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Cancer Epidemiology, Biomarkers & Prevention
Reducing Bioavailable Sex Hormones through a Comprehensive Change in Diet: the Diet and Androgens (DIANA) Randomized Trial1 Franco Berrino,2 Cristina Bellati, Giorgio Secreto,
increased phytoestrogen intake decreases the
Edgarda Camerini, Valeria Pala, Salvatore Panico,
bioavailability of serum sex hormones in hyperandrogenic
Giovanni Allegro, and Rudolf Kaaks
postmenopausal women. Additional studies are needed to
Unit of Epidemiology (F. B., C. B.,V. P.), Unit of Nuclear Medicine (G. S.), determine whether such effects can reduce the risk of
Unit of Laboratory Medicine (E. C.), Istituto Nazionale Tumori, 20133 Milan, developing breast cancer.
Italy; Department of Clinical and Experimental Medicine, Federico IIUniversity, 80131 Naples, Italy (S. P.); Association Le Cinque Stagioni, 10018Ivrea, Italy (G. A.); and Nutrition and Cancer Unit, International Agency forResearch on Cancer, 69372 Lyon, France (R. K.) Introduction
Recent prospective studies have provided strong evidence thatthe risk of developing breast cancer in postmenopausal womenis increased by high serum levels of testosterone and estradiol, Abstract
low levels of sex hormone-binding globulin, and, hence, high High serum levels of testosterone and estradiol, the
circulating levels of free steroid sex hormones (1–7). Evidence bioavailability of which may be increased by Western
is accumulating that Western dietary habits contribute this dietary habits, seem to be important risk factors for
high-risk hormonal profile, but the efficacy of changes in diet postmenopausal breast cancer. We hypothesized that an
in reducing the availability of sex hormones has not been ad libitum diet low in animal fat and refined
carbohydrates and rich in low-glycemic-index foods,
Chronic hyperinsulinemia may be a key link between monounsaturated and n-3 polyunsaturated fatty acids,
nutrition-related life-style factors, development of a high-risk and phytoestrogens, might favorably modify the
steroid hormone profile, and increased breast cancer incidence hormonal profile of postmenopausal women. One
hundred and four postmenopausal women selected from
(8). Insulin inhibits the hepatic production of sex hormone- 312 healthy volunteers on the basis of high serum
binding globulin (9) and stimulates the ovarian production of testosterone levels were randomized to dietary
androgens (10, 11). Women who are overweight, especially intervention or control. The intervention included
those with large intra-abdominal fat stores, which in postmeno- intensive dietary counseling and specially prepared group
pausal women are often associated with increased risk of breast meals twice a week over 4.5 months. Changes in serum
cancer (12), often have insulin resistance (9, 13), low serum levels of testosterone, estradiol, and sex hormone-binding
levels of sex hormone-binding globulin (14), and high sex globulin were the main outcome measures. In the
hormone levels (15). Epidemiological studies suggest an asso- intervention group, sex hormone-binding globulin
ciation of breast cancer risk with increased serum levels of increased significantly (from 36.0 to 45.1 nmol/liter)
insulin (16) and also with increased activity of insulin-like compared with the control group (25 versus 4%,; P <
0.0001) and serum testosterone decreased (from 0.41 to
The availability of steroid sex hormones in the blood may 0.33 ng/ml; ؊20 versus ؊7% in control group; P ؍
also be reduced by the dietary intake of phytoestrogens (18 – 0.0038). Serum estradiol also decreased, but the change
21), plant-derived diphenolic compounds that display both es- was not significant. The dietary intervention group also
trogenic and antiestrogenic activities and may protect against significantly decreased body weight (4.06 kg versus 0.54
breast cancers (22). Phytoestrogens include isoflavones from kg in the control group), waist:hip ratio, total cholesterol,
soy (23), lignans from flax and other seeds and fiber-rich fasting glucose level, and area under insulin curve after
vegetables (24, 25), and coumestrol from alfalfa sprouts and oral glucose tolerance test. A radical modification in diet
other legumes (26). Indole-3-carbinol, a compound that occurs designed to reduce insulin resistance and also involving
in cruciferous plants, also exhibits antiestrogenic activity (27).
