By Kim Dalzell, PhD, RD, Founder, Cancer Nutrition IQ
Those I know who are living with metastatic breast cancer choose to feed themselves with things that support overall health and vitality. There is no talk of cure which opens the door for living well intentionally every day. I believe this mindset makes food choices a little easier, knowing that you can consume something that will feed cancer stability and possibly stave off any side effects from ongoing treatment. A targeted nutrition plan can make your decisions a little more confident when deciding what to eat or which dietary supplements to take.
One of the most serious side effects related to chemotherapy used to treat metastatic breast cancer is the weakening of the heart muscle, leading to heart damage that can impact your quality of life. And the cardiac side effects from chemo, like an enlarged heart or congestive heart failure, can appear during cancer treatment or years down the road. A recent study found that having a cardiovascular event, like a heart attack or stroke, may make breast cancer grow faster. (Nature Med, Jul 2020) Breast cancer survivors who developed specific cardiovascular diseases and events—namely heart attack, stroke, heart failure, coronary artery disease, or arrhythmia—had a 59% higher risk of breast cancer coming back and a 60% higher risk of dying from breast cancer than women who did not develop cardiovascular disease.
Along with your doctor who monitors for cardiotoxicity, there are some things you can do from a nutritional standpoint to decrease the negative impact of chemotherapy on your heart and support your goal of a stable diagnosis. Here are three classes of chemotherapy associated with damage to the heart muscle and the nutritional recommendations for each:
Anthracycline drugs like daunorubicin (Cerubidine), doxorubicin (Adriamycin, Doxil), epirubicin (Ellence), idarubicin (Idamycin), and valrubicin (Valstar) kill cancer cells by destroying their genetic material and preventing them from reproducing. This killing spree causes a buildup of unstable oxygen molecules which leads to the development and progression of coronary artery disease. Researchers have discovered that if you can upregulate a gene called SESN2, the damaging cells clear out and you are more protected from heart damage. (J Mol Cell Cardiol, Aug 2019) Choosing foods that increase SESN2 activity may aid this process!
Fruits and vegetables like strawberries, apples, mangoes, persimmons, kiwis, grapes, tomatoes, onions, and cucumbers contain a natural compound called fisetin which upregulates SESN2. Fisetin also may decrease inflammation and stop the spreading of cancer cells. (Adv Exp Med Biol, 2016) One laboratory study found that fisetin dramatically inhibited the growth of primary breast tumors and reduced lung metastasis in triple negative breast cancer cells. (Front Pharmacol, Jul 2018)
5-fluorouracil (Adrucil) is one of the oldest chemotherapies for breast cancer and is used as palliative treatment for metastatic breast cancer patients. It is the second most common chemotherapeutic drug, after anthracyclines, associated with damage to the heart muscle. Cancer cells die when they incorporate anti-metabolites because their DNA and RNA become dysfunctional, preventing them from reproducing and making vital proteins. Unfortunately, this type of chemotherapy also causes collateral damage to the endothelium (the membrane that lines the inside of the heart and blood vessels). (Can J Cardio, Jul 2016) Choosing foods to support a healthy endothelium may help protect you against cardiotoxicity!
Population studies and clinical trials reveal that omega-3 fatty acids can prevent cardiotoxicity and improve blood vessel responsiveness. Additional benefits of omega-3 fatty acids may include alleviating chemobrain and pain associated with chemotherapy (Nutrients, May 2019) and animal studies indicate a diet rich in omega-3 fatty acids protects against mouth or gut soreness and inflammation. (BMC Nutr, Mar 2016) High omega-3 foods include flaxseeds, chia seeds, fish, walnuts, tofu, shellfish, canola oil, navy beans, brussels sprouts, and avocados. It's almost impossible to get enough omega-3s through the diet. For synergistic cardioprotective benefits, choose an omega-3 supplement that contains a blend of balanced fatty acids combined with hawthorn berry, known to exert anti-cancer effects on human breast cancer cells. (Food Chem, Nov 2013)
By the way, natural products containing folic acid may increase the effects of 5-FU, leading to more serious side effects like anemia, infections, and nerve damage so check your dietary supplement labels carefully.
Alkylating agents, like cyclophosphamide (Cytoxan), kill cancer cells by slowing or stopping their growth. The incidence of acute heart failure is anywhere between 7% and 33% of patients receiving a total dose of more than 150 mg/kg cyclophosphamide. To work in the body, cyclophosphamide requires the metabolic activation of the cytochrome CYP3A4 enzyme. If CYP3A4 expression is altered, drugs that are not metabolized may not work as designed. Or they may stay in the bloodstream longer, build up in the blood and become toxic increasing the risk for muscle damage and heart arrhythmia.
Popular dietary supplements and foods that have a high risk for interaction with cyclophosphamide include grapefruit and grapefruit juice. Some less popular citrus fruits, such as Seville orange (bitter orange found in marmalade and savory dishes), pomelo, and star fruit, have similar properties to grapefruit and should be avoided as well. It is estimated that the inhibition of CYP3A4 can last for longer than 3 days after consuming grapefruit juice until new enzymes have been synthesized in the gut wall! (BMJ, Jan 2013)
Some natural combinations have been tested in conjunction with cyclophosphamide administration and show some promise. For example, curcumin and black pepper (piperine) offered strong cardioprotection in animals. (Indian J Pharmacol, Jan-Feb 2017) and dietary glutamine given to animals decrease cardiac tissue damage and offered protection against acute cardiotoxic effects of cyclophosphamide. (Nutrition, 2009). Nutrition recommendations include integrating turmeric and black pepper into meals and consuming glutamine-rich foods like chicken and fish, vegetables like beans, beets, cabbage, spinach, carrots, kale, and Brussels sprouts.
When it comes to nutritional therapy, a general approach of healthy eating gets you started; however, when you choose a targeted approach based on the type of chemotherapy you are being treated with, as well as the subtype of breast cancer, you can pinpoint the foods to consume and learn which ones to avoid. Food is meant to be enjoyed, and with a targeted plan, you can relax knowing the foods and dietary supplements you choose will provide you with the best healing opportunities.
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