Abstract
OBJECTIVES: Dietary patterns, characterised by protein, polyunsaturated fatty acids, and vitamin D, reduce the odds of malnutrition in cancer survivors. However, it is unclear whether these dietary patterns also improve prognosis. This study prospectively examined associations between dietary patterns linked to lower odds of malnutrition and the risk of all-cause and cancer mortality in adult cancer survivors from the UK Biobank cohort. DESIGN: Prospective observational study. SETTING AND PARTICIPANTS: Cancer survivors from the UK Biobank (mean ± SD, 7.1 ± 6.3 years since diagnosis) were included (n = 2415; 59.7 ± 7.1 years; 60.7% female). MEASUREMENTS: Dietary intake was estimated using the Oxford WebQ 24-h dietary assessment. Dietary patterns ('high oily fish and nuts', and 'low oily fish') were derived using reduced rank regression (response variables: protein (g/kg/day), polyunsaturated fatty acids (g/day) and vitamin D (μg/day)). Cox proportional hazard models estimated hazard ratios (HR) and 95% confidence intervals (CI) for all-cause and cancer mortality. Nonlinear relationships were examined using restricted cubic splines. Models were adjusted for demographic and health characteristics. Sub-group analyses investigated relationships in sub-samples of adults with i) high nutritional risk (lung, gastrointestinal, haematological, or head and neck tumours) and ii) recent cancer diagnosis (cancer diagnosis within two years prior to assessment). RESULTS: Deaths due to all-causes (n = 305) and cancer (n = 249) were identified during a median 10.4 (IQR: 10.2-10.8) years follow-up. There were no statistically significant linear associations between the dietary patterns and all-cause or cancer mortality. However, a U-shaped association between the 'high oily fish and nuts' pattern, characterised by higher intake of oily fish and nuts and seeds, and all-cause mortality (p-non-linearity = 0.004) was identified, as well as with all-cause (p-non-linearity = 0.006) and cancer mortality (p-non-linearity = 0.035) in adults with a high nutritional risk cancer diagnosis (lung, gastrointestinal, haematological, or head and neck tumours), indicating that both above and below mean intake was associated with increased risk. The 'low oily fish' pattern, characterised by lower oily fish but higher potato intake, also had a non-linear association with all-cause mortality (p-non-linearity = 0.046) where lower but not higher than mean intake increased mortality risk. No dietary patterns were significantly associated with mortality in adults with a recent cancer diagnosis. CONCLUSION: 'High oily fish and nuts' or 'low oily fish' dietary patterns that were protective against malnutrition were associated with risk of all-cause and cancer mortality in adults with cancer. Future research should assess the efficacy of these dietary patterns in the acute treatment period when malnutrition is most prevalent.