The B-Vitamin Paradox: Why My B6 and B12 Supplements Were Making Me Sicker, and the “Biochemical Refinery” Analogy That Changed Everything

Part 1: Introduction: The Question That Drove Me to the Brink

My story begins not in a textbook, but in the trenches of my functional medicine practice.

For years, I watched a frustrating pattern emerge.

Clients would arrive in my office, armed with bags of supplements and a story of exhaustion, brain fog, and a persistent, humming anxiety that colored their days.

They were doing everything “right,” following the standard advice from well-meaning doctors to take high-dose B-complex vitamins.

Yet, they felt profoundly wrong.

Their frustration was my own, because I was living the same paradox.

The breaking point, the moment that forced me to question everything I thought I knew, came in the form of a client I’ll call “Sarah.” She was the embodiment of the paradox.

Her blood work presented a baffling contradiction: her serum Vitamin B6 levels were alarmingly high, far above the normal range.

Yet, she was suffering from worsening peripheral neuropathy—a debilitating tingling, numbness, and pain in her hands and feet.¹

This was a textbook symptom of Vitamin B6

deficiency, not excess.³

It was a clinical impossibility that violated the simple logic of supplementation: if your levels are low, you take more; if your levels are high, you have enough.

Sarah’s case became my obsession.

It sent me deep into the scientific literature, searching for an answer to the question that now defined my practice: How can a vitamin, taken to alleviate a symptom, end up causing the very problem it’s meant to solve?

The answer I found was startling.

The symptoms of toxicity from high-dose B6 supplementation are, in many cases, nearly identical to the symptoms of deficiency.²

This wasn’t a simple side effect; it was a biochemical trap.

Research shows that while B6 deficiency can cause confusion, depression, and neuropathy, taking too much of the common supplemental form, pyridoxine, can trigger a lack of muscle control (ataxia), numbness, and the same debilitating peripheral neuropathy.¹

The mechanism behind this paradox is that flooding the body with the

inactive form of B6 can competitively inhibit the little bit of active B6 the body manages to produce, creating a functional deficiency at the cellular level, even with sky-high levels in the blood.²

This discovery was the key that unlocked a completely new way of understanding not just B vitamins, but our entire relationship with nutrition.

Part 2: The Epiphany: Your Body Isn’t a Bucket, It’s a Biochemical Refinery

For decades, the conventional model of supplementation has treated the human body like a passive bucket.

If a nutrient level is low, the logic goes, you simply pour more in until it’s full.

This model is simple, intuitive, and dangerously incomplete.

It ignores the complex, energy-intensive, and highly individual processes our bodies must perform to make use of what we consume.

My breakthrough in understanding Sarah’s paradox—and my own—came from the seemingly unrelated field of chemical engineering.

I realized the body is not a bucket; it’s a sophisticated biochemical refinery.

This refinery takes in “crude” raw materials (the inactive forms of vitamins from our food and most common supplements) and must process, convert, and purify them into high-grade “fuel” (the bioactive, coenzymated forms) that our cellular machinery can actually use.

The “Biochemical Refinery” analogy has three core concepts:

1. Crude Oil vs. Refined Fuel: Inactive vitamin forms, like pyridoxine (B6) and cyanocobalamin (B12), are the “crude oil.” They contain potential energy but are unusable in their raw state. The active, coenzymated forms, like Pyridoxal-5-Phosphate (P-5-P) for B6 and Methylcobalamin for B12, are the “refined fuel,” ready for immediate use.
2. The Refining Process: This is the series of enzymatic reactions, primarily in the liver, that convert the crude oil into refined fuel. This process requires energy and specific co-factors to run smoothly.
3. Refinery Efficiency: The health and efficiency of your personal refinery depend on factors like genetics, liver and kidney function, age, and overall nutrient status. A struggling refinery can lead to a dangerous situation: a buildup of unprocessed crude oil (toxicity) and a simultaneous shortage of essential refined fuel (deficiency). This is precisely what was happening to Sarah.

This mental model shifts the entire conversation.

The most important question is no longer “How much am I taking?” but rather, “What form am I taking, and how efficiently is my body refining it?”

Part 3: A Tour of the Refinery: The Critical B6 and B12 Production Lines

To understand why standard B-vitamin advice fails so many, we need to take a tour of two of the most important production lines in our biochemical refinery: the ones for Vitamin B6 and Vitamin B12.

The B6 Production Line: From Pyridoxine to P-5-P

The journey for most supplemental Vitamin B6 begins with a form called Pyridoxine Hydrochloride.

