Chocolate is a rich source of saturated fat, but also has some health-promoting properties. Components of the cacao tree (Theobroma cacao) bean have been shown to have antioxidant, anti-inflammatory, neuroprotective and antimutagenic actions in the laboratory. Generally speaking, dark chocolate, on which we focus in this webpage, has a higher micronutrient content than milk chocolate.
Dark chocolate (which we define as containing 70-85% cacao solids) is an excellent source of the flavanols catechin and epicatechin, as well as theobromine (which is chemically similar to caffeine) and stearic acid (a saturated fat). Dark chocolate is also a very good source of caffeine and ferulic acid, a good source of fiber, and contains some procyanidins. However, dark chocolate can have relatively high levels of metals such as cadmium, chromium, copper, iron, and lead, and may have significant levels of magnesium, manganese and zinc.
Like the coffee bean, the cacao bean has a complex and varied chemical makeup. However, chocolate consumption has not been as well studied as coffee consumption and the information concerning its health effects are limited and confounded by the fact that chocolate normally contains sugar and other additives.
Chocolate cardiovascular effects
Unlike other saturated fats, stearic acid does not appear to increase cardiovascular risks. Dark chocolate has been found to significantly improve coronary circulation in healthy adults (it improves endothelial function, decreasing both platelet aggregation and blood pressure). In fact, moderate consumption of dark chocolate appears to exert protective effects against the development of cardiovascular disease. Although milk chocolate and dark chocolate are calorie-dense foods, consumption of both has been linked to lower risk of stroke and heart attack.
Cacao extracts and cancer
Cacao extracts have been shown to have anticancer activity against human prostate, colon and adrenal cancer cells. A cacao polyphenolic extract has also been found to reduce the incidence of carcinogen-induced prostate tumors in laboratory rats. Stearic acid has been demonstrated to inhibit tumor growth and reduce proliferation of cancer cells in the laboratory. However, consumption of chocolate itself has been found in population studies to be associated with increased risk of stomach, pancreatic and colorectal cancer.
Breast cancer-related effects of eating chocolate
The beneficial effects of individual anticancer compounds in the cacao bean might be difficult to capture by consuming chocolate since it normally is high in sugar and is incorporated into a wide variety of high glycemic index foods. These are not favorable characteristics for breast cancer risk. One Italian study found that consumption of sweet desserts and sugar (including chocolate) was positively associated with the risk of breast cancer, even after adjusting for body mass index.
However, a 2020 prospective study using data from the Women’s Health Initiative Study (with 15-year average follow-up) reported that there was no significant association between chocolate candy intake and risk of invasive breast cancer.
Note that chocolate consumption has been linked to reduced bone density and strength in older women, suggesting that intake should be limited by those under going treatment with aromatase inhibitors, which also tend to reduce bone density.
Cell studies of cacao extracts
Several studies have reported that cacao extracts reduced breast cancer cell proliferation and proliferation. For example, one study reported that cocoa crude extract induced cell death in two hormone receptor positive (ER+/PR+) breast cancer cell lines without harming normal cells.
Chocolate components with anti-breast cancer effects
The most abundant phenolic compounds in cacao extracts are the flavonoids epicatechin and catechin. While green tea's epigallocatechin gallate (EGCG) is the most well-known catechin, chocolate also contains a large fraction of catechins.
Epicatechin and catechin have been shown to induce apoptosis (programmed cell death) in triple negative (ER-/PR-/HER2-) breast cancer cells. One 2021 study reported that epicatechin inhibited triple negative tumor growth as efficiently as Adriamycin (doxorubicin) in an animal model of triple negative breast cancer.
Epicatechin and catechin can be used to build more complex molecules such as proanthocyanidins. One study reported that a cocoa-derived procyanidin selectively inhibited the proliferation of ER+/PR+ and triple negative breast cancer cells while sparing normal breast cells.
Ferulic acid has been reported to induce programmed cell death in triple negative breast cancer cells. Ferulic acid has also been shown to synergistically enhance the treatment effects of both Taxol (paclitaxel) and epirubicin chemotherapy. In addition, ferulic acid has been found to reduce heart damage caused by Adriamycin in an animal study of Adriamycin-induced cardiomyopathy.
Stearic acid is a long-chain saturated fatty acid abundant in chocolate. Stearic acid has been shown to inhibit breast cancer cell proliferation, invasion, and migration, and to induce apoptosis in the laboratory. In addition, animal experiments have demonstrated that stearic acid and stearates (salts and esters of stearic acid) can decrease mammary tumor incidence and size.
One study reported that women with high circulating levels of stearic acid had a significantly lower risk of breast cancer than those with lower levels.
