Nootropics
Making The Connection Between B Vitamins And Cognitive Function
What's the deal with B vitamins? Can they really improve cognitive function?
January 28, 2018 · updated July 6, 2026
We’ve all seen vitamin ads telling us they’ll make us healthier than ever before.
That we can boost our immune system, improve concentration, and prevent heart disease… somehow…
This sounds great, but how can these vitamins do all this?
Or the better question is CAN these vitamins do what they’ve been promised to do?
Poor health reporting over the last 20 years has made it hard to differentiate what supplements are legit, and which ones are a waste of your time and money.
The purpose of this article is to investigate the role B vitamins have on cognitive health.
We’ll discuss what the major players are, and why they are so important. Then talk about ways you can ensure your B vitamin levels are on point with the best sources and the right supplemental doses.
What Are B Vitamins?
B vitamins consist of a carbon chain (like nearly all things in the human body), and an amine group. Amines in the most basic sense are molecules that contain the element nitrogen.
Nitrogen is a unique element… it offers the ability to make different chemical structures than the usual carbon atom can. It’s from this unique bonding property that makes nitrogen-containing groups special. In the case of B vitamins, they’re used as co-factors and coenzymes throughout the body.
This means they act like tools for enzymes to construct proteins and various other chemicals.
B Vitamins Are Diverse
One of the most interesting things about B vitamins is the vast difference between them.
They aren’t grouped according to any structurally similar traits (aside from the amine group shared with all true vitamins), rather, they’re grouped according to their shared solubility in water, and functionality as cofactors and coenzymes.
Have a look at the structural differences between vitamin B3 and B12 for example. B are used as coenzymes in the body yet B12 is more than 10 times the size and is immensely more complex in its structure than vitamin B3.
How B Vitamins Affect The Brain
All B vitamins are necessary cofactors in the process of energy production from carbohydrates, lipids, and proteins in different ways.
This makes it obvious why B vitamins are important for healthy brain function.
Without the ability to create energy, our brain can’t function.
This is the simple version. And is the reason why B vitamins can contribute to optimal brain function. Beyond energy production, there are three B vitamins that play specific roles in the brain and nervous system. Vitamins B6, B9, and B12 are considered the major players when it comes to brain health.
B6 (Pyridoxine)
Vitamin B6 is a medium sized molecule in comparison with the other seven B vitamins.
B6 is a necessary cofactor in over 140 different enzymatic processes that work with the synthesis, breakdown, and conversion of amino acids within the body 3Reference 3Vitamin B6.
Amino acids are used to build every protein in our bodies, including our enzymes and many of our neurotransmitters.
This also includes “homocysteine” which is linked to the development of cardiovascular disease, and cognitive disorders like Alzheimer’s disease.
Vitamin B6 works with B9, and B12 to reduce homocysteine levels throughout the body by converting it into its safe metabolite “cysteine” 1Reference 1Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease.
We’ll get into this later on because B9 and B12 are the major factors in controlling homocysteine.
A quick honesty check before we go further: the link between homocysteine and cognitive decline is real, but the jump from “B vitamins lower homocysteine” to “B vitamins prevent dementia” has not held up cleanly in trials. B vitamin supplementation reliably lowers blood homocysteine, and it can slow brain atrophy on MRI in people who already have elevated homocysteine 1Reference 1Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease. But large meta-analyses pooling more than 20,000 people across multiple randomised trials have found that lowering homocysteine this way does not produce a significant improvement in cognitive test scores or reduce dementia risk in the general population 8Reference 8Meta-analysisEffects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals9Reference 9Meta-analysisNeurobiology of Aging. So think of B6/B9/B12 as vitamins your brain genuinely needs (deficiency is bad for cognition), not as a proven cognitive-enhancement supplement for someone who isn’t deficient.
The most direct influence vitamin B6 has on cognitive function is through its role in neurotransmitter synthesis.
It’s from the essential role B6 plays in amino acid degradation and synthesis, that makes it a rate-limiting factor for neurotransmitter production. This means that if B6 levels are low, neurotransmitter production will also be limited. 3Reference 3Vitamin B6.
Neurotransmitters are the messenger molecules for our brains.
They’re what passes the signal along which results in muscle movement, emotions, and even homeostatic control.
Low neurotransmitter production is linked with all kinds of side effects like depression, anxiety, and brain fog.
Many nootropics (smart drugs) that target neurotransmitter health includes vitamin B6 for its crucial contribution to the process and to maximise the use of other ingredients.
Think of it like this; you are building a house (the neurotransmitter), and you order a shipment of brick and mortar to complete it. The bricks are the amino acid building blocks, and the mortar is the vitamin B6 needed to stick them together. The truck shows up and drops everything off, but there isn’t enough mortar to finish the job. You’ll build what you can until you run out of mortar, but will eventually be forced to stop.
Now, what you’re essentially left with is a pile of bricks on the front lawn, and a half-finished house.
This is the same with the neurotransmitters, and is the reason vitamin B6 is considered a “rate limiting factor”. You can’t build a house of bricks if you don’t have enough mortar.
