Vitamin B12 (cobalamin) is a water-soluble vitamin essential for maintaining healthy nerves, producing red blood cells, and synthesizing DNA. A deficiency can cause fatigue, memory problems, numbness or tingling in the hands and feet, and megaloblastic anemia.
| Function | Description |
|---|---|
| Nerve protection | Maintains myelin sheath surrounding nerves |
| Blood production | Helps form healthy red blood cells |
| DNA synthesis | Required for genetic material replication |
| Energy metabolism | Involved in breaking down fats and proteins |
People with type 2 diabetes who take metformin for extended periods are at risk of B12 deficiency. Research has shown that over 30% of patients on metformin for more than four years had low B12 levels (de Jager et al., 2010).
Consequences of B12 deficiency in diabetes:
Worsening peripheral neuropathy
Increased fatigue, reduced activity
Impaired cognitive function
CKD affects vitamin absorption and metabolism. In dialysis patients, water-soluble vitamins like B12 may be lost during treatment.
Studies also show that B12 supplementation can reduce homocysteine levels, which in turn helps lower cardiovascular risks in patients with kidney disease.
The answer is a clear NO.
Vitamin B12 is not synthesized by plants, so it is absent or present in only trace amounts in fruit and vegetables.
| Food | B12 Content (mcg/100g) |
|---|---|
| Beef liver | 70.7 |
| Salmon | 4.9 |
| Egg | 1.1 |
| Milk | 0.9 |
| Banana, apple, orange | 0 |
Some sources incorrectly list fruits like banana or avocado as rich in B12. In fact, these fruits contain vitamin B6 or folate (B9) but not B12.
Tip: Always check nutritional labels. Only fortified foods will contain B12 in a plant-based form.
If you are vegetarian, vegan, or a CKD patient on a restricted diet, here’s how you can safely obtain B12:
Fortified cereals, plant-based milk, nutritional yeast
Look for ingredients like cyanocobalamin or methylcobalamin
Read labels: many breakfast cereals provide 100% of the recommended daily value
People with diabetes or kidney disease often need 1,000–2,000 mcg/day
Oral tablets, sublingual drops, or injections available
Ask your doctor about monitoring blood levels of B12 regularly
Mr. Kim, who had been on metformin for over 10 years, began experiencing numbness in his feet. A blood test showed low B12 levels (180 pg/mL). After taking 1,000 mcg/day of B12 supplements, his symptoms improved within 2 months.
Ms. Jang, who avoided meat due to kidney disease, was found to be B12 deficient. Her nephrologist recommended fortified soy milk and nutritional yeast, and her blood levels normalized within 6 weeks.
| Question | Answer |
|---|---|
| Is B12 found in fruits? | No |
| Main sources of B12 | Animal-based foods, fortified foods, supplements |
| At-risk groups | Diabetes patients on metformin, CKD patients, vegetarians |
| How to supplement? | Fortified cereals, nutritional yeast, supplements (1,000–2,000 mcg/day) |
De Jager J, Kooy A, et al. Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B12 deficiency: randomised placebo controlled trial. BMJ. 2010;340:c2181.
NIH Office of Dietary Supplements: Vitamin B12 Fact Sheet
Spence JD. Homocysteine-lowering therapy in stroke prevention: where are we now? Stroke. 2005;36(6):1226-1229.
KDOQI 2020 Nutrition Guidelines for CKD
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