Soy isoflavones increase preprandial peptide YY (PYY), but have no effect on ghrelin and body weight in healthy postmenopausal women

What Was Tested

This randomized controlled trial paper looks at Peptide YY and Ghrelin.

Soy isoflavones show structural and functional similarities to estradiol.

Available data indicate that estradiol and estradiol-like components may interact with gut "satiety hormones" such as peptide YY (PYY) and ghrelin, and thus influence body weight.

Who Took Part

The study group was 34 women.

By PubMed's age tags, the people studied were middle-aged adults and older adults, women only.

How the Study Was Run

In design terms this was a randomized, double-blind, placebo-controlled and crossover study.

Random assignment meant chance, not the researchers, decided who got Peptide YY and who got the comparison, which limits bias.

As a double-blind Peptide YY study, the assignments were hidden from both participants and investigators until the end.

The comparison arm used a placebo, so changes seen with Peptide YY could be set against what happens without it.

Each person switched between Peptide YY and the comparison at some point, usually with a gap in between.

Plasma concentrations of ghrelin and PYY, as well as energy intake and body weight were measured at baseline and after four and eight weeks of each intervention arm.

What Was Measured

PubMed files the paper under topics including Fasting, Ghrelin, Isoflavones, Peptide Hormones, Peptide YY, Postmenopause and Soy Foods.

What This Means in Plain Language

The paper is a randomized, double-blind and placebo-controlled study of Peptide YY and Ghrelin in 34 women.

With fewer than 40 people, it is a small study, so it is better read as an early signal for further research than as a settled answer.

Its findings take up roughly 8 sentences of the abstract and are left out here on purpose; the source paper is the place to read them.

The publication is from 2006 (Journal of negative results in biomedicine), a journal based in England.

More context: the Peptide YY compound page and the Ghrelin compound page, all human trials.