Growth patterns and the risk of breast cancer in women

The Dutch famine and its long-term consequences for adult health

Small size at birth is linked with an increased risk of chronic diseases in later life. Poor maternal nutrition during gestation may contribute to restricted fetal growth, leading to increased disease susceptibility in later life. Animal studies have shown that undernutrition during gestation is associated with reduced life span and increased disease susceptibility. The Dutch famine is a unique counterpart for animal models that study the effects of restricted maternal nutrition during different stages of gestation. This paper describes the findings from a cohort study of 2414 people born around the time of the Dutch famine. Exposure to famine during any stage of gestation was associated with glucose intolerance. We found more coronary heart disease, a more atherogenic lipid profile, disturbed blood coagulation, increased stress responsiveness and more obesity among those exposed to famine in early gestation. Women exposed to famine in early gestation also had an increased risk of breast cancer. People exposed to famine in mid gestation had more microalbuminuria and obstructive airways disease. These findings show that maternal undernutrition during gestation has important effects on health in later life, but that the effects on health depend on its timing during gestation. Especially early gestation seems to be a vulnerable period. Adequate dietary advice to women before and during pregnancy seems a promising strategy in preventing chronic diseases in future generations.

Estrogen and -Fetoprotein Levels in Maternal and Umbilical Cord Blood Samples in Relation to Birth Weight

Birth weight has been associated with a subsequent risk of breast cancer. The present study examined associations between birth weight and pregnancy estrogens and alpha-fetoprotein (AFP). The concentrations of estradiol, estriol, and AFP were measured in maternal and umbilical cord blood samples from 194 women during pregnancy and at birth. Birth weight was significantly positively correlated with maternal serum estradiol and estriol levels in the 29th week (estradiol: r = 0.16, P = 0.03; estriol: r = 0.29, P = 0.001) and at delivery (estradiol: r = 0.20, P = 0.01; estriol: r = 0.41, P < 0.0001) after controlling for covariates. The umbilical cord estriol level was moderately but significantly correlated with birth weight (r = 0.15, P = 0.049). There was no significant association between umbilical cord serum estradiol and birth weight. There was no significant association between birth weight and maternal serum AFP in any gestational week. Umbilical cord AFP was significantly inversely correlated with birth weight (r = -0.16, P = 0.04). Umbilical cord AFP was unrelated to cord levels of estradiol and estriol. The data suggested a greater exposure to estriol and a lower exposure to AFP among high birth weight babies.

Timing of puberty determines serum insulin-like growth factor-I in late adulthood

CONTEXT

IGFs may play an important role in disease etiology, especially cancer. Changes in diet can alter acute levels, but little is known about life course influences on IGF levels.

OBJECTIVE

The objective of the study was to examine the association between timing of puberty and adulthood serum IGFs (IGF-I and IGF binding protein-3).

DESIGN

This was a retrospective cohort study.

SETTING

Male pupils who attended a single school in Southern England were part of the study.

PARTICIPANTS

Participants in the study were a cohort of 1028 men born between 1927 and 1956 with anthropometric measures between 9 and 18 yr and adulthood serum IGF levels.

MAIN OUTCOME MEASURE

The study measured serum IGF-I and IGF binding protein-3 at mean age 63 yr.

RESULTS

Age at peak height velocity (APHV) was inversely associated with adult IGF-I levels. IGF-I decreased by 3.7 ng/ml (95% confidence interval 1.0-6.4, P = 0.007) for each sd increase in APHV. Prepubertal childhood height and body mass index were both inversely associated with APHV (P trend < 0.001). APHV was positively associated with adult height and inversely associated with adult body mass index. Adjustment for childhood, adult anthropometry, and other lifestyle factors did not substantially alter the association between APHV and adult IGF-I.

CONCLUSIONS

This is the first study to document an association between timing of puberty and adult IGF-I levels. A better understanding of life course determinants of the IGF system may provide new insights into disease etiology and primary prevention.

