"The number of dietary supplements on the market has grown exponentially from an estimated 4,000 products in 1994 to an estimated 80,000 products in 2016, according to officials in the U.S. Department of Health and Human Services' (HHS) Food and Drug Administration (FDA). As the number of dietary supplements on the market has increased, specialty supplements that claim to address specific health issues, including those claiming to address memory or memory loss (referred to in this report as memory supplements), have emerged in the market. Available data indicate that memory supplements constitute a small segment of the overall dietary supplement market, but their sales nearly doubled in value from 2006 to 2015, increasing from $353 million to $643 million. Consumers searching to prevent or treat age-related memory loss, including Alzheimer's disease, have increasingly turned to dietary supplements for help."
Government Accountability Office: http://www.gao.gov/