Posting this here as a new thread so as not to interrupt the current iodine thread. The soy issue has come up on a couple of posts on that thread between Paleobird and JamesS. JamesS claims to have debunked those who are anti-soy, and if he cares to spend time on this topic, I'm certainly willing to read his take. But first, I'll tell why I don't eat soy. I think my reasons are probably shared by many on this forum.
I claim no science background and haven't spend endless hours pouring over medical studies. I was inspired to give up grains by reading The Primal Bluepring, MDA website and forum, and my own successes with doing so.
Soy is a grain and typical of grains is high in Omega 6 fatty acids, which increases the Omega 6 to Omega 3 ratio in the body. Within 2 weeks of following the Primal Blueprint, I was able to completely eliminate my need for asthma medications and have been med-free for 2.5 years. I credit eliminating grains (among other diet changes) and occasional supplementing with fish oil to balance my omega ratio.
Here's a short paragraph from wikipedia on Omega-6 fatty acids, which backs my thinking: "Modern Western diets typically have ratios of n−6 to n−3 in excess of 10 to 1, some as high as 30 to 1; the average ratio of omega 6 to omega 3 in the Western diet is 15/1–16.7/1. Humans are thought to have evolved with a diet of a 1-to-1 ratio of omega 6 to omega 3 and the optimal ratio is thought to be 4 to 1 or lower. A ratio of 2–3/1 omega 6 to omega 3 helped reduce inflammation in patients with rheumatoid arthritis. A ratio of 5/1 had a beneficial effect on patients with asthma but a 10/1 ratio had a negative effect. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 had no effect."
The other benefit to giving up soy (along with all grains), is that it's an easy means of cutting carbohydrates. Many of us here have also battled weight issues. I'm down 30 pounds from my peak weight just before starting PB. I never ate much soy prior anyway, so it was much easier to eliminate it than it was to give up wheat - yep, I still miss bread and pie.
That's my reasoning JamesS.