Radiation treatment (radiotherapy) can result in side effects such as short-term fatigue, short-term and long-term skin damage, and injury to the heart and lungs. While obtaining relief from these side effects obviously is desirable, it is important for breast cancer patients undergoing radiation treatment to avoid consuming foods or taking supplements that will lessen the cytotoxic impact of radiation on breast cancer cells.
Therefore, the diet we recommend during radiation treatment is to consume the foods that enhance the effectiveness of radotherapy, as well as those on the neutral food list (listed later in this article), while limiting or avoiding the foods that should not be consumed while undergoing radiation treatment, as well as those on our general avoid list.

Foods that enhance the effectiveness of radiation treatment

The following are good sources of compounds that have been shown to increase the anti-cancer effects of radiation treatment (i.e., to increase the cancer cells' radiosensitivity):
There is some evidence that limiting calories to some extent could heighten the treatment effects of radiation treatment. However, note that topical application of honey has been shown to be effective in reducing the severity of radiation-induced oral mucositis. Recent research suggests that cholesterol-lowering drugs could result in less radiation resistance among hormone receptor positive (ER+/PR+) and inflammatory breast cancer (IBC) patients who undergo radiotherapy.

Supplements for patients being treated with radiotherapy

There is no supplement or combination of supplements that has been proven to reliably reduce the risk of breast cancer recurrence in women. Attempting to take advantage of the apparent treatment effects of micronutrients and other dietary components by using supplements carries the risk of adverse and paradoxical effects, including promoting breast cancer growth and metastasis.
What is known is that when a beneficial micronutrient is administered at low doses by consuming food, it is likely to have subtle chemopreventive effects, whereas when the same micronutrient is administered at high doses, it is more likely to have pharmacological effects, with mostly unknown results. Therefore, it is best to obtain beneficial compounds by consuming food, if possible. The role of supplements is to make up for deficiencies that are difficult to correct through diet.
The following supplements generally have been found to be safe and beneficial for those being treated with radiation:
Supplement → Dosage
  • CoQ10 (if needed for heart health) → 100 to 400 mg/day
  • Fish oil → 1000 to 2000 mg/day
  • Vitamin D → 1000 to 2000 IU/day
Please consult your oncology team for advice concerning your situation and dosages. It might make sense to be tested for deficiency in vitamin D and plan for follow up to determine if your reading has reached a desirable level.

Foods that should be limited or avoided during radiation treatment

Most of the foods listed below are good sources of compounds that have been found to protect cells against radiation treatment (i.e., they are radioprotective) without having been shown not to interfere with the cytotoxic effects of radiotherapy. This means that they might have the potential to enable breast cancer cells to survive radiotherapy. Shellfish, especially raw shellfish, have the potential to cause illness that could interfere with the timely completion of treatment.

Supplements and other products that should not be used during radiation treatment

The vitamins and supplements listed below are sources of compounds that could reduce the effectiveness of radiotherapy.
Cigarette smoking during radiotherapy can result in increased treatment-related complications.

Neutral foods for use during radiation treatment

We have provided the list below in order to increase the number of foods that can be consumed while undergoing radiotherapy. It includes some foods for which we do not have enough information to put on our general recommended list, but that do not appear to promote breast cancer or interfere with radiation treatment (when consumed in moderation). It is important not to drive up blood sugar and insulin levels with high carbohydrate/low fiber meals. Consume the foods below in moderation, but concentrate on the foods that enhance the effectiveness of radiation treatment above.
Food should not be deep fried, barbequed, pan fried at high heat, roasted or smoked. The best cooking methods for starchy foods are steaming, boiling and baking. Very little salt should be used in preparing food.

Additional comments

We caution against taking apigenin, curcumin, epigallocatechin-3-gallate (EGCG), quercetin, melatonin or resveratrol in supplement form because of the possibility of unintended consequences. Safe and effective dosages for these supplements during radiation treatment have not been established. Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.