Among women from low-cancer-risk Asian populations, characterized by the consumption of fairly large quantities ofsoy products, serum levels of testosterone and estradiol havebeen found to be 20 –50% lower than in Western women Received 6/6/00; revised 10/12/00; accepted 11/5/00.
The costs of publication of this article were defrayed in part by the payment of (28 –31) and inversely related to the consumption of soy prod- page charges. This article must therefore be hereby marked advertisement in ucts (32). Furthermore, in two (29, 33) of four studies (28, 29, accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 31, 33), levels of serum sex hormone-binding globulin were This study was supported by grants from the CARIPLO Foundation, the Europe against Cancer Program of the European Union, and the Italian Association for higher among Asian women. Epidemiological studies have suggested a lowered risk of breast cancer with increased urinary 2 To whom requests for reprints should be addressed, at Epidemiology Unit, excretion of phytoestrogens (34, 35) but have not consistently Istituto Nazionale Tumori, Via Venezian 1, 20133 Milan, Italy. Phone: 39-02- found a negative association with increased consumption of soy 70-60-18-53 or 39-02-70-63-83-98; Fax: 39-02-23-90-762; E-mail: [email protected].
The DIANA Randomized Trial
We present here the results of the DIANA3 study. This Before the start and at the end of the intervention, fasting was a randomized dietary intervention in postmenopausal blood samples and 24-h urine samples were taken and stored at women with high plasma levels of testosterone. The hypothesis Ϫ30°C for hormone assays. An oral glucose tolerance test was of the study was that levels of testosterone and estradiol might also performed, involving collection of blood samples 1, 2, and be lowered, and levels of sex hormone-binding globulin in- 3 h after the ingestion of 100 g of glucose.
creased, by a radical change in diet. The new diet was ad Taking into account the intraindividual variation in hor- libitum and had two overlapping dimensions: (a) increasing mone levels (48), we estimated that the study had a statistical phytoestrogen intake and (b) other changes designed to reduce power of more than 90% for detecting a 20% change in the Increased phytoestrogen intake was ensured by increasing Dietary Intervention. Women in the intervention group were
the consumption of soy products, other legumes, whole-grain invited for common meals and cooking classes twice a week for cereals, flax and other seeds, seaweed, berries, crucifers, and 18 weeks. On each occasion the menu was different, but mainly based around Mediterranean vegetarian and macrobiotic reci- The plasma insulin-lowering aspect involved reducing to- pes. The foods used are described in the Appendix. We rec- tal fat intake, so as to help reducing body mass index and waist ommended that the same foods should be consumed on a daily circumference, which are major determinants of insulin resist- basis at home, but we did not prescribe menus. However, we ance (8, 37–39); increasing the proportion of n-3 polyunsatu-rated and monounsaturated fatty acids, which may improve provided written instructions that indicated how to substitute insulin sensitivity (40 – 43); reducing foods rich in sugar or meat, eggs, and dairy products with vegetable sources of es- highly refined carbohydrates, which lead to high postprandial sential amino acids, vitamins, and minerals; recommended that glycemic and insulinemic responses (44) and to insulin resist- meat, eggs, and dairy products should not be eaten more than ance (45); and increasing consumption of low-glycemic-index once a week; urged reducing the consumption of refined car- foods such as unrefined cereals, legumes, and vegetables (43– 46).
bohydrates (sucrose, white bread, refined flour), substituting The ultimate aim of the study was to determine whether whole-grain cereal products, using fruit or fermented cereal as such a diet might be worth investigating in long-term trials edulcorants; and recommended cooking with little added fat designed to reduce the risk of breast cancer.