It’s stable, inexpensive, and for this reason, it’s the form used in the vast majority of fortified foods and multivitamins.⁶

This is our “crude oil.”

For this pyridoxine to become useful, it must be sent to the liver.

There, a series of enzymes, such as pyridoxal kinase, work to convert it into the final, refined fuel: Pyridoxal-5-Phosphate (P-5-P).⁶

P-5-P is the biologically active coenzyme form that the body actually uses to drive more than 140 critical reactions, from creating neurotransmitters like serotonin and dopamine to metabolizing glucose and supporting immune function.⁶

This is where the paradox of B6 toxicity is solved.

When a person with a struggling refinery—perhaps due to a stressed liver, alcohol dependence, kidney issues, or simply the effects of aging—floods their system with high doses of “crude” pyridoxine, the conversion machinery gets overwhelmed.¹

This leads to a buildup of unprocessed pyridoxine in the bloodstream.

This excess pyridoxine then competitively blocks the small amount of refined P-5-P that

is produced from binding to its enzymes.²

The result is a functional deficiency of P-5-P at the cellular level, triggering the very neurological symptoms the supplement was meant to prevent.

The B12 Production Line: From Cyanocobalamin to Methylcobalamin

A similar, though distinct, refining process occurs with Vitamin B12.

The most common supplemental form is Cyanocobalamin.

It is a synthetic form, prized for its exceptional stability and low cost, which makes it ideal for multivitamins.¹³

Its stability comes from a cyanide molecule that is chemically bonded to the vitamin’s core cobalt ion.¹⁴

Before the body can use this form, its refinery must perform a multi-step process.

First, it has to cleave off and detoxify the cyanide molecule—a small metabolic cost, but a cost nonetheless.¹⁶

Then, the remaining cobalamin molecule must undergo further conversion to become one of the two active “refined fuel” forms:

Methylcobalamin or Adenosylcobalamin.¹⁷

Methylcobalamin is the body’s premier, ready-to-use fuel for the critical methylation cycle, which we’ll explore next.¹⁹

While research on bioavailability is mixed—with some studies suggesting cyanocobalamin is absorbed slightly better and others showing methylcobalamin is retained longer in the body—the clinical implication is clear.¹³

For individuals with a compromised refinery (due to genetic variants, digestive issues, or other health challenges), providing the pre-refined Methylcobalamin is a more direct and reliable strategy to fuel the body’s most important processes.¹⁴

Feature	Inactive “Crude” Form	Active “Refined” Form
Vitamin B6	Pyridoxine HCl	Pyridoxal-5-Phosphate (P-5-P)
Common Name	Pyridoxine	P-5-P
Chemical Reality	A stable precursor that requires activation.6	The body’s active coenzyme form.20
Body’s Task	Must be converted by the liver, a multi-step, energy-dependent process.21	Ready for immediate use by over 140 enzymes.10
Potential Bottlenecks	Impaired liver function, kidney disease, alcohol use, aging, genetic factors.1	Bypasses the primary conversion bottlenecks.
Best For…	General fortification for individuals with robust liver function.	Those with liver stress, known conversion issues, or requiring targeted neurological support.
Vitamin B12	Cyanocobalamin	Methylcobalamin
Common Name	Vitamin B12	Methyl-B12
Chemical Reality	Synthetic form stabilized with a cyanide molecule.14	Natural, active form with a methyl group, ready for methylation.19
Body’s Task	Must cleave off and detoxify the cyanide group, then convert to an active form.17	Ready for immediate use in the methylation cycle.16
Potential Bottlenecks	Genetic polymorphisms (e.g., MTHFR), digestive issues, low stomach acid.12	Bypasses conversion steps, making it more reliable for those with methylation issues.
Best For…	Cost-effective fortification of foods due to high stability.14	Directly supporting the methylation cycle, especially in those with MTHFR variants.

Part 4: The Master Assembly Line: How B6 and B12 Power the Methylation Cycle

Inside our biochemical refinery, there is a master assembly line called the methylation cycle.

This pathway is one of the most fundamental in the human body, running in every cell to perform critical jobs like repairing DNA, regulating gene expression, producing neurotransmitters, and detoxifying chemicals.²²

A key challenge on this assembly line is managing a byproduct called

homocysteine.

