I've recently discovered that a lot of the dietary issues I've had in terms of various forms of intestinal distress can be solved by taking fiber supplements. I'm using Metamucil, which is psyllium husk. I can now eat foods which I thought I was allergic to, and they are now digested just fine. (Note that in my case these food "allergies" were causing nothing worse than diarrhea)
Fiber has a lot of benefits. It reduces both diarrhea and constipation by providing bulk and structure that helps the body hold food and guide it through the digestion process.
Fiber also affects the rate of food absorption. Since soluble fiber lowers glycemic index, it could be used to make foods that are known for causing insulin spikes (eg sodas and other things high in simple carbs) less unhealthy.
It turns out that this sort of works. If you mix the added fiber into the food, you can substantially lower glycemic index and glycemic load, and there have been numerous experiments of adding it to bread and breakfast cereal. However, it turns out that you can't just take a fiber supplement before indulging in cake and get a good result.
This study found that the fiber has to be mixed in with the food itself in order for this trick to work
I'd love to see this with bread. I'd love to see this with sodas as well, though I'm not sure if this is possible to do without dramatically affecting the texture of the soda. If the government is going to start paying for healthcare, they should invest in encouraging the production and consumption of healthier foods. At that point, it's not a subsidy, it's an investment.