Chocolate components that could promote breast cancer
Coffee incorporates more caffeine than chocolate (eight ounces of black coffee contains approximately double the caffeine of two ounces of dark chocolate). However, clearly chocolate's caffeine content can add up, depending on intake. Note that while the theobromine found in chocolate is chemically similar to caffeine, it does not appear to stimulate the central nervous system or share it's potentially harmful effects.
An inverse relationship between caffeine intake and breast cancer has been reported. However, caffeine may have adverse effects for those (1) prone to benign breast disease, particularly atypical hyperplasia, which is associated with increased breast cancer risk; or (2) undergoing treatment with Adriamycin (doxorubicin) and other anthracycline chemotherapy.
Relatively high caffeine intake has been found to be associated with hormone receptor negative (ER-/PR-) breast cancer, as well as with breast tumors greater than 2 cm in size, among women with benign breast disease.
While copper does not appear to increase breast cancer risk, it may increase the risk of recurrence. Chocolate, including hot chocolate and chocolate bars, can contain relatively high levels of copper, which could contribute to angiogenesis (the growth of new blood vessels) and metastasis of breast cancer, especially in women with inflammatory breast cancer (IBC) or triple negative (ER-/PR-/HER2-) disease. Dark chocolate contains approximately 0.5 mg copper per ounce, whereas milk chocolate contains approximately 0.14 mg per ounce. Although copper is a vital nutrient, women with breast cancer probably should not exceed the RDA (recommended daily allowance) of approximately 0.9 mg.
While it is important to avoid iron deficiency anemia, the contribution of excess iron in the diet as a result of regularly consuming chocolate could be detrimental for some women. Dark chocolate contains approximately 3.37 mg iron per ounce, or 42% of the 8 mg Recommended Dietary Allowance (RDA) for postmenopausal women.
Tumors are iron consumers. Breast cancer cells have abnormal pathways of iron acquisition, storage and regulation, suggesting that reprogramming of iron metabolism is an important aspect of cancer cell survival. Iron has been shown to facilitate cancer cell proliferation, growth, and angiogenesis.
The addition of iron to breast cancer cells and their microenvironment has been demonstrated to protect them from being killed by natural killer cells. At the same time, iron depletion has been shown to lead to significant inhibition of breast cancer cell growth in the laboratory. Relatively high levels of iron in benign breast tissue was found in one prospective study to be associated with increased risk of subsequent breast cancer.
In addition, excess iron has been shown to have the potential to interfere with the treatment effects of the chemotherapy drugs Adriamycin and cisplatin.
As noted above, dark chocolate can also be a significant source of cadmium, a toxic heavy metal with estrogenic properties that has been shown to increase the risk of breast cancer. Some areas of South America, which incorporates the world's largest producers of cacao beans, have naturally high levels of cadmium in the soil, as well as cadmium derived from pesticides.
Stricter European rules on cadmium levels in cocoa and chocolate products may cause products with lower levels of cadmium to be diverted to the European market. Well-known U.S. chocolate brands are not necessarily low in cadmium. In addition, the organic label does not necessarily mean a low-cadmium product. Purchasing organic low-cadmium chocolate makes sense.
Although dark chocolate has a nutrient profile that is in many respects potentially beneficial (assuming it has a low level of sugar), it also has unfavorable properties that should limit intake for those with breast cancer. Based on the available evidence, modest dark chocolate consumption (up to two ounces per day) appears to be safe for most breast cancer patients and survivors. Those with the following circumstances should more sharply limit their chocolate intake:
- Undergoing treatment with anthracycline (e.g., Adriamycin, Ellence (epirubicin)) or platinum-based (e.g., cisplatin) chemotherapy.
- With benign breast disease or breast cancer preceded by benign breast disease.
- Diagnosed with osteopenia or osteoporosis, a family history of osteoporosis, or undergoing aromatase inhibitor treatment.
The highest levels of bioactive cacao compounds are found in products with the highest content of cocoa solids (i.e., cocoa liquor, cocoa powder and dark chocolate), while the lowest levels are found in milk chocolate, white chocolate and chocolate bars. In fact, the milk proteins in milk chocolate may inhibit the absorption of cacao flavonoids. Hot chocolate, with its relatively low cacao content and high milk and sugar content, is not likely to be beneficial with respect to breast cancer risk.
Sources of information provided in this webpage
The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Note that while we are continually searching for new evidence specifically concerning chocolate and breast cancer, there is not much interest in it among breast cancer researchers, so few directly relevant studies are available.
