The Gap Between Perceived and Objective Diet Quality in Patients with Lynch Syndrome

Background and Aims: Lynch syndrome (LS) confers a substantially elevated lifetime risk of colorectal cancer (CRC). While enhanced endoscopic surveillance and aspirin chemoprevention are the cornerstones of management, evidence suggests modifiable lifestyle factors like diet may help mitigate or modify hereditary cancer risk. Because specific LS dietary guidelines are lacking, general CRC prevention recommendations are often substituted. Therefore, the aim of this study was to conduct a detailed and comprehensive examination of dietary habits, cancer-related dietary beliefs, and overall cancer-related worry in individuals with Lynch syndrome who attend a Gastrointestinal (GI) Risk Management Clinic. Methods: A cross-sectional study was conducted using data collected between June 2025 and June 2026 from individuals with a confirmed LS diagnosis attending a tertiary Gastrointestinal Risk Management Clinic in Melbourne, Australia. Participants completed electronic questionnaires capturing demographics, clinical history, a Food Frequency Questionnaire, the 14-item Mediterranean Diet Adherence Screener (MEDAS), and the Cancer Worry Scale (CWS). Self-reported dietary beliefs regarding the relationship between food and cancer risk were captured. Lifestyle behaviors were benchmarked against the Australian Bowel Cancer Risk Reduction Recommendations. The MEDAS was primarily analysed as a population-specific top-vs-bottom half ("better adherence"), and secondarily as a priori "good" adherence (MEDAS > 7). Results: A total of 94 LS patients completed the study (65% female, median age ~51). A striking paradox was observed: 73.3% of participants believed they maintained a healthy diet, yet the cohort demonstrated poor objective adherence to a Mediterranean pattern (median MEDAS: 5 [IQR 4, 7]; range 0-10), with only 14.9% achieving a "good adherence" score (>7). Cancer worry was prevalent, with 60.9% having a CWS > 13, consistent with significant worry about future cancer, with no sex-based differences. However, higher cancer worry (CWS > 11: aOR 1.59, 95% CI 0.48-5.28) and a personal history of cancer (aOR 0.69, 95% CI 0.24-1.97) were not significantly associated with better dietary adherence. Aspirin use was a strong predictor of better Mediterranean diet adherence, yielding an aOR of 3.09 (95% CI: 1.10-8.68), likely reflecting improved overall engagement in health promotion. Only one participant (1.1%) met all objective bowel cancer prevention guidelines. Of the cohort, 37% intentionally restricted foods (primarily processed/red meats) and 21% intentionally included specific foods to prevent cancer; their primary information sources were doctors and the internet. Conclusions: A substantial gap exists between perceived diet quality and objective adherence to evidence-based cancer prevention recommendations among individuals with Lynch syndrome. High levels of cancer-related worry and a willingness to modify dietary choices do not automatically translate into optimal nutrition. These findings highlight a critical need for interventional trials to provide LS patients with evidence-based dietary guidelines to reduce their lifetime risk of CRC that are tailored to this highly motivated but clinically underserved population.