Whey Protein Isolate vs Soy Protein Isolate


In almost all of the DIY recipies I’ve seen people use whey protein. One thread kind of tackled this question already but the main point made was that soy protein contained a different mix of amino acids. I’m comparing an option for both Whey and Soy protein available within Australia with links below:


Comparing the two together (Vanilla for Soy) the soy protein isolate has a higher concentration of protein (92.8% vs 91.4%), is $80 cheaper AND contains more of EVERY amino acid listed over the Whey protein isolate.

Is there any reason why I should not go for the Soy Protein Isolate option?


There are a lot of contradicting information out there, but there are some concerns with phytoestrogens in soy protein. I’m not sure what to think about it. Some say its very bad for the body, others say its not bad at all, because plant based estrogen is not effecting the body very much.


I’d say that saving on protein and using soy is not worth the risk.


Have you got any sources or information to back that statement up FlameRunner?

Here’s some information I found regarding the estrogen found in soy:

“Daidzein is a key isoflavone found in soy that acts as a potent phyto-estrogen. It is structurally a very weak “pseudo-estrogen” (about 1000 times weaker than the body’s primary estrogen estradiol). This is good news to the bodybuilder because weak estrogens like daidzein will compete with stronger estrogens like estradiol for available receptor sites to “bind” to. By binding to the receptor sites daidzein then “blocks” the stronger estrogens from binding to and activating receptor sites. With the daidzein isolflavone attached, estrogen receptor sites remain inactive. This inactivity further minimizes the negative effects of estrogen in the body. Many researchers believe this effect is the reason soy protein is linked to a reduction in the risk for many forms of breast, endometrial, and prostate cancer. This mechanism works similarly to the prescription drug Nolvadex (tamoxifen citrate)–an anti-estrogen staple in the bodybuilding community.”

Source: http://www.timinvermont.com/fitness/soyvswhy.htm


I’m not saying ‘DON’T! It will kill you!’. I’m saying ‘we are not sure that it’s entirely safe and I believe that the saving isn’t worth the potential risk’.


Again I’m not trying to discredit you FlameRunner but without a source for your information or even an explanation as to what the “potential risk” is it’s hard to take your point seriously.

Everything I’m finding online seems to point to the fact that Soy was bashed based on a false understanding of the pseudo-estrogen content. Even once a better understanding of this compound became available it continued to be bashed due to either ignorance or a refusal to change their current processes.

The FDA identifies a few other potential issues with soy protein isolate in that it contains nitrogen (around 50ppm) however in a normal diet this would account for only 0.0075% of the nitrogen we intake so even scaled up to the volume consumed in a soylent diet I wouldn’t consider this an issue.

The last identified potential issue is the presence of Lysinoalanine however clinical trials on 5 mammal species including rats using dosages much larger than that found in soy protein isolate has failed to produce any notable renal cytomegalic changes.

Source: http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogslisting&id=327


Look again at the amino acid list. The whey protein is per 30g and the soy protein is per 100g. Whey protein has a better BCAA profile than soy does. For some people, like people that are lifting weights, this might make whey more worthwhile.

That said, I’ve said on here that phytoestrogens can be a problem, but since then I’ve looked at some more research here and elsewhere, and yeah, I’m less convinced about that now than I was.


My main concerns: pseudo-estrogen and amino acid profile. For me, that’s enough to not use soy protein. But it’s only my opinion. If you’ve found research results saying it’s fine to use soy then just use it. :slight_smile:

'Hacker School Soylent' recipe

My bad! Silly me for not noticing this. After getting those two amino acid profiles together it looks like a pretty level field. The Whey has noticably higher levels of Leucine and Lysine which the Soy has noticably higher levels of Aspartic Acid, Glutamic Acid, Glycine, Phenlalanine, Proline and Serine. (Notably = more than 1500 per 100g)

(Sidenote: my recipe has a separate source for Leucine so the deficiency in Soy for this is not an issue for me)

Overall Soy looks considerably more balanced across all the amino acids however I can definitely see the advantages of Whey for body building applications.

As I’m in no way a body builder and am happy with slow/medium muscle development over time I think I’ll start with soy to save start-up costs and provide a more balanced amino acid profile and then as either money or diet commands move into a mix of both Soy and Whey protein down the track.


No worries mate. It’s easy to get confused swimming in a sea of numbers like that.


Do you have a source for this that isn’t some guy’s webpage? It contradicts some other research that shows that the don’t compete but have an additive effect -

Casanova M, et al. “Developmental effects of dietary phytoestrogens in Sprague-Dawley rats and interactions of genistein and daidzein with rat estrogen receptors alpha and beta in vitro.” Toxicol Sci 1999 Oct;51(2):236-44


http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogslisting&id=327 from my own research and http://www.ncbi.nlm.nih.gov/pubmed/19524224 from zach’s research in this thread


Please stop spreading misinformation:

Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men