The women were also encouraged to eat at least one portion of a soy product (soy milk, miso soup, tofu, tempeh, or Subjects and Methods
soy beans) every day, to season moderately with unrefined Subjects. Three hundred and twelve healthy women, ages
olive oil and various seeds but not dairy fats, and to consume 50 – 65 years, from the Milan area (northern Italy) volunteered to take part in the study after advertisements had been placed in Every week, each woman received a 1-kg loaf of bread the local media. Eligibility criteria were: (a) postmenopausal made from whole wheat flour and 8% flax seed (half whole for at least 2 years; (b) presence of at least one ovary; (c) not seeds and half milled), occasionally mixed with oats or rye, and on hormonal replacement therapy for at least the previous 6 also a free pack of other recommended products that are not a months; (d) no history of cancer; (e) not following vegetarian, normal part of the northern Italian diet.
macrobiotic, or other medically prescribed diet; and (f) not In the first month of the study, participants were asked to change their habits gradually to prevent adverse reactions due Written informed consent was obtained from all of the to excessive fermentation in the bowel. The diet was ad libitum, women, and the Scientific and Ethical Committee of the Milan and no advice was given to reduce total food intake or to count Cancer Institute approved the study.
Study Design. Levels of testosterone in the serum of the vol-
unteers were determined (prebaseline), and the 104 women in
Assessment of Dietary Intake and Anthropometric Meas-
the upper tertile (testosterone, Ͼ0.38 ng/ml) were selected for urements. Before randomization, all of the women compiled a
the study. With the exception of two close friends, who were food frequency questionnaire developed for EPIC (49). During allocated to the same group, these women were individually the study, compliance with dietary recommendations was mon- randomized to the intervention and control groups (52 women itored by 24-h food frequency diaries, which were filled in 24 each), stratified for age (above or under the median of 58 times by the intervention group and 10 times by the control years), prebaseline serum testosterone (three levels), and pre- women. In the 4th month of the study, all of the women were baseline fasting insulin (three levels). We selected women on interviewed and asked to recall everything they had eaten in the the basis of the serum testosterone level because its measure- preceding 24 h, including quantities. Data were collected with ment is highly reliable (47), and it has been shown to predict the computerized EPIC 24-h dietary recall system (50), which breast cancer risk not less than estrogen levels (1, 2). The was then used to estimate absolute intakes of nutrients and women in the intervention group agreed to adhere to the diet energy in the two groups. The system makes use of the Italian described below for 4.5 months. The control women were not food composition database (51), which also includes several given any information about this diet, nor any dietary instruc- foods used in macrobiotic recipes. Average consumption of tion, but were advised to increase their consumption of fruit and
isoflavonoids and lignans by the intervention and the control vegetables according to the cancer prevention decalogue of the groups were estimated from available databases on the phy- Europe against Cancer program, a leaflet largely available to toestrogen content of foods (23–26, 52, 53) and from the food frequency diaries, using as standard portion sizes those derivedfrom the interviews.
Height, weight, waist circumferences (at natural waist when clearly identifiable or midway between lower rib and iliac The abbreviations used are: DIANA, diet and androgens; EPIC, European crest), and hip circumference (at crotch) were measured at the Prospective Investigation into Cancer and Nutrition; IRMA, immunoradiometricassay; MEIA, microparticles enzyme immunoassay.
beginning and at the end of the study.
Cancer Epidemiology, Biomarkers & Prevention
Laboratory Analyses. Circulating hormones were measured
tween the changes in the different variables. All of the Ps are using commercial kits: RIA kits from ORION Diagnostic (Turku, Finland) for testosterone and estradiol; IRMA kits fromFarmos (Oulunsalo, Finland) for sex hormone-binding globu-lin; and MEIA kits from ABBOTT (Abbott Park, IL) for insu- lin. The coefficients of intra- and interassay variation in eight The diet of the participating women before randomization, as replicates were, respectively: 4.2 and 12.5% for a testosterone estimated from the food frequency questionnaire, was typical of value of 0.420 ng/ml; 5.2 and 11.1% for an estradiol concen- northern Italy, with 42% of calories obtained from carbohy- tration of 10 pg/ml; 3.5 and 6.7% for a sex hormone-binding drates (mainly bread and pasta) and 37% from fat (mainly meat, globulin value of 34.0 nmol/liter; and 2.5 and 4.6% for an dairy products, and olive oil), without significant differences insulin value of 14.2 ␮IU/ml. For insulin, samples were ana- between women eventually randomized in the intervention lyzed within 2 weeks of collection. To reduce the effects of group and in the control group (Table 1). The diet-recall inter- interassay variability, for sex hormone-binding globulin, tes- views in the 4th month of intervention slightly underestimated tosterone, and estradiol, baseline and final serum samples of the the total caloric intake with respect to energy requirement (55) same woman were analyzed in the same batch. We have but showed a lower total energy intake in the intervention group previously shown that both estradiol and testosterone are stable than in the control group, about 250 kcal per day on average,mainly caused by a lower intake of total and saturated fat.
in serum preserved at low temperature (47).
