Home

What causes B12 deficiency?

Sun, 01/17/2010 - 17:21 — hugominney
Vitamin B12 is a water-soluble vitamin, like Vitamin C, so Vitamin B12 in circulation washes out of the body in the urine.
It is very important for a number of key biological pathways, including nerve function, cell growth, cell membranes and energy production. Mammals can’t make vitamin B12 and we have to eat it to get it, which means mammals have evolved special ways to retain as much as possible for as long as possible.
There are two main causes of Vitamin B12 deficiency – where the body can’t get B12 from your diet; and where the body can’t uses it. Both can develop over a period of years or happen suddenly.
B12 deficiency typically makes you extremely tired (including Chronic Fatigue Syndrome), have pins and needles, numbness or pain; you may lose your memory or ability to think and understand; you may develop Pernicious anaemia or other autoimmune diseases; you may develop Multiple Sclerosis and deficiency may even cause cancer.

B12 is safe, cheap and easy to obtain. Many people may be suffering from deficiency, but the medical profession doesn’t seem to be aware, preferring instead dangerous medicines and to write off people with supposedly unexplainable symptoms. We want to raise awareness, to improve diagnosis and treatment, and to ensure that treatment is tailored to patient need.

It is an essential nutrient available exclusively from bacterial sources, ie in the diet,  or through the action of gut bacteria [1] (see “where does B12  come from?”)

Vitamin B12 particularly affects cell membranes (which are vital for cells to take in nutrients and know when to grow or act), DNA (switching on and off genes at the right time), and some biochemical pathways (eg good mood/ low mood chemicals SAM and Homocysteine). This means that a deficiency in vitamin B12 can cause:

 

  • Blood diseases such as Pernicious anaemia
  • Neurological diseases such as MS, ataxia, dysphagia, neuralgia
  • Psychological conditions such as dementia, depression, confusion, fatigue

 

Who gets vitamin B12 deficiency?

Lots of people. According to some studies, 41% of Caucasians (white people of European descent) may be at risk. If your diet is short of Vitamin B12 then you could suffer. But if you are older, suffering from renal imbalance or diabetes, or have had any gastrointestinal surgery, then you may not be able to take it in from the food you eat, and may need more.

What food should it be in?

Vitamin B12 is manufactured by bacteria in animal guts, so you should be able to get it from red meat, all meat including fish, and dairy products. However with modern farming methods there may be a shortage in the meat as well.

What diseases could a B12 deficiency cause?

Vitamin B12 is very important to the body, and deficiency could cause a whole lot of symptoms, many of which are misdiagnosed as other diseases such as Anaemia, Multiple Sclerosis, Depression, Confusion, M.E., Neuralgia – we’ve dedicated a page to each please see the menu on the left. Note that Pernicious Anaemia is not a misdiagnosis – Pernicious Anaemia (PA) is always caused by vitamin B12 deficiency and will always make vitamin B12 deficiency worse. Please do check that you are getting the right care – go to your doctor to make sure you haven’t missed something obvious and important such as cancer. Vitamin B12 may be able to influence the development of cancer too.

Structure of B12 molecule - subject to copyright

Vitamin B12 is an essential nutrient available exclusively from bacterial sources, ie in the diet,  or through the action of gut bacteria [1] (see “where does B12  come from?”)

  It is a fairly large molecule consisting of amine rings with a cobalt molecule in the middle (molecular weight 1355.5) and so the process of digestion, absorption, transportation, conveyance into the cell, and utilisation by the cell is necessarily complex and problems can occur at many points in these pathways.

Problems can occur with:

Problem Occurs

 

Observe

Inadequate Intake

B12 is found in liver and to a lesser extent all animal products (see “where does B12 come from?”)

Vegetarian and vegan diets should be supplemented with yeast or B12 vitamin supplements

Many modern diets have the vitamins processed out of them, especially the water soluble vitamins (C and B12  along with the other B vitamins). 

B12 producing bacteria should be present in the gut, but modern eating habits do not encourage the ingestion of live bacteria <see notes on TransHepatoCirculation>

Some questions have been raised about cobalt in soil affecting B12 levels in animals grazing the soil and subsequently available to humans

May also be recorded as adequate in diet (may detect B12 but not a biologically useable form) but blood serum levels will be low or low normal

The Schilling test (provision of tracer B12 – usually in the form of mildly radioactive B12) tests for the ability of the gut to absorb B12 but does not take into account any further stages in the use of B12 .  The Schilling test is largely out of use now.

