Monday, December 8, 2008

Soy's dirty little secrets, episode 1: a Protein's menace

Soy.
An innocent little green bean esc legume with the popularity of Paris Hilton.
Due to the lovers quarrel many people have with soy, and because of the variety of misinformation out there about soy I'll be writing about some of the facts, myths, and legends about the legume.

First used in China almost 3000 years ago as a sacred plant, but surprisingly didn't make it as a main food crop until the discovery of Tofu (they made it into a paste and voila, Tofu). As a side note, the Chinese didn't eat soy until they started fermenting it into Tofu, nato, etc.

As a cheap crop to grow it became popular for farmers in the US and it's heavily subsidized by the government which is part of the reason it's in everything. Soy didn't really become popular as a heath food until the late 1970's with the introduction of soymilk by vitasoy (a company based in Hong Kong). Since then it's been toted as a health food in the US, great for weight trainers, gainers and losers a like, organic funkies, and corporate junkies. Soy's become a king.

(Note: due to the complex nature of the material some of the crap I'm going to write is going to be simplified, so if you want to know more I'll leave you some sources at the end of the series).

So that's the question, is soy the king of the heath food world?

Let's look at one of the claims that the proponents of soy tout as a major health benefit: soy has protein. And not just any protein, but a complete protein that contains all of the essential amino acids. That is true.

While that's true why not delve a little bit deeper. Complete protein, sure that's great, but there's also another part of the protein equation.

Trypsin.
Trypsin is an enzyme in your stomach that helps digest proteins. Once trypsin does its magic the proteins are ready to be absorbed and used in the body, if trypsin doesn't work those amino acid chains are too large for the body to use and they'll be passed on as waste. So trypsin and protein are a dream team for protein.

What does trypsin have to do with soy? Well soy's first dirty little secret is that it contains trypsin inhibitors (here)... Think about that for a second. A. Soy has protein B. Trypsin digests protein C. Soy contains trypsin inhibitors. So A + B + C = poor protein digestion.

What!!!

That's right, I'm telling you that when you eat soy you don't actually digest all of the protein contained in the legume.

Let me say that another way: You don't digest soy's protein well.

One more time for the slow ones: Soy's protein doesn't get to your system.

How about one step further, if you eat soy and meat proteins together you're not going to digest the proteins in the meat as well either.

Soy 0 Kian 1

Next time we'll talk about how soy can girlify you

Go well

-Kian

P.S. You might guess I'm not a very big fan of Soy, that's pretty true, but there are times when I think you can eat it guilt free.

2 comments:

Unknown said...

I knew the lunch ladies were trying to kill me with those cheap soy "hamburgers!"

KH said...

I like your blog man, I'd be interested to see your sources on the trypsin inhibitors, I just wanted to see what you're referencing. Do you know how much of our soy products get the trypsin inhibitors denatured by heat? I like your approach to nutrition on this blog, I'm wrapping up my med school nutrition course, and all the evidence is pretty straightforward, just easier to say than do. I signed up to get the feed from your site.

- C Bac (the one and only)