Intervention women also shifted from animal to vegetable We measured urinary daidzein and its metabolite equol by sources of protein and fat and from simple to complex carbo- gas chromatography after solid-phase extraction and high-per- hydrates, and consumed more vegetable fibers (Table 1). Ac- formance liquid chromatography purification. Coefficients of cording to the food frequency diaries compiled during the variation were 7.5% for low (14 ng/ml) and 10.7% for high study, the intervention women consumed meat or meat products (9982 ng/ml) daidzein concentrations, and 4.0% for low (80 twice a week against once a day in the control women, but ng/ml) and 2.9% for high (10,500 ng/ml) equol concentrations.
consumed fish more often (3 times a week versus 1.5 in con- All of the blood and urinary samples were analyzed blind to trols). Milk and cheese consumption was cut by half (0.4 versus 1.0 servings per day) and butter was virtually eliminated. A soy Compliance and Subjects Excluded from Statistical Analy-
product was consumed on average 1.7 times per day (SD, 0.6); sis. Fifty of the 52 women of the intervention group followed
flax seeds, either in bread or cookies or as such were eaten the whole dietary program. Two women followed only about every day (about 8 g per day), and seaweed was used every half of the program but were included in all of the analyses.
other day as ingredients of various dishes. The control women Only five women were absent more than five times from the 36 rarely, if ever, consumed any of these food items. Intervention lessons and common meals. Urinary daidzein and equol levels women also consumed the following much more often than were used as indicator of compliance with soy consumption.
controls: whole rice or other whole grain or whole-meal cereal Two women from the intervention group and one woman from products (2.5 versus 0.5 per day), walnuts, almonds, sesame the control group were excluded because they received hormo- and other seeds (1.2 versus 0.05), legumes (0.5 versus 0.1), nal drugs during the study period. Two other women from the cruciferous vegetables (0.8 versus 0.1), and berries (0.4 versus control group were excluded because they did not attend the 0.1). Other vegetables and fruits were consumed almost as final examination. A total of 99 women were analyzed: 50 in frequently by the control group as by the intervention group the intervention group and 49 controls. Of these, four (two in (2.2 and 2.3 times a day, respectively).
the intervention group and two controls) had missing values for We estimated that women in the intervention group con- fasting insulin, and five (one in the intervention and four in the sumed on average of ϳ38 – 45 mg of isoflavonoids per day. The control group) had missing values for the oral glucose toler- estimated average daily intake of lignans was more uncertain (9 –32 mg) because of large inconsistencies between differentmethods of chemical assay in food (24, 25). The corresponding Statistical Methods. The statistical analysis focused on
estimates for controls, however, were much lower (about 2 changes in hormonal and other relevant variables, calculated as mg/day isoflavonoids and 1 mg/day lignans). The high intake of the difference between end of study and baseline values for isoflavone-rich food by the intervention group was confirmed each woman. Hormone values were log-transformed to obtain by assay of daidzein and its metabolite equol in 24-h urine approximately normal frequency distributions. The statistical samples collected toward the end of the study period. Mean significance of mean changes in the intervention group com- cumulative excretion was 5,32 mg/24 h in the intervention pared with controls was assessed by ANOVA. Multivariate group (range, 0.02–10.18) versus 0.17 mg/24 h in controls ANOVA was used to perform an omnibus test for simultaneous (range, 0.01–1.09). In the control group, only one woman had changes in the main hormonal variables, circumventing the values above 1 mg/24 h, and 29 values were under 0.1 mg/24 problem of significance testing with multiple, partially inde- h; in the intervention group, nine women had values under 1 pendent comparisons for each parameter. All of the ANOVA mg/24 h and only three under 0.1 mg/24 h, including the two were stratified according to the blocking scheme used for the women who did not complete the intervention.
