Health, weight and gut flora
in Gut bacteria 
Bacteria
Do the bacteria you have in your gut affect your health and weight? The answer is probably yes, but it remains to be shown how much and in what way.
In recent years technological advances have made it easier to do research on the bacteria that comprise our gut flora. Increasingly, statistical correlations are found between certain types of bacteria and diseases, such as obesity and diabetes.
The problem is very common. Scientists and journalists are quick to conclude that statistical correlations imply causation. This is the way our brains work, they fabricate a plausible story in order to explain the findings and this often leads us the wrong way. Finding the truth is more complicated.
Do certain bacteria cause obesity, or does a certain lifestyle (for example junk food full of sugar) increase body weight AND affect what bacteria you have in your gut? This question is harder to answer.
Is it possible to cure disease or control your weight long-term by adding good bacteria (probiotics) to the gut? This largely remains to be proven. At the moment there are more questions than answers.
Krina
Look for fermented products that are still fermenting. With the sauerkraut I get, the lid pops audibly when opened because the bacteria is still fermenting and gives off gas. The farmer I get it from uses just the native bacteria on the cabbage (organic) and does not add a whey starter. Similarly, there are numerous different bacteria used for different yoghurts and Kefirs. I try to get a variety through different plain yoghurts, making sure in each case they are live cultures. I like to have a priopionic bacterium in one of them, as these bacteria produce propionic acid in the gut (a saturated fat that lowers blood pressure in studies). I also get kefir and yoghurt cultures from a cheese-making supply store and sometimes add some to the yoghurt I am eating.
Leafy greens are excellent because bacteria that feed on them create butyrate (an anti-inflammatory saturated fat). A recent study just found a correlation between reduced butyrate-making bacteria in the gut and type II diabetes. Eating some raw leafy greens with the native bacteria (i.e., those that feed on that plant) probably helps get the right bacteria in the gut.
what's your opinion about colostrum?
You say, "Is it possible to cure disease or control your weight long-term by adding good bacteria (probiotics) to the gut? This largely remains to be proven." I don't understand your hesitation. There is thousands and thousands of years of proof that eating probiotic foods was a big part of the diet that kept humans free of our modern degenerative diseases. There is current scientific evidence of the benefits of eating highly probiotic foods like real sauerkraut and kefir - you can find it on the Weston A. Price Foundation website, or in their journal, "Wise Traditions." Dr. Natasha Campbell-McBride (author of Gut and Psychology Syndrome) has cured thousands with her GAPS protocol of eating a traditional diet which has no processed foods, is high in animal fats (like butter, bone broths, stews, etc.), and has a focus on fermented foods.
If the advantage of adding highly probiotic foods to the diet is endorsed by people like you with large exposure, many more people will understand that something can be done to prevent and cure many of our modern disease epidemics. It isn't likely that Big Money will get behind research into this - no money to be made here by going back to the nourishing traditional diet of our ancestors that included highly probiotic foods. There are more probiotics in one serving of home-made fermented vegetables than in an entire bottle of high priced, high potency probiotics. So the studies which could provide more proof may be a long time coming. We already know that probiotic-rich foods in the diet add nourishment and they prevent/cure disease. They cause no harm. Why are you cautious about recommending this?
That's not proof, that's correlation. NOT the same thing, but a very common mistake to make.
That said, one has to make dietary decisions now, before the science can prove causation beyond reasonable doubt. Otherwise one becomes a Hamlet, paralyzed by the slightest uncertainty in absence of irrefutable proof, and starving to death before deciding what to eat. Instead, one gathers and ruminates on the evidence available and looks for plausible inferences to apply it to one's own metabolic quirks, and then observes the effect and adjusts.
So I go with my gut instinct. The accumulating pieces of evidence of benefits of probiotic make it more plausible for purposes of immediate decision-making to believe that fermentation of food is a health benefit. I have no vested interest in such a position and would readily alter upon more credible evidence suggesting otherwise. so I am not limited by confirmation bias. My wife remarks sometimes that my dietary goals keep changing. My response is that the evidence keeps changing. Keeping steady in the face of an evolving evidential landscape would be idealism and confirmation bias.
Fermeted veggies is an old preservetion metod, that make the nutrients stay, and in some cases make some new.. and the best thing is that it keep the bad bacteria away!
You know.. in sweden we even got fermented fish.. you should taste this.. its smells terebly!
http://www.youtube.com/watch?v=m-wQhSuf6mM
Soo.. then to probiotics.. its a preservation metod.. its free of poision, its an old and safe thing, it have some benefits.. like its a part of predigestion!
And to that.. any probiotic bacteria should die in our stomage, by the gut acid.. its the purpose of the gut acid.. to make deaminoation of amino acids like bacterias!
Soo whats the benefits of eating old fashion fermented food.. well its no toxic, it preserv the nutrients, and it make your guts have a lower PH thats in turn have benefits for your own lactid bacteria flora!
And then.. how to think about this.. well eat old fashion fermented food.. its safe, and could have some benefits for your gut flora!
But, then.. whats about those pills and new probiotic products.. avoid them like all other new industrial products.. and eat all the saurkrauts or surströming you wish!
Did you know.. Coleslawe made of saurkraut is good.. ie.. taste good!
And did you know.. saurkraut is perticaly good to sweinaxel.. ie, porklegg!
what's your opinion about bovine colostrum?