Reason: the amino acids in plant proteins tend to be incomplete (missing some essential amino acids), whereas meats tend to be complete, and "vegetable proteins are somewhat less digestible than animal proteins," so meats provide more bio-available sources of protein than plants. Plants also contain anti-nutrients that bind with nutrients (especially minerals and vitamins), thus further reducing their nutritional quality. In addition, the proteins in certain plants, such as wheat, have molecular structures very similar to those of the surface proteins in bacteria and influenza viruses, thus potentially stimulating autoimmune responses in the human body.

See also: 
> http://blog.nutritiondata.com/ndblog/2008/06/on-beans-rice-a.html 
> Cordain et al's research at http://www.thepaleodiet.com/published_research/
> NeanderThin by Ray Audette

Therefore, as large-prey-animals became more scarce and humans were forced to eat more and more grain and legume foods, people found, through experience, combinations that resulted in less nutritional deficiency symptoms, though they were not able to eliminate them completely and some people fared worse than others.

The only food combining benefit of bread that I know of is to avoid protein starvation when only lean meats are available, but there may be others.

> -----Original Message-----
> From: Paleolithic Eating Support List
> [mailto:[log in to unmask]] On Behalf Of pbarrett
> Sent: Saturday, August 16, 2008 11:37 AM
> To: [log in to unmask]
> Subject: food combining
> 
> Getting protein by combining foods occurs why? I note that Japanese
> gohan means both rice and a meal. Is this because in order to get
> protein, rice has to be combined with other typical ingredients in the
> diet? Is that why bread figures prominently in every meal in most
> cultures?
> ....