Tamoxifen (Nolvadex) is used to prevent and treat estrogen receptor-positive (ER+) breast cancer. Women who complete their prescribed anti-estrogen treatments have better recurrence and survival outcomes than those who do not. Some foods can enhance the effectiveness of tamoxifen treatment whereas others interfere with it.
Tamoxifen side effects
Since tamoxifen is life-saving, with proven effectiveness in preventing ER+ breast cancer and its recurrence, every effort should be made to complete treatment as prescribed. Side effects may be easier to tolerate if they are known to be typical. Knowledge of possible side effects can also encourage tamoxifen users to seek medical help, if needed.
The estrogen deprivation caused by tamoxifen results in some side effects (such as hot flashes) that are similar to symptoms experienced during menopause. Tamoxifen-induced estrogen deprivation can also cause some of the symptoms of chemo brain in some women. These symptoms appear to improve within a year after endocrine treatment ends (chemo brain may last longer if chemotherapy was part of breast cancer treatment). One major 2021 study found no links between use of endocrine treatments in non-metastatic breast cancer and risk of subsequent dementia.
Other side effects are specific to separate actions of the drug rather than estrogen suppression. Tamoxifen is associated with higher risk of certain gynecological side effects, including endometrial cancer in women who have not had a hysterectomy. However, there are some foods that can protect against endometrial cancer, again while not interfering with tamoxifen's effectiveness. Please see our article on the gynecological side effects of tamoxifen.
Tamoxifen is also associated with higher risk of developing blood clots. However, there are some foods that can protect against blood clots while not interfering with tamoxifen's effectiveness (see below). Tamoxifen can contribute to skin problems and hair loss in some women. There is also some evidence that long-term tamoxifen use might increase the risk of macular degeneration.
Tamoxifen influences cholesterol levels
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.
Tamoxifen and body weight
There is some evidence that somewhat overweight women have a more favorable prognosis than normal weight women after tamoxifen treatment. However, one study reported that secretions from adipose stem cells of obese women were able to counteract the treatment effects of tamoxifen, suggesting that being overweight could contribute to tamoxifen resistance. In addition, weight gain, which is common during tamoxifen treatment, has been found to be associated with less favorable prognosis.
Micronutrients may influence tamoxifen treatment
Vitamin D has been shown to inhibit the growth of tamoxifen-resistant breast cancer cells in the laboratory, although not all studies are in agreement. Resveratrol has also been found to reduce their proliferation. Selenium and conjugated linoleic acid (CLA) may enhance the effectiveness of tamoxifen, whereas vitamin E, red clover and tangeretin have been shown to reduce it. Sulforaphane, a compound found in cruciferous vegetables, can cause a synergistic increase in cell death in combination with tamoxifen. Most of these micronutrients should be consumed as part of food rather than supplements (see Supplements, vitamins & other exposures below).
There is also some evidence that exposure to bisphenol A (BPA), parabens, or cigarette smoke can also interfere with the effectiveness of tamoxifen treatment.
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 or safely reduce its side effects:
- Arctic char
- Bell peppers
- Black cumin
- Black pepper
- Blueberries & bilberries
- Bok choy
- Broccoli sprouts
- Brussels sprouts
- Butternut squash
- Celery & celery hearts
- Cherries, especially sour or tart
- Chicken, organic1
- Coffee, caffeinated
- Collard greens
- Cranberries & lingonberries
- Currants, black or red
- Flaxseed & flaxseed oil
- Garlic, fresh
- Grapes & grape juice, red
- Green tea
- Horseradish & wasabi
- Hot peppers
- Lake trout
- Mustard greens
- Olive oil, extra-virgin & olives
- Onions, green or red
- Pomegranates & pomegranate juice
- Rice, brown, black or purple
- Salmon, wild
- Seaweed, brown
- Turkey, organic
- Turnips & turnip greens
- Walnuts & walnut oil
- Watercress & garden cress
1Not chicken livers or skin
Regular aspirin use appears to enhance the effectiveness of tamoxifen.