B9 (Folate) and B12 (Cobalamin)
These vitamins are closely linked in their role in maintaining brain health. They are both connected in the folate and methionine cycles.
If B12 becomes deficient, folate will become “functionally” deficient.
A functional deficiency is one where there is enough of a certain nutrient or vitamin in the body, but it is not available for one reason or another, resulting in deficiency-like symptoms.
The reason B9 can become unavailable when B12 is low, is because if B12 isn’t in high enough amounts to perpetuate the folate-methionine cycle, folate will become trapped in the form of methyltetrahydrofolate 4Reference 4Vitamin B12, folic acid, and the nervous system.
When this happens, and folate is (functionally) deficient, DNA will start to become less stable, the neurons cannot function optimally, the protective myelin nerve sheaths can degrade, and the hippocampus can start to decay 5Reference 5Folic acid reverses endothelial dysfunction induced by inhibition of tetrahydrobiopterin biosynthesis.
B9 and B12 both a major role in the production of DNA and RNA, an essential part of not only our brain cells, but every cell in our body.
They also play a critical role in red blood cell formation.
Since red blood cells are responsible for delivering oxygen to the body, any reduction in red blood cell counts will have a negative impact on the efficiency of the brain, and could lead to hypoxia and cell death.
It should be noted that the hippocampus plays a key role in the storage and retrieval of past memories, the construction of location-based imagery in the brain, and the imagination of future events.
Damage to this brain structure is one of the first stages in the progression of Alzheimer’s disease 6Reference 6How the Hippocampus Influences Future Thinking.
The damage caused by folate deficiencies, including functional deficiencies caused by B12 deficiencies are easily prevented with B vitamin supplementation, or by eating a well balanced diet.
The myelin sheath is the protective “insulation” around nerve fibers.
This is what prevents the action potential that travels down a nerve from releasing a charge to neighbouring nerves. In conditions like multiple sclerosis, these myelin sheaths degrade or become damaged.
The central symptom of this disease is uncontrollable muscle tension, movements, and numbness. This is caused by the inability for nerve signals to travel successfully down the uninsulated nerve fibers, or from the action potentials “leaking” out to affect other nearby nerve fibers.
Even in people without multiple sclerosis, degraded myelin sheaths caused by B vitamin deficiencies, can dramatically affect cognitive ability. Keeping these sheaths healthy is paramount to optimising the ability of the human brain.
To summarise, these vitamins work closely together to regulate homocysteine levels in the blood. Too much homocysteine in the blood is a marker for cardiovascular and cognitive disease. If there is an imbalance between the two vitamins, the cycle can halt, leading to artery, nerve and brain damage.
Additionally, a deficiency in B12 can lead to a buildup of an unusable form of folate, which causes deficiencies in this vitamin as well.
When these vitamins are deficient, DNA and RNA can’t be produced, blood cell production will decrease, nerve sheaths can degrade, and overall brain function will decline.
How To Get B Vitamins From Food
B Vitamins are mainly produced in plants. They perform similar roles in plants as they do in our bodies, acting as cofactors and coenzymes.
B12 is slightly different. It’s found mainly in algae and bacteria. The bacteria in our gut naturally produce a small amount of this vitamin each day, 2Reference 2ReviewB Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review which we can boost with high fiber diets.
It’s interesting that over many thousands of years, human beings (and other mammals), have lost the ability to produce B vitamins naturally despite the critical need for them in daily life.
This probably has something to do with the abundant availability of these vitamins in the surrounding nature (plants).
All plants will offer B vitamins to some degree, except as we mentioned, vitamin B12. Processed foods tend to offer less B vitamins, which has lead to the creation of “enriched” flours, where these vitamins are added in during production.
Animals are also a great source of B vitamins, especially things like turkey, chicken, and tuna 7Reference 7Biochemical, Physiological, Molecular Aspects of Human Nutrition (2nd ed.). As grazing animals eat a vegetarian diet the B vitamins are distributed throughout their body. As these animals are consumed the B vitamins are passed up the food chain intact.
B12 is harder to get through plant-based sources but is produced in the colon from insoluble fibers and healthy gut flora. Algae and meat products offer high-quality sources of this vitamin, and supplemental versions are readily available as well.
The Benefits Of Supplementing B Vitamins For Cognition
Now that we’ve discussed the role B vitamins play regarding brain health and cognition, it’s worth being precise about what supplementing them can and can’t realistically be expected to do.
The main B vitamins that are usually taken for brain health are B6, B9, and B12.
This is through the direct role these vitamins play in the production of neurotransmitters, regulation of myelin sheaths, and the health of the hippocampus and other brain structures. They also tend to work together, which makes it important that all are taken in adequate amounts.
