Daughters of women who have had a breast cancer diagnosis or who have a BRCA1 or BRCA2 mutation are at higher risk for breast cancer than the general population. While there are some breast cancer risk factors such as height and age at first period over which parents have limited control, there are other sources of risk that they can influence.
These generally fall under diet and lifestyle factors, although minimizing exposure to certain pollutants and ionizing radiation are also important.
This topic has been divided into three time periods: prenatal period and infancy; childhood and puberty; and teenage years and young adulthood.
Diet of mother and other factors during pregnancy
Birth weight and breast cancer risk
Low birth weight has been found to be associated with decreased risk of premenopausal breast cancer and high birth weight has been reported to be associated with increased risk of breast cancer in adulthood, although not all studies are in agreement. High birth weight is associated with dense breasts, a known risk factor for breast cancer. Older mothers (over age 39) are also more likely to have daughters with dense breasts. Women who weighed more than 8.8 lbs at birth have been found to have a significantly higher risk of breast cancer than women who weighed less than 5.5 lbs. However, one study reported that birth length, rather than birth weight, is positively associated with breast cancer risk, especially among daughters of tall women.
Note that it does not make sense to under nourish babies in the womb by greatly restricting the mother's calorie intake. Severe calorie restriction during pregnancy has been shown to dramatically increase the risk of breast cancer in adulthood. One study examined the effects of the famine that took place in the Netherlands at the end of World War II from November 1944 until liberation in May 1945. People were surviving on an estimated 400 to 800 calories per day and the diet lacked variety. Daughters of women who endured famine conditions during the first trimester of their pregnancies were found to have 8.3 times the risk of dying of breast cancer during adulthood than daughters not exposed to famine in the womb.
In summary, while there is some limited evidence that excessive weight gain during pregnancy could increase breast cancer risk in daughters, greatly restricting calories in an attempt to limit birth weight does not appear to be a safe or effective risk reduction strategy. On the other hand, one animal study suggested that exercise during pregnancy could reduce breast cancer risk in daughters.
Effect of high BMI before pregnancy
Are overweight women more likely to have daughters who eventually develop breast cancer? There is no clear answer. One study found that sex hormone binding globulin (which is associated with reduced breast cancer risk) was inversely related to pre-pregnancy BMI and weight gain during pregnancy, and positively related to vegetable and legume intake. The authors concluded that avoiding excess calorie intake and emphasizing plant foods might contribute to reducing the risk of breast cancer in daughters. Another study found that daughters of women who were obese while pregnant were more likely to experience early puberty, a breast cancer risk factor.
However, yet another study that included 814 mothers of nurses with breast cancer reported that the mothers' pre-pregnancy BMI was not associated with the daughters' breast cancer risk during adulthood. Weight gain during pregnancy also was not found to be associated with daughters' breast cancer risk. The authors of this study concluded that the known association between birth weight and breast cancer risk is likely due to factors independent of mothers' pre-pregnancy BMI or weight gain during pregnancy.
There is also some limited evidence that a father's diet can influence subsequent breast cancer risk in his daughter. One study using a rat model of breast cancer reported that a paternal high-fat diet induced increased risk of mammary tumors in female offspring.
Folic acid supplementation during pregnancy and daughter's breast cancer
Currently, it is recommended that all women of childbearing age take 0.4 mg folic acid per day or to obtain this amount from fortified foods. This is because folic acid reduces the risk of neural tube defects such as spina bifida and anencephaly when taken before conception and during early pregnancy.
There are contradictory studies regarding the effect of folic acid supplementation of pregnant mice on the subsequent development of mammary tumors in offspring. Therefore, we suggest that women who plan to have children get their folate levels checked well before becoming pregnant. This will give them the opportunity to increase their circulating folate levels through their diets (see the list of foods below) and by eliminating alcohol consumption, if necessary. Women with folate levels in the high end of the normal range might not need folic acid supplementation during pregnancy. Those that are not able to achieve this level may need to take folic acid supplements.
