Background: Cancer-associated malnutrition, resulting from cancer and/or its treatments, is prevalent in patients with metastatic cancers. Evidence suggests that dietary supplements play a role in managing malnutrition in cancer but the response to dietary supplements may differ between patients with metastatic as compared to non-metastatic cancers, as metastatic cancer cells are associated with notable genomic and phenotypic alterations.
Objective: This scoping review aims to identify dietary supplements studied in patients with metastatic cancers and malnutrition, their proposed effects, mechanisms, outcome measures, and tools used.
Methods: A systematic search was conducted across MEDLINE, EMBASE, CINAHL, and clinical trial registries.
Results: Of the initial 6535 records screened, a total of 48 studies were included, covering a range of dietary supplements— vitamins (n = 13), minerals (n = 5), antioxidants (apart from vitamins and minerals) (n = 7), proteins (n = 3), amino acids (n = 14), fatty acids (n = 18), fibre (n = 1), and others (n = 5). The list of dietary supplements found were Vitamin A/B1/B6/B9/B12/C/D/E, Calcium, Iron, Selenium, Carbocysteine, Curcumin, Lipoic acid, Lycopene, Quercetin, Lactoferrin, Whey Protein isolate, All essential amino acids, Arginine, Branched chain amino acids, Carnitine, Glutamine, Hydroxymethylbutyrate, Omega-3, Fibre, β-hydroxybutyrate, Co-enzyme Q10, Muscadine grape extract, Dietary nucleotides, Royal jelly. Of the 31 dietary supplements studied across cancer types, omega-3 (n=18) and carnitine (n=7) were investigated most often. Dietary supplements were provided orally in 45/48 (94%) of the studies. Types of cancers studied include – Breast, Gastrointestinal, Skin, Colorectal, Gynaecological, Renal, Pancreatic, Prostate, Head and neck, Lung. Proposed relevant attributes of dietary supplements included their antioxidant, anti-inflammatory, anti-cancer, and immunomodulatory properties.
Conclusion: Overall, the studies examining dietary supplements in patients with metastatic cancers were heterogeneous and dissimilar depending on cancer types. More randomised controlled trials are warranted as there was also a dearth of primary interventional studies in this area.