Tamoxifen (Nolvadex) is effective in preventing and treating estrogen receptor-positive (ER+) breast cancer. Women who complete their prescribed anti-estrogen treatments have been found to have better recurrence and survival profiles than women who do not. There are some foods that appear to enhance the effectiveness of tamoxifen treatment and others that reduce it.
Tamoxifen is associated with higher risk of endometrial cancer for women who have not had a hysterectomy and higher risk of developing blood clots, among other side effects. However, there are some foods that can protect against endometrial cancer and blood clots while not interfering with tamoxifen's effectiveness.
Certain selective serotonin reuptake inhibitor (SSRI) antidepressants such as Paxil (paroxetine) and Prozac (fluoxetine), as well as the serotonin antagonist and reuptake inhibitor Oleptro (trazodone), have been found to interfere with tamoxifen treatment in some women and should be avoided. Exposure to light at night suppresses melatonin production, which in turn can lead to tamoxifen resistance. Regular aspirin use appears to enhance the effectiveness of tamoxifen.
Tamoxifen and body weight
There is some evidence that overweight women have a more favorable prognosis than normal weight women after tamoxifen treatment. However, weight gain, which is common during tamoxifen treatment, has been found to be associated with less favorable prognosis. Please see our article on the latest research concerning the impact of endocrine treatment on breast cancer prognosis.
Tamoxifen and cholesterol
Breast cancer typically eventually develops resistance to tamoxifen. Using tamoxifen can reduce cholesterol levels, which can rebound at the end of tamoxifen treatment. There is some evidence that breast cancer cells that don't respond to tamoxifen may be using cholesterol to shield themselves against the drug. While it is not clear that reducing dietary cholesterol would greatly affect this process, it may make sense for breast cancer patients on tamoxifen to reduce their cholesterol to low-normal levels.
Tamoxifen might increase risk of type 2 diabetes
It has been reported that tamoxifen use in breast cancer survivors is associated with an increased risk of type 2 diabetes. This risk may be higher in women who have other risk factors for diabetes.
Vitamin D and other micronutrients influence tamoxifen treatment
Vitamin D has been shown to inhibit the growth of tamoxifen-resistant breast cancer cells in the laboratory and resveratrol has been found to reduce their proliferation. Selenium and conjugated linoleic acid (CLA) may enhance the effectiveness of tamoxifen, whereas vitamin C, red clover and tangeretin have been shown to reduce it. In addition, brassica vegetables contain sulforaphane, an histone deacetylase (HDAC) inhibitor that may cause a synergistic increase in apoptosis and cell death in combination with tamoxifen
Foods that enhance the effectiveness of tamoxifen treatment
The following foods (or major components) have been found to increase the anti-breast cancer effects of tamoxifen treatment:
1Brazil nut consumption should be limited to no more than an average of one nut per day, to avoid consuming excess selenium.
Foods and supplements that should not be used during tamoxifen treatment
The following foods (or major components) and supplements have been found to reduce the effectiveness of tamoxifen and should be avoided during tamoxifen treatment:
- DIM or I3C supplements
- Corn oil
- Curcumin supplements
- Genistein & Daidzein supplements
- Goldenseal supplements
- Hormone replacement therapy (HRT), including bioidentical or natural hormones
- Orange or tangerine peel - found in orange tea, orange marmalade, Szechuan Orange Chicken
- Red clover supplements
- Safflower oil
- Sesame seeds
- Si-Wu-Tang - a Chinese medicine herbal preparation
- Soy protein isolate
- Soybean oil
- Soybean paste
- Sunflower oil
- Tangeretin supplements
- Vitamin E supplements
Foods that reduce the risk of endometrial cancer
The following foods (or major components) have been associated with lower risk of endometrial cancer while also protecting against breast cancer:
Foods that increase the risk of endometrial cancer
The foods and supplements listed below have been associated with increased risk of endometrial cancer. Sweets and other foods with high glycemic index, as well as animal fats, have been shown to increase the risk. Exposure to cadmium is associated with increased risk. Foods with high acrylamide content, such as French fries, cereal, potato chips, potatoes, and baked goods, have also been shown to increase risk of endometrial cancer.
- Bread, baguettes & croissants
- Cheese, full fat
- Cookies, candy and cake
- Fried ripe plantains
- Genistein & daidzein
- Milk, whole
- Potatoes, potato chips & French fries
- Sweet desserts
- Sweetened breakfast cereals
- Well done or fried meat
- White rice
Foods that reduce the risk of blood clots
The foods below have been reported to decrease the likelihood of blood clots while protecting against or being neutral with respect to breast cancer risk.
- Honey, minimally processed
- Lake trout
- Salmon, wild
- Walnuts & walnut oil
Foods that reduce cholesterol
The following foods have been shown to improve cholesterol profile while at the same time protecting against breast cancer:
Foods that increase cholesterol
The following foods have been shown to worsen cholesterol profile:
Tamoxifen is a selective estrogen receptor modulator (SERM), down-regulating ERα but not ERβ (in contrast, aromatase inhibitors such as Arimidex up-regulate ERβ). Tamoxifen is effective in preventing ER+ breast cancer and in treating early stages, but this effectiveness may be lost over time if the cancer progresses despite treatment. Also, tamoxifen does not prevent ER- breast cancer. Women who develop primary breast cancer or a recurrence despite tamoxifen treatment are at increased risk of developing ER- breast cancer, a more aggressive disease than ER+.
Therefore, it is important for women being treated with tamoxifen to eat a wide variety of the foods from our recommended list and limiting or avoiding those on our avoid list, in addition to paying particular attention to the foods listed above. Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.
Below are links to recent studies on this topic. For a more complete list of studies, please click on tamoxifen.