In the health and disease prevention world, we typically hear about how
nutrition is vital. But what if vitamin deficiency did more than make one tired
or weak? What if it was a sign, indicating more serious and underlying health
issues?
Vitamin B₁₂ (cobalamin) is one such nutrient. It is required for everyday
biological functioning, including nerve health, synthesis of DNA, and
production of red blood cells. There are times when a lack of cobalamin is not
merely a lack of dietary intake but serves as a precursor to possible hidden
gastrointestinal or autoimmune diseases, some of which may carry an increased
risk of cancer.
Let us look further into why the problem of Vitamin B₁₂ deficiency deserves
more than a fleeting thought.
Understanding Vitamin B₁₂: More
Than Just a Vitamin
Vitamin B₁₂ is an important water-soluble vitamin and has several important
jobs in the body. It is essential for DNA replication, particularly in cells
that replicate quickly (bone marrow cells). It also helps to maintain your
nervous system by keeping the myelin sheath around nerves intact, to allow for
the correct transmission of signals, and also essential for normal red blood
cell production so that you avoid a problem of megaloblastic anemia.
Megaloblastic anaemia is the phenomenon of red blood cells growing in size
abnormally, and no longer being effective.
Where Do We Get Vitamin B₁₂,
and How Much Do We Need?
Vitamin B₁₂ is found in animal foods like meat, dairy, eggs, and fish.
Fortified foods like breakfast cereals or plant milk serve as a crucial
alternative for vegetarians, and particularly for vegans. The daily requirement
is 2.4 micrograms (mcg) in adults, whereas pregnant or lactating women need up
to 2.8 mcg.
That said, when dieters have adequate dietary intake for Vitamin
B₁₂, but still exhibit symptoms of vitamin B₁₂ deficiency, it may be due to
absorption issues or due to taking another medication. Therefore, healthcare
providers should take into consideration the Vitamin B₁₂ level of a patient
with B₁₂ deficiency-type symptoms.
What Causes B₁₂ Deficiency?
1. Inadequate Intake
- Strict vegetarians or vegans not eating fortified
foods.
- Elderly or chronically ill patients with poor diet
- Chronic alcohol consumption impairs absorption
and appetite.
2. Malabsorption
- Atrophic gastritis or pernicious anaemia (autoimmune
destruction of intrinsic factor)
- GI conditions such as Crohn's, celiac disease, or bacterial overgrowth
- Surgical history: bariatric surgery, ileal
resection
3. Medications
- Proton pump inhibitors (PPIs): decrease stomach
acid, preventing B₁₂ release from food
- Metformin: linked to B₁₂ malabsorption in
diabetics
4. Other Causes
- Parasitic infestations (e.g., fish tapeworm)
- Congenital deficiencies of intrinsic factor
synthesis
How B₁₂ Deficiency Shows Up
Symptoms can affect multiple systems:
- Blood-related: Fatigue, pallor, breathlessness due to
megaloblastic anaemia
- Neurological: Tingling, memory loss, depression, unsteadiness
- Oral/Visual: Mouth ulcers, glossitis (swollen tongue), blurred
vision
Prolonged deficiency can result in permanent nerve damage - so early
detection and treatment are imperative.
Diagnosing a Deficiency
Diagnosis combines clinical signs with lab tests:
The process of diagnosing a Vitamin B₁₂ deficiency starts with serum B₁₂
level testing. Serum B₁₂ concentrations below 200 pg/mL are considered clearly
deficient and, typically, clinically symptomatic.
Serum B₁₂ levels between
200–300 pg/mL indicate a borderline status. Symptoms may be present, but there
is uncertainty about the clinical diagnosis. In these instances, testing may be
needed to rule out a true deficiency.
- Functional Markers: Methylmalonic Acid (MMA)
Methylmalonic acid is a very sensitive indicator of Vitamin B₁₂ deficiency.
In the state of low B₁₂ levels, MMA builds up in the blood as MMA needs to be
converted to succinyl-CoA by B₁₂, which is part of energy metabolism. High
levels of MMA are highly reactive to functional deficiency even if serum B₁₂ is
borderline or slightly low.
- Functional Markers: Homocysteine
Homocysteine is another compound that builds up when Vitamin B₁₂ is
lacking, as B₁₂ helps convert it into methionine. Elevated homocysteine levels
can indicate a deficiency in either Vitamin B₁₂ or folate. While not specific
to B₁₂ alone, high homocysteine levels—especially when paired with other
findings, strengthen the case for further investigation.
- Autoimmune Tests: Intrinsic Factor Antibodies
A key reason for deficiency in Vitamin B₁₂ is pernicious anaemia, an
autoimmune disease in which the body generates antibodies against intrinsic
factors, a protein required for the absorption of B₁₂ in the bowel. Intrinsic
factor antibody tests can be used to detect this underlying cause and inform
long-term management, including lifelong B₁₂ injections.
- Autoimmune Tests: Parietal Cell Antibodies
Parietal cells of the gastric lining secrete both intrinsic factors and
stomach acid. In autoimmune gastritis, the cells are attacked by antibodies,
disrupting both acid secretion and B₁₂ absorption. Parietal cell antibody testing
can aid the diagnosis of autoimmune gastritis, which frequently antedates or
coexists with pernicious anaemia.
