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.
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, 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:
- 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:
- Grapefruit & grapefruit juice
- High protein diet
- Orange or tangerine peel - found in orange tea, orange marmalade1
- Orange juice, commercial1
- Pineapple & pineapple juice
- Red meat
- 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. The role of supplements is 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.
- Goldenseal supplements
- Honey, propolis or royal jelly supplements
- HRT, combined (estrogen plus progestin), including bioidentical hormones
- L-carnitine supplements
- Lemon balm supplements
- Luteolin supplements
- Licorice root supplements
- Milk thistle supplements
- Quercetin supplements
- Red clover supplements
- Reishi mushroom (ok for IBC)
- Resveratrol supplements
- Rhein supplements
- Sage essential oil
- Sage supplements
- Si-Wu-Tang supplements
- Skullcap supplements
- St. John’s wort supplements
- Suan-Tsao-Ren-Tang supplements
- Tangeretin supplements
- Vitamin C supplements
- 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).
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. However not all studies have found a link.
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
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
Distribution of dyslipidemia in Chinese early breast cancer patients at diagnosis and comparison of dyslipidemia incidence following different endocrine therapies: a population-based cohort study
Wang J, Yin J, Qiu J, Jiang J, Hu Y, Zheng H, et al. Distribution of dyslipidemia in Chinese early breast cancer patients at diagnosis and comparison of dyslipidemia incidence following different endocrine therapies: a population-based cohort study. Research Square; 2021; 10.21203/rs.3.rs-298866/v1
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
Resveratrol as Chemosensitizer Agent: State of Art and Future Perspectives
Cocetta V, Quagliariello V, Fiorica F, Berretta M, Montopoli M. Resveratrol as Chemosensitizer Agent: State of Art and Future Perspectives. International Journal of Molecular Sciences. MDPI AG; 2021; 22:2049 10.3390/ijms22042049
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
Implications of Antidepressants Use in Breast Cancer: A Brief Review
Strazzanti A, Martorana F, Intagliata E, Lanzafame K, Pavone G, Mauro S, et al. Implications of Antidepressants Use in Breast Cancer: A Brief Review. Surgery, Gastroenterology and Oncology. Celsius Publishing House; 2020; 25:229 10.21614/sgo-25-5-229
The apple dihydrochalcone phloretin suppresses growth and improves chemosensitivity of breast cancer cells via inhibition of cytoprotective autophagy
Chen M, Gowd V, Wang M, Chen F, Cheng K. The apple dihydrochalcone phloretin suppresses growth and improves chemosensitivity of breast cancer cells via inhibition of cytoprotective autophagy. Food & Function. Royal Society of Chemistry (RSC); 2020; 10.1039/d0fo02362k
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
Coffee decoction enhances tamoxifen proapoptotic activity on MCF-7 cells
Funakoshi-Tago M, Tago K, Li C, Hokimoto S, Tamura H. Coffee decoction enhances tamoxifen proapoptotic activity on MCF-7 cells. Scientific Reports. Springer Science and Business Media LLC; 2020; 10 10.1038/s41598-020-76445-z
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
Sugar-containing beverages and their association with risk of breast, endometrial, ovarian and colorectal cancers among Canadian women
Arthur RS, Kirsh VA, Mossavar-Rahmani Y, Xue X, Rohan TE. Sugar-containing beverages and their association with risk of breast, endometrial, ovarian and colorectal cancers among Canadian women. Cancer Epidemiology. Elsevier BV; 2020; 70:101855 10.1016/j.canep.2020.101855
Black, pinto and white beans lower hepatic lipids in hamsters fed high fat diets by excretion of bile acids
Alves PLS, Berrios JDJ, Pan J, Yokoyama WH. Black, pinto and white beans lower hepatic lipids in hamsters fed high fat diets by excretion of bile acids. Food Production, Processing and Nutrition. Springer Science and Business Media LLC; 2020; 2 10.1186/s43014-020-00039-5
The effect of cranberry consumption on lipid metabolism and inflammation in human apo A-I transgenic mice fed a high-fat and high-cholesterol diet
Caceres C, Kim M, Bae M, Pham TX, Lee Y, Hu S, et al. The effect of cranberry consumption on lipid metabolism and inflammation in human apo A-I transgenic mice fed a high-fat and high-cholesterol diet. British Journal of Nutrition. Cambridge University Press (CUP); 2020;:1-8 10.1017/s0007114520004080
Protective Effects of Epigallocatechin Gallate (EGCG) on Endometrial, Breast, and Ovarian Cancers
Huang Y, Wang K, Chen H, Chiang Y, Hsia S. Protective Effects of Epigallocatechin Gallate (EGCG) on Endometrial, Breast, and Ovarian Cancers. Biomolecules. MDPI AG; 2020; 10:1481 10.3390/biom10111481
Effect of isoflavones on breast cancer cell development and their impact on breast cancer treatments
Hatono M, Ikeda H, Suzuki Y, Kajiwara Y, Kawada K, Tsukioki T, et al. Effect of isoflavones on breast cancer cell development and their impact on breast cancer treatments. Breast Cancer Research and Treatment. Springer Science and Business Media LLC; 2020; 10.1007/s10549-020-05957-z
Risk of fatty liver after long-term use of tamoxifen in patients with breast cancer
Yoo J, Lim YS, Kim MS, Lee B, Kim B, Kim Z, et al. Risk of fatty liver after long-term use of tamoxifen in patients with breast cancer. PLOS ONE. Public Library of Science (PLoS); 2020; 15:e0236506 10.1371/journal.pone.0236506
COVID-19 infection can cause chemotherapy resistance development in patients with breast cancer and tamoxifen may cause susceptibility to COVID-19 infection
Vatansev H, Kadiyoran C, Cumhur Cure M, Cure E. COVID-19 infection can cause chemotherapy resistance development in patients with breast cancer and tamoxifen may cause susceptibility to COVID-19 infection. Medical Hypotheses. Elsevier BV; 2020; 143:110091 10.1016/j.mehy.2020.110091
Levonorgestrel-releasing intrauterine system and the risk of breast cancer: A nationwide cohort study
Soini T, Hurskainen R, Grénman S, Mäenpää J, Paavonen J, Joensuu H, et al. Levonorgestrel-releasing intrauterine system and the risk of breast cancer: A nationwide cohort study. Acta Oncologica. Informa UK Limited; 2015; 55:188-192 10.3109/0284186x.2015.1062538
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