One of the cool things about the paleo diet is that it can help people zero in on their personal food sensitivities. So, even if you don't intend to follow paleo long term, a 30-day trial (for example) can really go a long way toward improving health. The idea is this: by eliminating all processed foods, grains, legumes, sugar and dairy for a period of time and then slowly adding them back in (preferably one at a time), you'll learn how your body reacts to each "food group." Then, you can decide for yourself what you want to incorporate into or leave out of your diet.
I think this is extremely beneficial for anyone who intends to get pregnant. Just think how much better someone would feel throughout pregnancy if she were able to stay away from things she knew her body did not like! It can be tough to figure these things out while following a Standard American Diet because the SAD contains so many toxins. How would someone know the root cause of the problem? Or that there is even a problem at all (a lot of people don't even realize that they aren't feeling great because we are all so used to feeling terrible, and as a result terrible just feels normal)?
I've long known that I'm sensitive or allergic to soy, many types of fish (including salmon and all shellfish), milk (not dairy in general -- just milk), oats, raw hazelnuts, MSG, most food additives/chemicals and artificial sweeteners (such as aspartame). Since starting paleo, I've also learned that rice is not my friend, that wheat is to blame for my headaches/sinus problems and that too much sugar leaves me feeling hungover. And I've determined that some non-paleo foods, like corn and quinoa, don't bother me at all.
I don't have any suggestions on how to conduct an elimination diet properly, but there are definitely tons of resources out there! Robb Wolf's book, The Paleo Solution, is a good place to start.
Another thing I want to mention real quick before I get back to sitting around waiting for the baby to be born: some people are sensitive/allergic to certain paleo foods as well. Eggs, nightshades (this includes bell peppers and tomatoes) and nuts are common culprits.
What are your thoughts on this? Did paleo or an elimination diet help you figure out your food sensitives?