If you're an older individual experiencing cognitive issues, your vitamin B12 levels may play a role. A new study in healthy older adults found that even in individuals who fall within the "normal" range of vitamin B12 levels, if they are on the lower end of that range, it could ultimately contribute to cognitive decline, negatively impacting their processing speed and conductivity (how well neurons communicate with one another).

What this recent study tells us is that even if an individual doesn't have a vitamin B12 deficiency—meaning they're considered to be within a normal range, based on current recommendations—they could still be at risk of declining cognitive function.

The main takeaway? Adequate vitamin B12 levels are key, and, ultimately, B12 recommendations should be tailored to an individual's unique needs. Keeping tabs on this marker will help you identify a deficiency, promote earlier intervention, and potentially even prevent cognitive decline.

B12 Status Panel Blood Test

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What does vitamin B12 do for the body?

Preventing a vitamin B12 deficiency, whether by consuming more B12-rich foods or taking supplements, is important for the central nervous system (CNS), the primary control center for your body, to develop and function properly. Your CNS includes your brain health and, thus, your cognition.

Vitamin B12 (also called cobalamin) keeps your red blood cells happy. In fact, a deficiency can lead to anemia—more specifically, megaloblastic anemia—because your body doesn't have enough healthy red blood cells. A lack of red blood cells means sufficient oxygen won't get to all the parts of your body, impacting how well they work. There are many reasons why a person might not have adequate B12 levels, from following a vegan diet, to advanced age, to an autoimmune disorder called pernicious anemia. One thing is for certain: adequate B12 levels are essential for optimal health.

So, getting an adequate amount of this vitamin is about more than protecting your brain. You need it to prevent the onset of anemia and support whole-body wellness.

How much vitamin B12 is safe?

You're not going to "overdose" on B12; there is no set tolerable upper limit because B12 has a very low potential for toxicity in the human body. What's more, people are much more at risk of a vitamin B12 deficiency than they are of getting too much. As the study suggests, we need to consider that even vitamin B12 levels that fall within the normal range (by today's standards) may not be high enough to support healthy brain aging.

Interestingly, the research also found that higher levels of a biologically inactive form of B12 were associated with increased levels of Tau proteins, which are linked to cognitive decline. In the body, vitamin B12 can be bound to different carrier proteins. When it's bound to a certain carrier protein, it cannot be taken up by cells for use. The researchers hypothesized that the retention of vitamin B12 by this carrier protein may decrease the bioavailability of B12 in the brain. More studies will need to be done to understand this association. Importantly, the relationship with Tau protein was not seen with the biologically active form of B12.

Still, regardless of whether or not your blood tests say that you have a vitamin B12 deficiency, lower vitamin B12 levels are associated with overall poorer health.

What is the best way for older adults to improve their vitamin B12 intake?

It's always ideal to get as many nutrients as you can from the food you eat before turning to supplements. Excellent dietary sources that can help combat a vitamin B12 deficiency include foods like organ meats, clams, oysters, salmon, tuna, red meat, poultry, milk, yogurt, and eggs. If you're vegan, look for foods like fortified cereals and fortified nutritional yeast. Many of these foods contain both vitamin B12 and folate.

Other foods that are good for your brain include spinach, kale, collards, artichokes, asparagus, cabbage, legumes, and Swiss chard. These are all rich in B vitamins like folate and B9, plus beta carotenoids.

You can be creative with your meals! Most of these foods can easily be included in soups, stews, and even smoothies. Smoothies, in particular, can help to mask kale's earthy taste!

What about vitamin B12 supplements? Studies suggest a high-quality B12 supplement could help support healthy cognition in aging individuals. But B12 benefits go beyond cognitive support; because of its involvement in red blood cells, avoiding a vitamin B12 deficiency is crucial for your entire body. Regardless of general guidelines, always speak with your doctor about B12 doses that make the most sense for your body.

Do vegans get enough B12?

Following a vegan diet may put you at an increased risk of a vitamin B12 deficiency, so supplements are a proactive way to ensure your body is getting enough B12. The body can experience other deficiencies when following vegan dietary patterns, so you'll want to get regular blood work to check on your nutritional status, including folate and B12 levels.

How do I know if I have a B12 deficiency?

Speak with your doctor or healthcare provider if you're experiencing fatigue, weakness, shortness of breath, numbness or tingling in your hands and feet, muscle weakness, or impaired cognitive function. These symptoms could indicate a B12 deficiency. However, the only way to confirm if it's a B12 deficiency or something else is with a blood test.

Your doctor may order a B12 blood test to determine if you are currently experiencing a vitamin B12 deficiency and, if so, if you're running the risk of neurological problems, anemia, etc.

In addition to documenting your symptoms, blood tests are an important part of understanding what your body is currently going through, and the results offer direction for how you can improve your health (and keep a track record for future reference!).

Ensuring you get an adequate amount of the many nutrients your body needs to thrive is a cornerstone of a healthy aging strategy.

References

• Beaudry-Richard A, et al. "Vitamin B12 Levels Association with Functional and Structural Biomarkers of Central Nervous System Injury in Older Adults." Annals of Neurology. February 2025. https://onlinelibrary.wiley.com/doi/10.1002/ana.27200
• Hanna M, et al. "B Vitamins: Functions and Uses in Medicine." Perm J. June 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9662251/
• Zhou L, et al. "Vitamin B12 supplementation improves cognitive function in middle aged and elderly patients with cognitive impairment." Nutr Hosp. August 2023. https://pubmed.ncbi.nlm.nih.gov/37334792/
• "Vitamin B12 Deficiency Anemia." Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/vitamin-b12-deficiency-anemia

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The Life Extension Health News team delivers accurate information about vitamins, nutrition and aging. Our stories rely on multiple, authoritative sources and experts. We keep our content accurate and trustworthy, by submitting it to a medical reviewer.