Tomatoes are highly recommended for breast cancer
Tomatoes are a rich source of the carotenoids lycopene, α-carotene, and β-carotene, as well as melatonin, the anthocyanidin delphinidin, and the flavanone naringenin, all of which have been found to have anti-cancer activities. Tomatoes have been shown to have anti-oxidant, anti-inflammatory, antimutagenic, and cardioprotective properties. Increased intake of tomatoes is associated with decreased cardiovascular disease and reduced risk of heart attack. Tomato consumption has been found to be associated with reduced risks of cancer of the mouth, breast, lung, stomach, pancreas, prostate, colon, ovary, and endometrium. However, tomatoes or lycopene have been shown not to have significant anticancer effects on renal cell, uterine, ovarian, and bladder cancers.Breast cancer-related effects of eating tomatoes
A number of studies have found an inverse association between breast cancer risk and increasing consumption of tomatoes, components of tomatoes, or vegetables that have high levels of carotenoids (including tomatoes). For example, one study comprising 84,805 postmenopausal women in the Women's Health Initiative Observational Study found that dietary α-carotene, β-carotene, and lycopene were each found to be inversely associated with the risk of ER+/PR+ breast cancer. Another study found that dietary carotenoids inhibit the cancer-promoting effects of both estradiol and genistein (the phytoestrogen found in soy), thereby reducing their harmful effect in hormone-dependent breast cancer. Studies of naringenin, a tomato flavanone, have shown that it also inhibits ER+ breast cancer cell growth and migration in the presence of estradiol. Delphinidin, an anthocyanin found in tomatoes, has been shown to block epidermal growth factor receptor (EGFR) signaling in breast cancer cells (EGFR is expressed at high levels in at least 30% of breast cancers and is associated with a poor prognosis). However, one large study found no association between dietary or plasma lycopene levels and the risk of breast cancer in middle-aged and older women.
Several studies of early-stage breast cancer survivors have found that higher levels of cartenoids in the blood are associated with both lower risk of break cancer recurrence and lower risk of a new primary breast tumor. Another study found that plasma levels of retinol (a form of vitamin A that is a by-product of β-carotene in the body) also are positively associated with breast cancer survival in postmenopausal women.
Several studies have shown that the cardioprotective effect of tomatoes and lycopene extends to reducing the impact of myocardial toxicity from doxorubicin chemotherapy by ameliorating cardiac cell injury.
Additional comments
Cherry tomatoes rank the highest of all tomatoes in lycopene and overall antioxidant content, presumably because of their high ratio of tomato skin to tomato flesh and rich color. However, lycopene is absorbed in greater quantities from cooked tomatoes than fresh tomatoes. The best sources of bioavailable lycopene are tomato paste and tomato sauce. Frying greatly reduces the lycopene content of fresh tomatoes. While tomato ketchup has a relatively low overall carotenoid content compared to fresh tomatoes or tomato sauce, it is a good source of lycopene. However, note that high fructose corn syrup is the second most abundant ingredient in regular ketchup and that versions without this ingredient are available.
Ready-made tomato soups can have high levels of sodium nitrite, a known carcinogen. Check the labels of canned or otherwise pre-made soups and avoid those containing sodium nitrite. The table salt content of such soups can also be acceptably high for those who must limit their sodium intake.
Beta carotene, vitamin A and lycopene should be obtained from food rather than supplements. Generally speaking, synergistic interactions between the biologically active components in a given fruit or vegetable are important to its potential health-related characteristics. Supplementation by β-carotene and lycopene both have been found to be ineffective in reducing the risk of breast cancer. In addition, β-carotene supplementation has been linked to increased risk of lung cancer in high-risk persons and high serum β-carotene concentrations (presumably also resulting from supplementation) have been associated with increased risk of aggressive prostate cancer.
