I would look into the following conditions, which affect your entire body, involve your diet, and may give you headaches or other issues. Celiac Disease - 1 in 133 have it in Europe and the states, 3% are diagnosed (when they do randomized studies). Your symptoms are classic (aside from the fruit part) for silent celiac disease - three members of my family were diagnosed within the last year, all with those symptoms, actually. A gluten free diet takes care of the symptoms. Fructose malabsorption - involves the majority of fruit, causes symptoms. Solved through diet. Sulfite sensitivity, Tyramine sensitivity, and histamine sensitivity - involve broad ranges of foods, tend to cause headaches and other problems, and are solved by diet. You might also want to check out any resources on migraine diets or headache diets - books on these tend to have a lot of lists of foods that can cause headaches, and why.