Adult height, age at attained height, and incidence of breast cancer in premenopausal women

Adult height has been positively associated with breast cancer risk in epidemiologic studies, and recent evidence suggests that the timing and rate of growth may also influence risk. We examined both adult height and age at attained height, an indicator of the timing of the pubertal growth spurt, in relation to incidence of premenopausal breast cancer in the Nurses' Health Study II. Participants were 108,829 premenopausal women who reported their height in 1989; of these, 37,572 provided information on their age at attained height on a later supplementary questionnaire. During 12 years of follow-up, 1,041 cases of invasive breast cancer were identified (402 with age at attained height). Cox proportional hazards models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). Adult height was positively associated with breast cancer incidence; the multivariate RR for participants 1.75 m or taller compared to those shorter than 1.60 m was 1.57 (95% CI: 1.23-2.01, p trend < 0.0001), and each 5-cm increment corresponded to an 11% increase in risk (95% CI: 6-17%). There was no overall association for age at attained height, however, with a multivariate RR of 0.96 (95% CI: 0.66-1.39) for women who attained their maximum height at age 18 or older compared to those who reached it before age 14 (p trend = 0.65). These results confirm previous findings that taller adult height is associated with increased risk of premenopausal breast cancer but do not provide evidence that age at attained height is related to risk.

The sensitivity of the child to sex steroids: possible impact of exogenous estrogens

The current trends of increasing incidences of testis, breast and prostate cancers are poorly understood, although it is assumed that sex hormones play a role. Disrupted sex hormone action is also believed to be involved in the increased occurrence of genital abnormalities among newborn boys and precocious puberty in girls. In this article, recent literature on sex steroid levels and their physiological roles during childhood is reviewed. It is concluded that (i) circulating levels of estradiol in prepubertal children are lower than originally claimed; (ii) children are extremely sensitive to estradiol and may respond with increased growth and/or breast development even at serum levels below the current detection limits; (iii) no threshold has been established, below which no hormonal effects can be seen in children exposed to exogenous steroids or endocrine disruptors; (iv) changes in hormone levels during fetal and prepubertal development may have severe effects in adult life and (v) the daily production rates of sex steroids in children estimated by the Food and Drug Administration in 1999 and still used in risk assessments are highly overestimated and should be revised. Because no lower threshold for estrogenic action has been established, caution should be taken to avoid unnecessary exposure of fetuses and children to exogenous sex steroids and endocrine disruptors, even at very low levels.

Diet during pregnancy and levels of maternal pregnancy hormones in relation to the risk of breast cancer in the offspring

Birth weight is positively associated with the risk of breast cancer in the offspring and the underlying process is likely to involve the pregnancy endocrine milieu. We have examined the association of diet and related factors during pregnancy with the levels (at the 16th and 27th gestational week) of maternal pregnancy oestradiol, oestriol, sex hormone-binding globulin (SHBG), progesterone and prolactin, in a cohort of 270 Caucasian women who delivered in a major hospital in Boston, USA. Oestradiol and oestriol were not strongly associated with any of the diet-related variables, but SHBG was significantly and consistently related inversely to pre-pregnancy body mass index and weight gain during pregnancy, and positively to vegetable and pulses intake. Pregnancy progesterone was associated positively with alcohol and inversely with polyunsaturated lipid and vitamin B12 intake, whereas pregnancy prolactin was inversely associated with cereal consumption. If the pregnancy hormones studied are indeed involved in the intra-uterine origin of breast cancer, these findings, if confirmed, would focus dietary advice to pregnant women, with a view to reducing the risk of breast cancer in the offspring, towards avoidance of excess energy intake and an emphasis on plant foods. This advice does not contradict current dietary advice on prudent diet during pregnancy and throughout life.

Early life factors and incidence of proliferative benign breast disease

Proliferative benign breast disease is a marker of increased breast cancer risk, yet little is known about its etiology. Most studies of benign breast disease have focused only on risk factors in adulthood, despite growing evidence that factors in early life influence breast cancer risk. We explored the relations of several early life factors with incidence of proliferative benign breast disease among 71,896 premenopausal women in the Nurses' Health Study II who recalled their body fatness at young ages, physical activity in adolescence, birthweight, and history of being breastfed. Between 1991 and 1997, 901 of these women were identified as having proliferative benign breast disease from a centralized pathology review. Relative risks (RR) and 95% confidence intervals (95% CI) were estimated from Cox proportional hazards models. Greater childhood body fatness (ages 5-10) was associated with decreased risk of proliferative benign breast disease; the multivariate RR (95% CI) for the most overweight compared with the most lean was 0.61 (0.44-0.86; P(trend) < 0.0001) and remained significant after adjustment for current body mass index. Body mass index at age 18 was also inversely associated with incidence of proliferative benign breast disease, with a multivariate RR (95% CI) of 0.67 (0.52-0.88) for those who were > or =25 kg/m(2) compared with those who were <19 kg/m(2) (P(trend) = 0.001). There were no clear associations for physical activity in adolescence, birthweight, or being breastfed. These results indicate that premenopausal women who were heavier at young ages have lower incidence of proliferative benign breast disease, consistent with previous findings for breast cancer.

