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Grape Seed Extract inhibits aromatase

Supplements containing Grape Seed Extract (GSE) may well lower estradiol levels. This would make GSE an interesting supplement for athletes who want to lose weight faster or just tone up their body a bit more. Cancer researchers at the Beckman Research Institute in California demonstrated the anti-estrogenic effect of GSE in tests they did on cells.

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Lowering aromatase
GSE, an extract from grape seeds, consists of 75 percent proanthocyanidins. Of these, it seems likely that the procyanidin B dimers are the active ones. These are also found in red wine, and the researchers had already shown that these compounds inhibit aromatase, the enzyme that converts testosterone and androstenedione into estradiol.

This is of interest to cancer researchers because it's estradiol that's responsible fro the growth of many forms of breast cancer. Tumours often make their own aromatase.

So it would be even better if there were naturally occurring substances that not only deactivate aromatase, but also prevent cells from making aromatase in the first place. Which of course leads to the 64 million dollar question: is GSE capable of doing this?

Grape Seed Extract inhibits aromatase

To answer this question, the researchers first looked at whether GSE indeed inhibits aromatase. They put increasing concentrations of the extract in test tubes with aromatase producing cells, and then measured how much estradiol was produced. The figure below shows that the more GSE there was in a test tube, the less estradiol was produced.

Grape Seed Extract inhibits aromatase

But how exactly does GSE work? The researchers do know which pieces of the aromatase gene [or more precisely, the exones] the cells have to read to make aromatase. Genes on the DNA are like building models. And RNA copies the components that the cells need to make a protein. The RNA then introduces the copies into the cells, where molecular 'factories' produce the components and put them together.

The researchers added GSE to cells and then looked at whether the cells could still read all bits of the DNA. They noticed that the extract made the cell miss bits.

When the researchers looked at why that happened, they saw that GSE sabotages two transcription factors that the cell needs to read the gene for aromatase.

If you compare DNA with an old-fashioned LP [long playing record for those of you under 40] and the rest of the cell with an equally old-fashioned record player, then a transcription factor is the needle that you place on the record to transcribe it. The metaphor doesn't quite work, because a cell has lots of transcription factors and a record player only one, but you get the idea.

Glucocorticoid receptor
One of the transcription factors that is inhibited by GSE is an interesting one for power athletes: the glucocorticoid receptor. This is the protein that the muscle-destroying hormone cortisol attaches itself to. The figure below shows the effect of GSE on the number of glucocorticoid receptors.

Grape Seed Extract inhibits aromatase

Lots of phenols have a cortisol inhibiting effect. Quercetin is one of these. Natural athletes who've experimented with mega-doses of quercetin (500 to 1500 mg per day) notice that they lose some abdominal fat, according to Ergo-Log sources.

In vitro, not in vivo
Of course, we're talking here about research done with substances in test tubes. We don't know whether humans actually make less estradiol if they take GSE. Researchers often ignore the role of digestion and metabolism. They forget that the body sometimes hardly takes up a substance at all, and the minute amounts absorbed are converted in no time at all an inactive compounds.

In the case of GSE, however, the scenario might not be too bad. The body does actually absorb most substances in GSE pretty well.

Cancer Res. 2006 Jun 1;66(11):5960-7.

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Grape Seed Extract
Lowering Estradiol

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