Everybody has gut bacteria, or flora, that are usually present. These are determined by the usual diet. The usual gut flora contain quite a variety of bacteria. You can change your gut flora in two different ways – 1. By changing what you usually eat. Different bacteria thrive on particular foods. If you change the type of food you eat in some way you will change the proportion of the various bacteria that grow in your gut. Prebiotics is the name given to the process of changing your flora by changing the food eaten. [“pre” = “before”]. If your usual food is high in grains/ bread/ pasta one type of bacteria will predominate. If your usual food is high in meats, fish, chicken or legumes different bacteria will thrive. Well cooked starches may encourage different bacteria to those produced after soft cooked breads. 2. The other way to change your gut flora is to feed yourself different bacteria. This is called Probiotics. This happens when you eat food containing live bacteria, such as in yoghurt with acidophilus. Since digestion occurs all along the gut, many of the bacteria do not suvive to make a difference to your usual flora in the intestine. Those bacteria thought to survive to be useful in the bowel are those in Nestle LC1 and Valalia GG and Yacult. You need only 1/4 cup / day. However you need to keep having these every day or you will revert to your usual flora. If someone is extremely sick, such as infants with diarrhoea in developing countries, or people with severe medical problems in the gut, researchers have found that feeding probiotics has been useful. The research has shown that providing new flora has helped enhance gut wall health and normal function. Research in Europe shows that use of Lactobacillus GG enhances normal function in immunological and non-immunological mechanisms that provide barriers to absorption of undesirable antigens. This is particularly so where there is inflammation of the gut. The important question for those who suspect food sensitivity is “Does it help if you have an inherited allergy to some food?” At this time we do not know. Are probiotics useful after a gut infection or after antibiotics? After a gut infection, or after using antibiotics, it appears wise to re-establish preferred gut flora using a probiotic food. Are probiotics useful in intolerance to natural and added chemicals? In Australia those working with food sensitive families have not seen useful improvements in food tolerance after families have used probiotic foods to find out. This may be because probiotics do not affect absorption of natural and added chemicals in those who are sensitive to them. Are probiotics useful in those allergic to whole foods? The European research supports its use here, especially in infants, especially where diarrhoea is present. The main problem is that most infants with allergies cannot tolerate dairy foods, and so cannot be given a yoghurt to provide the preferred bacteria. If you have an infant you are concerned about, do discuss this with your doctor or dietitian. You may need to find a bacterial preparation with the desired bacteria with no dairy solids in it. This discussion raises an important idea. Usually, most thinking about food sensitivity is about what foods and chemicals should be excluded. Further research will look at the next layer in this complex issue. That is, can we change factors affecting digestion, absorption, metabolism or excretion so that reactions are lessened. At present, it is best to concentrate on doing “diet detective work” to ensure you have the diet right for you and your family.