Malabsorption from diet

Defective release of cobalamin from food

1)    Gastric achlorhydria (failure to produce acid needed for digestion)

2)    Partial gastrectomy

3)    Drugs that block acid secretion (PPI, H2 blockers, etc)

4)    Defective release can be exacerbated by environmental factors such as Nitrous oxide, alcohol, by-products of smoking tobacco

 

Absence of Intrinsic Factor (which enables the absorption of B12 through the intestinal wall) – could be congenital or caused by auto-immune disease

Autoimmune disease can be detected by looking for Intrinsic Factor (IF) antibodies or Parietal Cell antibodies (Parietal Cells are the cells that manufacture stomach acid).  Diseases like MS are autoimmune diseases

Receptors are needed to transport the hydroxyl-B12 (or cyano-B12 if using artificial supplements) across the intestine wall

 

There are a whole lot of genetic abnormalities of haptocorrins (the TransCobalamins – the proteins that transport B12 across the intestine wall, around the blood stream and into the tissues) which could cause this

Disorders of terminal ileum

1)    Tropical Sprue/ non Tropical Sprue

2)    Regional enteritis

3)    Intestinal resection

4)    Neoplasm and granulomatous disorders

Competition eg Fish tape worm, bacteria

Drugs such as P. Aminosalicylic acid, colchicines, neomycin

Tropical sprue and non-tropical sprue may be caused if the colon (the last part of the intestine) microbes manage to get into the small intestine (where most of the food is absorbed).  The exact mechanism isn’t known but it could be that these bacteria produce a different form of vitamin B12 which can’t be used by humans and other mammals.

Transport and conversion

Trans-cobalamin II complex are needed to transport B12 to the tissues around the body to be utilised for cell maturation and function

Normal or high levels of B12 in the blood may be recorded where:

  • Forms of B12 which cannot be used are present
  • IF antibody may interfere with the usability of serum B12[2]

Utilisation in the cell

Failure to convert from hydroxyl to active forms for use in cells

May exhibit normal or high blood serum levels but patient still exhibits neurological symptoms

Levels of homocystine in the blood may also be tested as methyl-B12 converts this ‘bad mood’ chemical to a protein required for the body; but this test is far from specific and not accurate for B12 deficiency

This table based on [3]

Vitamin B12 absorption Am Fam Phys

Diagram from [4]

Classic Addisonian symptoms (macrocytosis or oversized red blood cells)[5] will be rare nowadays because food fortification and supplementation with folic acid (B9 – sometimes also called Vitamin M) masks/ corrects the macrocytosis even when B12 deficiency is present.

 

Citations

 

1.         Markle, H.V., Cobalamin. Crit Rev Clin Lab Sci, 1996. 33(4): p. 247-356.

2.         Hamilton, M.S., S. Blackmore, and A. Lee, Possible cause of false normal B-12 assays. BMJ, 2006. 333(7569): p. 654-5.

3.         Baboir, B.M. and H.F. Bunn, Pernicious Anaemia, in Harrison's Principles of Internal Medicine. 2005. p. 601-607.

4.         Oh, R. and D.L. Brown, Vitamin B12 deficiency. Am Fam Physician, 2003. 67(5): p. 979-86.

5.         Biermer, A., Über eine Form von progressiver perniciöser Anämie. Correspondenz-Blatt Schw. Ärzte., 1872. 2: p. 15-17.

 

Most Recent Five Posts

Title Post date Teaser
Poem: B12 deficiency - a silent death Tue, 08/31/2010 - 20:28

I am, I see, I think and I feel why does no one recognise me.
I want to shout out in the darkness
'Why the loneliness, isolation and a desperate helplessness;
Please someone comfort me'.
Are you B12-deficient? Fri, 08/06/2010 - 11:24

The first stage is to check your Signs and Symptoms.  Symptoms of B12 deficiency are generally non-specific, that is, they could be caused by a number of different things.  It's only when you have a number of different symptoms, occurring at the same time, that it makes sense to look for a common cause such as B12 deficiency.
Why is B12 deficiency more common now? Fri, 08/06/2010 - 11:05

I have a theory.  Now I must tell you that I’m not a doctor and have no medical qualifications so I can’t advise you; but I can share my experience.  In the past, Caucasians (white Europeans and colonists) got our B12 from meat.  People living nearer the equator had more vegetables in their diet, so if they weren’t really efficient at “scavenging” B12 – recycling i
Entero-hepatic circulation of B12 – or Why don’t vegetarians get B12 deficiency? Wed, 08/04/2010 - 16:25

When you stop eating B12 in your diet (for example by becoming a vegetarian), you may not notice if it on your B12 level for 10 years or more.
Conversely, when you develop a condition like pernicious anaemia, the effects can be devastating and very fast. We wondered why this was?
Pernicious Anaemia and B12 deficiency Wed, 07/28/2010 - 10:55

 Dr Chandy and I travelled to Bridgend to provide video interviews for the Pernicious Anaemia society. They have assembled some really top-quality people for these interviews, including local GPs and many experts in the field -- we were delighted to be invited.