The following foods are good sources of folate:
Note that both green and black tea reduce intestinal absorption of folate and should not be consumed with high-folate foods by those wishing to increase their circulating folate levels.
Some plastics contain endocrine disruptors such as bisphenol A (BPA), styrene, and phthalates that can leach into food when the plastics are heated, microwaved, put under pressure, or simply scuffed and worn. Prenatal exposure to BPA and phthalates has been shown to alter breast development in animal experiments and to increase the likelihood of early puberty in girls, thereby increasing the subsequent risk of breast cancer.
Plastics that may leach these substances include (1) polyvinyl chloride (PVC), which may be found in cling wrap, some plastic squeeze bottles, and cooking oil bottles; (2) polystyrene, which may be found in styrofoam food containers and disposable cups and bowls; and (3) polycarbonates, which may be found in soup and soda can linings, plastic baby bottles, water bottles, and clear plastic sippy cups. Pregnant and nursing women should avoid all but temporary, low temperature uses of these products. Plastic containers may be marked with a number in a triangle-like icon. Plastics marked 1, 2, 4 or 5 use less toxic additives in their manufacture. Products that use polyvinyl chloride should be marked with 3, polystyrene with a 6, and polycarbonate with a 7—these are the ones to avoid.
Exposure to pesticides
Girls whose mothers worked in greenhouses in the first trimester of pregnancy have been found to have earlier breast development than girls without such prenatal exposure. This appears to be because some currently approved pesticides possess endocrine disrupting properties.
Prenatal exposure to maternal smoking has been found to be associated with early first period, which in turn is linked to increased risk of breast cancer. Exposure to second-hand smoke during both the prenatal period and infancy have been found to be associated with increased risk of breast cancer in adulthood.
Omega-3 to omega-6 fatty acid ratio during pregnancy
There is also evidence that a relatively high omega-3 to omega-6 fatty acid ratio in the maternal diet may reduce the risk of subsequent breast cancer in daughters. This means emphasizing foods such as walnuts and walnut oil, as well as sources of marine fatty acids, and de-emphasizing corn oil, soybean oil and other high omega-6 vegetable oils.
Flaxseed is another dietary source of omega-3 fatty acids, but flaxseed can accumulate unacceptable levels of cadmium (a known breast cancer promoter). We recommend that pregnant women consume only flaxseed that is stated to have low levels of cadmium. Refined flaxseed oil has negligible levels of cadmium and other heavy metals.
In addition, while fatty fish are the best sources of marine omega-3 fatty acids, it may be best for pregnant women to consume high quality fish or krill oil supplements that have low levels of contaminants like mercury, PCBs and dioxins, instead of eating fatty fish.
Maternal consumption of whole grains during pregnancy has been found to be associated with lower risk of subsequent breast cancer in offspring, possibly by enhancing DNA damage repair mechanisms. There is also some evidence that adequate choline consumption during pregnancy is crucial.
However, it is important to avoid brown rice with high arsenic levels during pregnancy. Prenatal arsenic exposure has been shown to alter mammary gland development in ways that increase the risk of eventually developing breast cancer. Rice grown in California tends to have lower levels of arsenic than rice from the Louisiana, Arkansas, Missouri, Texas, or non-U.S. countries.
Foods to include during pregnancy and nursing
The following foods may reduce the subsequent risk of breast cancer in daughters when included in the mother's diet during pregnancy and while nursing:
Foods and supplements to limit or avoid during pregnancy and nursing
The following foods and supplements may increase the subsequent risk of breast cancer in daughters when consumed frequently during pregnancy or while nursing:
Prenatal exposure to cadmium or artificial sweeteners also has the potential to alter mammary gland development in unfavorable ways.
