Cancer patients may try special diets to make their treatment work better, prevent side effects from treatment, or to treat the cancer itself. However, for most of these special diets, there is no evidence that shows they work.

Vegetarian or vegan diet

• It is not known if following a vegetarian or vegan diet can help side effects from cancer treatment or the patient's prognosis.
• If the patient already follows a vegetarian or vegan diet, there is no evidence that shows they should switch to a different diet.

Macrobiotic diet

• A macrobiotic diet is a high-carbohydrate, low-fat, plant-based diet.
• No studies have shown that this diet will help cancer patients.

Ketogenic diet

• A ketogenic diet limits carbohydrates and increases fat intake. The purpose of the diet is to decrease the amount of glucose (sugar) the tumor cells can use to grow and reproduce.
• It is a hard diet to follow because exact amounts of fats, carbohydrates and proteins are needed.
• However, the diet is safe.
• Several clinical trials are recruiting glioblastoma patients to study whether a ketogenic diet affects glioblastoma tumor activity.
• Patients with glioblastoma who want to start a ketogenic diet should talk to their doctor and work with a registered dietitian.
• However, benefits of ketogenic diet remain unproven in glioblastoma.