Foods that should be limited or avoided during tamoxifen treatment
The following foods (or major components) have been found to reduce the effectiveness of tamoxifen:
- Açaí berries
- Chamomile tea
- Grapefruit & grapefruit juice
- High protein diet
- Mint or mint tea
- Orange or tangerine peel - found in orange tea, orange marmalade1
- Orange juice, commercial1
- Pineapple & pineapple juice
- Red meat
- Sage tea
- Sesame seeds
- Soy foods, especially soybeans, soy protein isolate, soybean paste
- Vegetable oils with high omega-6 content: corn oil, safflower oil, soybean oil, sunflower oil
1See oranges for a more complete explanation.
Supplements for patients taking tamoxifen
There is no supplement or combination of supplements that has been proven to reliably reduce the risk of ER+ breast cancer recurrence in women. Attempting to take advantage of the apparent treatment effects of micronutrients and other dietary components by using supplements carries the risk of adverse and paradoxical effects, including promoting breast cancer growth and metastasis.
What is known is that when a beneficial micronutrient is administered at low doses by consuming food, it is likely to have subtle chemopreventive effects, whereas when the same micronutrient is administered at high doses, it is more likely to have pharmacological effects, with mostly unknown results. Therefore, it is best to obtain beneficial compounds by consuming food, if possible. Supplements should be used if medically necessary or to make up for deficiencies that are difficult to correct through diet.
The following supplements generally have been found to be safe and beneficial for those being treated with tamoxifen:
Please consult your oncology team for advice concerning your situation and dosages. It might make sense to be tested for deficiency in vitamin D and plan for follow up to determine if your reading has reached a desirable level.
Supplements, vitamins & other exposures to be avoided on tamoxifen
The supplements below have been found to reduce the effectiveness of tamoxifen or increase its side effects. That is not to say that most other supplements are safe to take; there are no relevant scientific studies concerning the interactions between most supplements and tamoxifen.
- Apigenin supplements
- Astragalus or huang qi supplements
- Black cohosh supplements
- Bromelain supplements
- CBD or cannabidiol
- Curcumin or turmeric supplements
- Danshen supplements
- Genistein, daidzein or equol suppls.
- Ginseng supplements
- Goldenseal supplements
- Green tea extract or EGCG supplements
- Honey, propolis or royal jelly supplements
- Horny goat weed supplements
- HRT, combined (estrogen plus progestin), including bioidentical hormones
- L-carnitine supplements
- Lemon balm supplements
- Luteolin supplements
- Licorice root supplements
- Maca root supplements
- Milk thistle supplements
- Quercetin supplements
- Red clover supplements
- Reishi mushroom (ok for IBC)
- Resveratrol supplements
- Rhein supplements
- Sage essential oil
- Sage & red sage root supplements
- Si-Wu-Tang supplements
- Skullcap supplements
- St. John’s wort supplements
- Suan-Tsao-Ren-Tang supplements
- Tangeretin supplements
- Vitamin C, high-dose
- Vitamin E supplements
There is abundant cell and animal study evidence that the curcumin found in turmeric can enhance the effectiveness of tamoxifen. Turmeric consumed as food is likely to be beneficial. However, turmeric or curcumin supplements could interfere with tamoxifen treatment (see Tamoxifen and turmeric or curcumin supplements).
Exposure to light at night suppresses melatonin production, which in turn can lead to tamoxifen resistance.
Foods that reduce the risk of blood clots
The foods below have been reported to decrease the likelihood of blood clots while protecting against breast cancer risk.
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 effective in preventing ER+ breast cancer and in treating early stage disease, but this effectiveness may be lost over time. Also, tamoxifen does not prevent ER- breast cancer. If the cancer progresses despite tamoxifen treatment, it is more likely to recur as ER- disease, which is normally more aggressive than ER+ breast cancer.
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 various stages of treatment and recovery.
