Limited data exist on consumer beliefs and practices on the role of omega-3 fatty acid and vitamin D dietary supplements and health. For this reason, the Global Health and Nutrition Alliance conducted an online survey in 3 countries (n = 3030; United States = 1022, Germany = 1002, United Kingdom = 1006) of a convenience sample of adults (aged 18-66 years) who represented the age, gender, and geographic composition within each country. More than half of the sample (52%) believed they consume all the key nutrients needed for optimal nutrition through food sources alone; fewer women (48%) than men (57%), and fewer middle-aged adults (48%) than younger (18-34 years [56%]) and older (≥55 years [54%]) adults agreed an optimal diet could be achieved through diet alone. Overall, 32% reported using omega-3s (45% in United States, 29% in United Kingdom, and 24% in Germany), and 42% reported using vitamin D dietary supplements (62% in United States, 32% in United Kingdom, and 31% in Germany). Seventy eight percent of the sample agreed that omega-3 fatty acids are beneficial for heart health; however, only 40% thought that their diet was adequate in omega-3 fatty acids. Similarly, 84% agreed that vitamin D was beneficial to overall, and 55% of adults from all countries were unsure or did not think they consume enough vitamin D in their diet. For most findings in our study, US adults reported more dietary supplement use and had stronger perceptions about the health effects of omega-3s and vitamin D than their counterparts in the United Kingdom and Germany. Nevertheless, the consistent findings across all countries were that adults are aware of the importance of nutrition, and most adults believe their diet is optimal for health. Our data serve to alert dietitians and health professionals that consumers may have an elevated sense of the healthfulness of their own diets and may require guidance and education to achieve optimal diets.