The following foods and other products may increase the risk of other cancers or birth defects in daughters or cause problems for the pregnancy when consumed regularly during pregnancy:
Exposure to oncogenic viruses
Certain viruses have been reported to be associated with breast cancer. These include mouse mammary tumor virus (MMTV), bovine leukemia virus (BLV), Epstein-Barr virus, human papilloma virus (HPV), human cytomegalovirus (Human Herpes virus 5), and measles virus. The topic is controversial, in part because of problems with methodology and inconsistent findings. In any case, it makes sense to reduce or avoid exposure to these viruses.
Steps should be taken to avoid transmitting herpes during pregnancy or childbirth. Children should be vaccinated against measles as young toddlers and HPV as older children.
Infancy and subsequent breast cancer
Parents should avoid using baby care products containing lavender or tea tree oil, which have been shown to produce estrogenic effects in children, and parabens, which are suspected to increase female breast cancer incidence. In addition, herbal treatments for colic containing fennel (Foeniculum vulgare) should not be used since they may cause premature breast development. Also to be avoided are clear plastic baby bottles, sippy cups, and toys containing polycarbonates, which have been shown to be carcinogenic. Plastic products containing polycarbonates may be marked on the base with a triangle containing the number 7.
Having been breastfed as an infant does not appear to influence the risk of breast cancer in adulthood. However, breastfeeding has other advantages for babies and it appears to reduce the risk of breast cancer in the mother, even if undertaken only for a short period of time. The more difficult question is whether infant formula made from cow's milk or soy is safer for our high risk daughters (little evidence is available for other types of infant formula). This is a topic that can lead to highly emotional reactions. We summarize the available scientific evidence in the following two sections.
Cow's milk formula
Although milk consumption during adulthood has been found to be associated with higher risk of breast cancer, milk has been found to protect against breast cancer when consumed in infancy and childhood. A partial explanation for this finding is the fact that milk is a very good source of calcium, which is known to protect against breast cancer.
Soy infant formula contains phytoestrogens, which have been shown to accelerate puberty in female rats and delay puberty in male rats. However, female rats fed soy protein isolate (the principal ingredient of soy formula) have been found to have reduced incidence of carcinogen-induced mammary tumors. Soy formula could adversely affect thyroid function and, based on animal studies, might increase body weight and reduce eventual fertility. Nevertheless, the few studies that have compared the health of milk formula-fed children with soy formula fed children have not found any adverse effects for soy. Based on the available evidence, boys fed soy formula could suffer from subtle demasculinization effects. In addition, while isoflavone-rich diets in mice during pregnancy and lactation reduce breast cancer in offspring, soy formula may have unforeseen and unintended long-term effects.
Pregnant women who themselves have an elevated risk of breast cancer should eat a wide variety of the foods on our recommended food list and limit or avoid those on our avoid list, in addition to paying particular attention to the foods and other products on the lists above.
Below are links to recent studies on this topic. For a more complete list of studies, please click on prenatal exposure or protecting our children.
Selected breast cancer studies
New insights on the effects of endocrine-disrupting chemicals on children
Predieri B, Alves CA, Iughetti L. New insights on the effects of endocrine-disrupting chemicals on children. Jornal de Pediatria. Elsevier BV; 2021; 10.1016/j.jped.2021.11.003
Presence of parabens, phenols and phthalates in paired maternal serum, urine and amniotic fluid
Bräuner EV, Uldbjerg CS, Lim Y, Gregersen LS, Krause M, Frederiksen H, et al. Presence of parabens, phenols and phthalates in paired maternal serum, urine and amniotic fluid. Environment International. Elsevier BV; 2022; 158:106987 10.1016/j.envint.2021.106987
Maternal exposure to bisphenol A induces fetal growth restriction via upregulating the expression of estrogen receptors.