randomization. Interaction terms were used to test whether the The high compliance of the intervention women with magnitude of the effect of the dietary intervention differed for dietary recommendations was confirmed by the analysis of women with different baseline values of testosterone or insulin.
changes in serum cholesterol levels and anthropometric vari- Because the numbers of observations within the various blocks ables. Total cholesterol levels decreased from 240.0 to 206.5 were not equal, all of the ANOVA used generalized linear mg/dl in the intervention group (Ϫ14%) versus 240.6 to 230.4 models, using the SAS statistical software package (54). Fi- in the control group (Ϫ4%; P ϭ 0.0005). Intervention women nally, Spearman correlation coefficients were computed to lost more weight (P Ͻ 0.0001) than control women: 4.06 kg evaluate cross-sectional relations between anthropometric and (range, Ϫ0.6 to Ϫ8.8 kg) versus 0.54 kg (range, ϩ2.2 to 5.3 kg; hormonal variables at baseline and longitudinal relations be- Table 2); with similar differences in waist circumference (P Ͻ The DIANA Randomized Trial
Average energy and nutrient intake of intervention and control women as estimated before the start and towards the end of the study Intake in the 4th month of the study (24-h recall Dietary intake before randomization (from food frequency questionnaire) a The estimated mean energy requirement, calculated from body weight measured at time of the 24-h recall interview and assuming a sedentary life style (55), was 1955and 1979 kcal/day, respectively, for intervention and control women, suggesting that the frequency questionnaire overestimated and that the 24-h recall interviewunderestimated energy intake by about 10%.
in the intervention group. The changes in sex hormone-binding Mean values of anthropometric variables in intervention and control women before and after dietary intervention globulin and testosterone levels were significantly larger in theintervention than in the control group (P Ͻ 0.0001 and P ϭ 0.0038, respectively) whereas the changes in estrogen did not differ significantly between the groups (P ϭ 0.13). The ratio of testosterone:sex hormone-binding globulin decreased in all ex- cept two of the intervention women (P Ͻ 0.001; Table 4).
Fasting glycemia and the total area under the insulin curve during the glucose tolerance test also decreased significantly in the intervention group compared with controls (P ϭ 0.0260 and ϭ 0.0404, respectively); however, the change in fasting insulin was not significant (Table 3).
At baseline, body mass index correlated strongly with serum estradiol levels (Spearman coefficient of correlation r,0.60) and negatively with sex hormone-binding globulinlevels (r, Ϫ0.53), but not with testosterone levels (r, 0.19).
In the intervention group, changes in body weight were 0.0001), hip circumference (P Ͻ 0.0001), and waist:hip ratio significantly correlated with changes in serum levels of sex hormone-binding globulin (r, Ϫ0.33) but not with changes in Using multivariate ANOVA, we found a statistically sig- levels of insulin (r, 0.20), testosterone (r, 0.19), and estradiol nificant change (P Ͻ 0.0001) in the intervention group com- (r, 0.09). The ratio of testosterone:sex hormone-binding pared with controls for the five major hormonal and metabolic globulin decreased markedly in women who lost over 4.5 kg outcomes combined (sex hormone-binding globulin, testoster- of body weight but decreased also in women who lost less one, estradiol, fasting insulin, and fasting glycemia). Thechange was also significant (P Ͻ 0.0002) when the first three than 3 kg (Table 4). After adjustment for weight changes, of these variables were combined with area under insulin curve however, the differences between changes in hormonal lev- and area under glucose curve, instead of fasting insulin and els in the intervention and in the control group were no more statistically significant (Table 3), which suggests that the Serum sex hormone-binding globulin levels increased hormonal effects of dietary intervention could be largely (ϩ25.2%) and serum levels of testosterone and estradiol de- mediated through changes in body weight. Among women creased (Ϫ19.5% and Ϫ18.0%) in the intervention women who initially had high testosterone levels, the dietary inter- (Table 3). In the control group, there were also small changes vention caused a larger decrease in testosterone levels than in sex hormone-binding globulin (ϩ3.6%), testosterone in women with initially low levels, but the interaction was (Ϫ7.1%), and estradiol (Ϫ5.5%) levels, in the same direction as not significant (P ϭ 0.0849).