Serum gastrin is a hormone that stimulates gastric acid production. In
autoimmune gastritis, the compromised parietal cells cause reduced acid output,
and this reduced acid output triggers an increase in gastrin because the body
attempts to make up for it. Increased serum gastrin is an indirect stomach
dysfunction marker and usually presents in chronic atrophic gastritis cases.
- Complete Blood Count (CBC)
A CBC is a routine blood count that may uncover macrocytic anaemia, in
which the red cells are larger than usual as a result of defective DNA
synthesis, a characteristic of B₁₂ deficiency. An additional frequent finding
is hypersegmented neutrophils (abnormally segmented nuclei in white cells),
which again points towards the diagnosis of a megaloblastic process.
High Vitamin B12 Levels: A
Hidden Warning Sign
Although B₁₂ deficiency itself is not a cause of cancer, it may be an
indicator of cancer risk-increasing conditions.
1. Gastric Cancer
- Pernicious anaemia and autoimmune gastritis cause
damage to stomach lining and parietal cells.
- Chronic inflammation results in atrophic gastritis, intestinal
metaplasia, and possibly gastric cancer.
- Studies evidence 6-fold increased risk of
gastric cancer in pernicious anaemia patients.
2. Colorectal Cancer
A few patients with early colorectal cancer exhibit reduced levels of B₁₂,
perhaps because:
- Tumour-associated malabsorption
- Altered gut microbiota
- Damaged intestinal mucosa
3. Elevated B₁₂: A Paradox
Surprisingly, elevated B₁₂ levels (in the absence of supplementation) may
be equally disturbing:
- Associated with liver disease or solid tumours
(e.g., lung, colorectal cancer)
- Can be a sign of compromised hepatic
clearance, rather than excess nutrition
B₁₂ Deficiency: A Marker, Not
a Cause
Think of Vitamin B₁₂ deficiency as a sm smoke alarm, not the fire. It
often signals something deeper:
- Autoimmune gastritis
- Hidden malignancies
- Chronic GI disease
For example: Treating fatigue with B₁₂ pills alone might mask early
cancer or autoimmune disease if no further testing is done.
Treatment & Monitoring
Good management outperforms supplements. Finding and treating the
underlying cause is most important for long-term recovery and prevention.
1.
Diet & Lifestyle
Add more
B₁₂-containing foods like meat, fish, eggs, and dairy. For vegetarians,
fortified cereals, nutritional yeast, and plant milk make suitable substitutes.
Vegans need to take a trusted daily B₁₂ supplement to ensure they are satisfied
and avoid long-term deficiency.
2. Supplementation
Oral B₁₂
(1,000–2,000 mcg/day) is sufficient for most individuals, even in the presence
of somewhat impaired absorption. In severe deficiency, pernicious anaemia, or
following gastrointestinal surgery, injections are needed. The standard
injection regimen starts with daily or alternate-day injections for 1–2 weeks,
weekly injections for a month, and then monthly for maintenance.
3. Treat the Cause
Adjusting B₁₂ levels is only half the story,
treating the underlying cause is essential. This could involve modifying
medications such as proton pump inhibitors or metformin which interfere with
absorption. Underlying gastrointestinal diseases including Crohn's disease,
celiac disease, or bacterial overgrowth will also need to be addressed. Those
with autoimmune gastritis or pernicious anaemia may require regular endoscopy
to check for pre-cancerous changes in the stomach.
4. Ongoing
Monitoring
After beginning
treatment, B₁₂ levels need to be checked again every 3–6 months to confirm
stability. Though blood symptoms usually resolve within a few weeks,
neurological symptoms such as tingling or memory impairment can take several
months to get better and may not improve completely if treatment is late.
Regular follow-up will prevent relapse and detect any underlying conditions
early.
When to See a Doctor
Symptoms That Need Medical
Review
- Fatigue or anaemia not explained by low iron
- Tingling, memory loss, or balance issues
- Blurred vision or recurring mouth ulcers
- No improvement despite supplements
Red Flags Suggesting Cancer or
Autoimmune Disease
- Unexplained weight loss
- Chronic bloating, diarrhoea, or GI bleeding
- History of autoimmune disease or gastric surgery
- Older adults with unexplained cognitive
decline
Expect These Tests
- Blood tests: B₁₂, MMA, homocysteine
- Autoimmune screening: intrinsic factor, parietal antibodies
- Endoscopy/colonoscopy (if symptoms persist or
cancer risk exists)
Final Thoughts
Vitamin B₁₂ deficiency is not always an easy nutritional insufficiency, it
can be a key diagnostic lead. It is the body's method of communicating that
something more serious might be amiss. B₁₂ is essential for blood cell
production, nerve function, and DNA synthesis.
When it is low, signs can mimic
severe illnesses like dementia, anaemia, or even cancer. That's why ongoing or
unexplained deficiency should never be dismissed; it requires a thorough
medical examination. Treating the underlying cause - not simply replacing the
vitamin - is crucial. With early detection and proper intervention, long-term
complications can be prevented, and in some cases, lives can be saved.
