BACKGROUND: Online forums play a crucial role for cancer patients seeking nutrition-related information and support. This study investigated the most common nutrition-related questions and concerns among members of the Women's Self-Help Association Against Cancer, focusing on emotional, physical, and practical aspects of dietary changes in cancer patients. METHODS: A mixed-methods approach was used, combining qualitative and quantitative content analysis of 5314 forum responses. The themes identified included common questions, patient contributions, physician involvement, and the impact of the COVID-19 pandemic on the discussions. RESULTS: In total, 2246 posts across 22 threads were analyzed, spanning 3867 days and receiving 654,100 visits. Key topics included 41 themes and 356 questions, with common inquiries like "Has your diet changed since your diagnosis?" (45 responses) and "Is sugar allowed in your diet?" (29 responses). There were 4958 contributions, with 558 evidence-based responses (e.g., recommending balanced diets) and 200 non-evidence-based responses (e.g., fasting, cancer-specific diets). Concerns regarding sugar (188 responses), dairy (121 responses), and emotional stress (187 responses) were common. Despite evidence-based recommendations from healthcare professionals supporting balanced diets, members frequently encounter non-evidence-based advice on fasting- and cancer-specific diets, leading to significant emotional and nutritional challenges. Additionally, Members emphasized the need to balance the enjoyment of food with dietary restrictions. CONCLUSION: The forum is a valuable resource for sharing experiences and advice
however, non-evidence-based content underscores the need for moderation and expert input. Collaboration between medical professionals and moderators can improve content reliability, enabling informed dietary decisions for cancer patients.