A narrative review examined preclinical and limited clinical data on ketogenic dietary interventions in breast cancer, focusing on metabolic effects, body‑composition changes, quality‑of‑life outcomes, and potential metabolic risks.
Study and findings
The authors performed a structured literature search across PubMed, Scopus, Web of Science and ScienceDirect, supplemented by manual reference screening. Eligible reports included meta‑analyses, systematic reviews, randomized controlled trials and other clinical studies published between 2015 and 2026 that investigated ketogenic dietary protocols in cancer, with a particular emphasis on breast cancer. Because breast‑cancer‑specific trials are scarce, data from other malignancies were incorporated to illustrate mechanistic rationale. The review identified that most mechanistic evidence derives from animal models, where classic ketogenic diet (≈90% energy from fat, 6% protein, 4% carbohydrate) or its variants (e.g., medium‑chain triglyceride diet, modified Atkins diet) reduce glucose availability and elevate circulating ketone bodies. Preclinical studies report reduced tumor growth and enhanced sensitivity to chemotherapy in several breast‑cancer models. Clinical investigations, however, are few, involve small cohorts, short intervention periods, and heterogeneous diet protocols. Reported outcomes include modest changes in body‑mass index, lean‑mass preservation, and improvements in self‑reported mental well‑being, but statistical significance and effect sizes are often unclear. The authors also note metabolic risks such as dyslipidaemia, electrolyte disturbances, and gastrointestinal symptoms that may exacerbate malnutrition.
Clinical interpretation
The preclinical data provide a plausible biological basis: limiting carbohydrate intake lowers insulin and glucose signalling pathways that many breast‑cancer cells rely on, while ketone bodies may serve as an alternative fuel that normal cells can utilise more efficiently. Translating these mechanisms to patients is uncertain because the clinical literature does not yet demonstrate a consistent impact on tumor response or survival. Observed improvements in body composition or quality of life should be interpreted as potential supportive effects rather than evidence of anticancer efficacy. Moreover, the metabolic risks identified—particularly lipid profile alterations and gastrointestinal intolerance—highlight the need for careful monitoring when ketogenic protocols are employed alongside standard oncologic therapies.
Limitations and open questions
Key limitations stem from the heterogeneity of diet formulations (classical ketogenic diet versus modified Atkins or MCT‑based regimens), variable macronutrient ratios, and lack of standardized ketosis monitoring. Small sample sizes and high attrition rates reduce statistical power and limit generalisability. Few studies isolate the effect of the diet from concurrent chemotherapy or radiotherapy, making causal inference difficult. Open questions include: (1) whether a defined ketogenic protocol can improve objective oncologic outcomes in breast cancer; (2) the optimal duration and degree of carbohydrate restriction needed to achieve metabolic benefits without compromising nutritional status; and (3) the patient subgroups (e.g., hormone‑receptor status, metabolic phenotype) that might derive the greatest benefit. Well‑designed randomized controlled trials with adequate follow‑up, standardized dietary targets, and comprehensive metabolic monitoring are required to address these gaps.
Source
Szołtysek J, Szymańska B, Piwowar A. The Ketogenic Diet as Adjunctive Strategy in Cancer Treatment-Therapeutic Benefits and Metabolic Risk Using Breast Cancer as an Example. Nutrients. 2026;18(17):2917. doi: 10.3390/nu18172917. PMID: 42739089.