Does growth hormone cause cancer?

The ability of GH, via its mediator peptide IGF-1, to influence regulation of cellular growth has been the focus of much interest in recent years. In this review, we will explore the association between GH and cancer. Available experimental data support the suggestion that GH/IGF-1 status may influence neoplastic tissue growth. Extensive epidemiological data exist that also support a link between GH/IGF-1 status and cancer risk. Epidemiological studies of patients with acromegaly indicate an increased risk of colorectal cancer, although risk of other cancers is unproven, and a long-term follow-up study of children deficient in GH treated with pituitary-derived GH has indicated an increased risk of colorectal cancer. Conversely, extensive studies of the outcome of GH replacement in childhood cancer survivors show no evidence of an excess of de novo cancers, and more recent surveillance of children and adults treated with GH has revealed no increase in observed cancer risk. However, given the experimental evidence that indicates GH/IGF-1 provides an anti-apoptotic environment that may favour survival of genetically damaged cells, longer-term surveillance is necessary; over many years, even a subtle alteration in the environmental milieu in this direction, although not inducing cancer, could result in acceleration of carcinogenesis. Finally, even if GH/IGF-1 therapy does result in a small increase in cancer risk compared to untreated patients with GH deficiency, it is likely that the eventual risk will be the same as the general population. Such a restoration to normality will need to be balanced against the known morbidity of untreated GH deficiency.

Seizing the moment: California's opportunity to prevent nutrition-related health disparities in low-income Asian American population

Asian Americans and Pacific Islanders (AAPI) have the fastest growing rate of overweight and obese children. Aggressive programs are urgently needed to prevent unhealthy acculturation-related changes in diet and physical activity and to promote the healthier aspects of traditional lifestyle habits. We conducted focus groups and key informant interviews to explore knowledge, attitudes, dietary practices, and physical activity levels among three low-income Asian American ethnic groups, Chinese, Vietnamese, and Hmong, in California. Content analysis was used to identify similarities and differences among the groups. Several common health beliefs clearly emerged. Participants noted the importance of fresh (not frozen) fruit and vegetable consumption and physical activity for general health. The concept of good health included having a harmonious family, balance, and mental and emotional stability. All groups also expressed the general belief that specific foods have hot or cold properties and are part of the Yin/Yang belief system common to Asian cultures. The lure of fast food, children's adoption of American eating habits, and long work hours were identified as barriers to a healthy, more traditional lifestyle. A California campaign for Asian Americans using multilevel strategies is recommended to counter the alarming rise of obesity among AAPI youth. Strategies directed to individual, community, and policy levels should emphasize maintenance of healthy traditional diets, informed selection of mainstream U.S. foods, and promotion of active lifestyles to prevent an impending burden from cancer and nutrition-related chronic diseases in AAPI populations.

Adult mortality at age 57 after prenatal exposure to the Dutch famine

Prenatal famine exposure has previously been shown to be associated with cardiovascular disease and type II diabetes in adulthood. In the current study, we could not demonstrate an effect of prenatal exposure to famine in 2254 term singletons born during the 1944-1945 Dutch famine on adult mortality up to the age of 57 years. Follow-up of this cohort will resolve whether famine exposure is linked to increased adult mortality.

Enhanced tumorigenesis in p53 knockout mice exposed in utero to high-dose vitamin E

The limited antioxidative capacity of the embryo and fetus may increase their risk for cancer initiation and/or promotion by reactive oxygen species (ROS)-mediated oxidative DNA damage and/or signaling. To determine if cancer can originate in utero, a high dietary dose of the antioxidant vitamin E (VE) (10% dl-alpha-tocopherol-acetate) was given to cancer-prone p53 knockout mice throughout pregnancy. Although reducing fetal death (P < 0.05), in utero exposure to VE enhanced postnatal tumorigenesis in both +/- (P < 0.04) and -/- (P < 0.0008) p53-deficient offspring. VE did not alter maternal weights, offspring p53 genotypic distribution or tumor spectrum. Constitutive embryonic DNA oxidation in untreated -/- p53 embryos [gestational day (GD) 13] was higher than in +/- and +/+ p53 littermates (P < 0.05). VE reduced DNA oxidation in -/- p53 embryos (P < 0.05) without affecting +/- and +/+ p53 littermates. VE had contrasting, tissue-dependent effects on fetal (GD 19) DNA oxidation, with reductions in -/- and +/- p53-deficient fetal brains (P < 0.01), increases in skin (P < 0.05) and no effect in liver and thymus. The 250-fold increase in dietary VE levels produced only 1.6-6.3-fold, tissue-dependent increases in tissue concentrations. The greatest increase, in fetal skin, correlated with increased DNA oxidation in that tissue in -/- and +/- p53-deficient fetuses and enhanced tumorigenesis in these genotypes. These results show that some cancers may originate in utero and the risk can be enhanced by embryonic and fetal exposure to high dietary levels of VE. The elevated DNA oxidation in some tissues of untreated -/- p53 offspring suggests that ROS may contribute to their higher baseline tumor incidence. The limited and tissue-dependent disposition of VE indicates substantial conceptal regulation. The similarly selective and contrasting effects of VE on DNA oxidation may contribute to its controversial protective efficacy and suggest that its effects on tumorigenesis are cell-specific, possibly in high doses involving a pro-oxidative mechanism.