Selected studies
The epigenetic basis of the tumorigenic action of retinoic acid American Association for Cancer Research (AACR) Meeting, April 2010The present study was designed to investigate the role of retinoic acid in the prevention or development of breast cancer. Preformed vitamin A, or retinol, is found in animal foods such as liver and whole milk, and in some fortified processed foods. Certain carotenoids such as beta-carotene are also efficiently converted into retinol. Once retinol is converted into its bioactive form, retinoic acid, it plays important roles in cell division, cell death, and cell differentiation. In the study, retinoic acid was found to regulate a network of tumor suppressor genes governing cell death, proliferation, differentiation, migration, and invasion through retinoic acid receptor alpha. Retinoic acid can exert a double-edged action according the authors: it can either inhibit or promote the formation of cancer according to the functional status of one of its receptors, retinoic acid receptor alpha. In fact, retinoic acid was found capable of exerting a clear tumor-promoting action (concomitant with epigenetic silencing of the tumor suppressor gene network) due to loss/functional inhibition of retinoic acid receptor alpha. This raises the question whether dietary sources of retinoic acid, or retinoic acid precursors, can also promote can development in cells with impaired retinoic acid receptor alpha. To perform the investigation, athymic female nude mice were implanted with subcutaneous xenograft tumors consisting of one of two clonal lines of estrogen receptor alpha positive (ERα+) T47D breast cancer cells: one with a functional retinoic acid receptor alpha-regulated gene network (T47DLXC5) and one without functional retinoic acid receptor alpha (T47DDNC8). The mice were administered a diet with either retinoic acid (5 or 10 mg/kg) or retinol (50 mg/kg) for six weeks. These diets were found to induce opposite effects on xenograft tumor growth, depending on whether the tumor cells had functioning retinoic acid receptor alpha. T47DDNC8 xenograft tumors were stimulated to grow and metastasize to distant sites by both retinoic acid and retinol, whereas the growth of T47DLXC5 xenograft tumors was inhibited by retinoic acid and retinol, and the cells did not become invasive. In breast cancer, retinoic acid receptor alpha function often is impaired due to a variety of upstream causes, including faulty retinoic acid transport by CRABP2 onto the retinoic acid receptor alpha and/or loss of ERα, a pivotal retinoic acid receptor alpha transcriptional regulator. The authors comment that early detection of epigenetic silencing of tumor suppressor genes of the retinoic acid receptor alpha network may be used to prevent tumorigenic effects of dietary sources of retinoic acid.
Circulating Carotenoids, Mammographic Density, and Subsequent Risk of Breast Cancer Cancer Research, November 2009
The present nested case-control study was designed to investigate whether the association between carotenoid consumption and risk of breast cancer is related to mammographic density. High breast density as measured by mammography has been reported to be a powerful indicator of increased breast cancer risk. The study included 604 breast cancer cases and 626 cancer-free controls in the Nurses' Health Study for whom circulating carotenoid (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin) levels had been measured and mammograms obtained prospectively. Using a computer-assisted method to determine mammographic density, circulating carotenoids were not found to be associated with mammographic density. However, mammographic density significantly influenced the association between total circulating carotenoids and risk of breast cancer (P heterogeneity = 0.008). Total circulating carotenoid levels were found to be inversely associated with overall breast cancer risk (P trend = 0.01). Among women in the highest third of mammographic density, total circulating carotenoids were associated with a 50% lower risk of breast cancer (odds ratio = 0.5; 95% confidence interval = 0.3 - 0.8). Similarly, among these women, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were found to be associated with a significant 40% to 50% reduction in risk of breast cancer (P trend < 0.05). On the other hand, no such inverse association was observed between circulating carotenoids and breast cancer risk among study participants with low mammographic density. The authors conclude that plasma levels of carotenoids may play a role in reducing risk of breast cancer, especially among women with high breast density.
Circulating melatonin and the risk of breast and endometrial cancer in women Cancer Letters, August 2009
This review summarizes current findings with respect to melatonin and breast and endometrial cancer. Melatonin appears to have a role in cancer prevention. Laboratory studies indicate that the mechanism of action of melatonin against breast cancer is multi-faceted, including antioxidant, antimitotic, and antiangiogenic activity, as well as effects in the immune system and fat metabolism. Melatonin might be involved in the regulation of tumor growth. Melatonin appears to block estrogen receptor alpha (ERα) and affect aromatase. Epidemiologic studies have found a relationship between night shift work and melatonin production. Both case-control and prospective population studies have linked night shift work with higher breast cancer risk and, more recently, endometrial cancer (also highly sensitive to estrogen). The support for an association between sleep duration and risk of breast cancer is less convincing. The authors comment that additional studies are needed to further delineate the potential of melatonin in cancer prevention.