Cancer Epidemiology, Biomarkers & Prevention
Mean values of hormonal variables in intervention and control women before and after dietary intervention a Value after additional adjustment for effects related to weight change.
b SHBG, sex hormone-binding globulin.
The observed weight reduction is consistent with the re- Distribution of participating women according to change in the testosterone:SHBGa ratio from baseline to the end of the dietary intervention sults of previous randomized controlled studies of low-fat adlibitum diet, which showed that weight can be lost merely by reducing the fat content of the diet without restricting food intake (56 –58), which would compromise satiety, quality of life, and, in the long run, compliance. A drop in body weight of 3.52 kg (4.06 in the diet group minus 0.54 in the control group) corresponds to a cumulative energy deficit of about 26,400 kcal (7.5 kcal per gram of adipose tissue) and, hence, to an average reduction of about 200 kcal per day over 4.5 months, which fits well with the estimated difference in energy intake between the a SHBG, sex hormone-binding globulin.
intervention and control groups: 255 (1805 Ϫ 1550) kcal perday measured close to the end of the study period when theintervention was being fully implemented (Table 1). This re- Discussion
duced energy intake was achieved through increased consump- We observed significant and favorable changes in hormonal tion of highly satiating bulky food with low-energy density, indicators of breast cancer risk in a group of postmenopausal which implies reducing both total energy and the proportion women living in northern Italy, initially with high serum levels derived from fat. The effect of the consumption of sugars on of testosterone, who followed an ad libitum diet of radically
appetite and food intake is controversial (59), but we suspect modified composition for 4.5 months. The main results were that the reduction of the glycemic load may have contributed to that serum sex hormone-binding globulin levels were increased and serum testosterone and estradiol levels were decreased. We The observed decrease in the quantity of insulin required also found decreased body weight, decreased insulinemic re- to deal with a standard glucose load after overnight fast indi- sponse to oral glucose, decreased fasting glucose, and de- cates that we succeeded in improving insulin sensitivity. Sev- creased cholesterol: all of these changes were anticipated by the eral observational studies have shown a direct relationship study hypothesis. Minor changes in the same direction were between total or saturated fat intake on the one hand and indices observed also among women in the control group, who were of insulin resistance and development of glucose intolerance on blind to the dietary strategy of the study but may have slightly the other (42, 43, 60, 61), but previous intervention studies that changed their diet following publicly available cancer preven- reduced dietary fat content showed only weak or no effect (39).
In most of these studies, however, energy intake was held These results suggest that the multifactorial dietary inter- constant to maintain body weight (isocaloric substitution of vention applied in this study may prevent breast cancer if carbohydrates for fats), and the substituting carbohydrates had continued in the long term. An intrinsic limitation, however, is relatively high glycemic indices and the intervention periods that multifactorial intervention precludes estimation of the con- were short (1–3 weeks). The improvement in insulin sensitivity tributions of individual factors to the overall effect. It is of observed in the present study may therefore be attributable not interest, therefore, to examine our results in relation to pub- only to the decrease in total fat and energy intake and subse- lished, mostly unifactorial, intervention studies.
quent body weight loss (39) but also to the increased proportion The DIANA Randomized Trial
of unsaturated fats (40 – 43) and lower glycemic index of car- in prolongation of the menstrual cycle but has no effect on bohydrate-rich foods (44 – 46; Table 1).