If not cleared efficiently, homocysteine can become toxic, damaging blood vessels and neurons.¹¹

Fortunately, the body has two “escape routes” to clear homocysteine from the assembly line:

1. The Remethylation Pathway (The Recycling Route): This is the main pathway. Homocysteine is recycled back into the essential amino acid methionine. This process requires two indispensable workers: active Vitamin B12 (as Methylcobalamin) and active Folate (as L-5-MTHF).²⁴
2. The Transsulfuration Pathway (The Disposal Route): This is a secondary, one-way exit. Homocysteine is converted into other beneficial compounds, most notably cysteine, which is a precursor to the body’s master antioxidant, glutathione. This entire disposal route is critically dependent on one key worker: active Vitamin B6 (as P-5-P).²²

Now, we introduce a common wrench in the works: the MTHFR gene variant.

This common genetic polymorphism acts like a slowdown on the primary recycling pathway.

Specifically, it impairs the body’s ability to convert folic acid into the active folate needed for the remethylation cycle to work efficiently.²⁸

This is more than just a “folate problem”; it’s a systemic stressor with a ripple effect that places a greater demand on both B12 and B6.

When the primary recycling route (remethylation) is slowed by an MTHFR variant, the body must rely more heavily on the secondary disposal route (transsulfuration) to prevent a toxic buildup of homocysteine.

This means that the B6-dependent transsulfuration pathway becomes absolutely essential for maintaining metabolic balance.

This reveals why the standard advice for MTHFR—”just take methylfolate”—is often insufficient.

A truly comprehensive strategy must support the entire system.

It requires not only providing the active forms of folate and B12 to help the struggling recycling pathway but also bolstering the now-overburdened disposal pathway with its key worker: active Vitamin B6 in the P-5-P form.

Recent research supports this systems-based approach, showing that a combination of all three active B vitamins is the most effective strategy for lowering homocysteine levels in individuals with these genetic polymorphisms.³¹

Part 5: The Practitioner’s Framework: A New System for Precision Supplementation

The “Biochemical Refinery” paradigm isn’t just a theory; it’s the foundation of a practical framework I use to guide my clients from confusion to clarity.

It moves beyond the generic question of “What should I take?” to the more precise questions of “How is my body functioning?” and “What fuel does it need?”.

Step 1: Assess Your Refinery’s Efficiency

Become a detective of your own health.

Start by looking for the classic signs of an inefficient refinery: persistent fatigue, brain fog, mood changes, anxiety, or neurological symptoms like tingling and numbness.³²

Key lab tests can provide objective data.

A homocysteine level test is one of the best functional markers for the health of your methylation cycle.

Elevated homocysteine is a red flag that your B-vitamin assembly line is struggling.

Step 2: Choose the Right Fuel (Prioritize Active Forms)

Based on your assessment, prioritize the “refined fuel.” If you have elevated homocysteine, a known MTHFR variant, digestive conditions that impair absorption (like gastritis, Crohn’s, or celiac disease), or significant liver or kidney stress, using the active forms of B vitamins is not just an upgrade; it’s a necessity.¹

Choosing P-5-P and Methylcobalamin bypasses the compromised conversion steps, delivering the nutrients your cells need in a form they can use immediately.

Step 3: The Power of Synergy

These vitamins are a team.

They don’t work in isolation.

As we saw with the methylation cycle, B6, B12, and folate are deeply interconnected.

The most effective protocols recognize this synergy, combining active B6 (P-5-P), active B12 (Methylcobalamin), and active Folate (L-5-MTHF) to support the entire metabolic assembly line.²²

Step 4: Don’t Forget the Raw Materials (Whole Foods)

Supplements are powerful tools, but they are not a substitute for a nutrient-dense diet.

Ground your supplementation strategy in whole foods.

Excellent sources of B6 include poultry, fish, potatoes, and chickpeas.¹

B12 is found almost exclusively in animal products like meat, fish, eggs, and dairy.³⁷

Notably, the B12 from dairy products appears to be particularly well-absorbed by the body.¹⁷

User Profile	Primary Goal	Recommended B6 Form & Dose Range	Recommended B12 Form & Dose Range	Key Considerations
General Wellness	Maintaining baseline health in a healthy individual.	Pyridoxine or P-5-P (5–25 mg)	Cyanocobalamin or Methylcobalamin (100–500 mcg)	Focus on a high-quality B-complex from a reputable brand. Food sources are primary.
High Stress/Fatigue	Supporting energy production and mood regulation.	P-5-P (25–50 mg)	Methylcobalamin (500–1,000 mcg)	P-5-P directly supports neurotransmitter synthesis.6 Methylcobalamin bypasses energy-intensive conversion steps.19
Known MTHFR / High Homocysteine	Directly supporting methylation and clearing homocysteine.	P-5-P (25–100 mg)	Methylcobalamin (1,000–5,000 mcg)	Using active forms is essential to bypass genetic bottlenecks. Must be taken with active folate (L-5-MTHF) for synergistic effect.31
Vegetarian/Vegan	Preventing inevitable B12 deficiency.	Pyridoxine or P-5-P (as needed)	Methylcobalamin (1,000 mcg daily or 2,500 mcg weekly)	B12 supplementation is non-negotiable as B12 is not reliably found in plant foods.37

