Let me answer your questions drawing on the science, theory and research of the diet approach;
The first question is about testing to see which foods are reactive to the person with MS. This is important so that the person can determine his or her trigger foods. MS is a dynamic disease with constant changes, though often very subtle. Usually, when a person pays attention to his or her body after they eat, they will note some discomfort, a change in symptoms, or an odd sensation, if they have ingested a food to which they are sensitive. This is a marker that the particular meal caused an immune reaction setting up the cascade of events that lead to symptoms--even if it is very subtle. The goal is to discover what foods are triggers for the particular person, and to stop ingesting them so that the disease activity is stopped.
Now for some people whose symptoms are so all encompassing, they may not have the sensory aliveness to perceive these subtle reactions. Major symptoms build up from these small reactions. There are several strategies, mentioned in the book for discovering the person's unique sensitivities. Stopping one food, I believe I never wrote one week, but for several weeks, may be sufficient to determine whether that particular food is a trigger. Re-adding the food, in large quantities for several days (to go beyond the rotation and moderation principle which really can prevent reactions), is another way to see. By stopping all the five food groups, plus saturated fats and sugars for a time is another strategy. By doing this the disease process stops pretty quickly. If the person chooses to test out one food and then another, it will take longer to stop the disease process. When the person feels comfortable with his or her recovery and mastery of the diet, the person can test these foods they stopped eating to see which ones are the triggers. Allergy theory suggests that it takes three months of abstention from a food to lose sensitivity. From what I can determine, it is highly individual, like everything else in MS. There are some tests, mentioned in the book which can also help determine the food sensitivities. Each person needs to come to understand his or her own body in this.
It should be clear that all the discussion about starting and stopping various foods is for the purpose of determining which foods are triggers. If a food is found to be a trigger, the person should stop ingesting it altogether since it fuels the disease process. It may be months or years that the person has to stop eating the trigger foods to get complete recovery. As described in the chapter on Maintaining Your Recovery, these foods may be reintroduced when recovery is well along and they have mastery of the diet.
Seeing improvement is a different process. The first goal is to stop the disease activity--the diet, finding the trigger foods and not ingesting them, accomplishes that. Once the disease process is stopped then the body begins to heal. If you think about it, relapsing remitting MS is a balancing between when the disease activity overwhelms the body and when the disease activity subsides enough (not eating quite the same, less stress, or the body is healthier at that point in time) the body can heal. When the MS is secondary progressive, ie constant symptoms, the disease activity is too strong for the body to make headway in healing. The time lapse between starting the diet and seeing results is because the body has much to do, rebuilding the nerves and myelin which can be quite damaged. Several people have returned for MRIs after their recovery and the lesions have disappeared. So, the time it takes depends on the damage that has been done and the individual person’s ability to heal.
In your wife's case, where her MS symptoms are pretty stable, but still there, suggests that she is at a balance point--her health is good enough and the disease process isn't being fed enough to do any further damage. I would also speculate, which of course you would need to test out, that she has a limited number of triggers. And, if you read the chapter on Maintaining Your Recovery, I suspect that over time, she would be able to return to normal eating. A note on her supplements--lecithin is soy or egg based and it they are triggers. It could cause her problems.
In answer to your question about low uric acids and MS, there are many studies that have been published showing altered body chemistry in people with MS--in the saliva, in the cervical lymph nodes, in the level of various elements. The problem here is that there is no context for any of these findings. They are all just descriptive. No one understands MS enough to know if these changes are part of the disease process or part of the body's attempt to heal. There are all kinds of treatments that seem to help some people--removing mercury is one, bee sting therapy is another. Both are based on solid science, the problem with them is that, I would speculate, they work only on people for which that factor plays a more major role. As discussed in the book, there are many factors that contribute to the manifestation of the disease and they do not appear to be consistent. There does not appear to be one or two smoking guns that would explain all cases.
You ask if the diet will work for everyone. We have no studies because the institutions of medicine will not fund such a comprehensive study on diet as would be needed for the dietary approach. The usual reductionist model for research does not meet the required complexity of research design needed for this treatment. MS is really not understood at all by any discipline or approach. Though the proponents of the diet approach have solid science and theory behind us, we don't have all the answers to MS either. What we do know from over the 50 years that the diet has been developed and refined, is that it works. As explained in the book there seem to be two distinct disease pathways; lesions and axonal death under normal appearing white and gray matter. A further complication is that the lesions are not consistent--there are four types, which indicates four disease processes.
My answer is yes the diet will work for the vast majority of people. Because, no matter which disease pathway manifests in the central nervous system, it is a universal in MS that activated immune cells crossing the blood brain barrier feed the disease process in all MS cases. The diet's target is to stop the immune cells from being activated in the first place. (As an aside it is interesting that the most effective drug so far, Tysabri, which has great risks and does not promise a recovery, operates by tying up the activated immune cells and prevents them from crossing the barrier). Since the activated immune cells feed the disease in all cases, it is logical that stopping the cause of immune activity would be effective for everyone. The diet does that. As it is described in the book stress, fatigue and other illnesses also activate the immune system and feed the disease process. But, it is our experience that as the person heals, the body becomes stronger and these are less of a factor. The diet has worked for a great many people over many years with wonderful results. There is no other treatment that even promises the reversal of symptoms that the diet approach achieves on a regular basis.
There have been so many cases of a return to full health. Some people do choose to tolerate some low level of activity because they want to keep eating certain foods that cause them problems. But when they come to that decision, it is their choice--not the choice of the disease. Even if there are some residue symptoms, it is far better than to have the full blown disease.
I hope that this helps you and feel free to ask other questions. Best of luck to you and your wife, Ann