serum sex hormone-binding globulin (84 – 87) or testosterone The changes in sex hormone-binding globulin and sex (87, 88); however, estradiol serum levels react more erratically, hormones could also have been attributable to the combined being reduced after soy milk (84, 86) and a variety of soy food effects of lowered total energy intake and increased fiber and (89) but not with the introduction of soy protein isolates (85, 87, phytoestrogen consumption. The study design did not allow us 90) or flax seeds (88). In postmenopausal women, supplemen- to disentangle a possible aspecific effect of weight loss from the tation with soy protein did not increase sex hormone-binding effect of specific changes in dietary composition. Weight re- globulin (91–94), but isocaloric substitution of 25% of the duction was part of the intervention strategy, which aimed at dietary calories with a variety of soy foods did (95). This reducing body mass index and waist:hip ratio to reduce insulin pattern suggests that several phytoestrogen-rich foods may be resistance. However, the observation that hormonal changes more effective than soy protein isolate, which is consistent with lost statistical significance after additional adjustment for the results of the present study. However a study that compared weight change does not imply that they are entirely mediated by the effects of soy powders containing very high levels of this intermediate variable. Energy-restriction trials to reduce isoflavones (2 mg/kg/day) with those containing low levels (0.1 weight in obese women have consistently shown increased mg/kg/day), showed a modest but significant decrease in serum serum sex hormone-binding globulin levels (62– 67) and cor- estradiol (Ϫ12%) and a small increase in sex hormone-binding responding decreases in free testosterone (64 – 66) but generally globulin (ϩ4%) in postmenopausal women who consumed without reductions in total serum estradiol (62, 63) or total testosterone [Refs. 63, 65, 67; although energy restriction may The concentrations of phytoestrogens that have a signifi- reduce total testosterone in obese women with polycystic ova- cant metabolic effect on steroid hormone synthesis in vitro are ries (68)]. By contrast low-fat interventions, mostly in nonobese higher than those in human blood after intake of phytoestrogen- women (56, 69 –71), have shown no increase in plasma sex rich foods. However, significant in vitro effects can also be hormone-binding globulin levels, although in some of these obtained by accumulating various lignans and isoflavonoids, experiments (56, 70), average body weight losses were similar each in concentrations similar to those observed in the plasma to those in the present study. We speculate that the lack of effect of Japanese (whose diet is rich in isoflavonoids) or of Western of low-fat diets on sex hormone-binding globulin levels may vegetarians (whose diet is rich in lignans; Ref. 18). The effect have been attributable to increased intake of carbohydrate-rich of phytoestrogens in our study may have been substantially foods with high glycemic indices, so that there would be no higher than in previous studies in which the usual diet was improvement in insulin sensitivity; however, the studies cited supplemented with a single phytoestrogen source. Furthermore, do not give details of the food consumed or recommended.
the bioavailability of phytoestrogens may have been higher in A recent review of 13 dietary intervention studies sug- our study because of changes in the intestinal microflora. Phy- gested that low-fat diets (10 –25% of total calories) could sig- toestrogens are present in food as glycosides, which must be nificantly reduce plasma estradiol concentrations. The mean hydrolyzed by the gut microflora to produce absorbable agly- figures cited were Ϫ7.4% before menopause (9 studies) and cones. Compared with the usual Western microflora, the gut of Ϫ23.0% after menopause (4 studies; Ref. 72). However, in macrobiotic or vegetarian subjects may be richer in lactobacilli most of these studies, the intake of fiber-rich foods also in- and bifidobacteria, which can hydrolyze numerous plant gly- creased significantly. We obtained a similar reduction of serum cosides present in the human diet, and poorer in clostridia, estradiol (18%) with a much lower reduction of fat intake (from which degrade diphenolic to monophenolic compounds (96).
about 37 to 31% of total calories) but with a major shift from Dietary supplementation with isolated phytoestrogen rich prod- animal to vegetable fat and from high- to low-glycemic-index ucts, therefore, may be less effective than a comprehensive dietary change, which may also modify bowel function and Intervention studies in which particular types of dietary fiber (73–76) or fiber-rich food (77, 78) were supplemented In the present study, the effects of dietary intervention on found no significant increases in plasma sex hormone-binding hormonal levels were clearer than those of previous trials globulin levels, although plasma estradiol levels were usually involving a single factor intervention, e.g., reducing total fat [but not always (75)] reduced, an effect that may be attributable intake or supplementing with cereal fibers, soy protein, or to fiber inhibition of steroid reabsorption from the gut (79). A flaxseed. We suggest that these favorable changes are to be lack of effect of wheat fiber supplementation on plasma sex attributed to the cumulative effects of a comprehensive dietary hormone-binding globulin is consistent with the lack of effect strategy that combines lowered total fat intake, lowered pro- of single-fiber-type supplementation on postprandial and fast- portion of saturated fatty acids, and lowered consumption of ing plasma insulin levels (80), in contrast to whole-grain food high-glycemic-index foods with increased intake of dietary (81). In the present study, women were requested to rely on the fibers from cereals, legumes, and vegetables, and a high cumu- recommended foods and to avoid fiber or other supplements.