Longitudinal study of serum carotenoid, retinol, and tocopherol concentrations in relation to breast cancer risk among postmenopausal women American Journal of Clinical Nutrition, May 2009
The current study was designed to evaluate the associations between levels of carotenoids, retinol, and tocopherols in the blood with postmenopausal breast cancer risk. Prospective population studies previously have examined such associations, however, the studies only assessed exposure at one point in time, whereas the present study used both baseline and repeated serum measurements. The study included 6% and 1% subsets of participants in the Women's Health Initiative clinical trials. Serum concentrations of α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein + zeaxanthin, retinol, α-tocopherol, and γ-tocopherol were measured at baseline and at years one, three, and six for the 6% sample. In addition, the 1% group was sampled at baseline and at year three. The association of baseline levels and breast cancer risk was estimated by Cox proportional hazards models. Repeated measurements were also analyzed as time-dependent covariates. Of 5,450 women with baseline measurements, 190 incident cases of breast cancer were found during a median follow-up period of eight years. After multivariable adjustment, risk of invasive breast cancer was found to be inversely associated with baseline serum α-carotene concentrations (hazard ratio for highest compared with the lowest third: 0.55; 95% CI: 0.34 - 0.90; P = 0.02). However, the risk of breast cancer was found to be positively associated with baseline lycopene levels (hazard ratio: 1.47; 95% CI: 0.98, 2.22; P = 0.06). Analysis of repeated measurements showed that α-carotene and β-carotene were inversely associated with risk of breast cancer and that γ-tocopherol was associated with increased risk. The authors conclude that this study adds to the evidence of an inverse association of specific carotenoids with breast cancer. They note that the unexpected positive associations observed for lycopene and γ-tocopherol require confirmation.
Longitudinal Biological Exposure to Carotenoids Is Associated with Breast Cancer–Free Survival in the Women's Healthy Eating and Living Study Cancer Epidemiology, Biomarkers & Prevention, February 2009
Some population studies have found a diet high in vegetables to be associated with less likelihood of recurrence in breast cancer survivors. Carotenoids, which are found primarily in vegetables and fruit, are thought to have biological activities that may specifically reduce the progression of breast cancer. The present study was designed to examine the relationship between plasma carotenoids at enrollment and at points in time one, two or three, four, and six years, and breast cancer-free survival. Cases were 3,043 participants in the Women's Healthy Eating and Living Study who had been diagnosed with early-stage breast cancer. The primary end point was time to either a second breast cancer recurrence or a new primary breast cancer. The analysis was adjusted for prognostic and other confounding factors. 508 (16.7%) breast cancer events (recurrence or new primary breast cancer) took place over a median 7.12 years of follow up. Compared with the lowest third, the hazard ratio for the medium/high plasma carotenoid tertiles was 0.67 (95% confidence interval, 0.54-0.83). The authors conclude that higher biological exposure to carotenoids was associated with greater likelihood of breast cancer–free survival when assessed over the time frame of the study.
Plasma Retinol and Prognosis of Postmenopausal Breast Cancer Patients Cancer Epidemiology, Biomarkers & Prevention, January 2009
The current prospective study was designed to assess the long-term prognostic role of retinol (vitamin A) plasma levels in postmenopausal breast cancer patients. Beta-carotene is broken down in the body to retinol. The cases were 208 postmenopausal women operated on for T1-2N0M0 early stage breast cancer who participated in a chemoprevention trial as controls and did not receive chemotherapy or hormone therapy. Blood samples were collected at a median of three months post surgery. Minimum and median follow-up were at 12 and 15 years, respectively (assuming survival). The main analyses were performed on all women and on also a subgroup aged 55 years (and assumed too far along in years to be in perimenopause). The main end point was death from breast cancer and the results were stratified for age (where relevant) and recruitment period, and adjusted for tumor size and histology. At the 12-year mark, patients with low levels of plasma retinol (< 2.08 µmol/L, median of distribution) were found to have lower rates of breast cancer survival than those with high retinol (log-rank P = 0.052); the difference was statistically significant for women 55 years (log-rank P = 0.006). The adjusted hazard ratios for low versus high levels of retinol were 2.11 (95% confidence interval, 1.08-4.14) for all women and 3.58 (95% confidence interval, 1.50-8.57) for those 55 years. The authors conclude that low plasma retinol strongly predicts poorer prognosis in postmenopausal breast cancer patients.