Growth in precocious puberty

Growth in precocious puberty is a subject of concern to families and clinicians alike. The definition of precocious puberty and the role of obesity in the age of onset have also been areas of debate since the Lawson Wilkins Society recommended a lowering of the age of onset of precocious puberty in US girls. An understanding of growth patterns in normal children with earlier or later onset of puberty and the variable rate of progression between individuals with central precocious puberty as well as the imprecision in available height prediction methods are important in assessing height outcomes in this condition. In the absence of randomised controlled trials in this area, only qualified conclusions about the effectiveness of interventions can be drawn. In general, it appears that height outcome is not compromised in untreated slowly progressive variants of central precocious puberty. In rapidly progressing central precocious puberty in girls, gonadotrophin releasing hormone agonists (GnRH agonists) appear to increase final height by about 5 cm in girls treated before the age of eight, but there is no height benefit in those treated after eight years. Scanly data is available to assess treatment effects in boys. GnRH agonists appear to be relatively safe. The decision to treat central precocious puberty should take into account rate of progression of pubertal changes as well as biochemical markers and may need to address other factors (for example psychosocial and behavioural issues) as well as height outcome.

Epidemiology and the causes of breast cancer

This article describes the characteristics of 3 dominant features of breast cancer epidemiology. These characteristics include the association of disease risk with childbearing, its relationship to ovarian activity and its international variation (particularly as the latter differs in the years before and after menopause). Equivocal tests of one hypothesis that reconciled some of these features through variations in levels of the fractions of estrogen are described. Other hypotheses with a similar objective are needed. The 3 known causes of human breast cancer, ionizing radiation, exogenous ovarian hormones and beverage alcohol, offer some preventive possibilities but do little to explain the epidemiologic features of the majority of cases of the disease that occur in their absence.

Prevalence and incidence of precocious pubertal development in Denmark: an epidemiologic study based on national registries

OBJECTIVE

To our knowledge, no population-based epidemiologic studies on the incidence and prevalence of precocious pubertal development have been published. Danish national registries provide sufficient data for estimating the prevalence and incidence of this condition. The aim of this study was to estimate the prevalence and incidence of precocious pubertal development in Denmark in a 9-year period.

METHODS

The age- and gender-specific incidence rates as well as prevalence rates of precocious pubertal development in Denmark were estimated using data from the Danish National Patient Registry and Statistics Denmark from 1993 to 2001.

RESULTS

Overall, 670 children with precocious pubertal development were registered with a diagnosis of precocious puberty (PP) from 1993 to 2001, corresponding to 50 to 70 new cases of PP per year in Denmark. The incidence of PP was constant during the study period from 1993 to 2001. The incidence of PP subdivided by gender and age at diagnosis was approximately 0.5 per 10000 in girls who were younger than 2 years, decreasing to levels below 0.05 per 10000 in girls aged 2 to 4 years, thereafter gradually rising to 8 per 10000 for girls aged 5 to 9 years. For boys who were younger than 8 years, the incidence was very low (<1 per 10000) and increased only slightly to 1 to 2 per 10000 in boys aged 8 to 10 years. The prevalence of PP was approximately 20 to 23 per 10000 in girls, whereas the prevalence was fivefold lower for boys (<5 per 10000).

CONCLUSIONS

From this first epidemiologic study based on national registries, we estimated that 0.2% of all Danish girls and <0.05% of Danish boys had some form of precocious pubertal development.

