiency, but this ignorance can lead to dangerous situations.
For this reason, it is advisable to make sure that we have an adequate intake of it through food, or if this is not possible for the reasons described above, then taking a dietary supplement containing it can be very valuable.
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