Selected antioxidants and risk of hormone receptor–defined invasive breast cancers among postmenopausal women in the Women's Health Initiative Observational Study American Journal of Clinical Nutrition, April 2008
The present study was designed to evaluate the association between dietary and supplemental intakes of carotenoids and vitamins C and E and the risk of breast cancer according to estrogen receptor (ER) and progesterone receptor (PR) status. The study group included 84,805 postmenopausal women in the Women's Health Initiative Observational Study. During an average follow-up period of 7.6 years, there were 2,879 new cases of invasive breast cancer, of which 2,509 had receptor data. Dietary α-carotene (highest versus lowest quintile: RR = 0.83; 95% CI = 0.70- 0.99; P for trend = 0.019), β-carotene (highest versus lowest quintile: RR = 0.78; 95% CI = 0.66-0.94; P = 0.021), and lycopene (highest versus lowest quintile: RR = 0.85; 95% CI = 0.73-1.00; P = 0.064) were each found to be inversely associated with the risk of ER+/PR+ breast cancer, but not with other breast cancer groups as defined by ER and PR status. Total or supplemental β-carotene and dietary intakes of lutein+zeaxanthin and β-cryptoxanthin were not found to be associated with breast cancers defined by ER and PR status. Vitamin E (regardless of source) and dietary vitamin C were found not to be associated with breast cancer. However, both total (dietary plus supplemental) and supplemental vitamin C intake were found to be weakly positively associated with breast cancer. The authors conclude that dietary intake of certain carotenoids might be differentially associated with risk of invasive breast cancers jointly defined by ER and PR status among postmenopausal women.
Comparisons of food intake between breast cancer patients and controls in Korean women Nutrition Research and Practice, September 2007
The current case-control study was designed to compare the diets of a group of Korean breast cancer patients with a healthy control group. The cases included 97 women with newly confirmed diagnoses of breast cancer at the inpatient or outpatient clinic of Yeouido St. Mary’s Hospital in Seoul, and excluded women with any history of liver diseases, diabetes mellitus, respiratory disorders and cardiovascular diseases. The 97-person control group also excluded women with known malignant, hormonal, gynecological or endocrine diseases. Intake of nutrients in 117 food items were estimated in the breast cancer patients and age-matched healthy controls using a quantitative food frequency questionnaire administered by a trained dietitian. The questionnaire also included general information (age, sex and marital status), age at menarche, and pregnancy history. It was found that the average caloric intake of the breast cancer patients and the healthy controls did not differ significantly. However, the breast cancer patients consumed significantly less fat and antioxidant nutrients such as vitamin A, retinol, beta-carotene, vitamin C and vitamin E than did the controls. Consumption of eggs (p<0.01), legumes (p<0.05), vegetables (p<0.05), seasonings (p<0.001), and oils and fats (p<0.01) was significantly lower in the breast cancer patients. However, the level of energy from fat is relatively low in Korean patients compared to their Western counterparts, and fat consumption may not be an independent risk factor at this level of intake. With respect to particular foods, in addition to eggs, the breast cancer patients consumed a significantly lower quantity of bean curd (tofu), onion, garlic, green pepper, sweet pepper, kale, cucumber, seasoned bean sprouts, sesame leaf, zucchini, radish, mushroom, crown daisy, red pepper paste, bean paste, spicy bean paste, orange juice, grape juice, and tomato juice than the controls. On the other hand, the breast cancer patients consumed significantly greater quantities of cooked rice, noodles, deep fried chicken, satsuma mandarin, Korean melon, kimchi and coffee than the controls. The authors conclude that since the breast cancer patients consumed less soy and vegetables, they had a lower intake than the controls of rich sources of antioxidant nutrients, phytosterols, fiber and non-nutritional components that may reduce the risk of cancer. In addition, the breast cancer patients in this study consumed lower quantities of red pepper paste, bean paste and spicy bean paste, causing their intake of pepper flavonols (which may have a protective effect on breast cancer risk) to be lower than that of the controls.