Mechanisms mediating the effects of prepubertal (n-3) polyunsaturated fatty acid diet on breast cancer risk in rats

Dietary exposures during childhood may influence later breast cancer risk. We tested in an animal model the hypothesis that prepubertal intake of (n-3) PUFAs, present mainly in fish, reduces susceptibility to breast cancer. Between postnatal days 5 to 25, rat pups were fed (n-3) PUFA-containing diets at a 2:1 ratio of (n-6):(n-3) PUFAs (typical of prehistoric societies) or a control (n-6) PUFA diet at a 17:1 ratio of (n-6):(n-3) PUFAs (comparable with current Western societies). These fatty acids were given in a low- or high-fat context (16 or 39% energy from fat). The low-(n-3) PUFA diet reduced while the high-(n-3) PUFA diet increased carcinogen-induced mammary tumorigenesis. The low-(n-3) PUFA diet reduced mammary cell proliferation and increased apoptosis, particularly in the terminal end buds (the mammary source of malignant breast tumors). The high-(n-3) PUFA diet had opposite effects on these 2 key biomarkers and increased phospho-Akt levels, a survival factor. Microarray analyses identified genes that were permanently upregulated in the low-(n-3) PUFA-exposed glands and function in oxidative damage repair. Serum levels of 8-hydroxy-2'deoxyguanosine, a marker of DNA damage, were significantly reduced in these low-(n-3) PUFA-fed rats, and increased in the high-(n-3) PUFA-exposed group. The latter group exhibited reduced expression of BRCA1, a DNA repair gene. Our results indicate that the opposing susceptibilities to mammary tumorigenesis between the low- versus high-fat (n-3) PUFA-exposed groups were associated with altered DNA damage repair and gene expression linked to proliferation, survival, and differentiation.

Hormonal aspects in the causation of human breast cancer: epidemiological hypotheses reviewed, with special reference to nutritional status and first pregnancy

Epidemiology of breast cancer has identified early age at menarche, late first pregnancy, low parity and late menopause as risk factors, but in addition genetic factors, height, weight and living in western countries play a significant role. The international variation in incidence is almost exclusively due to non-genetic factors. Hypotheses in prevention-oriented research are reviewed: 1. obesity-related oestrogen production as a stimulus of the tumour in postmenopausal women; 2. nutritional status and energy expenditure during puberty and adolescence, developed for fertility and fecundity and extended later to breast cancer; 3. reproductive life during early adulthood, age at first pregnancy and its specific effects on breast tissues. The message of preventability of breast cancer is that mammary epithelial differentiation should come early. Our insight concerning events in puberty and early adulthood can be consolidated in one concept on the risk of extended proliferation of breast epithelium during early adulthood in the absence of full differentiation induced by pregnancy. The combined effects of Western-type nutrition, lack of exercise and Western-type women's emancipation sets the stage for breast cancer already at a young age. Since it is unlikely that emancipated women in affluent societies will return to the original life-style of getting pregnant as soon as it is biologically possible, a novel daring way of protection has to be considered. Could a "Breast Differentiation Pill" be developed to offer protection?

Diet, nutrition, and the life-course approach to cancer prevention

Cancer results from the interaction of genetic susceptibility and environmental exposures. The diagnosis of cancer is age related; there is a marked increase in cancer incidence after the reproductive years. Nutrient and toxicant exposures are important contributors to the risk of some cancers. Nutrition, as a determinant of growth and body composition, also influences cancer risk, directly due to carcinogens in foods or indirectly by the hormonal and metabolic response to growth and obesity. There is strong evidence that obesity and rapid growth enhance the risk of cancer. The prevention of cancer should start before conception; mothers should start pregnancy with a healthy weight and avoid excessive or low weight gain during pregnancy. Key micronutrients are important for normal embryonic development and fetal growth. Infant growth should be assessed based on optimal health across all stages of the life course, rather than following the present approach of "bigger is better. " This model may increase cancer risk in later life, because bigger is closely linked to fatter. Recent studies of energy expenditure in children indicate that excess energy intakes may have been recommended over the past decades, contributing to the surge in global obesity. Food preferences and habits regarding physical activity and play become set relatively early in life; parents and teachers provide key guidance leading to the adoption of a healthy or an unhealthy lifestyle. Thus, cancer prevention efforts should begin with childhood and continue through all stages of the life course.

Empirically derived dietary patterns and risk of postmenopausal breast cancer in a large prospective cohort study

BACKGROUND

Inconsistent associations have been reported between diet and breast cancer.

OBJECTIVE

We prospectively examined the association between dietary patterns and postmenopausal breast cancer risk in a US-wide cohort study.