Selected breast cancer studies
Weight Gain after Hormone Receptor-Positive Breast Cancer
Goyal A, Milner GE, Cimino-Mathews A, Visvanathan K, Wolff AC, Sharma D, et al. Weight Gain after Hormone Receptor-Positive Breast Cancer. Current Oncology. MDPI AG; 2022; 29:4090-4103 10.3390/curroncol29060326
Adjuvant Hormone Therapy–Related Hot Flashes Predict Treatment Discontinuation and Worse Breast Cancer Prognosis
Zeng E, He W, Smedby KE, Czene K. Adjuvant Hormone Therapy–Related Hot Flashes Predict Treatment Discontinuation and Worse Breast Cancer Prognosis. Journal of the National Comprehensive Cancer Network. Harborside Press, LLC; 2022; 20:683-689.e2 10.6004/jnccn.2021.7116
Alteration in glucose metabolism in the brain associated with tamoxifen treatment: Study in postmenopausal animal model
Koerich S, Silva FC, Itinose AM, Bellozi PMQ, Sandrini F, Schneider SCS, et al. Alteration in glucose metabolism in the brain associated with tamoxifen treatment: Study in postmenopausal animal model. Toxicology and Applied Pharmacology. Elsevier BV; 2022; 442:116002 10.1016/j.taap.2022.116002
EGFR inhibition reverses epithelial‑mesenchymal transition, and decreases tamoxifen resistance via Snail and Twist downregulation in breast cancer cells
Takeda T, Tsubaki M, Matsuda T, Kimura A, Jinushi M, Obana T, et al. EGFR inhibition reverses epithelial‑mesenchymal transition, and decreases tamoxifen resistance via Snail and Twist downregulation in breast cancer cells. Oncology Reports. Spandidos Publications; 2022; 47 10.3892/or.2022.8320
Functional network analysis of p85 and PI3K as potential gene targets and mechanism of oleanolic acid in overcoming breast cancer resistance to tamoxifen
Ibadurrahman W, Hanif N, Hermawan A. Functional network analysis of p85 and PI3K as potential gene targets and mechanism of oleanolic acid in overcoming breast cancer resistance to tamoxifen. Journal of Genetic Engineering and Biotechnology. Springer Science and Business Media LLC; 2022; 20 10.1186/s43141-022-00341-4
Metformin reverses tamoxifen resistance through the lncRNA GAS5-medicated mTOR pathway in breast cancer
Jiang Y, Qian T, Li S, Xie Y, Tao M. Metformin reverses tamoxifen resistance through the lncRNA GAS5-medicated mTOR pathway in breast cancer. Annals of Translational Medicine. AME Publishing Company; 2022; 10:366-366 10.21037/atm-22-795
Diethylhexyl Phthalate and Bisphenol A Promote Vincristine and Tamoxifen Resistance in Vitro
Uyar R, Yurdakok-Dikmen B, Turgut Y, Filazi A. Diethylhexyl Phthalate and Bisphenol A Promote Vincristine and Tamoxifen Resistance in Vitro. Chemical Research in Toxicology. American Chemical Society (ACS); 2022; 10.1021/acs.chemrestox.2c00002
Insights into the Protective Effects of Thymoquinone against Toxicities Induced by Chemotherapeutic Agents
Farooq J, Sultana R, Taj T, Asdaq SMB, Alsalman AJ, Mohaini MA, et al. Insights into the Protective Effects of Thymoquinone against Toxicities Induced by Chemotherapeutic Agents. Molecules. MDPI AG; 2021; 27:226 10.3390/molecules27010226
Cholesterol Depletion Modulates Drug Resistance Pathways to Sensitize Resistant Breast Cancer Cells to Tamoxifen
HENRIQUES PALMA GB, KAUR M. Cholesterol Depletion Modulates Drug Resistance Pathways to Sensitize Resistant Breast Cancer Cells to Tamoxifen. Anticancer Research. Anticancer Research USA Inc.; 2021; 42:565-579 10.21873/anticanres.15514
Baicalein resensitizes tamoxifen‐resistant breast cancer cells by reducing aerobic glycolysis and reversing mitochondrial dysfunction via inhibition of hypoxia‐inducible factor‐1α
Chen Y, Zhang J, Zhang M, Song Y, Zhang Y, Fan S, et al. Baicalein resensitizes tamoxifen‐resistant breast cancer cells by reducing aerobic glycolysis and reversing mitochondrial dysfunction via inhibition of hypoxia‐inducible factor‐1α. Clinical and Translational Medicine. Wiley; 2021; 11 10.1002/ctm2.577