Lycopene and other carotenoids inhibit estrogenic activity of 17β-estradiol and genistein in cancer cells Breast Cancer Research and Treatment, August 2007
Population studies have found that carotenoid consumption is associated with lower risk of several types of cancer, including breast and endometrial cancers. Estrogens are the most important risk factors for these types of cancer. Genistein, a phytoestrogen found mainly in soy, has been found to have significant estrogenic activity at concentrations found in human blood. The present study was designed to determine whether the carotenoids lycopene, phytoene, phytofluene, and β-carotene inhibit signaling of steroidal estrogen and phytoestrogen, activity which could help explain their cancer preventive role. Treatment of MCF-7 and T47D breast cancer cells and ECC-1 endometrial cancer cells with genistein was found to induce cell proliferation, cell-cycle progression and transactivation of the estrogen response element (ERE). The actions were similar to the known effects of 17β-estradiol in promoting cancer. Each of the tested carotenoids were found to inhibit cancer cell proliferation induced by 17β-estradiol and genistein. Lycopene's inhibition of cell growth was found to be accompanied by a slowdown of G1 to S phase cell-cycle progression. Additionally, the carotenoids inhibited estrogen-induced transactivation of the estrogen response element that was mediated by both estrogen receptors (ERα and ERβ). Whether this inhibition resulted from competition of carotenoid-activated transcription systems with the ERE transcription system was tested. Although cotransfection of endometrial and breast cancer cells with four different coactivators (SRC-1, SRC-2, SRC-3, and DRIP) strongly stimulated ERE reporter gene activity, it did not act to oppose the inhibitory effect of the carotenoids. The authors conclude that dietary carotenoids inhibit estrogen signaling of both 17β-estradiol and genistein, and reduce their harmful effect in hormone-dependent malignancies.
Whole-Food Sources of Vitamin A More Effectively Inhibit Female Rat Sexual Maturation, Mammary Gland Development, and Mammary Carcinogenesis than Retinyl Palmitate Journal of Nutrition, June 2007
The current study examined the effects of vitamin A within a human food-based diet (i.e., whole food diet) on sexual maturation, mammary gland development, and sensitivity to carcinogenesis in laboratory rats. A prior study using an adolescent rat model for breast cancer found an increase in mammary tumor occurrence in animals fed a chemopreventive dose of vitamin A. Animal models for nutrient-cancer interactions using strictly defined diets do not replicate the complexity of the human diet and may not be adequate to investigate food patterns associated with cancer risk in humans. Starting at age 20 days, female rats were fed either a whole-food diet with adequate levels of vitamin A (control diet), a diet with a 5.5-fold increase in vitamin A from fruits and vegetables, or a diet with a 6.2-fold increase in vitamin A provided as retinyl palmitate. The dietary intervention period was from age 20 days to age 63 days in order to determine the effect of the diets on pubertal mammary gland development. On day 66, the rats were injected with the mammary carcinogen 1-methyl-1-nitrosourea. Compared with adolescent rats that consumed the control diet, consumption of the fruits and vegetables and vitamin A diets were found to reduce mammary tumor multiplicity (relative risk 0.7, P 0.002), which was associated with a decrease in alveolar gland development. The fruits and vegetables diet suppressed the onset of sexual maturation (P < 0.001) and inhibited markers of mammary alveologenesis more than the vitamin A diet. The authors conclude that the amount and source of vitamin A consumed by adolescent female rats can influence the onset of puberty, mammary gland alveolar development, and breast cancer risk. The study highlights the relevance of using whole-food diets to evaluate the impact of dietary factors in cancer prevention.
Fruits, vegetables, soy foods and breast cancer in pre- and postmenopausal Korean women: a case-control study International Journal for Vitamin and Nutrition Research, March 2007
The present Korean case-control study was designed to examine the relationship between fruit, vegetable, and soy intake and the risk of breast cancer. The study subjects consisted of 359 breast cancer cases and 708 hospital-based controls selected from the same hospitals. Usual dietary habits were determined using a semi-quantitative 98-item food frequency questionnaire. Odds ratios (OR) and 95% confidence intervals (95% CI) were determined by unconditional logistic regression after adjusting for menopausal status. In premenopausal women, high tomato consumption was found to be associated with lower breast cancer risk (OR = 0.59, 95% CI = 0.38-0.89, p for trend = 0.04). In postmenopausal women, high grape consumption was found to be associated with lower breast cancer risk (OR = 0.59, 95% CI = 0.35-0.95; p for trend = 0.05), as was high green pepper consumption (OR = 0.60, 95% CI = 0.43-0.96, p for trend = 0.03) and high soybean intake (OR = 0.61, 95% CI = 0.34-0.89, p for trend = 0.02). The authors conclude that high intake of some fruits, vegetables, and soybeans may be associated with reduced breast cancer risk.