Cao Y, Chen Z, Zhang M, Shi L, Qin S, Lv D, et al. Maternal exposure to bisphenol A induces fetal growth restriction via upregulating the expression of estrogen receptors.. Chemosphere. Elsevier BV; 2022; 287:132244 10.1016/j.chemosphere.2021.132244
Early-life exposures and age at thelarche in the Sister Study cohort
Goldberg M, D’Aloisio AA, O’Brien KM, Zhao S, Sandler DP. Early-life exposures and age at thelarche in the Sister Study cohort. Breast Cancer Research. Springer Science and Business Media LLC; 2021; 23 10.1186/s13058-021-01490-z
Dietary Habits and Relationship with the Presence of Main and Trace Elements, Bisphenol A, Tetrabromobisphenol A, and the Lipid, Microbiological and Immunological Profiles of Breast Milk
Castro I, Arroyo R, Aparicio M, Martínez MÁ, Rovira J, Ares S, et al. Dietary Habits and Relationship with the Presence of Main and Trace Elements, Bisphenol A, Tetrabromobisphenol A, and the Lipid, Microbiological and Immunological Profiles of Breast Milk. Nutrients. MDPI AG; 2021; 13:4346 10.3390/nu13124346
Developmental exposure to phytoestrogens found in soy: New findings and clinical implications
Suen AA, Kenan AC, Williams CJ. Developmental exposure to phytoestrogens found in soy: New findings and clinical implications. Biochemical Pharmacology. Elsevier BV; 2021;:114848 10.1016/j.bcp.2021.114848
Prenatal EGCG exposure-induced heart mass reduction in adult male mice and underlying mechanisms
Zhang S, Ou K, Huang J, Fang L, Wang C, Wang Q. Prenatal EGCG exposure-induced heart mass reduction in adult male mice and underlying mechanisms. Food and Chemical Toxicology. Elsevier BV; 2021; 157:112588 10.1016/j.fct.2021.112588
In Utero Exposure to trans-10, cis-12 Conjugated Linoleic Acid Modifies Postnatal Development of the Mammary Gland and its Hormone Responsiveness
Berryhill GE, Gloviczki JM, Trott JF, Kraft J, Lock AL, Hovey RC. In Utero Exposure to trans-10, cis-12 Conjugated Linoleic Acid Modifies Postnatal Development of the Mammary Gland and its Hormone Responsiveness. Journal of Mammary Gland Biology and Neoplasia. Springer Science and Business Media LLC; 2021; 10.1007/s10911-021-09499-y
A Comprehensive Assessment of Associations between Prenatal Phthalate Exposure and the Placental Transcriptomic Landscape
Paquette AG, MacDonald J, Lapehn S, Bammler T, Kruger L, Day DB, et al. A Comprehensive Assessment of Associations between Prenatal Phthalate Exposure and the Placental Transcriptomic Landscape. Environmental Health Perspectives. Environmental Health Perspectives; 2021; 129:097003 10.1289/ehp8973
Morphological and molecular effects of overexpressed GH on mice mammary gland
Bojorge MA, Cicconi NS, Cebrón JR, Fang Y, Lamb CA, Bartke A, et al. Morphological and molecular effects of overexpressed GH on mice mammary gland. Molecular and Cellular Endocrinology. Elsevier BV; 2021;:111465 10.1016/j.mce.2021.111465
Never-smokers and the fraction of breast cancer attributable to second-hand smoke from parents during childhood: the Norwegian Women and Cancer Study 1991–2018
Gram IT, Wiik AB, Lund E, Licaj I, Braaten T. Never-smokers and the fraction of breast cancer attributable to second-hand smoke from parents during childhood: the Norwegian Women and Cancer Study 1991–2018. International Journal of Epidemiology. Oxford University Press (OUP); 2021; 10.1093/ije/dyab153
Prenatal exposure to a mixture of different phthalates increases the risk of mammary carcinogenesis in F1 female offspring
