If you’re feeling foggy, sluggish, forgetful or just generally out of sorts, you might be thinking you need to prioritize sleep or get a better handle on your stress levels. But what if you’re actually dealing with a nutrient deficiency?
For a vitamin that isn’t exactly top of mind for most people, vitamin B-12 plays a surprisingly large role in nervous system functioning and overall brain health, including supporting memory, focus, mental health, and keeping brain cells healthy. When B-12 levels drop too low, the brain is one of the first places you might see the effects, with symptoms like forgetfulness and brain fog.
B-12 deficiency is more common than most people realize, affecting around 6% of Americans younger than 60 and around 20% of those older than 60, though the exact numbers vary. Many different causes can play into B-12 deficiency, including the food you eat, medications you take, and issues with absorption and your age, with older adults being more susceptible.
“Vitamin B12 deficiency is one of the few reversible causes of cognitive decline,” said Dr. Majid Fotuhi, a neurologist and adjunct professor at Johns Hopkins University. “Catching it early can prevent long-term brain damage and restore mental clarity.”
Here’s what you need to know about vitamin B-12 and your brain, including why it’s so essential, how to get enough of it and the ways a deficiency might show up.
How Vitamin B-12 Supports A Healthy Brain
Vitamin B-12 affects brain health in many different ways. It helps build and maintain myelin, which is a protective covering around nerve fibers that allows brain cells to communicate quickly and efficiently. It also helps support DNA synthesis and keeps brain tissue healthy over time.
B-12 is also essential for producing neurotransmitters like dopamine and serotonin, which help regulate mood, focus and motivation.
Another important role of vitamin B-12 is helping the body break down homocysteine, which is an amino acid that can build up when B-12 levels are low. Elevated homocysteine has been linked to increased oxidative stress and poorer blood vessel function, which can worsen cognitive decline.
“Together, these roles make B-12 essential for sharp thinking, memory, and mental energy,” Fotuhi said.
When B-12 levels are low, nerve signals can slow down or misfire, making brain cells more vulnerable to damage. Over time, a B-12 deficiency can lead to confusion, balance problems, slower thinking and difficulty concentrating. Some research has also linked higher homocysteine levels to cognitive decline and neurodegenerative conditions like Alzheimer’s disease and other forms of dementia.
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Signs You May Be Dealing With Low B-12
If you’re low in vitamin B-12, you can experience symptoms throughout your body. These include fatigue and weakness due to anemia, numbness or tingling in the hands and feet, heart palpitations, memory problems, difficulty concentrating, trouble with balance, and mood changes like irritability, depression and apathy.
Anemia is common when someone has a B-12 deficiency, but you can experience neurological symptoms even without anemia when your B-12 levels are low, said Dr. Brian J. Copeland, a neurologist at University Medical Center New Orleans.
Symptoms of a B-12 deficiency can develop gradually and may not be obvious at first, but they may worsen over time.
“Symptoms of a B-12 deficiency may not appear until B-12 levels are significantly low in the body,” said registered dietitian Patricia Kolesa. “Serum vitamin B-12 levels of 200 pg/ml or below would confirm a deficiency, however measuring homocysteine and methylmalonic acid can also offer insight into vitamin B-12 activity.”
In a recent study, some older adults showed signs of cognitive and neurological issues despite B12 levels that were technically within the normal range but on the lower end.
If you’re worried about your memory or experiencing fatigue or weakness, having trouble with balance, or dealing with any symptoms we’ve mentioned, speaking with a health care professional and having your B-12 levels checked can be a helpful step in protecting your brain health.
“Vitamin B12 deficiency is common, underrecognized, and relatively easy to diagnose and treat,” said Dr. Joel Salinas, a clinical associate professor in the department of neurology at the New York University Grossman School of Medicine. “Because its neurologic and cognitive effects can mimic more serious brain disorders, it is routinely assessed in evaluations for cognitive decline.”
Different Factors Can Put You At Risk For A B-12 Deficiency
Vitamin B-12 is crucial for the production of red blood cells. In order for your body to get enough of it, you have to eat foods that contain B-12, and your body has to properly absorb the B-12. A protein called intrinsic factor that’s released by cells in the stomach helps with B-12 absorption. Your body cannot make vitamin B-12 on its own, so if you don’t eat enough foods rich in B-12, take B-12 supplements or have trouble with absorption for any reason, you could be at risk for a deficiency.
“Vegetarians and vegans are at increased risk for a B-12 deficiency, given that vitamin B-12 is primarily in animal food sources,” Kolesa said.
People with gastrointestinal issues that affect B-12 absorption, like Crohn’s disease or celiac disease, pernicious anemia, a history of stomach or bariatric surgery, or heavy alcohol use, may also be at risk for low B-12 levels. Older adults are also at higher risk for a B-12 deficiency because absorption often decreases with age.
People taking metformin and acid-suppressing drugs like proton pump inhibitors over long periods of time may also develop a B-12 deficiency and should be monitored, Salinas said.
What To Do If You Have Low B-12
Eating a diet rich in B-12 can help maintain healthy levels. Some good food sources include fish, meat, eggs, dairy, nutritional yeast and fortified breakfast cereals. But people who are deficient may need to take B-12 supplements orally or via injections. Your primary care doctor can test your levels through a basic blood panel to determine whether you’re deficient or low in vitamin B-12.
“Oral B12 supplements are effective for most patients, while injectable forms are used in more severe cases,” Salinas said. “Blood testing is the most reliable way to determine whether dietary intake alone is adequate.”
Testing is an important way to catch a B-12 deficiency before it progresses to the point where it cannot be reversed. When a B-12 deficiency is treated early, memory loss, mood changes and problems with focus can completely resolve. But without treatment, permanent memory loss can occur, Copeland explained.
“In the most severe forms, this can progress to frank dementia with behavioral symptoms including psychosis,” he said. “This demonstrates the importance of testing vitamin B-12 levels in anyone with memory loss without a known cause.”