B12 is a weird vitamin with a unique chemical structure. Your body manufactures very little itself and your only major source is from eating animal protein, ie meat and fish.
Yet vitamin B12 is essential for healthy cells and a healthy nervous system.
A study published in the American Journal of Clinical Nutrition (AJCN) in 2009 indicates that approximately 6% of all persons aged 60 or more in Europe and North America are deficient in vitamin B12. The study also shows that this deficiency increases as we get older.
By contrast another study published in the same year in the Journal of the American Board of Family Medicine (JABFM) found that the rate of vitamin B12 deficiency among diabetics in Europe and North America averages 22%… more than three-and-a-half-times the overall average rate.
This study in the JABFM also showed that the deficiency was highest among diabetics who used Metformin to control their blood glucose levels.
In developing countries, according to the study in the AJCN, a deficiency in vitamin B12 is much more common and starts earlier in life. It gets worse as the patient ages.
Low consumption of animal flesh (meat and fist) is considered the main cause. Indeed in countries where a vegetarian diet is the norm, more than two-thirds of the population are deficient in B12.
In addition, in older persons, poor absorption during digestion is considered the predominant cause of the deficiency.
So, if you are diabetic, a vegetarian or elderly, it is essential to get your vitamin B12 levels checked regularly.
A simple blood test does the trick. Your levels should be between 191 and 663 pg/mL (picogram per millilitre… a picogram is one trillionth of a litre).
This measures the amount of vitamin B12 in your bloodstream, ie the amount that has been absorbed into your body after digestion.
Why vitamin B12 is vital
There are two reasons why vitamin B12 is vital:
 It is essential because it is needed to assist folate in making DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), which carry and transmit the genetic information of every living cell.
Genetic information tells cell how to function. This information must be passed along to the new cell each time a cell divides.
 Vitamin B12 also has a function in the production of myelin, which covers and protects nerve fibres. Without enough B12, the myelin sheath does not form properly or remain healthy.
As a result, nerve transmission suffers. Eventually the nerve damage becomes irreversible.
How your body gets and uses vitamin B12
B12… aka cyanocobalamin or cobalamin… is unique among vitamins.
This vitamin is water soluble and has a more complex chemical structure than all other vitamins, including those of the B complex. And it is the only vitamin to contain an inorganic element (cobalt) as an integral part of its makeup.
Only bacteria and microorganisms can make vitamin B12.
Bacteria in the intestines make some vitamin B12 but far, far less than the amount you need every day. Thus the only way to get enough B12 is to eat the foods that contain it or to take supplements.
Bacteria are also at work in animals creating vitamin B12. Hence it is found in a wide variety of foods made from animals.
Plant foods do not contain any vitamin B12 unless they have been fortified. However, vitamin B12 is added to some processed foodstuffs.
Here are the main food sources of vitamin B12:
- Beef liver and clams… the most abundant sources of B12
- Fish, meat, poultry, eggs, milk, and other dairy products… good sources of B12
- Fermented bean products, such as tempeh… lesser sources of B12
- Some breakfast cereals, nutritional yeasts etc that have been fortified with B12.
But ingesting enough vitamin B12 is not sufficient to keep you healthy. Your body also needs to be able to use it.
The absorption of vitamin B12 from the food you eat is a two-step process.
Firstly, your stomach acid has to separate the B12 from the protein to which it is attached in the food you swallow.
Then the B12 has to combine with intrinsic factor, another protein made by the stomach, so that it can be absorbed into your body.
If you body is unable to produce intrinsic factor, you will be unable to absorb vitamin B12 and will end up with pernicious anaemia (a lack of healthy red blood cells). Should this happen, your only solution will be to have regular injections of B12.
How much vitamin B12 do you need?
The recommended amount of vitamin B12 you should get is 2.4 micrograms (mcg) a day for adults, 2.6mcg a day for pregnant women, and 2.8mcg for women who are breast-feeding.
The usual American and European diet provides anywhere from 7 to 30mcg of B12, well in excess of your daily requirements.
In addition, the average well-fed person can store a supply of B12 in the liver (unlike other vitamins) that can last for five years or more.
But if you are a vegan (strict vegetarian who does not eat eggs or drink milk) or are a diabetic who is following the Beating-Diabetes Diet… which excludes eggs and dairy products and minimises your consumption of meat… you will need a daily supplement to ensure that your intake is sufficient.
Certain medications can interfere with your body’s ability to absorb or use vitamin B12:
- Chloramphenicol (Chloromycetin®), an antibiotic used to treat certain infections
- Proton pump inhibitors, such as omeprazole (Prilosec®) and lansoprazole (Prevacid®), used to treat acid reflux and peptic ulcers
- Histamine H2 receptor antagonists, such as cimetidine (Tagamet®), famotidine (Pepcid®), and ranitidine (Zantac®), used to treat peptic ulcers
- Metformin, used to treat type 2 diabetes
Effects of a vitamin B12 deficiency
When the supply of vitamin B12 in the body is low, the production of red blood cells slows down as DNA and RNA become less available. This causes anaemia. The production of the cells that line the intestine is also slowed.
