Breast cancer is one of the most common cancers. Almost 25 percent of people newly diagnosed with cancer have breast cancer. One in 5 people with breast cancer have a type called HER2-positive.

HER2-positive breast cancer tests positive for HER2 protein. HER2 stands for human epidermal growth factor receptor 2.

This means that the cancer cells have a gene that makes HER2 protein. This protein causes cancer cells to grow and spread quickly. HER2-positive breast cancers may develop or grow differently than other kinds.

Treatments for HER2-positive breast cancer target the cells that make the protein. This helps to slow the cancer’s growth and stop it from spreading.

Your daily diet can affect your overall health. Approximately 20 to 30 percent of all cancers may be related to diet, physical activity, and other similar modifiable risk factors.

While no food or diet alone can prevent or treat any kind of cancer, food is an important part of your treatment plan.

Some foods may slow the growth of HER2-positive breast cancer by reducing how much HER2 protein is made. Other foods may block cancer cells from getting nutrition or make them more sensitive to drug treatment. This causes the HER2-positive cancer cells to shrink or die.

Similarly, some foods may worsen breast cancer and other kinds of cancers. They may make it easier for the cancer cells to grow and spread.

Citrus fruits

Citrus fruits contain antioxidants called flavonoids that may help slow the growth of HER2-positive cancer cells.

Consider eating the following citrus fruits:

  • oranges
  • grapefruits
  • bergamots
  • lemons
  • limes

A research study found two specific flavonoids in citrus fruits: naringenin and hesperetin. In a lab setting, the flavonoids helped stop HER2-positive cancer cells from growing.

Citrus fruits may also help make cancer cells more sensitive to medications that stop them from spreading to other parts of the body.

Black pepper

Black pepper contains an active compound called piperine.

Research in a lab setting suggested that piperine has an anti-tumor effect on HER2-positive breast cancer cells. This means that it stops the cells from growing and causes them to die. Piperine was also found to stop the HER2 gene from making HER2 proteins.

Vegetables with phytoestrogens

Some vegetables may help slow or stop the growth of HER2-positive cells. They may also help improve the efficacy of certain cancer drug treatments.

Consider eating more vegetables and herbs, including:

  • Chinese cabbage
  • celery
  • parsley
  • bell peppers
  • rutabagas
  • lettuce

These vegetables all contain phytoestrogens, or flavones, which are plant-based compounds.

A 2012 lab study suggested that a phytoestrogen called apigenin helped block the growth of HER2-postive breast cancer cells.

Omega-3 fatty acids

Foods that are high in healthy unsaturated fats called omega-3 fatty acids are good for your overall health. These healthy fats can lower and balance cholesterol levels and help treat HER2-positive breast cancer and other types of breast cancer.

Foods that are high in omega-3 fatty acids include:

  • olive oil
  • flax seed
  • chia seeds
  • pumpkin seeds
  • pine nuts
  • walnuts
  • navy beans
  • avocados
  • algae
  • salmon
  • sardines
  • mackerel
  • trout
  • tuna

An animal study suggested that extra virgin olive oil helped to slow the spread of HER2-positive breast cancer cells.

Another research study found that using flax seed along with chemotherapy drugs had better results than chemotherapy alone. The combination of flaxseed and chemotherapy was able to stop breast cancer cells from growing.

Both olive oil and flax seed contain omega-3 fatty acids and other chemicals that may help your body fight against cancer cells.

Melatonin foods

You may know that melatonin helps you sleep better. This natural chemical may also have anti-cancer properties.

One study suggested that melatonin helps block HER2-positive breast cancer cells from dividing. It may also prevent the cancer from spreading to other parts of the body.

Your body makes melatonin in small amounts. You can also get a healthy dose of melatonin from the following foods:

  • eggs
  • fish
  • nuts
  • mushrooms
  • sprouted legumes
  • sprouted seeds

Soy foods

Soy is somewhat controversial, as earlier studies have suggested that it isn’t good for breast cancer. However, more recent studies show that this may be incorrect.

A 2013 medical review found that women in some parts of Asia have a lower risk of breast cancer than women in the United States. Eating plenty of unprocessed soy foods may be one reason for this, but more research is needed.

Soy contains several kinds of flavones. These plant-based compounds may help to slow or stop the growth of breast cancer cells.