lative dose of diverse phytoestrogens from various food In vitro, several phytoestrogens inhibit enzymes involved sources. The very high compliance obtained in this study, in the synthesis of endogenous steroid sex hormones (18, 20, however, required about 150 h of teaching and counseling 21) and stimulate the liver synthesis of sex hormone-binding sessions over 4.5 months, which would not be feasible in globulin (19). In vivo, the possibility that phytoestrogen intake large-scale public health intervention programs and may not be can affect the bioavailability of endogenous sex hormones has
sustainable in the long run. Additional studies are needed to been examined using various study designs, end points, and establish strategies for successful long-term dietary changes in dietary or supplemental strategies. Cross-sectional observa- tional studies (82, 83) suggest that the consumption of lignansis associated with reduced total and free sex hormones but do Acknowledgments
not show a consistent relationship with sex hormone-binding We thank the personnel at the Associazione Attivecomeprima, where the globulin. Before menopause, phytoestrogen supplementation fieldwork was carried out. We thank A. Burrone, S. Gastaldi, C. Gazzola, and Dr.
with soy protein isolates, soy milk or flax seeds, usually results A. Ricciuti, all of whom helped with the logistic organization of the project; E.
Cancer Epidemiology, Biomarkers & Prevention
Appendix
Foods recommended for home consumption and used to prepare common meals for the intervention group in the DIANA study The cumulative consumption over 36 meals/lessons is also given (g per woman).
Isoflavonoids, lignans, linolenic acid, fiber, Tofu (598), Soy milk (577), Miso (171), soy sauce (Shoyu or Tamari) (110), soy ice cream (98), soybeans or tempeh (75) Azuki beans, mung beans or black soy beans (143), green-peas (160), other beans (115), lentils (100), alfalfa sprouts (68),chick-peas (56) Whole bread (1884), flour or pasta of unrefined wheat (1039), whole rice (648), seitan (wheat gluten) (346), corn or cornflour (283), whole wheat (115), oat or oatmeal (76), couscous(72), millet (70), buckwheat (70), barley (60), spelt (60), riceflour or pasta (32) Lignans, fibers, PUFA, vitamins, minerals Flaxseeds (187), sesame or tahini (141), almonds (103), walnuts (43), hazelnuts (31), sunflower (58), coconut (19), pistachio,pine, pumpkin, or mustard seeds (27) Olive oil (282), corn, sesame, or sunflower oil (59) Indole-3-carbinol, coumestrol, fiber, LGIC White, red, or savoy cabbage (287), cauliflower (126), brussels sprouts (80), broccoli (65), daikon or radish (258), turnip (135),rocket (94), water-cress (75) Phytoestrogens, essential fatty acids, fiber, LGIC, Carrot (1557), onion or leek (1449), green leafy vegetables (912), squash (468), potato (260), pepper (130), parsley (118), stringbean (86), dried Shitake or other mushrooms (64), ginger (41),purslane (27), garlic (16), other vegetables (468) Phytoestrogens, vitamins, trace elements, sugar Apple (661), strawberry (420), bilberry or other berries (273), naturally fermented rice or barley malt (240), apple juice (236),citrus fruit (183), amasake (fermented rice) (100), maple,black-currant, or apple syrup (68), raisin (56), dried apricots(33) Kombu (56), wakame (28), hijiki (27), arame (23), ohers (18) Trout (168), cod (190), anchovies (135), other sea fish (215), Yogurt (40), vinegar (32), arrow root (29), umeboshi (19), wine (13), brewer’s yeast (13), egg (8), cocoa (5), unrefined sea salt,cinnamon, oregano, sage, saffron a LGIC, low glycemic index carbohydrates; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids.
b Fruit was not usually served as such but was recommended for consumption between meals.
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