A lack of vitamin B12 can also seriously damage your nervous system. If the lack continues for a long time, the damages to the nerves can become irreversible.
The symptoms of a vitamin B12 deficiency
If you are only slightly low on B12, you may not have any symptoms at all.
The symptoms of a mild deficiency in vitamin B12 include… tiredness… weakness… loss of appetite… weight loss… constipation. These symptoms can also be caused by other medical conditions and the underlying problem is not always easy to discern.
Very low levels of B12 can result in serious complications, such as:
- pernicious anaemia
Pernicious anaemia means you do not have enough healthy red blood cells. This deprives your cells of oxygen.
According to a study in the Journal of Oral Pathology Medicine less than 20% of persons with a B12 deficiency experience pernicious anaemia.
The symptoms of anaemia include… fatigue… pale skin… chest pain… dizziness… headache… loss of sense of taste… loss of sense of smell… fast or irregular heartbeat… shortness of breath.
Paresthesia is a burning or itchy sensation of the skin, usually on the arms, hands, legs, and feet. Some people experience numbness, tingling, or a prickly feeling.
Neuropathy or nerve damage can be caused by prolonged deficiency in B12. The symptoms are the same as diabetic neuropathy (caused by high blood glucose over a long period) and include pain, numbness and weakness in the feet and hands (called peripheral neuropathy).
Severe, long-term B12 deficiency can cause loss of mobility, difficulty walking, memory loss, delusions, and depression. It may even lead to dementia.
Treatment of B12 deficiency
Treatments for deficiency involve ingesting supplementary B12 vitamin in the form of:
- tablets that are swallowed… either as part of multi-vitamin or stand-alone B12 tablets
- sublingual tablets that are dissolved under the tongue
- nasal gels
A lack of vitamin B12 usually results from your body’s inability to absorb it… not from a lack of B12 in your diet.
This means that people who are deficient in B12 must take large doses of supplements. In order to ensure absorption they need to take far more than they would actually need.
This is not a problem as there are no reports that vitamin B12 causes toxicity or adverse effects even in extremely large amounts. In fact, it is often used as a placebo because it is non-toxic.
Indeed 1,000 mcg of B12 a day is a common recommendation, sometimes starting with 2,000 mcg a day for the first month. These huge amounts, several hundred times the recommended daily amount, ensure that at least some of it gets absorbed, even without intrinsic factor.
This is borne out by medical studies that show that large amounts of active vitamin B12 can be absorbed, even if your body cannot create intrinsic factor.
For example, methylcobalamin, one form of vitamin B12, can be absorbed when given in very large doses.
Received opinion is that sublingual administration of B12 is thought to bypass the absorption problems related to intrinsic factor as it allows the vitamin to be absorbed directly into the venous plexus… the complex of blood vessels located in the floor of the mouth.
But there is no evidence that the B12 from letting a tablet dissolve under the tongue is absorbed better than swallowing.
The efficacy of nasal gels is also unproven.
Pernicious anaemia is usually treated with injections of 50 or 100 mcg of vitamin B12 three times a week. As these go straight into your blood, they bypass the need for intrinsic factor. These injections may need to continue throughout life.
You need to ensure that you that you ingest adequate amounts of vitamin B12 and that your body can use it effectively:
- Vitamin B12 is vital for healthy cells and a healthy nervous system.
- Compared to non-diabetics, diabetics are three to four times more likely to be deficient in B12.
- Diabetics and vegans should have their B12 levels checked regularly.
- B12 is vital because it is needed to make: DNA and RNA for new cells each time a cell divides… myelin to protect nerve fibres.
- Your body makes very little B12 itself… your main sources are foods made from animals.
- To be absorbed, B12 must combine with intrinsic factor, a protein made in your stomach.
- If you body is unable to produce intrinsic factor, you won’t be able to use the B12 you ingest.
- If you are European or American you are probably getting plenty of B12, unless you are: a vegan… diabetic and are taking Metformin… following the Beating-Diabetes diet… taking medicines that interfere with your body’s ability to absorb or use B12
- Very low levels of B12 can result in… pernicious anaemia (not enough healthy red blood cells)… paresthesia (burning or itchy skin)… neuropathy (nerve damage that is similar to diabetic neuropathy)… loss of mobility, loss of memory, dementia etc
- Treatments consist of taking B12 as a supplement in very high doses to ensure that some of it is absorbed… you can have… tablets that are swallowed… sublingual tablets that are dissolved under the skin… nasal gels… injections
- B12 is not toxic and you cannot overdose