A method of attenuating, treating or preventing cognitive aging in an individual who does not have dementia includes administering to the individual a therapeutically effective amount of a composition containing an omega-3 fatty acid, a nitric oxide releasing compound, and Vitamin B12. The composition is administered in a daily dose that provides 50 to 500 times the recommended daily requirement (RDA) of Vitamin B12 per day, for example about 200 times the RDA of Vitamin B12 per day. Optionally Vitamin B6 and/or Vitamin B9 can be included in the composition. The method can achieve a benefit that is one or more of decreasing brain atrophy, increasing or maintaining number of synapses, increasing amyloid-β phagocytosis, or decreasing or maintaining neuroinflammation in the non-demented individual. The method can prevent dementia in an individual at risk thereof, for example an elderly human.