Ketogenic diets are high in fat, moderate in protein and low in carbohydrates, with weak to preliminary evidence of anticancer effects, relief of side effects, and benefits on your body terrainthe internal conditions of your body, including nutritional status, fitness, blood sugar balance, hormone balance, inflammation and more.
Safety and precautions
A ketogenic diet (KD) is a complex diet to follow and may cause side effects, some of which may be serious: weight loss, nutrient deficiencies, and more. Unless weight loss is desirable, this could be a concern. “As cancer patients are particularly susceptible to clinically significant malnutrition in the form of weight loss from both fat and muscle mass, this side effect should be most carefully evaluated before applying the diet in clinical settings.”1Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72. Individualized close monitoring of the diet and ongoing education and support is recommended to improve safety and enhance completion of the KD.2Karen Collins, MS, RDN, CDN, FAND, Oncology Dietitian and Nutrition Advisor to the American Institute for Cancer Research. Presentation March 2017: “Culinary Translation in Breast Cancer Care and Survivorship” in Washington, DC; Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72; Oliveira CL, Mattingly S, Schirrmacher R, Sawyer MB, Fine EJ, Prado CM. A nutritional perspective of ketogenic diet in cancer: a narrative review. Journal of the Academy of Nutrition and Dietetics. 2017 Mar 30. pii: S2212-2672(17)30115-6; Winters N, Kelley JH. The Metabolic Approach to Cancer: Integrating Deep Nutrition, the Ketogenic Diet, and Nontoxic Bio-Individualized Therapies. Vermont: Chelsea Green Publishing. 2017; Lise Alschuler, email communications, September 18, 2017 and October 24, 25, 26, 2017.
Also, because any anticancer effects of a ketogenic diet are due to metabolic changes, we highly recommend you be carefully assessed by a qualified physician or practitioner to determine the specific manipulation that might work best in relation to the metabolic characteristics of your cancer.
Preliminary evidence of low adherence and completion rates among people following a ketogenic diet; researchers interpret these as an indication that side effects or quality of life during KD are a barrier to participation or adherence
- Low rate of acceptance of the KD dietary restrictions by people with cancer—only 37% of those on the KD were able to follow the diet for the duration of the study—in a review of clinical studies3Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72.
- Quality of life was a factor in decisions to decline participation in a trial which also had poor retention—only 4 of 12 patients completed the 3-month diet—among people with glioblastoma in a small RCT4Martin-McGill KJ, Marson AG et al. Ketogenic diets as an adjuvant therapy for glioblastoma (KEATING): a randomized, mixed methods, feasibility study. Journal of Neuro-oncology. 2020 Mar;147(1):213-227.
Other small studies found that a ketogenic diet was reasonably well tolerated as shown by compliance rates of 50% or higher.5Dardis C, Renda L et al. ACTR-15. Therapeutic ketogenic diet (KD) with radiation and chemotherapy for newly diagnosed glioblastoma—preliminary results from NCT02046187. Neuro-Oncology. 2017 Nov;19(suppl_6):vi4; Santos JG, Da Cruz WMS et al. Efficacy of a ketogenic diet with concomitant intranasal perillyl alcohol as a novel strategy for the therapy of recurrent glioblastoma. Oncology Letters. 2018 Jan;15(1):1263-1270.
Side effects and adverse events
Short-term effects in early implementation of this diet, usually transient and easily managed:6Branco AF, Ferreira A et al. Ketogenic diets: from cancer to mitochondrial diseases and beyond. European Journal of Clinical Investigation. 2016 Mar;46(3):285-98; Schmidt M, Pfetzer N, Schwab M, Strauss I, Kammerer U. Effects of a ketogenic diet on the quality of life in 16 patients with advanced cancer: a pilot trial. Nutrition & Metabolism. 2011 July 27;8(1):54.
- Nausea and vomiting (most common)
- Constipation
- Gastroesophageal reflux (heartburn)
- Acidosis (a condition resulting from blood being too acidic, especially due to dehydration)
- Dehydration
- Lethargy
- Low blood sugar (hypoglycemia)
- Weight loss
People with advanced metastatic tumors following a ketogenic diet had stable diarrhea but worse nausea and vomiting over time7Schmidt M, Pfetzer N, Schwab M, Strauss I, Kammerer U. Effects of a ketogenic diet on the quality of life in 16 patients with advanced cancer: a pilot trial. Nutrition & Metabolism. 2011 July 27;8(1):54.
“As cancer patients are particularly susceptible to clinically significant malnutrition in the form of weight loss from both fat and muscle mass, this side effect should be most carefully evaluated before applying the diet in clinical settings.”8Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72.
Other short-term effects observed in clinical studies:9Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72.
- Anemia
- Bad breath (halitosis)
- Decreased amino acid levels
- Eye nerve damage (optic neuropathy)
- Flu-like symptoms or fatigue
- Functional changes in basal ganglia, granulocytes (neutrophils) and thrombocytes (platelets)
- High uric acid levels in blood (hyperuricemia)
- Inflammation of the pancreas (pancreatitis)
- Itching (pruritus)
- Low blood calcium levels (hypocalcemia)
- Low blood magnesium levels (hypomagnesemia)
- Low or high blood potassium levels (hypo- or hyperkalemia)
- Swelling of feet
Common long-term effects:10Branco AF, Ferreira A et al. Ketogenic diets: from cancer to mitochondrial diseases and beyond. European Journal of Clinical Investigation. 2016 Mar;46(3):285-98; Sharman MJ, Kraemer WJ et al. A ketogenic diet favorably affects serum biomarkers for cardiovascular disease in normal-weight men. Journal of Nutrition. 2002 Jul;132(7):1879-85.
- High blood lipids (hyperlipidemia): most common, although with conflicting reports of improvement in lipid profile
- Heart muscle disease (cardiomyopathy)
- High cholesterol (hypercholesterolemia), although with conflicting reports of improvement in cholesterol
- Kidney stones (nephrolithiasis)
Other long-term side effects observed in clinical studies:11Erickson N, Boscheri A, Linke B, Huebner J. Systematic review: isocaloric ketogenic dietary regimes for cancer patients. Medical Oncology. 2017 May;34(5):72.
- Thickening and hardening of the walls of the arteries (arteriosclerosis)
- Carnitine deficiency, a metabolic state in which carnitine concentrations in plasma and tissues are less than the levels required for normal function
- Decreased growth in children and adolescents
- Deficiencies of vitamins, minerals and enzymes
- Irregular menstrual periods
- Loss of bone density (osteopenia or osteoporosis) or bone fractures
References