Selected breast cancer studies
Long-term cadmium exposure induces epithelial-mesenchymal transition in breast cancer cells by activating CYP1B1-mediated glutamine metabolic reprogramming in BT474 cells and MMTV-Erbb2 mice
Li J, Gao P, Qin M, Wang J, Luo Y, Deng P, et al. Long-term cadmium exposure induces epithelial-mesenchymal transition in breast cancer cells by activating CYP1B1-mediated glutamine metabolic reprogramming in BT474 cells and MMTV-Erbb2 mice. Science of The Total Environment. Elsevier BV; 2024; 918:170773 10.1016/j.scitotenv.2024.170773
Breast cancer risk for the joint exposure to metals and metalloids in women: Results from the EPIC-Spain cohort
Fernández-Martínez NF, Rodríguez-Barranco M, Huerta JM, Gil F, Olmedo P, Molina-Montes E, et al. Breast cancer risk for the joint exposure to metals and metalloids in women: Results from the EPIC-Spain cohort. Science of The Total Environment. Elsevier BV; 2024; 912:168816 10.1016/j.scitotenv.2023.168816
Heavy metals in biological samples of cancer patients: a systematic literature review
Coradduzza D, Congiargiu A, Azara E, Mammani IMA, De Miglio MR, Zinellu A, et al. Heavy metals in biological samples of cancer patients: a systematic literature review. BioMetals. Springer Science and Business Media LLC; 2024; 10.1007/s10534-024-00583-4
Effect of zinc and selenium on breast cancer risk: a NHANES cross-sectional study and mediation analysis
wang y, du z, Du H, Zhao J, Duan Y, Wang A. Effect of zinc and selenium on breast cancer risk: a NHANES cross-sectional study and mediation analysis. Research Square Platform LLC; 2024; 10.21203/rs.3.rs-3939938/v1
A critical examination of human data for the biological activity of quercetin and its phase-2 conjugates
Williamson G, Clifford MN. A critical examination of human data for the biological activity of quercetin and its phase-2 conjugates. Critical Reviews in Food Science and Nutrition. Informa UK Limited; 2024;:1-37 10.1080/10408398.2023.2299329
Interplay of Ferroptosis and Cuproptosis in Cancer: Dissecting Metal-Driven Mechanisms for Therapeutic Potentials
Wang J, Li J, Liu J, Chan K, Lee H, Lin KN, et al. Interplay of Ferroptosis and Cuproptosis in Cancer: Dissecting Metal-Driven Mechanisms for Therapeutic Potentials. Cancers. MDPI AG; 2024; 16:512 10.3390/cancers16030512
Polymeric Copper Chelator for Long-term Inhibition of Breast Cancer Proliferation and Lung Metastasis
He X, Pan S, Ma Z, Yuan R, Wei Y, Yang L, et al. Polymeric Copper Chelator for Long-term Inhibition of Breast Cancer Proliferation and Lung Metastasis. Chemistry of Materials. American Chemical Society (ACS); 2023; 10.1021/acs.chemmater.3c02717
New theobromine derivative as apoptotic anti-triple-negative breast cancer targeting EGFR protein: CADD story
Eissa IH, Yousef RG, Elkady H, Elkaeed EB, Husein DZ, Ibrahim IM, et al. New theobromine derivative as apoptotic anti-triple-negative breast cancer targeting EGFR protein: CADD story. Journal of Molecular Structure. Elsevier BV; 2023; 1294:136336 10.1016/j.molstruc.2023.136336
Threat or treat: Exposure assessment and risk characterisation of chemical contaminants in soft drinks and chocolate bars in various Polish population age groups
Marincich L, Protti M, Mandrioli R, Mercolini L, Woźniak Ł. Threat or treat: Exposure assessment and risk characterisation of chemical contaminants in soft drinks and chocolate bars in various Polish population age groups. EFSA Journal. EFSA Journal.; 2023; 21 10.2903/j.efsa.2023.e211011
Dissecting copper biology and cancer treatment: ‘Activating Cuproptosis or suppressing Cuproplasia’
Yang Y, Li M, Chen G, Liu S, Guo H, Dong X, et al. Dissecting copper biology and cancer treatment: ‘Activating Cuproptosis or suppressing Cuproplasia’. Coordination Chemistry Reviews. Elsevier BV; 2023; 495:215395 10.1016/j.ccr.2023.215395
Complementarity between Microbiome and Immunity May Account for the Potentiating Effect of Quercetin on the Antitumor Action of Cyclophosphamide in a Triple-Negative Breast Cancer Model