DESIGN

Data were analyzed from 40 559 women who completed a self-administered 61-item Block food-frequency questionnaire in the Breast Cancer Detection Demonstration Project, 1987-1998; 1868 of those women developed breast cancer. Dietary patterns were defined by using principal components factor analysis. Cox proportional hazard regression was used to assess breast cancer risk.

RESULTS

Three major dietary patterns emerged: vegetable-fish/poultry-fruit, beef/pork-starch, and traditional southern. The vegetable-fish/poultry-fruit pattern was associated with higher education than were the other patterns, but was similar in nutrient intake to the traditional southern pattern. After adjustment for confounders, there was no significant association between the vegetable-fish/poultry-fruit and beef/pork-starch patterns and breast cancer. The traditional southern pattern, however, was associated with a nonsignificantly reduced breast cancer risk among all cases (in situ and invasive) that was significant for invasive breast cancer (relative hazard = 0.78; 95% CI = 0.65, 0.95; P for trend = 0.003). This diet was also associated with a reduced risk in women without a family history of breast cancer (P = 0.05), who were underweight or normal weight [body mass index (in kg/m(2)) < 25; P = 0.02], or who had tumors positive for estrogen receptor (P = 0.01) or progesterone receptor (P = 0.003). Foods in the traditional southern pattern associated with reduced breast cancer risk were legumes, low mayonnaise-salad dressing intake, and possibly cabbage.

CONCLUSIONS

The traditional southern diet or its components are associated with a reduced risk of invasive breast cancer in postmenopausal women.

Type I Insulin-like Growth Factor Receptor as a Therapeutic Target in Cancer: Figure 1

Data from experimental model systems and population studies have implicated type I insulin-like growth factor receptor (IGF1R) signaling in many different human cancers. Drugs to disrupt IGF1R function have been developed and are now entering clinical trial. This brief review will identify key areas to consider as these clinical trials move forward.

Body fatness and physical activity at young ages and the risk of breast cancer in premenopausal women

We examined the relationship between body fatness, sports participation and breast cancer risk in 1560 premenopausal cases and 1548 controls, from three related population-based case–control studies in the UK. Half of the women with breast cancer were aged less than 36 years at diagnosis. Women who perceived themselves as plump at age 10 years had a relative risk of 0.83 (95% confidence interval 0.69–0.99, P=0.03) as compared with those who perceived themselves as thin. Self-reported obesity compared with leanness at diagnosis was associated with a relative risk of 0.78 (95% confidence interval 0.56–1.06, P=0.11). Women who reported having been plump at age 10 years and overweight or obese at diagnosis had a relative risk of 0.75 (95% confidence interval 0.56–1.01, P=0.06) as compared with those who reported being thin at age 10 years and at diagnosis. Findings for three related measures of body fatness suggested that obesity is associated with a reduced risk of premenopausal breast cancer. There was no association between sports participation and breast cancer risk in these premenopausal women. The relative risk for spending an average of more than 1 h per week in sports compared with less from ages 12 to 30 years was 1.00 (95% CI 0.86–1.16, P=0.98).

Breast-feeding and cancer: the Boyd Orr cohort and a systematic review with meta-analysis

BACKGROUND

Having been breast-fed has been suggested to influence cancer risk in adulthood. We investigated associations between breast-feeding during infancy and adult cancer incidence and mortality in a cohort study and meta-analyses of published studies.

METHODS

The Boyd Orr cohort consisted of 4999 subjects who were originally surveyed in 1937-39, when they were 0-19 years of age. Cancer outcomes from 1948 through 2003 were available for 4379 (88%) subjects, and 3844 had complete data on all covariates. Associations of breast-feeding with cancer were investigated using proportional hazards models. We also identified 14 studies on infant feeding and cancer published from 1966 through July 2005, of which 10 could be combined with the Boyd Orr cohort results in a meta-analysis of breast cancer using random-effect models.

RESULTS

In the Boyd Orr cohort, ever having been breast-fed, compared with never having been breast-fed, was not associated with the incidence of all cancers (hazard ratio [HR] = 1.07, 95% confidence interval [CI] = 0.89 to 1.28) or of any individual cancer type examined (prostate HR = 1.43, 95% CI = 0.58 to 3.52; breast HR = 1.62, 95% CI = 0.89 to 2.94; colorectal HR = 0.86, 95% CI = 0.45 to 1.63; gastric HR = 1.22, 95% CI = 0.47 to 3.15). In the meta-analysis, there was also no association between breast-feeding and breast cancer (regardless of menopausal status) (relative risk [RR] = 0.94, 95% CI = 0.85 to 1.04). However, breast-fed women had a reduced risk of premenopausal breast cancer (RR = 0.88, 95% CI = 0.79 to 0.98) but not of postmenopausal breast cancer (RR = 1.00, 95% CI = 0.86 to 1.16).

