Is a strict vegan or vegetarian diet an indication for a vitamin B12 lab test?

Vitamin B12 Testing for Strict Vegan/Vegetarian Diets

Yes, a strict vegan or vegetarian diet is a clear indication for vitamin B12 laboratory testing, as vitamin B12 is found almost exclusively in animal-based foods, putting these individuals at high risk for deficiency. 1, 2

Risk of B12 Deficiency in Vegetarians/Vegans

• Vitamin B12 is restricted to animal sources only, making those who follow diets that exclude animal products particularly vulnerable to deficiency 1
• Studies show high prevalence of B12 deficiency among vegetarians and vegans, with rates ranging from 11% to 90% depending on the population studied 3
• Higher deficiency rates are reported among vegans compared to vegetarians, and among those who have followed plant-based diets since birth compared to those who adopted such diets later in life 3
• Even lacto-ovo-vegetarians (who consume dairy and eggs) run the risk of becoming B12 deficient 4

Clinical Implications of B12 Deficiency

• B12 deficiency that progresses for longer than 3 months may produce permanent degenerative lesions of the spinal cord 2
• Untreated deficiency can lead to serious and sometimes irreversible pathological symptoms including:
  • Neurological problems (peripheral neuropathy, myelopathy, balance issues) 1
  • Cognitive difficulties (concentration problems, memory loss) 1
  • Optic nerve dysfunction (blurred vision, visual field loss) 1
  • Macrocytic anemia 1
  • Fatigue 1

Testing Recommendations

• The British Medical Journal recommends testing for B12 in people who follow diets that exclude or are low in animal source foods 1
• Active B12 (serum holotranscobalamin) is considered more accurate than total B12 (serum cobalamin) as it measures the biologically active form available for cellular use 1, 5
• For more comprehensive assessment, consider measuring methylmalonic acid (MMA) levels, especially with indeterminate B12 results 5
• Regular testing is recommended for all vegetarians and vegans, regardless of demographic characteristics, place of residence, or type of vegetarian diet 3, 4

Prevention and Management

• Vitamin B12 supplementation is essential for those following vegan diets 2, 6
• A vegetarian diet is specifically listed as a risk factor requiring B12 supplementation in FDA drug labeling 2
• Small, frequent (daily) doses appear more effective than infrequent large doses for those who can absorb B12 6
• Pregnant and lactating vegetarian/vegan women should ensure adequate B12 intake for their developing babies 6
• Fortified foods can help maintain B12 levels, but supplements are often necessary 6

Common Pitfalls to Avoid

• Relying solely on plant foods for B12 is ineffective - claims that fermented foods, spirulina, or certain seaweeds provide adequate B12 are unreliable 7
• Some seaweeds (Nori, Chlorella) may provide some bioavailable B12, but amounts are inconsistent and often insufficient 7
• Folic acid supplementation without B12 may mask hematologic symptoms while allowing neurological damage to progress 2
• Many vegetarians/vegans are not diligent about supplementation despite awareness of risks 8
• B12 deficiency can occur even without anemia, so testing should not be limited to those with hematologic abnormalities 6

In conclusion, regular B12 testing is essential for anyone following a strict vegetarian or vegan diet to prevent potentially serious and irreversible health consequences.