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Vitamin B12 deficiency

Vitamin B12 is crucial to our health yet many of us are unaware how common deficiency can be, and its link with conditions such as Alzheimer’s disease, Multiple Sclerosis, autoimmune disease and cancer.



Vitamin B12, or cobalamin, is a water-soluble vitamin containing the trace element cobalt, and it plays a key role in the health of our nervous system, brain, DNA and red blood cells. Deficiency of this vitamin appears to be prevalent in Western countries, with research finding that as many as 40% of participants aged between 26 and 83 were in the low-normal range, within which neurological issues can be triggered.

What are the symptoms of vitamin B12 deficiency?

Deficiency symptoms are wide-reaching and can include pale skin, a smooth tongue, fatigue, weakness, lightheadedness, shortness of breath, brain fog, memory problems, cognitive decline, depression, developmental delay in children, fertility problems, numbness and tingling, increased risk of autoimmune disease, stroke and heart disease.

Where is vitamin B12 found in our diets?

Contrary to popular belief, you can’t get vitamin B12 from plant foods. It is found exclusively in animal foods, including meat, cheese, liver, and seafood.

What can cause B12 deficiency?

There are several factors relating to diet, lifestyle and health conditions that may impair absorption of vitamin B12 leading to a deficiency.

• Low stomach acid impacts on vitamin B12 absorption because pepsin is required to free the vitamin from the animal protein, and this relies on adequate hydrochloric acid to be present. Stress, poor diets, ageing and the use of antacid medication can lead to lower levels of stomach acid.

• Atrophic gastritis, involving thinning of the stomach lining, can lead to poor absorption of B12.

• Pernicious anaemia, an autoimmune disorder characterised by a lack of the ‘intrinsic factor’ needed for the absorption of B12 in the intestines, can lead to deficiency that needs lifelong correction.

• Vegetarian or vegan diets lacking animal foods may fall short of this nutrient leading to deficiency. Even children who follow a vegan diet may become deficient quite quickly, putting them at risk of cognitive impairment and problem solving abilities at an early age.

• Research has found that even a moderate intake of alcohol in healthy, well-nourished individuals may diminish vitamin B12 status.

• Inflammatory intestinal disorders such as celiac disease, Crohn’s disease or colitis may impact on B12 status due to reduced absorption and increased losses.

B12 and chronic disease

Vitamin B12, along with other B vitamins, is needed by the body in order to methylate properly. Methylation is a complex process impacting on the health of all bodily systems, involving the addition and subtraction of methyl groups from other molecules. It cannot happen effectively in the presence of vitamin B12 deficiency, and one consequence of this is for homocysteine levels to rise, increasing the risk of heart disease, stroke, cancer and Alzheimer’s disease.

Vitamin B12 has also been found in research to increase the length of a protective chemical structure found at the end of each chromosome, called a telomere. Telomeres get shorter over time, leaving the chromosome more vulnerable to damage, which in turn increases our risk of chronic disease, obesity and accelerated ageing.

Testing for B12 levels

Conventional serum B12 testing is unreliable and may miss many cases of B12 deficiency. This is partly due to a wide reference range – in their book ‘Could it be B12?’, Sally Pacholok and Jeffrey Stuart claim that a ‘grey area’ towards the bottom of the standard reference range is considered by many experts to be too low, and those whose B12 levels fall within this area still need treatment. Levels of B12 in the blood may also not reflect actual B12 status in the cells. Other blood chemistry markers of note that indicate B12 anemia are MCV, MCHC and MCV.

More accurate testing would involve looking at several markers together, including homocysteine as mentioned above, plus the holotranscobalamin test and methylmalonic acid (MMA). Holotranscobalamin testing looks at the active form of B12 that can be delivered to the cells; and MMA is a breakdown product of amino acid metabolism that can become elevated when B12 levels are low. Checking these markers together provides a more accurate and reliable indication of B12 levels in the body.

B12 deficiency treatment

If you suspect or know you have a vitamin B12 deficiency, it’s best to work with a professional who can investigate the underlying cause before looking at supplementation or dietary approaches. There are many forms of B12 available – cyanocobalamin is commonly found on the high street, but may not be well absorbed. More effective forms of B12 include methylcobalamin, adenosylcobalamin and hydroxocobalamin. Depending on your levels and unique genetic needs, you may tolerate one better than another and could need to raise levels slowly and carefully, alongside other nutrients, depending on your health status and test results. As a general rule though, B12 is best absorbed sublingually as a spray or lozenge, to prevent losses that may occur through the digestive system when swallowing a capsule or tablet. Injections are also available and may be recommended if your levels are very low.


Written by Emma Rushe

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