When we think about neurodegenerative diseases like Alzheimer’s or Parkinson’s, our minds often jump to cutting-edge therapies—immunotherapy, gene therapy, or the latest pharmaceutical breakthroughs. And while these treatments are essential, a silent factor lurking in the background could be worsening the problem: nutritional deficiencies. Among them, Vitamin B12 plays an astonishingly crucial role in brain function, yet many people—especially older adults—might not even know they are deficient.
For an in-depth exploration of the latest research, check out the full study published (on 10.02.25) in PubMed here.
What is Vitamin B12 and Why is It Important?
Vitamin B12, also known as cobalamin, is an essential nutrient that plays a critical role in nerve function, red blood cell formation, and DNA synthesis. Since the body cannot produce B12 on its own, it must be obtained through diet or supplementation.
Where Can You Get Vitamin B12?
B12 is naturally found in:
🥩 Animal Products – Meat, fish, dairy, and eggs are the primary natural sources of B12.
🌾 Fortified Foods – Certain cereals, plant-based milk, and nutritional yeast are enriched with B12.
💊 Supplements – B12 tablets, sprays, or injections can help those at risk of deficiency.
Why Are Many Older Adults and Vegetarians Deficient?
Older adults often experience reduced stomach acid production, which is necessary for absorbing B12 from food.
Vegetarians and vegans lack sufficient dietary sources of B12 since it is primarily found in animal products.
Individuals taking certain medications, such as proton pump inhibitors (PPIs) and metformin, may have impaired B12 absorption.
Vitamin B12: The Brain’s Unsung Hero – Could It Be the Missing Link?
Imagine your brain as a high-speed train. The nerves are like railway tracks, ensuring smooth and rapid transmission of electrical signals. Vitamin B12 acts as the maintenance crew, constantly repairing the tracks and preventing derailments. Without enough of it, the tracks begin to erode, slowing the train down and causing signal failures—manifesting as cognitive decline, memory loss, or even neurodegenerative diseases.
B12 is essential for:
Fatty Acid Metabolism – ensuring neurons get the energy they need ⚡
Myelin Integrity – the protective sheath around nerve fibers that enables fast communication 🔌
Nucleotide Synthesis – vital for DNA repair and healthy cell function 🧬
Not Just Deficiency – Even “Normal” Levels May Not Be Enough – Are We Underestimating the Risk?
Current medical guidelines define B12 deficiency as levels below 148 pmol/L. However, new research suggests that even individuals within the “normal” range may experience neurological effects. A groundbreaking study by Beaudry-Richard et al. (2025) challenges this threshold and suggests that a re-evaluation is necessary.
But this isn’t the first study to highlight the issue. Previous research has already pointed to the risks of subclinical B12 deficiency:
Alvarez & Garrido (2024) – Showed that proton pump inhibitors (PPIs) may contribute to cognitive decline by reducing B12 absorption.
Proton pump inhibitors (PPIs) are medications commonly used to treat acid reflux and stomach ulcers by reducing stomach acid production. However, they can also interfere with the absorption of Vitamin B12)
Wu et al. (2024) – Found that Alzheimer’s can progress even when traditional biomarkers (including B12 levels) appear normal, raising questions about whether B12 deficiency is a cause or simply a marker of cognitive decline.
Menon et al. (2025) – Highlighted the combined role of Vitamin D and B12 deficiencies in memory decline.
Dawson & Willette (2025) – Suggested that B12 should be examined alongside folate levels to better understand its role in cognitive aging.
This growing body of research reinforces the idea that B12 levels—even when considered “normal”—may not be enough to support long-term brain health.
The Difference Between Active and Inactive B12 – Are You Measuring the Right Type?
Most blood tests measure total B12, but not all of it is available for use. The study differentiates:
Holo-transcobalamin (Holo-TC) ✅: The biologically active B12 responsible for cellular function.
Holo-TC is the fraction of Vitamin B12 that is immediately available for uptake and use by cells, making it the most reliable indicator of B12 status.
Holo-haptocorrin (Holo-HC) ❌: The inactive form, which may actually correlate with neurodegeneration.
Holo-HC binds to most of the circulating B12 but does not deliver it to cells, meaning high levels could indicate poor B12 utilization rather than sufficiency.
Low Holo-TC levels were associated with cognitive slowing and structural brain damage, while high Holo-HC levels were linked to increased Tau protein, a key factor in Alzheimer’s disease.
Why This Matters for Aging and Cognitive Decline – Should We Start Testing Sooner?
Aging adults with low active B12 showed significantly worse processing speed and cognitive performance. This suggests that B12 monitoring should become a routine part of aging care—ideally, before symptoms even appear.
What Can You Do? – How Can You Protect Your Brain?
Test the Right Markers 🩸 – Ask for Holo-TC levels instead of relying on total B12 tests.
Optimize Absorption 🍽️ – If you take medications like proton pump inhibitors (PPIs), they may impair B12 absorption.
Consider Supplementation 💊 – Particularly for those at risk (older adults, vegetarians, or individuals with gut health issues).
Don’t Rely Solely on Nutrition 🐟 – While a B12-rich diet (eggs, fish, dairy) is important, supplementation might be necessary.
Support Holistic Health 🧘 – Pairing proper nutrition with exercise and medical therapies ensures the best outcomes.
Final Thoughts: Rethinking B12 in Brain Health – Could This Be a Game Changer?
The link between Vitamin B12 and neurodegeneration is becoming clearer, yet current guidelines may still be underestimating the importance of maintaining optimal levels. And this isn’t just a revelation from one new study—multiple research efforts over the past few years have been pointing to the same conclusion.
By making small changes today—getting tested, supplementing wisely, and staying informed—you could be protecting your brain from damage years down the line.
So, the next time you think about brain health, don’t just focus on the latest medical breakthroughs—consider the nutritional foundation that supports it all.
Let’s Dive Deeper
Could we be missing a crucial piece of the puzzle when it comes to brain health? Should we rethink the thresholds for B12 deficiency, given new research? What if early B12 intervention could actually slow cognitive decline in older adults? And could inactive B12 be quietly fueling neurodegeneration? I’d love to hear your thoughts and spark a conversation around these questions!
