Beneficial and Adverse Effects of Dietary Estrogens on the Human Endocrine System Clinical and Epidemiological Data

Doris M. Tham

Stanford University School of Medicine, 300 Pasteur Drive, Room S-308, Stanford,

California 94305-5208, USA

E-mail: [email protected]

Dietary estrogens, also known as phytoestrogens, represent a family of plant compounds which are of biological interest because they exhibit both in vivo and in vitro weak estrogenic and anti-estrogenic properties. Phytoestrogens appear to exert their physiological effects through a variety of possible mechanisms, such as their ability to bind to estrogen receptors and their actions on tyrosine kinases and growth factors. Phytoestrogens can be classified into three main categories consisting of isoflavones, lignans, and coumestans. A variety of commonly consumed foods contains appreciable amounts of these plant compounds which have been identified in various human body fluids, such as plasma, urine, bile, saliva, feces, breast milk, prostatic fluid and semen. Accumulating evidence from both clinical and epidemiologi-cal studies has suggested that dietary estrogens may potentially affect the human endocrine system. The existing evidence reviewed here will identify the current research in this area, which will include both the possible beneficial and adverse effects which dietary estrogens may have on the human endocrine system as it relates to breast, prostate and colon cancer, endogenous hormones, the menstrual cycle, menopausal symptoms, coronary heart disease, and osteoporosis. Moreover, the issue of infants fed soy-based formulas will be addressed.

Keywords: Isoflavone, Lignan, Cancer, Menopause, Coronary heart disease

1 Introduction 71

2 Metabolism of Dietary Estrogens 72

3 Sources and Typical Intake Levels of Dietary Estrogens 76

4 Biological Potencies of Dietary Estrogens 77

5 Potential Health Benefits of Dietary Estrogens 79

5.1 Breast Cancer 80

5.2 Prostate Cancer 83

5.3 Colon Cancer 85

5.4 Endogenous Hormones 86

5.5 Menstrual Cycle 88

5.6 Menopausal Symptoms 88

5.7 Coronary Heart Disease 90

5.8 Osteoporosis 93

The Handbook of Environmental Chemistry Vol. 3, Part M Endocrine Disruptors, Part II (ed. by M. Metzler)

© Springer-Verlag Berlin Heidelberg 2002

6 Infant Soy Formula 95

7 Potential Adverse Effects of Dietary Estrogens 98

8 Conclusions 100

9 References 101

Abbreviations

AOM

azoxymethane

CHD

coronary heart disease

DMBA

dimethylbenz[a]anthracene

E2

17ß-estradiol

EGF

epidermal growth factor

ER

estrogen receptor

FSH

follicle-stimulating hormone

GC-MS

gas chromatography-mass spectrometry

HDL

high density lipoprotein

HPLC

high performance liquid chromatography

HRT

hormone replacement therapy

HO

hydroxyl

ISP

isolated soy protein

LP(a)

lipoprotein a

LDL

low density lipoprotein

LH

luteinizing hormone

NAF

nipple aspirate fluid

NCEP

National Cholesterol Education Program

NMU

N-methyl-N-nitrosourea

O-Dma

O-demethylangiolensin

PSA

prostate specific antigen

PTK

protein tyrosine kinase

RBA

relative binding affinity

SFBA

San Francisco Bay Area

SHBG

sex hormone-binding globulin

SMA

serum modified access

TGF

transforming growth factor

UK

United Kingdom

US

United States

VLDL

very low density lipoprotein

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