Brain week challenges memory myth

During Brain Week, held from March 16 to 22, 2020, myths about the human brain were examined, including the idea that memory gaps are always caused by a lack of vitamin D. Another common deficiency after age 60, vitamin B12 deficiency, can also be a cause.

Study links B12 deficiency to dementia risk

A study published in July 2026 in Frontiers in Nutrition, involving 258,000 adults, suggests that low levels of B12 are associated with a 30% increased risk of dementia and Alzheimer’s disease. However, an association does not necessarily mean a cause-and-effect relationship.

B12 sources and absorption

Vitamin B12 is mainly found in animal products. To be absorbed, it must be released from food by stomach acid and then bind to intrinsic factor, a protein produced by the stomach. With age, these mechanisms can become less effective. Some medications, such as metformin (for diabetes) and proton pump inhibitors (PPIs, for acid reflux), can also contribute to a deficiency. Another major risk factor is a strictly plant-based diet, which requires B12 supplementation.

Symptoms of B12 deficiency

A deficiency in vitamin B12 can cause anemia, persistent fatigue, a painful tongue, numbness, paleness, weight loss, or cognitive issues and depression. A blood test can measure B12 levels, sometimes combined with a test for methylmalonic acid. Thresholds depend on the laboratory and clinical context. If a deficiency is found, certain foods are especially beneficial: liver, oysters, mackerel, sardines, meat, eggs, and dairy products. If you don’t consume animal products, supplementation is essential. According to Anses, the recommended daily intake for adults is 4 µg. However, correcting a deficiency may be necessary, but it does not guarantee the recovery of long-standing memory issues.