The brain is roughly 60% fat by dry weight and the single most metabolically expensive organ you own. Omega-3 DHA builds the neuronal membranes that all signaling depends on; choline becomes acetylcholine (memory + attention) as well as the phosphatidylcholine those membranes are made of; and the B-vitamins + iron run neurotransmitter synthesis and the energy supply neurons need to fire. Shortfalls tend to surface first as the soft symptoms — brain fog, low mood, poor focus — long before anything shows up structurally. These 48 whole foods are ranked by how many of the key brain nutrients a typical serving delivers (≥10% DV each).