There are more than 50 million people with dementia worldwide. By 2050, this number is expected to triple. Both medical treatments and preventive therapies are being rapidly investigated for all dementia pathologies, especially Alzheimer’s Dementia. In recent years, many modifiable risk factors associated with dementia, such as diabetes, hypertension, smoking, and obesity, have been identified. Nutrition and diet are among the most significant risk factors. The pathogenesis of cognitive impairment encompasses neuroinflammation, oxidative stress, and impaired autophagy. Appropriate treatment of dementia-related risk factors can stop neuroinflammation and oxidative damage, reduce neuronal damage, and prevent neuronal apoptosis and cognitive decline. In this chapter, we will first focus on the types of dementia, their clinical courses, and modifiable risk factors. Then, we will examine the pathophysiological processes that lead to cognitive decline and the impact of micronutrients on these processes at the preclinical level. We will also identify dietary patterns and discuss the interventions that have been implemented to date to prevent dementia. It may be possible to reduce the risk of developing dementia with a plant-based diet, especially in middle age.