Vitamin B-12 supports brain health, but many people are low

Vitamin B-12 helps protect nerve function, memory and mood, and deficiency is common — affecting about 6% of Americans under 60 and roughly 20% of those over 60.

Vitamin B-12 is linked to nervous system function and aspects of cognition such as memory, focus and mood. Deficiency can first show in the brain with symptoms like forgetfulness or ‘‘brain fog,’’ and it is more common than many expect. Experts say catching a deficiency early can restore clarity in some cases and help avoid lasting harm. Key points: - Biological role: B‑12 helps form and maintain myelin, supports DNA synthesis, and contributes to production of neurotransmitters; it also helps break down homocysteine, a compound associated with oxidative stress and blood vessel changes. - How common: Published estimates in the article note about 6% of Americans younger than 60 and about 20% of those older than 60 have a B‑12 deficiency, though figures can vary by study. - Symptoms and testing: Reported signs include fatigue, weakness, numbness or tingling, memory and concentration problems, balance issues, and mood changes; neurological symptoms can occur even without anemia. The article notes serum B‑12 at or below about 200 pg/ml is often used to confirm deficiency, and markers such as methylmalonic acid and homocysteine can offer additional information. - Risk factors and treatment approaches: People who eat little or no animal products, have gastrointestinal conditions (like Crohn’s or celiac disease), pernicious anemia, a history of stomach or bariatric surgery, heavy alcohol use, or long-term use of metformin or acid-suppressing drugs may be at increased risk. The article reports oral B‑12 supplements are effective for most patients, while injectable forms are used in more severe cases. Summary: Vitamin B‑12 plays multiple roles that support cognitive function and nerve health, and low levels are relatively common, especially with advancing age or certain medical conditions. Testing through routine blood measures and additional markers is reported as a standard way to identify deficiency, and early treatment is reported to reverse cognitive and neurologic symptoms in many cases; ongoing research is focused on benefits for people with lower-but-still-normal levels.