Herceptin (trastuzumab) is a monoclonal antibody used to treat HER2/neu overexpressing (HER2+) breast cancer. HER2/neu has a role in the signaling pathways leading to cell growth and differentiation, which accounts for the reputation of aggressiveness of this type of breast cancer. Herceptin binds selectively to the HER2 protein, thereby reducing cancer cell growth and proliferation. Herceptin normally is administered intravenously alone or in combination with a chemotherapy regimen. There are a few foods and spices that have been shown to amplify the effects of Herceptin, thereby increasing its effectiveness.

Herceptin and other similar monoclonal antibodies can result in side effects such as flu-like symptoms (fever, nausea, vomiting, diarrhea, increased cough, headache), low white blood cell count, anemia, increased infections, muscle pain, and lung and heart damage. There are some foods that support heart health while also being associated with lower risk of breast cancer or its recurrence. Other foods could have the opposite effect.

Foods that amplify the anti-cancer effects of Herceptin

The following foods are good sources of compounds that have been found to amplify the effects of Herceptin against HER2-overexpressing breast cancer:

Flaxseed oil
Extra-virgin olive oil
Green tea
Walnuts
There is also some preliminary evidence that cruciferous vegetable consumption might increase the effectiveness of Herceptin. Olive oil and green tea both may counteract Herceptin resistance.

Foods that counteract Herceptin's toxic side effects

Flaxseed has been found to protect the lungs. The other foods below have been found to support heart health while also protecting against breast cancer:

Arugula
Broccoli
Buckwheat
Cabbage
Canola oil
Cherries
Collard greens
Flaxseed
Herring
Kale
Lake trout
Mackerel
Mushrooms
Mustard greens
Olive oil
Pomegranates
Saffron
Salmon, wild
Sardines
Tomatoes
Turmeric
Turnip greens
Walnuts

Breast cancer patients receiving chemotherapy at the same time as Herceptin should also incorporate the food choices for Taxol or Adriamycin, as appropriate.

Foods that could worsen Herceptin's side effects

Grapefruit should be avoided during Herceptin and chemotherapy treatment because of potential grapefruit-drug interactions. Although we do not recommend supplementation with CLA (conjugated linoleic acid), we wish to advise those who do to avoid the t10,c12-CLA isomer (referred to on some supplement labels as Trans-10, Cis-12). The t10,c12 CLA isomer can damage the heart and was found to enhance mammary tumor development in two separate rodent experiments. While curcumin has been shown to have a cytotoxic impact on microbes, one study also showed that long-term use of low-dose curcumin supplements suppressed immunity against pathogens whose elimination primarily involved inflammation. Curcumin also has been shown to be an iron chelator, which could negatively impact those undergoing chemotherapy. Because their immune systems are compromised, those undergoing cancer treatment should avoid raw shellfish and other possible sources of parasitic infection.

One study reported that alcohol can increase the heart damage potentially caused by Herceptin. The following foods have been found to be detrimental to heart health as well as being associated with increased risk of breast cancer and should be limited or avoided:

Alcohol
Beef
Butter
Gravy
Lamb
Pork
Processed meats
Salt, excessive

Additional comments

We caution against taking curcumin, epigallocatechin-3-gallate (EGCG), 3,3'-diindolylmethane (DIM), indole-3-carbinol (I3C), or CLA in supplement form because of the possibility of unintended consequences. Safe and effective dosages for these supplements during Herceptin treatment or chemotherapy have not been established. The Chinese medicine Si-Wu-Tang has been shown to interfere with the effectiveness of Herceptin. There is some preliminary evidence that taking anti-oxidant vitamin supplements could potentially enable early-stage HER2-positive tumor cells to survive when they otherwise would die.

Breast cancer patients and survivors with HER2/neu-overexpressing breast cancer should eat a wide variety of the foods on our recommended list and limit or avoid those on our avoid list, in addition to emphasizing the foods and spices on the lists above.

Below are links to recent studies on this topic. For a more complete list of studies, please click on Herceptin.