Part 6: The Long-Term Dividends: The Future of Your Health with Optimized B-Vitamins

Adopting the refinery model isn’t just about resolving current symptoms; it’s about investing in long-term health.

The latest research from 2024 and 2025 is revealing just how critical B-vitamin optimization is for our neurological, mental, and cardiovascular future.

Neurological Health: Redefining “Deficiency”

The old paradigm focused on preventing overt diseases like anemia or severe neuropathy.

The new paradigm is shifting toward optimization for brain health.

A groundbreaking UCSF study published in February 2025 found that even “low-normal” B12 levels in older adults were associated with more white matter lesions and slower cognitive processing speeds.⁴⁰

This suggests our current definition of “deficiency” is far too narrow and may be missing a massive opportunity to prevent age-related cognitive decline.

While large trials show mixed results for preventing dementia across the general population, the evidence is stronger for slowing decline in individuals with known risk factors like high homocysteine or a low B-vitamin status to begin with, underscoring the need for personalized, early intervention.⁴¹

Mental Health: A Double-Edged Sword

The simple story of “B vitamins for mood” is being replaced by a much more complex and nuanced picture.

While past studies showed correlations between low B vitamins and depression, a landmark Mendelian randomization meta-analysis from 2025 reveals a more intricate causal relationship.⁴⁴

This advanced genetic analysis suggests that while B vitamins are crucial for brain chemistry, their effects are highly specific.

For instance, the analysis found that genetic predispositions leading to higher B6 levels might protect against Alzheimer’s but could increase the risk for major depressive disorder.

Similarly, factors leading to higher B12 might protect against autism spectrum disorder but increase the risk for bipolar disorder.⁴⁵

This doesn’t mean B vitamins cause these conditions, but it powerfully illustrates that their roles are not one-size-fits-all.

Blanket supplementation without understanding an individual’s unique neurochemistry could be unhelpful or even counterproductive, reinforcing the core message of the refinery model: personalization is paramount.

Cardiovascular Health: A Specific Role for B6

The initial excitement that B-vitamin supplementation could be a silver bullet for heart disease by lowering homocysteine has cooled, as large-scale trials have produced inconsistent results.¹

However, a new pattern is emerging from recent large-scale observational studies.

Research from 2023 and 2024 consistently finds that higher

dietary intake of Vitamin B6, specifically, is associated with a lower risk of cardiovascular disease.⁴⁷

This association is stronger for B6 than for folate or B12, suggesting that B6 may have protective mechanisms that go beyond its role in homocysteine metabolism, opening an exciting new avenue for research.⁴⁹

Part 7: Conclusion: Becoming the Master of Your Own Biochemistry

My journey, and that of my clients like Sarah, has been a shift from a world of frustration to one of empowerment.

We moved from the simplistic, one-size-fits-all “bucket” model to the nuanced, personalized “biochemical refinery” paradigm.

The goal is not to have you memorize every enzyme, but to grasp the single most important principle: form is function.

Understanding that your body must actively work to process and activate the nutrients you consume changes everything.

It transforms you from a passive recipient of generic advice into an active participant in your own health.

It empowers you to look at a supplement label and see not just a nutrient, but a raw material that your body must refine.

The next time you consider a B-vitamin supplement, I urge you to stop asking only, “How much should I take?” and start asking the more important questions: “Which form is this?” and “How well is my personal refinery equipped to handle it?” By asking these questions, you can begin to have more intelligent conversations with your healthcare providers and become the master of your own unique biochemistry, turning frustration into clarity and reclaiming control over your health.

