Abstract
BACKGROUND: The effect of supplements on mortality risk in patients with cancer remains uncertain and has scarcely been investigated in subgroups of patients with varying characteristics. This study aimed to investigate the association between two popular supplements, fish oil and glucosamine, and mortality risk in a large population-based cohort and determine whether cardiovascular health and clinical prognosis influence these associations. METHODS: This prospective cohort study analyzed the data of UK Biobank participants who were diagnosed with cancer. The associations of fish oil and glucosamine consumption with mortality were analyzed using Cox proportional hazards models. Subgroup analyses were performed to assess the effects of Life Essential 8 [LE8] scores (a measure of cardiovascular health) and cancer prognosis (grouped according to the survival rates of specific cancer types) on the associations between supplement use and mortality. RESULTS: This analysis included 14,920 participants (mean age = 59.9 years; 60.2% female). One third (34.1%) of the participants reported using fish oil, and one fifth (20.5%) reported using glucosamine. Over a median follow-up of 12.0 years, 2,708 all-cause deaths were registered. The use of fish oil was associated with reduced risks of all-cause mortality (adjusted hazard ratio [aHR] = 0.89, 95% Confidence Interval [CI] = 0.81-0.97) and cancer mortality (aHR = 0.89, 95% CI = 0.81-0.98). Similarly, glucosamine use was associated with reduced risks of all-cause mortality (aHR = 0.83, 95% CI = 0.74-0.92) and cancer mortality (aHR = 0.83, 95% CI = 0.74-0.93) in the fully adjusted model. Subgroup analyses revealed that the protective effects of fish oil and glucosamine against mortality risk were only observed in patients with LE8 scores lower than the mean score or a poor cancer prognosis. Additionally, the association between glucosamine use and a reduced risk of CVD-related mortality was only observed in patients with lower LE8 scores. CONCLUSIONS: This large cohort study identified the potential differential impact of LE8 scores and cancer prognosis on the associations of fish oil and glucosamine supplementation with survival in patients with cancer. This suggests the importance of considering these factors in future research on supplements and in the provision of personalized integrative cancer care.