Dietary Supplement Use and Interactions with Tamoxifen and Aromatase Inhibitors in Breast Cancer Survivors Enrolled in Lifestyle Interventions
Harrigan M, McGowan C, Hood A, Ferrucci LM, Nguyen T, Cartmel B, et al. Dietary Supplement Use and Interactions with Tamoxifen and Aromatase Inhibitors in Breast Cancer Survivors Enrolled in Lifestyle Interventions. Nutrients. MDPI AG; 2021; 13:3730 10.3390/nu13113730
Time to update evidence-based guideline recommendations about concurrent tamoxifen and antidepressant use? A systematic review
Bradbury M, Hutton B, Beltran-Bless A, AlZahrani M, Lariviere T, Fernandes R, et al. Time to update evidence-based guideline recommendations about concurrent tamoxifen and antidepressant use? A systematic review. Clinical Breast Cancer. Elsevier BV; 2021; 10.1016/j.clbc.2021.10.003
Abstract 737: Estrogen receptor inhibition with tamoxifen mediates radiosensitization of ER+ breast cancer models
Michmerhuizen AR, Pesch AM, Schwartz R, Wilder-Romans K, Liu M, Azaria R, et al. Abstract 737: Estrogen receptor inhibition with tamoxifen mediates radiosensitization of ER+ breast cancer models. Endocrinology. American Association for Cancer Research; 2021; 10.1158/1538-7445.am2021-737
Association of Endocrine Therapy and Dementia in Women with Breast Cancer
Thompson MR, Niu J, Lei X, Nowakowska M, Wehner MR, Giordano SH, et al. Association of Endocrine Therapy and Dementia in Women with Breast Cancer. Breast Cancer: Targets and Therapy. Informa UK Limited; 2021; Volume 13:219-224 10.2147/bctt.s300455
Abstract PS19-28: Thymoquinone and tamoxifen co-treatment synergistically inhibit proliferation, invasion and induce apoptosis in human breast cancer cell lines in vitro and in vivo
Yahiya I, Helmy H, Sultan A. Abstract PS19-28: Thymoquinone and tamoxifen co-treatment synergistically inhibit proliferation, invasion and induce apoptosis in human breast cancer cell lines in vitro and in vivo. Poster Session Abstracts. American Association for Cancer Research; 2021; 10.1158/1538-7445.sabcs20-ps19-28
Levonorgestrel intrauterine system for endometrial protection in women with breast cancer on adjuvant tamoxifen
Romero SA, Young K, Hickey M, Su HI. Levonorgestrel intrauterine system for endometrial protection in women with breast cancer on adjuvant tamoxifen. Cochrane Database of Systematic Reviews. Wiley; 2020; 10.1002/14651858.cd007245.pub4
Reduction in Tamoxifen Metabolites Endoxifen and N-desmethyltamoxifen With Chronic Administration of Low Dose Cannabidiol: A CYP3A4 and CYP2D6 Drug Interaction
Parihar V, Rogers A, Blain AM, Zacharias SRK, Patterson LL, Siyam MA. Reduction in Tamoxifen Metabolites Endoxifen and N-desmethyltamoxifen With Chronic Administration of Low Dose Cannabidiol: A CYP3A4 and CYP2D6 Drug Interaction. Journal of Pharmacy Practice. SAGE Publications; 2020;:089719002097220 10.1177/0897190020972208
The Potential Role of Nutraceuticals as an Adjuvant in Breast Cancer Patients to Prevent Hair Loss Induced by Endocrine Therapy
Dell’Acqua G, Richards A, Thornton MJ. The Potential Role of Nutraceuticals as an Adjuvant in Breast Cancer Patients to Prevent Hair Loss Induced by Endocrine Therapy. Nutrients. MDPI AG; 2020; 12:3537 10.3390/nu12113537
Tamoxifen and curcumin binding to serum albumin. Spectroscopic study
Maciążek-Jurczyk M, Maliszewska M, Pożycka J, Równicka-Zubik J, Góra A, Sułkowska A. Tamoxifen and curcumin binding to serum albumin. Spectroscopic study. Journal of Molecular Structure. Elsevier BV; 2012; 1044:194-200 10.1016/j.molstruc.2012.11.024
Influence of Tangeretin on Tamoxifen's Therapeutic Benefit in Mammary Cancer
Bracke ME, Depypere HT, Boterberg T, Van Marck VL, Vennekens KM, Vanluchene E, et al. Influence of Tangeretin on Tamoxifen's Therapeutic Benefit in Mammary Cancer. JNCI Journal of the National Cancer Institute. Oxford University Press (OUP); 1998; 91:354-359 10.1093/jnci/91.4.354