Works cited

1. Vitamin B-6 – Mayo Clinic, accessed on August 2, 2025, https://www.mayoclinic.org/drugs-supplements-vitamin-b6/art-20363468
2. Vitamin B6 Toxicity – StatPearls – NCBI Bookshelf, accessed on August 2, 2025, https://www.ncbi.nlm.nih.gov/books/NBK554500/
3. Vitamin B6: Benefits, dosage, food sources, and deficiency symptoms – Medical News Today, accessed on August 2, 2025, https://www.medicalnewstoday.com/articles/219662
4. Pyridoxine deficiency and toxicity – MedLink Neurology, accessed on August 2, 2025, https://www.medlink.com/articles/pyridoxine-deficiency-and-toxicity
5. Does an elevated Vitamin B6 (Vit B6) level indicate impaired conversion or absorption?, accessed on August 2, 2025, https://www.droracle.ai/articles/70016/is-a-high-b6-level-mean-it-is-not-being-converted-or-absorbed
6. Vitamin B6 – Wikipedia, accessed on August 2, 2025, https://en.wikipedia.org/wiki/Vitamin_B6
7. Vitamin B6 – Health Professional Fact Sheet – NIH Office of Dietary Supplements, accessed on August 2, 2025, https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
8. Vitamin B6, Pyridoxal and Pyridoxine in Cell Culture – Sigma-Aldrich, accessed on August 2, 2025, https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/mammalian-cell-culture/pyridoxal
9. Vitamin B6 (Pyridoxine; Pyridoxal 5′-Phosphate) – Alternative Medicine Review, accessed on August 2, 2025, https://altmedrev.com/blog/resource/vitamin-b6-pyridoxine-pyridoxal-5-phosphate/
10. P-5-P (Pyridoxal 5-Phosphate) – Seeking Health, accessed on August 2, 2025, https://www.seekinghealth.com/products/p-5-p-pyridoxal-5-phosphate
11. Vitamin B6 • The Nutrition Source, accessed on August 2, 2025, https://nutritionsource.hsph.harvard.edu/vitamin-b6/
12. Vitamin B12 Deficiency: Symptoms, Causes & Treatment – Cleveland Clinic, accessed on August 2, 2025, https://my.clevelandclinic.org/health/diseases/22831-vitamin-b12-deficiency
13. Methylcobalamin vs Cyanocobalamin: What’s the Difference? – Healthline, accessed on August 2, 2025, https://www.healthline.com/nutrition/methylcobalamin-vs-cyanocobalamin
14. Methylcobalamin vs Cyanocobalamin: Choosing a B12 Supplement – Verywell Health, accessed on August 2, 2025, https://www.verywellhealth.com/methylcobalamin-vs-cyanocobalamin-8423403
15. Which B12 Is Better? Cyanocobalamin vs Methylcobalamin – YouTube, accessed on August 2, 2025, https://www.youtube.com/shorts/2DsxuIYUvcY
16. Step 2 in MTHFR Support: How To Choose The Right B12 For You, accessed on August 2, 2025, https://www.mthfrsupport.com.au/2016/09/step-2-in-mthfr-support-how-to-choose-the-right-b12-for-you/
17. Vitamin B12 – Health Professional Fact Sheet – NIH Office of Dietary Supplements, accessed on August 2, 2025, https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
18. Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements With Potential to Mitigate B12-related Genetic Polymorphisms, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC5312744/
19. Methylcobalamin vs. Cyanocobalamin: Why Natural Vitamins Matter …, accessed on August 2, 2025, https://mobileivnurses.com/blog/methylcobalamin-vs-cyanocobalamin-why-natural-vitamins-matter/
20. Pyridoxal phosphate – Wikipedia, accessed on August 2, 2025, https://en.wikipedia.org/wiki/Pyridoxal_phosphate
21. Systemic Manifestations in Pyridox(am)ine 5′-Phosphate Oxidase Deficiency – PMC, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC6008785/
22. The Impact of B Vitamins on Methylations, Regeneration and Epigenetics: Results of a Randomized Double-Blind Study of Synthetic versus Plant-based Vitamin Complexes – OAText, accessed on August 2, 2025, https://www.oatext.com/the-impact-of-b-vitamins-on-methylations-regeneration-and-epigenetics-results-of-a-randomized-double-blind-study-of-synthetic-versus-plant-based-vitamin-complexes.php
23. B Vitamins and One-Carbon Metabolism: Implications in Human …, accessed on August 2, 2025, https://www.mdpi.com/2072-6643/12/9/2867
24. Methylation and Homocysteine: A Brief Overview – Food for the Brain, accessed on August 2, 2025, https://foodforthebrain.org/nutrition-for-healthcare-professionals/methylation-and-homocysteine/
25. Chapter 13: Homocysteine, vitamin B12, folates, vitamin B6, choline, betaine – Clinical Laboratory Diagnostics, accessed on August 2, 2025, https://clinical-laboratory-diagnostics.com/k13.html
