>How do we know that they affect people?  I doubt there have been any sort of
>blind clinical studies.

I found this one:

"In 1991, the Royal Prince Alfred Hospital (RPAH) allergy clinic in Sydney
looked at data for 1105 people who had attended the clinic and undergone
challenge diets with various food substances, including MSG. They found
that 44% reacted to MSG, though no-one was sensitive to MSG alone. The most
common additional substances provoking reactions in MSG-sensitive people
were salicylates (73%) and amines (60%). These are often found in acidic
fruit (salicylates) or cheese and chocolate (amines) -- quite common foods.
So MSG-sensitive people often experience problems with meals where large
amounts of amines, salicylates and MSG are eaten in combination -- for
example, Asian, Lebanese or Italian meals, pizzas and certain fast foods.

People attending an allergy clinic for one reason or another (common
reasons for attending an allergy clinic include itchy skin, irritable bowel
syndrome, migraine or asthma) are clearly a self-selected group, and may be
unrepresentative of the population at large. However, results of food
challenge tests in a small number of 'healthy' people led specialists at
the RPAH allergy clinic to conclude that a minor degree of intolerance to
MSG and other food substances is likely to be quite common in the wider
community." - http://www.choice.com.au/articles/a100241p4.htm

I also found a reference to a double-blind study of 20,000 patients at the
same hospital but I'm having trouble finding the study itself:

"The only way to determine if you child has a problem is to put them on an
elimination diet.
Fortunately, says Sue, Australia has one of the best, most thoroughly
researched elimination diets in the world. Created by Sydney's Royal Prince
Alfred Hospital, it was devised from double-blind, placebo-controlled
studies over 20 years with 20,000 food intolerant patients.

For three to six weeks, foods known to cause a reaction in people are
avoided. These include 50 additives, some natural chemicals called
salicylates found in fruit and vegetables, and sometimes dairy foods and
wheat. Gradually foods are reintroduced one at a time to pinpoint the
problem." - http://www.motherinc.com.au/editorial/ShowStory.asp?StoryID=27

Here's another page quoting many studies:

http://www.asehaqld.org.au/food_mood_and_behaviour.htm

>An interesting question is --- do children of aboriginal tribal
>hunter-gatherers (who have been isolated from modern society) get ADHD ?

ADHD doesn't really appear until you expose the kids to modern stressful
living.  Even in that article, he said the kid is quite often fine until
you expose him to a school.  I'm not sure how relevant such a study would
be?  My symptoms often disappear if I don't have to go to work or drive a
vehicle.

Don't get me wrong, I'm not knocking the paleo diet.  Quite the
opposite.  I feel much better since I started it.  However, the fruits were
bothering me and giving me all sorts of digestive problems, so I had to cut
them out.  I feel even better now without the fruits and I have more energy
at the gym, but I don't feel 100%, and I can't help wondering if another
paleo food or chemical is to blame (amines, benzoates, etc.).

Kat.