# When did soy become complete?

**URL:** <https://boards.straightdope.com/t/when-did-soy-become-complete/205982>\
**Category:** Factual Questions\
**Created:** [October 7, 2003, 2:18am UTC](https://boards.straightdope.com/t/when-did-soy-become-complete/205982 "2003-10-07T02:18:50Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\
**Post date:** [October 7, 2003, 2:18am UTC](https://boards.straightdope.com/t/when-did-soy-become-complete/205982/1 "2003-10-07T02:18:50Z")

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As in complete protein. I noticed a local health food store advertising that soy is a complete protein. Looking on the web I find the same. I was under the impression plant proteins are not. What is the SD?

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**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\
**Post date:** [October 7, 2003, 3:48am UTC](https://boards.straightdope.com/t/when-did-soy-become-complete/205982/2 "2003-10-07T03:48:43Z")

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From _The Tufts University Guide to Total Nutrition_:

> [@](#):
>
> Soybeans and many nuts contain all the essential amino acids, but they don’t have enough of one or more of them to make them effective in completely meeting protein needs. Soybeans are limited in methionine, so if they are combined with wheat, which has high levels of that amino acid, the result is a complete protein source."

Unless you are gluten intolerant, it is extremely likely in U.S. culture, vegetarian or not, that you will regularly take in sufficient products made of wheat so that the soy will be both complete and in full amounts. But it is stretching the meaning of the term complete by a bit.

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**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\
**Post date:** [October 7, 2003, 4:29am UTC](https://boards.straightdope.com/t/when-did-soy-become-complete/205982/3 "2003-10-07T04:29:43Z")

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Soybeans have always been a good protein source. You may be thinking of corn, which is normally low in the essential amino acid lysine. However, [high lysine corn](http://web.aces.uiuc.edu/value/factsheets/corn/fact-hi-lysine.htm) is now available.