Effects of Nutritional Supplementation on Tumor Growth: A Systematic Review and Meta-Analysis of Studies Using Animal Models of Mammary Cancer

Breast cancer remains the most prevalent malignancy among women worldwide, and experimental tumor models are essential for evaluating new therapeutic approaches before clinical application. The Walker-256 carcinoma model exhibits biological behavior comparable to human carcinoma and allows short-term assessment of tumor progression. This study aimed to conduct a systematic review and meta-analysis of the effects of dietary supplementation on Walker-256 tumor growth. We followed the PRISMA guidelines and searched the PubMed, Embase, and Cochrane databases without time restrictions. The meta-analysis included clustering based on the type of supplementation received, comparing treatment groups with control groups. Twenty-one studies were included, analyzing 18 different supplements, and 12 studies were considered for quantitative synthesis. The overall effect indicated a significant reduction in tumor growth with supplementation (SMD = 2.83, 95% CI = 1.99-3.66, <i>p</i> < 0.001), despite high heterogeneity (I² = 93.3%). Oils had the greatest impact, particularly fish oil (SMD = 6.99, 95% CI = 3.15-10.83, <i>p</i> < 0.001) and shark liver oil (SMD = 4.43, 95% CI = 2.19-6.67, <i>p</i> < 0.01).