CONCLUSION

Ever having been breast-fed was not associated with overall breast cancer risk, although the meta-analysis revealed a reduced risk of premenopausal breast cancer in women who had been breast-fed.

Genomes optimize reproduction: aging as a consequence of the developmental program

Natural selection shapes genomes for reproduction, not for postreproductive survival. One hypothesis then is that the developmental program, optimized for reproduction, inadvertently regulates aging in mammals. Herein we review, revive, and refine the developmental theory of aging. Implications and experimental approaches for studying the progressive deterioration of physiological function that we call aging are also discussed.

Effects of obesity on growth and puberty

Nutrition is an important regulator of the tempo of human growth. Infancy may represent a critical "window" where variations in nutrition have longer-term consequences for growth and development. Rapid weight gain during infancy is associated with accelerated growth and early pubertal development. Rapid weight gain in infancy is also associated with the development of insulin resistance and an exaggerated adrenarche. Such circulating hormonal changes, together with elevated leptin levels and integral effects of fat cells on hormone action through local 11beta-steroid dehydrogenase and aromatase activity could effect rate of progression of pubertal development in obese subjects. The secular trends in growth and maturation are partly attributed to changing nutrition. Recent data suggest that age at menarche may be static, but there is a debate as to whether the first signs of puberty are being seen much earlier in obese girls. Rapid early weight gain, obesity and early development may have implications for later health through the development of PCOS and overall association with cancer risk.

Preschool diet and adult risk of breast cancer

Events before puberty may affect adult risk of breast cancer. We examined whether diet during preschool age may affect a woman's risk of breast cancer later in life. We conducted a case-control study including 582 women with breast cancer and 1,569 controls free of breast cancer selected from participants in the Nurses' Health Study and the Nurses' Health Study II. Information concerning childhood diet of the nurses at ages 3-5 years was obtained from the mothers of the participants with a 30-item food-frequency questionnaire. An increased risk of breast cancer was observed among woman who had frequently consumed French fries at preschool age. For one additional serving of French fries per week, the odds ratio (OR) for breast cancer adjusted for adult life breast cancer risk factors was 1.27 (95% confidence interval [CI] = 1.12-1.44). Consumption of whole milk was associated with a slightly decreased risk of breast cancer (covariate-adjusted OR for every additional glass of milk per day = 0.90; 95% CI = 0.82-0.99). Intake of none of the nutrients calculated was related to the risk of breast cancer risk in this study. These data suggest a possible association between diet before puberty and the subsequent risk of breast cancer. Differential recall of preschool diet by the mothers of cases and controls has to be considered as a possible explanation for the observed associations. Further studies are needed to evaluate whether the association between preschool diet and breast cancer is reproducible in prospective data not subject to recall bias.

Embryonic and fetal programming of physiological disorders in adulthood

In the past decade, data from numerous epidemiological studies have indicated strong inverse associations between birth weight and risk of coronary heart disease, hypertension, type 2-diabetes, and other diseases in adulthood. The "Barker hypothesis" thus postulates that a number of organ structures and functions undergo programming during embryonic and fetal life. This developmental programming determines the set points of physiological and metabolic responses in adult life. Alterations of nutrient availability during gestation may lead to developmental adaptations, via hormonal maneuvers by the embryo and fetus that readjust these set points. These adaptive measures have short-term benefits to the embryo and fetus, so that the newborn will be better prepared for the adverse environment (e.g., undernutrition). However, adequate nutritional support during postnatal life that enables catch-up growth may create metabolic conflicts that predispose the adult to aberrant physiological functions and, ultimately, increased risk of disease. It is plausible that other adverse in utero conditions, including exposure to developmental toxicants, may similarly alter adult disease susceptibility. This article provides an overview of the Barker hypothesis, its supporting evidence, the current advances in understanding the biological mechanisms underlying this phenomenon, and its implications for developmental toxicology.

Body silhouette, menstrual function at adolescence and breast cancer risk in the E3N cohort study

We analysed the relation between adult breast cancer risk and adiposity in ages 8-25, and among 90 509 women included in the E3N cohort study, and investigated the potential modification effect of certain factors. Participants completed a questionnaire that included a set of eight silhouettes corresponding to body shape at different ages. During the follow-up (mean=11.4 years), 3491 breast cancer cases were identified. Negative trends in risk of breast cancer with increasing body silhouettes at age 8 and at menarche were observed, irrespective of menopausal status, with relative risks of 0.73 (0.53-0.99) and 0.82 (0.66-1.02) for women who reported a silhouette equal or greater than the fifth silhouette at age 8 and at menarche, respectively. We observed no clear effect modification by age at menarche, delay between age at menarche, regular cycling, regularity of cycles in adult life or body mass index at baseline.