de Freitas T, Zapaterini JR, Moreira CM, de Aquino AM, Alonso-Costa LG, Bidinotto LT, et al. Prenatal exposure to a mixture of different phthalates increases the risk of mammary carcinogenesis in F1 female offspring. Food and Chemical Toxicology. Elsevier BV; 2021;:112519 10.1016/j.fct.2021.112519
Isoflavones alter male and female fertility in different development windows
Sleiman HK, de Oliveira JM, Langoni de Freitas GB. Isoflavones alter male and female fertility in different development windows. Biomedicine & Pharmacotherapy. Elsevier BV; 2021; 140:111448 10.1016/j.biopha.2021.111448
Application of an in Vitro Assay to Identify Chemicals That Increase Estradiol and Progesterone Synthesis and Are Potential Breast Cancer Risk Factors
Cardona B, Rudel RA. Application of an in Vitro Assay to Identify Chemicals That Increase Estradiol and Progesterone Synthesis and Are Potential Breast Cancer Risk Factors. Environmental Health Perspectives. Environmental Health Perspectives; 2021; 129:077003 10.1289/ehp8608
Paternal High-Fat Diet Exposure Induces Adverse Effects on Offspring Health: a Systematic Review of Animal Studies
Gonçalves MdS, Perez GdS, Ferreira LdJD, Santos LSd, Cordeiro GdS, Couto RD, et al. Paternal High-Fat Diet Exposure Induces Adverse Effects on Offspring Health: a Systematic Review of Animal Studies. Brazilian Archives of Biology and Technology. FapUNIFESP (SciELO); 2021; 64 10.1590/1678-4324-2021190123
Epigenetic Reprogramming Mediated by Maternal Diet Rich in Omega-3 Fatty Acids Protects From Breast Cancer Development in F1 Offspring
Abbas A, Witte T, Patterson WL, Fahrmann JF, Guo K, Hur J, et al. Epigenetic Reprogramming Mediated by Maternal Diet Rich in Omega-3 Fatty Acids Protects From Breast Cancer Development in F1 Offspring. Frontiers in Cell and Developmental Biology. Frontiers Media SA; 2021; 9 10.3389/fcell.2021.682593
Maternal fish oil consumption has a negative impact on mammary gland tumorigenesis in C3(1) Tag mice offspring
Ion G, Akinsete JA, Witte TR, Bostan M, Hardman WE. Maternal fish oil consumption has a negative impact on mammary gland tumorigenesis in C3(1) Tag mice offspring. European Journal of Nutrition. Springer Science and Business Media LLC; 2021; 10.1007/s00394-021-02546-8
The association of women’s birth size with risk of molecular breast cancer subtypes: a cohort study
Sandvei MS, Opdahl S, Valla M, Lagiou P, Vesterfjell EV, Rise TV, et al. The association of women’s birth size with risk of molecular breast cancer subtypes: a cohort study. BMC Cancer. Springer Science and Business Media LLC; 2021; 21 10.1186/s12885-021-08027-9
Early-life risk factors for breast cancer - prospective follow-up in the Northern Finland Birth Cohort 1966
Tastula A, Jukkola A, Alakokkare A, Nordström T, Eteläinen S, Karihtala P, et al. Early-life risk factors for breast cancer - prospective follow-up in the Northern Finland Birth Cohort 1966. Cancer Epidemiology Biomarkers & Prevention. American Association for Cancer Research (AACR); 2021;:cebp.1442.2020 10.1158/1055-9965.epi-20-1442
In Utero and Lactational Exposure to an Environmentally Relevant Mixture of Brominated Flame Retardants Induces a Premature Development of the Mammary Glands
Gouesse R, Dianati E, McDermott A, Wade MG, Hales B, Robaire B, et al. In Utero and Lactational Exposure to an Environmentally Relevant Mixture of Brominated Flame Retardants Induces a Premature Development of the Mammary Glands. Toxicological Sciences. Oxford University Press (OUP); 2020; 179:206-219 10.1093/toxsci/kfaa176