Abstract Background With rising obesity rates in Western societies, analyzing changes in dietary patterns is paramount. While nutritional surveys have been informative, traditional cookbooks have historically shed light on national cuisines and its changes. Despite the growing popularity of online platforms for food information, cookbooks might still reflect prevalent dietary trends and the diets people follow. This study examined (1) the changes in nutritional content and food group usage in the best-selling cookbooks from 2008 to 2018, and (2) the correlation between the food groups in these cookbooks and dietary patterns (inferred from household purchases) over the same timeframe. Methods An exploratory ecological study was conducted on 20 main course recipes of each of the five best-selling cookbooks in Flanders annually between 2008 and 2018. Trends in macronutrients and food group usage in these recipes were analyzed using generalized linear models. Additionally, these trends were compared to household purchase data in Flanders using correlation matrices. Results Our results reveal a rising trend towards the use of plant-based ingredients and meat alternatives in cookbooks over the period 2008–2018. There was an increase in the usage of vegetables, nuts & seeds, and cheese. Conversely, there was a decline in the usage of meat, sugar & sweeteners, alcohol, and dairy (all p-values < 0.05). In terms of macronutrient content, there was an upswing in carbohydrate, fibre, and sugar levels, while the total fat content showed a decrease (all p-values < 0.05). The levels of protein and saturated fat remained consistent over time. Notably, shifts in plant-based and animal-based food group preferences in popular cookbook recipes align with the trends seen in actual household purchases of these food groups (all p-values < 0.05). Conclusion These findings indicate that cookbook content evolves over time, potentially reflecting shifts in population dietary patterns. Future research is needed to (1) ...