Where the evidence is genuinely solid: correcting an actual deficiency in B6, B9, or B12 improves the neurological and cognitive symptoms caused by that deficiency. Where the evidence is weak: giving extra B vitamins to someone who isn’t deficient, in the hope of boosting memory or preventing dementia, has not been reliably shown to work in large randomised trials 8Reference 8Meta-analysisEffects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals9Reference 9Meta-analysisNeurobiology of Aging. If you eat a varied diet and aren’t in one of the higher-risk groups below, there’s little reason to expect a nootropic effect from extra B vitamins beyond topping up what your body already has enough of.
How Much B Vitamins Should I Take?
Many nootropic formulas intended to optimise thinking, memory storage and retrieval, and mental clarity include one or all of these B vitamins.
B6 is especially useful in formulas aimed at stimulating neurotransmitter synthesis because it’s a limiting factor in their production.
As such, a great way to get a daily dose of intelligently formulated B vitamins is by taking a high-quality nootropic supplement combined of course with a well balanced diet.
Although the three vitamins mainly discussed in this article, B6, B9, and B12, all have a direct link to cognitive function, the other B vitamins should not be overlooked.
If your diet consists of a healthy balance of meats, veggies, and polyunsaturated fatty foods, there should be no worries about the amount of B vitamins consumed in the diet.
People with poor dietary choices, or who are on medications that inhibit the absorption of B vitamins may need to supplement them. The best option for these people, is to take a B complex. This is the name given to supplements that contain all the B vitamins rather than a focus on just one.
B Vitamin Sources
Vitamin B6 (pyridoxine) is widely distributed in food, which makes outright deficiency uncommon in people eating a varied diet. Good sources include chickpeas, poultry, fish (salmon, tuna), potatoes and other starchy vegetables, fortified cereals, bananas, and beef liver.
Vitamin B9 (folate) is found mainly in leafy green vegetables (spinach, kale, romaine), legumes (lentils, black beans, chickpeas), asparagus, avocado, citrus fruit, and fortified grains and flours (folic acid, the synthetic form, is added to bread and cereal by law in a number of countries specifically to prevent neural tube defects in pregnancy).
Vitamin B12 (cobalamin) is the outlier: it’s produced only by bacteria and archaea, not by plants, so reliable dietary sources are essentially all animal-derived — meat, fish, eggs, and dairy. Fortified plant milks, nutritional yeast, and some breakfast cereals are the main fortified options for people avoiding animal products.
Who’s actually at risk of deficiency:
- Vegans and strict vegetarians — B12 is the vitamin to watch, since there’s no reliable unfortified plant source. Supplementation or fortified foods are the standard recommendation.
- Older adults — stomach acid declines with age, and B12 needs to be split from food protein by stomach acid before it can be absorbed, so a meaningful share of people over 50 absorb food-bound B12 poorly even while eating enough of it.
- People on certain medications — long-term metformin use (for type 2 diabetes) is associated with lower B12 levels; proton-pump inhibitors and other acid-reducing drugs can impair B12 absorption for the same reason as ageing; and some anticonvulsants can lower folate levels.
- Pregnant people — folate needs rise substantially in pregnancy, which is why folic acid supplementation before and during early pregnancy is a standard public health recommendation to reduce neural tube defects.
- People with malabsorption conditions (Crohn’s disease, celiac disease, prior gastric bypass surgery) — anything that disrupts absorption in the small intestine or removes stomach tissue can blunt B12 and folate uptake regardless of diet.
If you fall into one of these groups, a B-complex or targeted B12/folate supplement is a reasonable, low-risk way to close the gap — this is a very different claim from “extra B vitamins sharpen a healthy brain.”
References
- Seshadri, S., Beiser, A., Selhub, J., Jacques, P. F., Rosenberg, I. H., D’Agostino, R. B., … & Wolf, P. A. (2002). Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease. New England Journal of Medicine, 346(7), 476-483. Link
- Kennedy, D. O. (2016). B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review. Nutrients, 8(2), 68. Link
- Dakshinamurti, S., & Dakshinamurti, K. (2013). Vitamin B6. In Zempleni, J., Suttie, J.W., Gregory, J.F. III, Stover, P.J. (Eds.), Handbook of Vitamins (5th ed.). CRC Press.
- Reynolds, E. (2006). Vitamin B12, folic acid, and the nervous system. Lancet Neurology, 5(11), 949-960. Link
- Moat, S. J., Clarke, Z. L., Madhavan, A. K., Lewis, M. J., & Lang, D. (2006). Folic acid reverses endothelial dysfunction induced by inhibition of tetrahydrobiopterin biosynthesis. European Journal of Pharmacology, 530(3), 250-258. Link
- Boston University Medical Center (2016). How the Hippocampus Influences Future Thinking. ScienceDaily. Link
- Stipanuk, M. H. (2006). Biochemical, Physiological, Molecular Aspects of Human Nutrition (2nd ed.). Saunders Elsevier.
- B-Vitamin Treatment Trialists’ Collaboration (Clarke, R., et al.). (2014). Effects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals. American Journal of Clinical Nutrition, 100(2), 657-666. Link
- Efficacy of B Vitamin Supplementation on Global Cognitive Function in Older Adults: A Systematic Review and Meta-analysis. (2023). Neurobiology of Aging. Link