Het eten van sojarijk voedsel (isoflavonen) vermindert met 18% het risico op het krijgen van borstkanker blijkt uit grote epidemiologische studie bij Chinese vrouwen in Singapore. De uitkomsten  van de resultaten uit deze studie zijn gepubliceerd in het British Journal of Cancer. Hier twee abstracten van grote studies onder elkaar waarvan ik van de meest recente de resultaten heb geprobeerd zo letterlijk mogelijk te vertalen.

Resultaten:

In relatie tot vrouwen die minder soja (minder dan gemiddeld sojagebruik (<10.6 mg isoflavone per 1000 Kcal) gebruikten in hun voedingspatroon  toonden vrouwen met een hoger sojagebruik  (boven gemiddeld) een significant minder risico (18%) op het krijgen van borstkanker  (relative risk (RR)=0.82, 95% confidence interval (CI)=0.70-0.97). Deze omgekeerde associatie werd significant bevonden bij postmenopausale vrouwen (in leeftijd voor de overgang) (RR=0.74, 95% CI=0.61-0.90), en was niet significant bij vrouwen in leeftijd voor de overgang geconstateerd  (RR=1.04, 95% CI=0.77-1. 40). Onder postmenopausal vrouwen, was de soja-borstkanker relatie sterker bij vrouwen met een bovengemiddled gewicht BMI (RR=0.67, 95% CI=0.51-0.88) dan bij slankere vrouwen (RR=0.83, 95% CI=0.62-1.11). Het postieve efect werd dubel zo groot bij de vrouwen die 10 jaar of langer bovengemiddled soja gebruikten. Noch oestrogeen noch progesteron receptor status ovan de tumorne gaf  verschillend efect op de relatie tussen soja en borstkanker risico. Deze prospectieve resultaten suggereren dzt gemiddeld 10 mg isoflavones per dag, verkregen in een dagelijks voedingspatroon van tofu kan langdurende positieve effecten hebben op het ontwikkelen van borstkanker. 

Soy intake and breast cancer risk in Singapore Chinese Health Study.

Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA. annawu@usc.edu

We investigated the effects of soy isoflavone intake on breast cancer in a prospective study of 35,303 Singapore Chinese women enrolled during April 1993 to December 1998 in the Singapore Chinese Health Study. At recruitment, each subject was personally administered a validated semiquantitative food frequency questionnaire covering 165 food and beverage items. As of December 31,2005, 629 had developed breast cancer following an accumulation of 338,242 person-years. Using Cox regression and adjusting for age at interview, year of interview, dialect group, education, family history of breast cancer, age when periods became regular, parity, menopausal status, body mass index (BMI), n-3 fatty acid, and other covariates, we found breast cancer risk was reduced significantly in association with high soy intake. Relative to women with lower (below median) soy intake (<10.6 mg isoflavone per 1000 Kcal), women with higher (above median) intake showed a significant 18% risk reduction (relative risk (RR)=0.82, 95% confidence interval (CI)=0.70-0.97). This inverse association was apparent mainly in postmenopausal women (RR=0.74, 95% CI=0.61-0.90), and was not observed in premenopausal women (RR=1.04, 95% CI=0.77-1. 40). Among postmenopausal women, the soy-breast cancer association was stronger in those above median BMI (RR=0.67, 95% CI=0.51-0.88) than in leaner women (RR=0.83, 95% CI=0.62-1.11). Duration of follow-up modified the soy-breast cancer association, the effect being twice as large among women with 10+ vs fewer years of follow-up. Neither oestrogen nor progesterone receptor status of the tumours materially influenced the association. These prospective findings suggest that approximately 10 mg of isoflavones per day, obtained in a standard serving of tofu, may have lasting beneficial effects against breast cancer development.

PMID: 18594543 [PubMed - indexed for MEDLINE]

1: Br J Cancer. 2008 Jan 15;98(1):9-14. Epub 2008 Jan 8. Links

Epidemiology of soy exposures and breast cancer risk.

Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9175, USA. annawu@usc.edu

Most of the early studies published on soy and breast cancer were not designed to test the effect of soy; the assessment of soy intake was usually crude and few potential confounders were considered in the analysis. In this review, we focused on studies with relatively complete assessment of dietary soy exposure in the targeted populations and appropriate consideration for potential confounders in the statistical analysis of study data. Meta-analysis of the 8 (1 cohort, 7 case-control) studies conducted in high-soy-consuming Asians show a significant trend of decreasing risk with increasing soy food intake. Compared to the lowest level of soy food intake (<or=5 mg isoflavones per day), risk was intermediate (OR=0.88, 95% confidence interval (CI)=0.78-0.98) among those with modest ( approximately 10 mg isoflavones per day) intake and lowest (OR=0.71, 95% CI=0.60-0.85) among those with high intake (>or=20 mg isoflavones per day). In contrast, soy intake was unrelated to breast cancer risk in studies conducted in the 11 low-soy-consuming Western populations whose average highest and lowest soy isoflavone intake levels were around 0.8 and 0.15 mg per day, respectively. Thus, the evidence to date, based largely on case-control studies, suggest that soy food intake in the amount consumed in Asian populations may have protective effects against breast cancer.

PMID: 18182974 [PubMed - indexed for MEDLINE]