Do antioxidants encourage the spread of cancer cells?

Expert Guidelines

Dietary Supplements

National Comprehensive Cancer Network (NCCN) guidelines on survivorship include the following recommendations on dietary supplement use:

• Taking dietary supplements is not recommended for most cancer survivors unless a patient has a known nutritional deficit, an inadequate diet or other indication (for example, osteoporosis).
• Little data exist to support the use of vitamins or other dietary supplements for cancer prevention, control or recurrence.
• Taking vitamin supplements does not replace the need for a healthy diet. Patients should try to get nutrients from the foods they eat and the beverages they drink.
• Providers should ask about supplement use at regular intervals, about a patient’s reasons for using supplements and the ingredients in those supplements.
• Survivors of certain cancers are at risk of vitamin deficiencies based on cancer treatment (e.g., gastric cancer patients who have had a gastrectomy may be at risk of vitamin B12 and iron deficiencies).
• NCCN recommends calcium and vitamin D supplements for people who have been prescribed denosumab or a bisphosphonate to treat bone metastasis or osteoporosis.
• Patients taking multiple supplements and those in need of nutritional support should be referred to a registered dietitian or nutritionist, preferably one who is trained in supporting oncology patients. 

Nutrition for people diagnosed with cancer

The National Comprehensive Cancer Network (NCCN) recommends the following for cancer survivors: 

• Think about your food choices and amount of fruits, vegetables and unrefined grains you eat compared with red and processed meats, alcohol, and foods or drinks with added fat or sugar. 
• Think about your eating habits, including portion size, snacking, how often you eat out and use of added fats or sugars.
• All survivors should be encouraged to:
  • Make informed choices about food to ensure variety and adequate nutrient intake.
  • Limit refined sugars.
  • Eat a diet that is at least 50% plant-based, consisting mostly of vegetables, fruit and whole grains.
  • Track calorie intake; monitoring of calories is an effective way to manage weight.
  • Minimize alcohol intake to no more than one drink per day for a woman and two drinks per day for a man.
• For patients desiring further dietary guidelines, the USDA approximate food plate volumes are:
  • Vegetables and fruits should comprise half the volume of food on the plate
  • Vegetables: 30% of plate; Fruits 20% of plate
  • Whole grains: 30% of plate
  • Protein: 20% of plate
• Recommended sources of nutrients:
  • Fat: plant sources such as olive or canola oil, avocados, seeds and nuts, and fatty fish.
  • Carbohydrates: fruits, vegetables, whole grains and legumes.
  • Protein: poultry, fish, legumes, low-fat dairy foods, and nuts.

The Academy of Nutrition and Dietetics, the United States Office of Disease Prevention and Health Promotion  and the American Institute for Cancer Research also publish expert guidelines on nutrition and health. 

Questions To Ask Your Health Care Provider

• Are there foods I should eat or avoid after I have had cancer?
• What level of antioxidants should I include in my diet?  
• Are there supplements I should take or avoid?
• Can you refer me to a nutritionist?

Open Clinical Trials

The following are studies focused on nutrition for people diagnosed with breast cancer. 

• NCT04000880: AMPLIFY: An Online Weight Loss Study Specifically for Cancer Survivors. AMPLIFY is a nation-wide, web-based diet and exercise study recruiting overweight survivors of early-stage breast, prostate, ovarian, renal, colorectal, endometrial cancer and multiple myeloma in people age 50 and older who are interested in becoming more active, eating better and losing weight.
• NCT04298086: A Study of the Body's Response to Exercise and a Plant-Based Diet in Overweight Postmenopausal Women With Breast Cancer. This study is looking to find out what effects exercise and a plant-based diet have on aromatase levels in postmenopausal women who are overweight and being treated with an aromatase inhibitor for their HR+ breast cancer. 
• NCT04365569 Evaluating the Effectiveness of an Individualized Nutrition and Physical Activity Counseling Program. This pilot study looks at whether a tailored in-person and telephone-based nutrition and exercise counseling program can help breast cancer patients improve weight and fitness and thus improve cancer outcomes.

Visit our Featured Research Page and Research Search and Enroll Tool to find additional studies enrolling people with, or at high risk for cancer.