Eating more soy protein rather than animal protein may also lower cholesterol and unhealthy fats in the body, which can help your body fight against breast cancer.

Consider adding the following soy foods to your daily diet:

  • soy milk
  • tofu
  • tempeh
  • miso
  • edamame beans
  • soybean sprouts
  • soybean oil
  • natto

Grapes

Grapes and grape seeds contain a number of healthy compounds that may help treat HER2-positive breast cancer.

A medical study reported that extract from the skin and seeds of red grapes may prevent HER2-positive breast cancer cells from growing and spreading.

Red and purple grapes are rich in an antioxidant called resveratrol. It may improve the results of breast cancer treatments, including radiation therapy and chemotherapy. This is thought to be because resveratrol can balance natural estrogen hormones in the body.

It’s important to note that the studies mentioned above investigated the relationship between particular compounds in foods, not the foods themselves.

Sugary foods

Sugary foods can increase your risk of health problems, including some cancers. Researchers found that too much sugar may also worsen all types of breast cancers.

An animal study found that up to 58 percent of mice on a high-sugar diet developed breast cancer. The mice were given a diet with as much sugar as a typical Western diet.

According to the researchers, sugary foods may increase the chances of getting breast cancer and cause cancer cells to grow faster. This may be because sugar causes inflammation in the body.

Sugary foods include refined or simple carbohydrates or starches. The World Health Organization recommends that added sugars should make up less than 10 percent of your daily caloric intake.

Avoid added sugars in foods and drinks. These sugars may be listed as:

  • sucrose
  • fructose
  • glucose
  • dextrose
  • maltose
  • levulose

You should also avoid simple or starchy carbohydrates, including:

  • corn syrup or high-fructose corn syrup
  • soda
  • fruit juices
  • energy drinks
  • white bread and pasta
  • white rice
  • baked goods that contain white flour

Alcohol

An imbalance of the hormone estrogen has been linked to breast cancer. Drinking alcohol may make this worse.

A research study found that alcohol has a hormonal effect in the body, providing the nutrients needed for cancer cells to develop.

Saturated and trans fats

Diets that are high in saturated and trans fats may make it easier for HER2-positive breast cancer cells and other types of breast cancer cells to grow.

Eating too many saturated fats can raise your cholesterol levels. on mice suggests a link between high cholesterol and breast cancer risk. A type of cholesterol called low density lipoprotein (LDL) may trigger breast cancer cells to grow larger and spread faster.

This might happen because LDL helps the cancer cells make the proteins it needs to grow. Keep your LDL cholesterol low to help prevent breast cancer and for overall good health.

Avoid foods with saturated and trans fats that can elevate LDL, including:

  • partially hydrogenated vegetable oils
  • margarine
  • shortening
  • non-dairy creamers
  • deep-fried foods
  • packaged cookies and crackers
  • cake mixes
  • cake frosting
  • pies and pastries
  • processed chips and snacks
  • frozen dinners

Meats

Eating too much meat can raise your cholesterol levels. All types of meat and poultry have saturated fats.

A found that a high-fat diet is strongly linked to HER2-positive breast cancer. Animal products also lower melatonin levels in the body. These factors may cause HER2-positive breast cancer to grow and spread.

According to a 2012 study, obesity and excess weight may lead to a worse prognosis.

Staying active can help you balance your weight. Talk to your doctor about the right exercise program for you. Exercise and a healthy diet may also give you better treatments results.

Along with a balanced diet, supplements may help you get the right nutrients. Omega-3 fatty acid supplements add healthy fats to your diet and help lower your cholesterol levels.

Some herbs and spices have anti-cancer properties. Turmeric contains an antioxidant called curcumin to prevent breast cancer cells from growing. Add this spice to your cooking or take it as a supplement.

Your diet may be a factor in helping to prevent and treat a variety of health conditions. More research is needed on specific foods for HER2-positive breast cancer.

Research on specific components of food and breast cancer cells is normally tested in a lab setting. Many of the studies are done on cancer cells only or on cancer cells in mice and other animals. Results may differ when investigating dietary intake in people who are at risk for breast cancer.

Diet alone can’t prevent or treat any type of cancer. Talk to your doctor or nutritionist about the best diet and exercise program for you. Some healthcare providers have diet and exercise programs specifically for people undergoing cancer treatment.