New book in Dutch

Eet vet word slank

Eet vet word slank gepubliceerd januari 2013

In dit boek lees je o.a.: * heel veel informatie ter bevordering van je gezondheid; * hoe je door de juiste vetten te eten en te drinken kan afvallen; * hoe de overheid en de voedingsindustrie ons, uit financieel belang, verkeerd voorlichten; * dat je van bewerkte vetten ziek kan worden.

Trick and Treat:
How 'healthy eating' is making us ill
Trick and Treat cover

"A great book that shatters so many of the nutritional fantasies and fads of the last twenty years. Read it and prolong your life."
Clarissa Dickson Wright

Natural Health & Weight Loss cover

"NH&WL may be the best non-technical book on diet ever written"
Joel Kauffman, PhD, Professor Emeritus, University of the Sciences, Philadelphia, PA

Soy Online Service

Plant isoflavones' effect on human cancers

Dietary estrogenic isoflavones are potent inhibitors of beta-hydroxysteroid dehydrogenase of P. testosteronii.

Keung WM. Biochem Biophys Res Commun 1995 Oct 24 215:3 1137-44


The isoflavones daidzein, genistein, biochanin A and formononetin selectively inhibit the gamma-isozymes of mammalian alcohol dehydrogenase (ADH).

Since gamma-ADH is the only ADH isoform that catalyzes 3 beta-hydroxysteroid oxidation, it was conjectured that these isoflavones might also inhibit other enzymes involved in 3 beta-hydroxysteroid metabolism. P. testosteronii beta-hydroxysteroid dehydrogenase (beta-HSD) was used to evaluate this hypothesis.

Indeed, all isoflavones that inhibit gamma-ADH were found to be potent inhibitors of beta-HSD. Both the 3 beta- and 17 beta-HSD activities of the enzyme are inhibited.

Kinetic analyses with pregnenolone (3-beta-OH) and testosterone (17-beta-OH) as substrates reveal that daidzein and genistein inhibit beta-HSD competitively with respect to the sterol substrates. Their Ki values are very similar and range from 0.013 to 0.02 microM.

These results suggest that isoflavones may exert some of their biological effects by modulating activities of enzymes that metabolize steroids critical to hormonal and/or neuronal functions.

Estrogen-specific 17 beta-hydroxysteroid oxidoreductase type 1 (E.C. as a possible target for the action of phytoestrogens.

Mäkelä S, Poutanen M, Lehtimäki J, Kostian ML, Santti R, Vihko R.

Proc Soc Exp Biol Med 1995 Jan 208:1 51-9.


Several plant estrogens, especially coumestrol and genistein, were found to reduce the conversion of [3H]estrone to [3H] 17 beta-estradiol catalyzed by estrogen-specific 17 beta-hydroxysteroid oxidoreductase Type 1 (E.C. in vitro.

Coumestrol, the most potent inhibitor in our experiments, is the best inhibitor of the enzyme known to date.

All compounds with inhibitory effects were also estrogenic. However, structural demands for 17 beta-HSOR Type 1 inhibition and estrogenicity of tested compounds in breast cancer cells (judged by increased cell proliferation) were not identical.

Zearalenone and diethylstilbestrol, both potent estrogens, did not inhibit 17 beta-HSOR Type 1. Thus, changes in the estrogen molecule may discriminate between active sites of 17 beta-HSOR Type 1 and estrogen binding sites of the ER. The effects of these compounds in vivo cannot be predicted on the basis of these results.

Inhibition of 17 beta-HSOR Type 1 enzyme could lead to a decrease in the availability of the highly active endogenous estrogen. However, these compounds are estrogenic per se, and they may thus replace endogenous estrogens.

Additional studies are needed to further understand the role of these plant estrogens in the etiology of hormone-dependent cancers. It is not easily conceivable how the chemopreventive action of Asian diets, possibly mediated by phytoestrogens in soya products, can be based on the inhibition of estrone reduction at the target cells by phytoestrogens or related compounds, unless they are ''incomplete estrogens'' (i.e., unable to induce all effects typical of endogenous estrogens).



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