Why food intolerance hits in our 20's/30's/40's?

So I’ve been wondering if there’s been any research (or maybe past discussion) on why we can tolerate certain foods for years and eventually they start to give us migraines or cause us other health problems?

I started drinking tea at probably 4 years old already and coffee probably when I was 8 or 9. Later when I was about fifteen I remember drinking 3 five or six ounce cups of coffee before starting work at 4:30 in the morning. For years I drank as much caffeine as I wanted and pretty much any time I wanted. I had no trouble sleeping, no headaches, no restless leg syndrome.

In the last six or seven years (I’m 33 now) I started having more tension headaches. Eventually I found out that caffeine was affecting my sleep so I stopped drinking it in the afternoon/evening. A couple years ago I started having trouble with chronic tension on my right side, starting right below my shoulder blade, extending upwards along my spine, spreading throughout my shoulder, up the full length of my neck, into my skull and up into my temples. I visited a chiropractor that I’m convinced was a quack. He said I had hypoglycemia (no blood test) and that I needed to get off caffeine. I think he was spot on with getting me to reduce sugar and caffeine but he went on to try to sell me a bunch of enzymes. Basically, he told me that I had run my body down so bad that I could no longer tolerate things I could previously tolerate. He wanted me to keep coming back and keep buying his $40 bottles of enzymes so that I could restore my adrenal system which would then prevent headaches.

After only a couple months I quit going to him and stopped taking any of his enzymes. I started up the caffeine again but ever since I’ve been very careful about how much I drink, usually only about 8 oz in the morning and that’s it.

It’s really too early to tell for sure, but it appears that caffeine is in fact one of the primary triggers for my recently diagnosed MAV. I’m currently working on getting off of it but am having to drink very small amounts to alleviate the excruciating headaches I get when I go cold turkey. In fact, my Thanksgiving Day was spent in tremendous pain because I went cold turkey the day before, and I decided to just stick it out. That is, until about eight in the evening when I found that drinking about 3 or 4 oz of hot tea resolved my headache. Today I had a similar amount and tomorrow I expect to have even less.

So I think the real question I’ve been working up to here, why do we become sensitive to certain foods over time? Is this a sign of some bigger imbalance in our body?

I’ve wondered at times if our modern environment, diet, and lifestyle has put everything so out of kelter that we are experiencing far more disease and illness than people did in ages past, although I admit that history does reveal some really grim health problems (such as plagues, smallpox, mumps, measles, rubella, etc) along with a great deal of medical ignorance. Given a choice it seems like it would be preferable to live in the current age but sometimes I still wonder if medical science is really headed in the right direction. I think it’s more reactive rather than proactive - we’d rather pop pills than make diet and lifestyle changes. If this is really the case, my complaint is that it seems like everything is against us when it comes to correcting our diet and lifestyle (think restaurants, Wal-Mart, sedentary jobs, etc). But I think I’m getting off track here so I digress. Are there any theories as to why we become sensitive to, allergic to or otherwise intolerant of certain foods or substances in our middle life?

Good Questions you pose,
Let’s hope someone has some answers. I wonder why I was totally fine my whole life…never even a headache…and then I get whacked with MAV …no family history…it’s hard to understand…but I have to accept it since so many pieces fit together now…