Alzheimer ' s disease AD is a major global neurodegenerative disease and the most common type of cognitive impairment. Currently modifiable risk factors for AD particularly nutritional interventions have attracted significant attention in the prevention and control of cognitive impairment. Numerous randomized controlled trials investigating the relationships between dietary patterns nutrient intake functional nutritional foods and cognitive impairment prevention or AD treatment indicate that the efficacy of nutrition in maintaining cognitive function in the elderly remains controversial posing challenges to establishing effective prevention measures. This review summarizes the associations between various dietary patterns key nutrient levels and supplementation functional food-derived bioactive compounds and cognitive decline. It explores the potential roles and mechanisms of dietary patterns and nutritional supplementation in AD prevention and treatment. Dietary patterns such as the Mediterranean diet MIND diet Mediterranean-DASH Intervention for Neurodegenerative Delay and ketogenic diet as well as nutrients including B vitamins vitamin D vitamin E Omega-3 fatty acids selenium and zinc and functional bioactive compounds such as anthocyanins and soy isoflavones may help reduce the risk of cognitive decline offering additional protective effects particularly for APOEε4 carriers. Future research should integrate genetic and metabolic factors enhance long-term follow-up studies and leverage multi-omics data to explore more precise and personalized nutritional intervention strategies. This approach aims to optimize cognitive management and provide scientific evidence for AD prevention and control.