The acronym SMASH stands for salmon, mackerel, anchovies, sardines and herring. These are the fish that are safest and healthiest to eat. They are nutrient-rich, high in omega-3s, and are low in mercury.
SMASH fish are all small fish because the larger the fish and the longer its lifespan, the higher its mercury content.
Mercury, in excess, can impair vision, coordination, and speech, and can cause muscle weakness.
Research, including a study published in a 2020 issue of the journal Biomolecules, has associated higher levels of mercury in the brains of patients with Alzheimer's disease.