Breast cancer and childhood anthropometry: emerging hypotheses?

In this issue of Breast Cancer Research, Baer and colleagues report a strong protective effect of childhood and adolescent body fatness on premenopausal breast cancer risk based on a large prospective study. Methodological issues are discussed, as are tentative biological interpretations regarding the findings.

Body fatness during childhood and adolescence and incidence of breast cancer in premenopausal women: a prospective cohort study

INTRODUCTION

Body mass index (BMI) during adulthood is inversely related to the incidence of premenopausal breast cancer, but the role of body fatness earlier in life is less clear. We examined prospectively the relation between body fatness during childhood and adolescence and the incidence of breast cancer in premenopausal women.

METHODS

Participants were 109,267 premenopausal women in the Nurses' Health Study II who recalled their body fatness at ages 5, 10 and 20 years using a validated 9-level figure drawing. Over 12 years of follow up, 1318 incident cases of breast cancer were identified. Cox proportional hazards regression was used to compute relative risks (RRs) and 95% confidence intervals (CIs) for body fatness at each age and for average childhood (ages 5-10 years) and adolescent (ages 10-20 years) fatness.

RESULTS

Body fatness at each age was inversely associated with premenopausal breast cancer incidence; the multivariate RRs were 0.48 (95% CI 0.35-0.55) and 0.57 (95% CI 0.39-0.83) for the most overweight compared with the most lean in childhood and adolescence, respectively (P for trend < 0.0001). The association for childhood body fatness was only slightly attenuated after adjustment for later BMI, with a multivariate RR of 0.52 (95% CI 0.38-0.71) for the most overweight compared with the most lean (P for trend = 0.001). Adjustment for menstrual cycle characteristics had little impact on the association.

CONCLUSION

Greater body fatness during childhood and adolescence is associated with reduced incidence of premenopausal breast cancer, independent of adult BMI and menstrual cycle characteristics.

High ponderal index at birth predicts high estradiol levels in adult women

Inter-individual variation in levels of sex hormones results from differences in genetic, developmental, and environmental factors. We tested a hypothesis that programming of the fetal neuroendocrine axis may predispose some women to produce higher levels of steroid hormones during their menstrual cycles as adults. One hundred forty-five regularly menstruating 24- to 36- year-old women collected daily saliva samples for one menstrual cycle. Data on women's birth weights and birth lengths were obtained from medical records. A positive relationship was observed between ponderal index at birth (an indicator of nutritional status, calculated as birth weight/(birth length)(3)) and levels of estradiol (E2) in menstrual cycles, after controlling for potential confounding factors. Mean E2 was 16.4 pmol/l in the low ponderal index tertile, 17.3 pmol/l in the moderate ponderal index tertile, and 19.6 pmol/l in the high ponderal index tertile (the high ponderal index group had significantly higher E2 than both low and moderate ponderal index groups, P=0.0001). This study shows a positive association between ponderal index recorded for women at birth and levels of E2 measured during their menstrual cycles as adults. This suggests that conditions during fetal life influence adult production of reproductive hormones and may contribute to inter-individual variation in reproductive function. In addition, because large size at birth is one of the factors linked with an increased risk of breast cancer, our findings provide a physiological link for the observed positive relationship between indicators of energetic conditions during fetal growth and breast cancer in women.

The role of nutrition in cancer development and prevention

Nutrition has long been suspected to play an important role in cancer etiology. The biologic properties of nutrients make them prime candidates to aid in cancer prevention. Indeed, early epidemiologic cancer studies seemed to confirm the relevance of diet. These studies, however, were plagued by recall bias and confounding and may have thus been misleading. The results from large, prospective cohorts do not support a strong relation between nutrition and cancer. Given the difficulties in precisely assessing habitual diet, modest associations may exist, which may be impossible to capture when relying on self-reported dietary information. Energy balance, reflected in a low body weight and high level of physical activity, has been more convincingly related to lower cancer rates. The potential importance of more extreme dietary regimens and of nutrition during earlier periods of life remains to be explored. Finally, epigenetic research is likely to contribute to the understanding of nutritional regulation of gene expression.