Naringenin inhibits cell growth and migration in human breast cancer cell lines The FASEB Journal, 2007 21:848.5
Naringenin is a flavanone which has been reported to have anti-proliferative effects in many cancer cell lines and to induce apoptosis via activation of NF-B. Naringenin is especially abundant in the Mediterranean diet (in citrus fruits and tomatoes). Previous studies have reported that naringenin has both estrogen agonistic and antagonistic activities in distinct cell types. Given that estrogens are cell growth promoters, the goal of the present study was to examine the effects of naringenin using MCF-7 estrogen receptor-dependent (ER+/ERß+) and SKBR-3 estrogen receptor-independent (ER–/ERß–) human breast cancer cell lines. Although cell viability was not affected by naringenin alone at any concentration used in either cell line (concentrations tested varied from 1 µM to 100 µM), incubation of cells with naringenin together with 1nM 17ß-estradiol resulted in decreased viability of MCF-7 cells but not of SKBR-3 cells. These findings are in accordance with previous findings in the literature, suggesting that naringenin's activity depends on the presence or absence of estrogen receptors (ER). Cell migration was also found to be affected by incubation with 10 µM naringenin. The authors conclude that naringenin exerts inhibitory effects on breast cancer cell growth and migration, and that these effects might be mediated by the presence of ER.
Micellar oleic and eicosapentaenoic acid but not linoleic acid influences the β-carotene uptake and its cleavage into retinol in rats Molecular and Cellular Biochemistry, August 2006
The current study was designed to investigate the influence of oleic, linoleic and eicosapentaenoic acids on the bioavailability of β-carotene, including plasma β-carotene response and its conversion to retinol (vitamin A). The study was conducted by using single (9 hour time course) and repeated (10 days) dose administrations in rats. After a single dose, the levels of plasma β-carotene and retinyl palmitate in the oleic acid and eicosapentaenoic acid groups were higher by 13, 7 and 11, 6 folds than in the linoleic acid group (p < 0.05). The liver β-carotene level in the oleic acid and eicosapentaenoic acid groups were higher by 3 and 1.2 folds than in the linoleic acid group (p < 0.05). After 10 days' repeated dose, the plasma β-carotene and retinyl palmitate levels in oleic acid (6.2%, 51.7%) and eicosapentaenoic acid (25.4%, 17.23%) groups were higher than in the linoleic acid group (p < 0.05). The liver β-carotene level in oleic acid (21.2%) and eicosapentaenoic acid (17.6%) groups also were higher than in the linoleic acid group (p < 0.05). In both the experiments, the activity of β-carotene 15,15′-dioxygenase in the intestinal mucosa and plasma triglyceride levels were also found to be higher in the oleic acid and eicosapentaenoic acid groups than in the linoleic acid group. β-carotene excreted through the urine and feces of the oleic acid and eicosapentaenoic acid groups was lower than that of the linoleic acid group. The authors conclude that the results demonstrate an improved absorption and metabolism of β-carotene when fed a diet supplemented with oleic acid or eicosapentaenoic acid compared to linoleic acid.