26. Homocysteine metabolism as the target for predictive medical …, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC8581606/
27. Homocysteine, Vitamins B6 and Folic Acid in Experimental Models of Myocardial Infarction and Heart Failure—How Strong Is That Link? – MDPI, accessed on August 2, 2025, https://www.mdpi.com/2218-273X/12/4/536
28. MTHFR gene: MedlinePlus Genetics, accessed on August 2, 2025, https://medlineplus.gov/genetics/gene/mthfr/
29. MTHFR Gene Mutation: Impacts on Methylation, Absorption, and Why You Should Choose Methylated Vitamins | Awesome Family Chiropractic, accessed on August 2, 2025, https://www.liveanawesome.life/blog/mthfr-gene-mutation-impacts-on-methylation-absorption-and-why-you-should-choose-methylated-vitamins
30. Understanding the MTHFR Gene Mutation and Its Link to Mental Health and Neurodevelopmental Disorders, accessed on August 2, 2025, https://www.bhcsmt.com/blog/mthfr-gene-mutation-mental-health
31. Effect of Methylfolate, Pyridoxal-5′-Phosphate, and …, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC11173557/
32. Vitamin B12 or folate deficiency anaemia – Symptoms – NHS, accessed on August 2, 2025, https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/symptoms/
33. Neurological symptoms of vitamin B12 deficiency: analysis of pediatric patients* – PMC, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC6884369/
34. 11 symptoms of vitamin B12 deficiency – Medical News Today, accessed on August 2, 2025, https://www.medicalnewstoday.com/articles/324265
35. Vitamin B6 – Consumer – NIH Office of Dietary Supplements, accessed on August 2, 2025, https://ods.od.nih.gov/factsheets/VitaminB6-Consumer/
36. Best 15 Vitamin B-6 Foods: Benefits and Recipes – Healthline, accessed on August 2, 2025, https://www.healthline.com/health/vitamin-b6-foods
37. Vitamin B-12 – Mayo Clinic, accessed on August 2, 2025, https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
38. Vitamin B12 benefits, food sources, deficiency symptoms, and more – Medical News Today, accessed on August 2, 2025, https://www.medicalnewstoday.com/articles/219822
39. Vitamin B12 in Foods, Food Supplements, and Medicines—A Review of Its Role and Properties with a Focus on Its Stability – MDPI, accessed on August 2, 2025, https://www.mdpi.com/1420-3049/28/1/240
40. ‘Healthy’ Vitamin B12 Levels Not Enough to Ward Off Neuro Decline | UC San Francisco, accessed on August 2, 2025, https://www.ucsf.edu/news/2025/02/429491/healthy-vitamin-b12-levels-not-enough-ward-neuro-decline
41. Vitamin B12 | Linus Pauling Institute | Oregon State University, accessed on August 2, 2025, https://lpi.oregonstate.edu/mic/vitamins/vitamin-B12
42. Cognitive Decline and Vitamins – PMC, accessed on August 2, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC11822773/
43. Results of 2-year vitamin B treatment on cognitive performance – Neurology.org, accessed on August 2, 2025, https://www.neurology.org/doi/10.1212/WNL.0000000000001050
44. Vitamin B-12 and depression: Are they related? – Mayo Clinic, accessed on August 2, 2025, https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/vitamin-b12-and-depression/faq-20058077
45. Causal relationship between B vitamins and neuropsychiatric disorders: A systematic review and meta-analysis – PubMed, accessed on August 2, 2025, https://pubmed.ncbi.nlm.nih.gov/39952338/
46. Supplemental Vitamins and Minerals for Cardiovascular Disease Prevention and Treatment: JACC Focus Seminar, accessed on August 2, 2025, https://www.jacc.org/doi/10.1016/j.jacc.2020.09.619
47. Which Vitamins Are Best for Heart Health? – Healthline, accessed on August 2, 2025, https://www.healthline.com/health/heart-health/vitamins-and-heart-health
48. Intakes of folate, vitamin B6, and vitamin B12 and cardiovascular disease risk: a national population-based cross-sectional study – Frontiers, accessed on August 2, 2025, https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2023.1237103/full
49. Dietary Folate and Vitamin B6 and B12 Intake in Relation to Mortality From Cardiovascular Diseases | Stroke – American Heart Association Journals, accessed on August 2, 2025, https://www.ahajournals.org/doi/10.1161/strokeaha.110.578906