Despite past concerns about specific foods (especially soy), current dietary guidelines don’t list any foods as completely off-limits for everyone with estrogen receptor-positive (ER-positive) breast cancer. But depending on your medication, metabolism, and comorbidities (coexisting health conditions), you may want to shift your diet in a specific direction to improve your overall health. For example, some health experts say that eating low-carb or following a vegetarian diet improves breast cancer outcomes.

Ultimately, if you’re struggling to keep weight on during breast cancer treatment, your health care provider may advise you against being too restrictive with your diet. Replacing foods that interact with your medication or affect your hormones can be important, but it’s also best to avoid making a lot of unnecessary or burdensome changes.

While each situation is different, following are some foods that you can ask your health care provider if you need to avoid.

1. Citrus Fruits

Oncologists often recommend the medication tamoxifen (Soltamox) for ER-positive breast cancer. When taken as prescribed, tamoxifen significantly reduces the risk of breast cancer spreading or recurring (coming back). However, some citrus fruits — especially grapefruit and tangerines — can reduce the effectiveness of treatment.

Studies suggest that a high intake of oranges or orange juice may cause tamoxifen to be less effective. Although oranges offer several health benefits, including fiber and vitamin C, it may be best to limit your consumption if you’re on tamoxifen.

Fortunately, researchers found that potential side effects and interactions were caused by a high intake of oranges — around six oranges per day. With orange juice, the totals can add up quickly: Around 2 cups is considered a high intake.

Your health care provider can help you understand how much and what types of citrus fruits are safe to include in your diet.

2. Cow’s Milk

Cancer research suggests that cow’s milk may play a role in the development of ER-positive breast cancer when consumed in high amounts during certain times of life (such as during pregnancy). Various aspects of cow’s milk may affect breast health, including its natural hormones and the environmental pesticides and plastics used in processing.

For many people, dairy is often an important source of calcium, protein, and other nutrients. For people with ER-positive breast cancer, consuming fermented dairy products, such as yogurt and cheese, may be preferable to cow’s milk.

3. Some Supplements and Herbs

Along with some medications, several herbs and supplements interact with tamoxifen and other breast cancer treatments. For example, St. John’s Wort, valerian, ginger, curcuma (turmeric), and ginseng may all interfere with the effectiveness of tamoxifen or lead to toxicities.

No dietary supplements have been found to help treat or cure breast cancer. Moreover, health experts recommend that people try to meet their nutritional needs through foods instead of relying on supplements. However, doctors will sometimes recommend supplements for people with certain nutritional deficiencies. You should speak with your health care team before starting any supplements so as to avoid any interactions or potential harm.

4. Alcoholic Beverages

Some evidence suggests that consuming alcohol may increase a person’s risk for developing ER-positive breast cancer or having a recurrence. Alcohol may also reduce the effectiveness of tamoxifen.

For your health, consider limiting your intake of alcohol or eliminating it completely from your diet. Talk to your oncologist to see if your drinking habits could interfere with your specific breast cancer symptoms or treatment.

What’s the Deal With Soy?

There’s still some controversy and confusion about whether people with ER-positive breast cancer should avoid soy because of its natural estrogen-like compounds (called phytoestrogens).

“I have been on a plant-based diet also since I was diagnosed. The only problem I find with vegan is most protein comes from soy-based products, and I have not been able to get a clear answer if soy raises estrogen levels or not,” said a MyBCTeam member.

While you should always defer to your doctor or dietitian’s medical advice, most experts say that a moderate intake of soy milk and soybeans, including tofu and edamame, is likely safe and potentially beneficial for all types of breast cancer. While soy foods can be a healthy part of your diet, healthy experts usually don’t recommend soy supplements.

Talk With Others Who Understand

On MyBCTeam — the social network for people with breast cancer and their loved ones — more than 65,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Do you avoid specific foods as a result of a hormone receptor breast cancer diagnosis? How have the side effects of cancer and cancer treatment impacted your ability to maintain a healthy weight and consume a healthy diet? Share your experience in the comments below, or start a conversation by posting on your Activities page.