Overview
- B12 (also known as Cobalamin) is an important vitamin for maintaining healthy nerves and cells. Some B12 is used by the body and some B12 is stored in the liver for many years
- It is obtained from food we eat, and/or by supplementing the vitamin
- Foods High in B12 include meat, eggs, fish, dairy
- When we eat B12 containing foods it is often bound to protein.
- Digestion begins in the mouth
- Partially digested food, including proteins, travel to the stomach where more digestion occurs
- From here, the B12 complex travels to the small intestine
- In the small intestine, more digestion occurs because of substances released by the pancreas
- The B12 continues to travel to the end of the small intestine and is absorbed into the blood
- It joins two different transport carriers
- One of the carriers is only given~ 20% capacity out of the total B12 that has entered the blood
- BUT…. this 20% is very important as it brings the vitamin to the body cells. This is termed active B12
- Vitamin B12 is used to keep the nerve and body cells healthy and help make new blood cells
- People can have low B12 if they do not eat enough foods containing B12, have a bacterial overgrowth in the small intestine (SIBO), or a condition called pernicious anaemia that affects B12 absorption.
- Symptoms can include weakness, fatigue, sore tongue, pale skin, difficulty walking, shortness of breath.
Testing
Vitamin B12 testing Ireland
You can get tested for Vitamin B12 with a serum blood test. It is a good idea that the B12 test will measure the level of active B12 in the blood. The widely used total serum B12 blood test may show within the normal range if the active B12 is not measured. As mentioned earlier, the active B12 comprises of about 20% of the total plasma B12 and it is this active B12 that is used by the body cells.
Vitamin B12 (Active B12) test is now available at GastroLife. Click on the button below to find out more information.
The testing kit is designed to be performed as a home test and sent back to the laboratory for analysis. The laboratory performing the analysis is fully accredited by ISO15189 International Standard for Medical Laboratories.
If you want to understand the cause of your deficiency, one option is to undertake a SIBO test in one of the clinic locations, or perform the test at home using a home testing kit. As mentioned above, SIBO or small intestinal bacterial overgrowth occurs when there is too much bacteria in the small intestine. The bacteria utilise or use the B12 for themselves, thereby reducing the amount of vitamin B12 that eventually enters the blood. Sometimes if the total serum B12 has been measured and a deficiency is not evident, you could repeat the blood test measuring the ‘active’ amount of B12 if you are symptomatic, as this is the portion of B12 that is carried to the cells in the body. If you want to discuss SIBO testing or Active B12 serum testing, you can call or email us for more information.
The Science Bit
Digestion begins in the mouth. The salivary glands also release a substance called ‘R-Binder’ (Transcobalamin 1). The protein and R-binder then travels down the oesophagus to the stomach. Hydrochloric acid and pepsin secreted by the stomach further assist the digestion of protein and release the B12. The stomach also releases Intrinsic factor (IF) which plays an important role later. The B12 binds with the R-Protein made by the salivary glands to form a B12 complex. This complex along with the IF travels to the first part of the small intestine called the duodenum.
Now we are in the small intestine, what happens next is the pancreas secrets enzymes called proteases to help further breakdown digested food travelling from the stomach. The Proteases break down proteins but also the R-Binder attached to the B12. Now that the B12 is single again, it is attracted the intrinsic factor and they couple (B12 IF complex). Together they travel all the way to the end of the small intestine. At the end of the small intestine, there are IF receptors on the surface of enterocytes that bind the B12 IF complex. This complex passes through the cell and into the plasma (portal blood supply).
The B12 in now in the plasma and here it binds to plasma proteins called transcobalamin. About 80% is bound to Transcobalamin 1 (R-Binder) and ~20% to transcobalamin II. The~ 20% is delivered to body cells while the ~80% is circulating and not available for tissues. If this active ~ 20% (Active-B12 holotranscobalamin) is measured with a blood serum active B12 test, it would reflect a deficiency in the active B12 better than if the widely used total serum B12 test was undertaken.
Now we know that transcobalamin II is delivered to body cells, what it does for the cells? Vitamin B12 will keep the nerves and cells healthy, produces RNA, and DNA, it is also involved in the formation of red blood cells. A deficiency in B12 can lead to anaemia, feeling fatigue, numbness/tingling ‘pins and needles’, shortness of breath, pale skin, staggering, a swollen or inflamed tongue (the cells in the tongue mucosa divide rapidly, so old cells cannot be replaced as quickly in the presence of a B12 deficiency).
One example of how B12 functions is the important role it plays in cell division through the synthesis of DNA. This happens when the B12 joins with a methyl group (from methyl tetrahydrofolate) to form Methylcobalamin + free tetrahydrofolate (THF). The THF joins with another methylene group (from serine – an amino acid within cells). Further cellular reactions take place and thymidine is produced as the end result. Thymidine is a nucleotide used to build DNA. But if we go back to the early reaction where methlycobalamin is produced as a result of the B12 joining a methyl group, the methyl group of the methylcobalamin transfers to homocysteine which then converts it to methionine which in turn reduces homocysteine levels. High levels of homocysteine (an amino acid) are linked to arterial damage and heart disease. When cell division is affected by B12 deficiency, red and white blood cells in the bone marrow are affected. In terms of red blood cells, the bone marrow produces macrocytes (large mature cells instead of small mature cells). These macrocytes are destroyed in the spleen which causes anaemia. The bone marrow responds to the decrease in red blood cells by releasing more cells to compensate for the cells destroyed by the spleen, but these compensating bone marrow red cell precursors are not properly developed and are termed megaloblasts which results in macrocytic megaloblast anaemia.
The mitochondria of cells can also use B12 in the form of adenosylcobalamin (B12 and adenosyl group). After further cellular conversions, the end result is a reduction in methamalonic acid. Elevated levels of methylmalonic acid affects the myelin sheath of neurons leading to impaired neurological function and muscle function*.
What causes a B12 deficiency? There are numerous reasons why one may develop a deficiency. It can occur as a result of eating foods that contain little or no B12, it can also occur from Small intestinal Bacterial Overgrowth (SIBO) as the bacterial utilise Vitamin B12 resulting in a deficiency. Another cause of deficiency is pernicious anaemia. This is an autoimmune condition where antibodies attack the parietal cells in the stomach. These parietal cells produce IF which is necessary to transport Vitamin B12 through the intestines and into the blood for use by the body. There may also be B12 deficiency as a result of inflammatory bowel disease where there may be impaired receptor binding or transcobalalamin binding in the distal small intestine. Post upper GI surgery, (e.g following a gastrectomy or gastric bypass), the binding of B12 with IF can be affected causing a deficiency.
Typical recommended dietary allowance is 2.4 mcg/day
Supplements
You can supplement your B12 if you are deficient or not obtaining adequate intake from your diet. Nutri Advanced have a range of vitamins, including B12. You can purchase directly though their Irish website and products are shipped the next working day www.nutriadvanced.ie You will need to create an account the first time you log in.
A useful tip, if you sign up using the practitioner account settings found here https://www.nutriadvanced.ie/customer/account/create/type/patient and use my practitioner code 3364944 you will get €5 off first order and then 10% off any future orders. If you want to get the discount, its important you use the code and register as working with a practitioner or else the discount will not be applied.
If you are unsure what supplement is best for you, you can call Nutri Advanced on 0212427396 and the team will talk you through the product range. If you order over the phone, make sure you give the practitioner code 3364944 so your discount will be taken off total price.
If you have any concerns, always consult with your GP.
*osmosis.org
