[1] https://www.sciencedirect.com/science/article/pii/S001502820...
Read study entirely and in context before judging effect size based on study alone but the data indicates further study is worth pursuing.
On the other hand: Ahhhh, figs.
The sample size is incredibly small (n=35), but it appears to be a well-constructed & controlled study. This merits further investigation. And that's exactly what the abstract ends with.
My husband and I switched to soy milk about 15 years ago. Anecdote, he had his testosterone tested recently and it was fairly high [he's completely bald], I have not had mine tested ever. We like soy milk because we get the raw stuff without the gross thickeners like xantham gum or carageenan, everything else seems to add that (oat, rice, hemp, almond, etc.).
But data is data.
Hopefully this isn't one of those "un-reproducable studies" but it was done by the NIH and not a university.
So more samples is worse for a study like this?
Seems counter-intuitive, but I'm not a stats guy.
That meta-analysis says: "Given that isoflavone-depleted isolated soy protein is not commercially available and the composition of the product is altered by the ethanol-washed processing used to extract isoflavones, the isoflavone-depleted isolated soy protein treatment groups used in three studies 39, 40, 62 were excluded from all analyses except the subgroup analysis of the effects of soy protein dose." Citation 40 is this article.
EDIT: I didn’t realize the study was from 2005. In that case the research predates the meme.
So whenever people make a dramatic switch to soy-based diet from a carnivore diet that we evolved with over millions of years, it's always important to acknowledge a possibility of side effects that we don't currently know about.