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Following a Healthy Diet When You Have HER2-Negative Metastatic Breast Cancer

Eating well can help support your immune system and maintain strength

Person preparing healthy fish platter with veggies in kitchen

When you’re living with HER2-negative metastatic breast cancer, you’re already balancing a lot. You have appointments to get to, treatment side effects to manage, and your mental health and well-being to attend to.


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It can be a lot to process and manage.

So, when your healthcare provider tells you about the importance of following a healthy diet, it can feel like just one more thing to worry about.

But in truth, following a healthy diet can help anyone live better — and that includes when you’re living with HER2-negative metastatic breast cancer.

“Paying attention to nutrition during treatment is important because not only can having a good diet help support a good immune system, but also it can help you maintain your strength and energy, which is going to help you get through your treatments,” says registered dietitian Nickie Michaelis, RD, LD.

Let’s be clear: No diet can cure HER2-negative metastatic breast cancer. Your healthcare team will recommend medical treatment options that are most appropriate for your condition (like chemotherapy, immunotherapy, radiation, hormone therapy and other measures). A healthy diet should be a tool you use alongside those other therapies, not instead of them.

What does a healthy diet look like when you’re living with HER2-negative metastatic breast cancer? Michaelis shares advice.

A diet for your individual needs

Some healthy eating advice rings true no matter if you’re living with cancer or not. A healthy diet for just about anyone is a matter of eating less processed foods and more nutrient-dense foods.

Consider these things to be the essentials of your healthy diet:

  • Eat a range of fresh fruits and veggies in a variety of colors.
  • Choose whole-grain breads, crackers and pasta over refined grains and white bread.
  • Prioritize lean proteins over red meats. That means more poultry, fish, tofu, lentils, beans and low-fat dairy. Less beef, pork and veal.
  • Opt for unsaturated fats (think extra-virgin olive oil, nuts and seeds).
  • Choose water over sweetened beverages.

Eating more of these foods and less processed foods is a good baseline for us all to start with. (And if you’re looking for more specific guidance, get familiar with the Mediterranean diet. It’s the gold standard for healthy eating.)

But when you’re living with HER2-negative metastatic breast cancer, it’s smart to consider a few additional tweaks to what you eat to help you live your best life.

Immunity-boosting foods

Some cancer treatments can take a toll on your immune system, particularly if you’re undergoing systemic treatments. A weakened immune system can leave you more vulnerable to infectious diseases — from colds and coughs to COVID-19, RSV and the flu.

Your healthcare provider will likely recommend keeping up vaccines to help protect you from illness. And those are important.

But in addition to vaccines, a healthy diet can help keep your immune system active and protect you from getting sick.

“The vitamins and minerals you get from natural foods can help your body stay as strong and healthy as it can,” Michaelis states.

Some foods are particularly helpful for boosting immunity, like:

  • Fatty fish.
  • Citrus fruits.
  • Garlic.
  • Ginger.
  • Turmeric.
  • Broccoli.
  • Bell peppers.
  • Spinach.
  • Yogurt.
  • Almonds.
  • Sunflower seeds.


Avoiding foodborne illness

If cancer treatments have affected your immune system, you may be more vulnerable to foodborne illness (aka food poisoning).

“If you're immunocompromised, you can be more susceptible to stomach bugs,” Michaelis warns. “And fighting off food poisoning can be harder. A bad infection could delay your treatments, too.”

No one wants to get food poisoning, but if you’re living with HER2-negative metastatic breast cancer, your provider may advise avoiding some foods that can carry a higher risk for foodborne illness.

Some of the most likely offenders?

  • Undercooked meat and fish (ask for meat to be well-done and choose cooked fish).
  • Unpasteurized products (like soft cheeses, raw milk products and “natural” juices and ciders).
  • Undercooked eggs (no “dippy” eggs).
  • Uncooked deli meats.
  • Raw honey.


Lowering your risk for food poisoning is more than a matter of choosing certain foods, though.

“You also want to be sure you’re practicing good food safety measures,” Michaelis advises. “Wash your hands well and often and promptly refrigerate leftovers.”

The U.S. Centers for Disease Control and Prevention (CDC) offers more tips that can help prevent food poisoning.

Managing your weight

Maintaining (or getting to) a healthy weight can also help to keep your body strong when you’re living with cancer.

Some people with HER2-negative metastatic breast cancer gain weight as they undergo treatment. Others lose it. And in either scenario, an unhealthy weight can make things more difficult.

Often when people lose weight during cancer treatment, they tend to lose muscle. And muscle loss can make things difficult.

“Unhealthy weight loss means less muscle. Less muscle means less strength. Less strength means more fatigue. Which means it’s harder to get through your treatment cycles and recover quickly,” Michaelis notes.

On the other hand, having overweight or obesity can complicate your condition and put you at higher risk for developing conditions like heart disease, high blood pressure, diabetes and more.

Following a healthy diet can help you achieve a healthy weight so you can more effectively and efficiently keep up with your treatments and live your life.

Michaelis offers these tips.

Advice to gain weight

Gaining weight in a healthy way isn’t just about loading up on high-calorie snacks. Those can help you put on some pounds, sure, but not in a way that will fuel your body properly.

Instead, focus on gaining weight safely by getting in more healthy fats, like:

  • Nuts.
  • Seeds.
  • Avocados
  • Full-fat dairy products.
  • Oral nutritional supplement products (like Boost® or Ensure®).

And make sure you’re talking with your healthcare team about the causes of your weight loss. For example, if the medications prescribed to you come with side effects like nausea or vomiting, your team may be able to prescribe additional medications to combat those effects.

Advice to lose weight

Crash diets that encourage severely reduced calories aren’t the answer for anyone. And when you’re living with a serious medical condition like HER2-negative metastatic breast cancer, fad diets can be even more problematic.

You need to eat adequate calories to nourish your body and keep up your strength. That’s critically important.

So, rather than turning to juice cleanses and other quick fixes that promise you’ll lose 10 pounds in a week, commit to making healthy eating a habit. And increase your physical activity, if approved by your healthcare providers.

Healthy eating is important to living a full life when you have HER2-negative metastatic breast cancer. If you’re concerned about getting proper nutrition, talk with a healthcare provider. They can help make sure you’re getting what you need to fuel your body and care for your overall well-being.


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