Manni A, Sun Y, Schell TD, Lutsiv T, Thompson H, Chen K, et al. Complementarity between Microbiome and Immunity May Account for the Potentiating Effect of Quercetin on the Antitumor Action of Cyclophosphamide in a Triple-Negative Breast Cancer Model. Pharmaceuticals. MDPI AG; 2023; 16:1422 10.3390/ph16101422
Cadmium contamination in cacao farms of Piura, North Peru: A comprehensive assessment of geogenic and anthropogenic sources and implications for future production
Guarin D, Hamamura NR, Cortez JB, Benavides J, Spargo J, Guiltinan M, et al. Cadmium contamination in cacao farms of Piura, North Peru: A comprehensive assessment of geogenic and anthropogenic sources and implications for future production. Environmental Challenges. Elsevier BV; 2023;:100765 10.1016/j.envc.2023.100765
Serum copper, zinc and copper/zinc ratio in relation to survival after breast cancer diagnosis: A prospective multicenter cohort study
Bengtsson Y, Demircan K, Vallon-Christersson J, Malmberg M, Saal LH, Rydén L, et al. Serum copper, zinc and copper/zinc ratio in relation to survival after breast cancer diagnosis: A prospective multicenter cohort study. Redox Biology. Elsevier BV; 2023; 63:102728 10.1016/j.redox.2023.102728
Novel Iron Chelator SK4 Drives Cytotoxicity through Inhibiting Mitochondrial Metabolism in Ovarian and Triple Negative Breast Cancer Cell Lines
Abdelaal G, Carter A, Cheung W, Panayiotidis M, Racey S, Tétard D, et al. Novel Iron Chelator SK4 Drives Cytotoxicity through Inhibiting Mitochondrial Metabolism in Ovarian and Triple Negative Breast Cancer Cell Lines. Biomedicines. MDPI AG; 2023; 11:2073 10.3390/biomedicines11072073
Origin, dietary exposure, and toxicity of endocrine-disrupting food chemical contaminants: A comprehensive review
Peivasteh-roudsari L, Barzegar-bafrouei R, Sharifi KA, Azimisalim S, Karami M, Abedinzadeh S, et al. Origin, dietary exposure, and toxicity of endocrine-disrupting food chemical contaminants: A comprehensive review. Heliyon. Elsevier BV; 2023;:e18140 10.1016/j.heliyon.2023.e18140
Exploring the mechanism by which quercetin re-sensitizes breast cancer to paclitaxel: network pharmacology, molecular docking, and experimental verification
Yang Y, Yan J, Huang J, Wu X, Yuan Y, Yuan Y, et al. Exploring the mechanism by which quercetin re-sensitizes breast cancer to paclitaxel: network pharmacology, molecular docking, and experimental verification. Naunyn-Schmiedeberg's Archives of Pharmacology. Springer Science and Business Media LLC; 2023; 10.1007/s00210-023-02510-9
Serum and urinary cadmium and zinc profiles in breast cancer patients and their association with estrogen and HER-2 receptors, and redox status
Matin M, Salehcheh M, Ahmadzadeh A, Khorasgani ZN, Khodayar MJ. Serum and urinary cadmium and zinc profiles in breast cancer patients and their association with estrogen and HER-2 receptors, and redox status. Research Square Platform LLC; 2023; 10.21203/rs.3.rs-2664095/v1
Pre-diagnostic levels of copper and zinc and breast cancer risk in the ORDET cohort
Pala V, Agnoli C, Cavalleri A, Rinaldi S, Orlandi R, Segrado F, et al. Pre-diagnostic levels of copper and zinc and breast cancer risk in the ORDET cohort. Cancer Epidemiology, Biomarkers & Prevention. American Association for Cancer Research (AACR); 2022; 10.1158/1055-9965.epi-21-1252
Copper depletion modulates mitochondrial oxidative phosphorylation to impair triple negative breast cancer metastasis
Ramchandani D, Berisa M, Tavarez DA, Li Z, Miele M, Bai Y, et al. Copper depletion modulates mitochondrial oxidative phosphorylation to impair triple negative breast cancer metastasis. Nature Communications. Springer Science and Business Media LLC; 2021; 12 10.1038/s41467-021-27559-z
Chocolate Candy and Incident Invasive Cancer Risk in the Women’s Health Initiative: An Observational Prospective Analysis
Greenberg JA, Neuhouser ML, Tinker LF, Lane DS, Paskett ED, Van Horn LV, et al. Chocolate Candy and Incident Invasive Cancer Risk in the Women’s Health Initiative: An Observational Prospective Analysis. Journal of the Academy of Nutrition and Dietetics. Elsevier BV; 2021; 121:314-326.e4 10.1016/j.jand.2020.06.014