Nutrition influences a wide range of physiological and cognitive mechanisms. Vegan (plant-based) diet is known to be associated with a healthy cardiovascular and cerebrovascular system. Studies on the Mediterranean diet have shown that diets high in fruits and vegetables are linked with better cognitive performance and lower rates of neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease. The present study assessed verbal memory and sleep quality in a cohort of sixty-two adults aged 40 and above. Participants were split into strictly defined diet categories: vegan, vegetarian, pescatarian, omnivores with low meat/fish consumption and omnivores with high meat/fish consumption, using a modified Mediterranean Diet Adherence Screener questionnaire. Verbal learning memory was assessed using the California Verbal Learning Test, and sleep quality was evaluated using the Pittsburg Sleep Quality Index. Diet was found to have a significant effect on memory but no significant effect on sleep quality. The sample size, diluted by the five diet categories, may have been insufficient to capture the effects on sleep. Unlike mainstream knowledge in the relationship between memory and eating animal-based food, this research has debunked that hypothesis by showing that there is no significant relationship between consuming animal products and having a better memory. Further research can elucidate the protective role of vegan diets on cognitive functions and even support a hypothesis that suggests that more plant-based eating habits would strengthen memory if gender is controlled with a larger sample size.