Dietary and Plasma Lycopene and the Risk of Breast Cancer Cancer Epidemiology, Biomarkers & Prevention, May 2005
Based on laboratory and observational studies, lycopene is thought to be potentially effective in the prevention of breast cancer. The present prospective cohort study of 39,876 women initially free of both cardiovascular disease and cancer was designed to evaluate this theory. Study participants completed a baseline food frequency questionnaire and provided information regarding their breast cancer risk factors. The women were divided into quintiles based on their dietary level of lycopene and lycopene food sources were recorded. During 9.9 years of follow-up, 1,076 of the women developed breast cancer. Women with increasing quintiles of dietary lycopene had multivariate relative risks (RR) of breast cancer of 1.00 (reference), 0.95, 1.00, 1.10, and 1.00 (P, linear trend = 0.71). Women consuming fewer than 1.5, 1.5 to under 4, 4 to lunder 7, 7 to under 10, and 10 servings per week of tomato-based products had RRs of 1.00 (reference), 1.00, 1.20, 1.18, and 1.16 (P, linear trend = 0.11). Neither of these trends were statistically significant. No individual lycopene food sources were found to be associated with breast cancer. In a nested case-control study, 508 breast cancer cases and 508 controls were matched by age, smoking, and follow-up time. Lycopene and other carotenoids in the blood were measured. Women in increasing quartiles of plasma lycopene had multivariate RRs of breast cancer of 1.00 (ref), 0.95, 1.15, and 0.93 (P, linear trend = 0.86), again not statistically significant. Nor were other carotenoids associated with breast cancer. The authors conclude that neither higher dietary nor plasma lycopene levels were associated with a reduced risk of breast cancer in middle-aged and older women.
Plasma Carotenoids, Retinol, and Tocopherols and Risk of Breast Cancer American Journal of Epidemiology, January 2005
The present nested case-control prospective study of women enrolled in the Nurses’ Health Study was designed to assess the associations between plasma α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein/zeaxanthin, retinol, α-tocopherol, and γ-tocopherol and the risk of breast cancer. 969 cases of breast cancer diagnosed after blood had been drawn and prior to June 1998 were individually matched to controls. The multivariate risk of breast cancer was found to be 25% to 35% lower for women with the highest fifth of plasma α-carotene compared to that for subjects with the lowest quintile of α-carotene (odds ratio (OR) = 0.64, 95% confidence interval (CI): 0.47- 0.88; ptrend (p) = 0.01). Similar but less powerful results were found for β-carotene (OR = 0.73, CI: 0.53-1.02; p = 0.01), lutein/zeaxanthin (OR = 0.74, CI: 0.55-1.01; p = 0.04), and total carotenoids (OR = 0.76, CI: 0.55-1.05; p = 0.05). The inverse association observed between α-carotene intake and breast cancer was found to be greater for invasive cancers with nodal metastasis. The authors conclude that consumption of some carotenoids are inversely associated with the risk of breast cancer. However, although the association was strongest for α-carotene, the high degree of collinearity among the various carotenoids prevented them from concluding that this association was specific to any individual carotenoid.
Fruits, Vegetables, and Micronutrients in Relation to Breast Cancer Modified by Menopause and Hormone Receptor Status Cancer Epidemiology, Biomarkers & Prevention, September 2004
The present population-based case-control study was designed to determine whether fruit, vegetable, and antioxidant micronutrient consumption was associated with a reduction in breast cancer incidence. Included were 1,463 breast cancer cases and 1,500 controls. Participants completed a food frequency questionnaire, which enabled assessment of the frequency and amount of 13 fruits and fruit juices and 16 vegetables. Also recorded was any use of multiple or single vitamin supplements. Included in the analysis was menopausal status and the clinical characteristics of the breast cancer cases. After controlling for age and energy intake, it was found that for postmenopausal women, the risk of breast cancer was lower for the highest quintile compared to the lowest quintile of consumption of any vegetables [odds ratios (OR), 0.63; 95% confidence intervals (CI), 0.46–0.86; P for trend (P) < 0.01] and leafy vegetables [OR=0.66; CI, 0.50–0.86; P = 0.03]. Adjusted ORs (95% CIs) were also lower for postmenopausal breast cancer in relation to high intake of carotenoids, α-carotene, ß-carotene, lutein, and, notably, lycopene [OR=0.66; CI, 0.48–0.90; P = 0.03]. Inverse associations for fruits and vegetables were strongest for postmenopausal women with estrogen receptor positive (ER+) tumors (OR=0.65; CI, 0.51–0.82) rather than ER– tumors (OR=0.92; CI, 0.64–1.32), but results were less consistent for micronutrients. No similar associations were observed among premenopausal women. Odds ratios did not appreciably differ by whether the cases were in situ or invasive breast cancer or by whether the cases had begun chemotherapy. The authors conclude that there is an inverse association between fruit and vegetable intake and breast cancer risk among postmenopausal but not premenopausal women and that this association may be stronger for women with ER+ tumors.
