Summary Science in the last five years is finally recognizing what many in the natural health industry have said for years about the harm of antibiotics, and the relationship between friendly and unfriendly bacteria.  Antibiotics kill all bacteria including needed friendly bacteria that keep the harmful bacteria in check. Mass killing of all bacteria by antibiotics causes weakened immune systems which in turn causes other diseases. Probiotics accomplish what most antibiotics are prescribed for without killing the friendly bacteria.

USProbotics.org "Probiotics are "live microorganisms which when administered in adequate amount confer a health benefit on the host...Scientists are learning more each day about the role of microbes in keeping people healthy and the multitude of health benefits associated with consuming the right type and levels of probiotic microbes...Some preliminary studies also report that certain probiotics can play a role in reducing the development of allergy in children,...and keeping healthy people healthy." (1)

Medicine Net.com "Probiotics are live microorganisms (in most cases, bacteria) that are similar to beneficial microorganisms found in the human gut. They are also called "friendly bacteria" or "good bacteria." Probiotics are available to consumers mainly in the form of dietary supplements and foods. They can be used as complementary and alternative medicine...Probiotics are the latest in the category of good-for-you foods. Basically, they are "good" bacteria added to foods or occurring naturally in certain yogurts, fermented dairy drinks, and in supplement form." (2)

Kathy Wong "Probiotics are considered beneficial and are sometimes referred to as "friendly" bacteria. Some of the ways they are thought to promote health include suppressing the growth of potentially harmful bacteria, improving immune function, enhancing the protective barrier of the digestive tract, and helping to produce vitamin K. There are over 400 species of microorganisms in the human digestive tract, including Lactobacillus and Bifidobacterium. A number of medical, diet, and lifestyle factors are believed to disturb the balance in the colon. This imbalance is called dysbiosis. Factors include:
* Inadequate dietary fiber  * Oral antibiotic therapy   * Infant formula feeding  * Ingestion of environmental toxins
No longer kept in check, less healthy bacteria and yeast may flourish, which is thought to increase the likelihood of conditions such as infectious diarrhea and vaginal yeast infections." (3)

Sources of Probiotics "Probiotics can be found in capsule, liquid, powder, or tablet form. Acidophilus drinks can be found in health food stores and some grocery stores and Asian grocers. Probiotics can also be found in cultured dairy products such as yogurt or kefir, however, the number of live organisms varies greatly from product to product due to differences in processing methods. Fermented foods such as sauerkraut also contain probiotics. (3)

Mayo Clinic "In addition, recent research suggests a number of new potential uses for probiotics. One study in Sweden found that a group of employees who were given probiotics missed less work due to illness than did employees who were not given probiotics. Other studies have found probiotics to be helpful in managing the signs and symptoms of irritable bowel syndrome (IBS).Some of the probiotics currently being studied include: * Enterococcus * Lactobacillus acidophilus * Saccharomyces boulardii * Bifidobacterium." (4)

Web Med "Probiotics are small organisms that help maintain the natural balance of organisms (microflora) in the intestines...In most circumstances, people use probiotics to prevent diarrhea caused by antibiotics." (5)

Mary Shomon's Thyroid Disease Blog "It is the bad microbes that cause disease. Good microbes work with the body’s immune system to keep the bad microbes at bay by crowding them out. In the symbiotic relationship between good and bad microbes, recent research has uncovered the importance of these good microbes. The good microbes – and this is where probiotics come in – keep the bad microbes in small numbers. But they also stimulate the immune system and improve our digestive function...Historically, until about five years ago, probiotics were considered only within the realm of complementary and alternative medicine. As our understanding of the immune system and how it works has expanded, so has the understanding of the importance of probiotics and probiotic microbes in the gastrointestinal track in regulating the immune system. "Today, the world of probiotics is emerging on the cutting-edge of mainstream medicine,” Huffnagle says." (6)

ProBiotics New Zeland "We know what bad bacteria can do to us-they make us ill-and hospitals and doctors have tried to clean them away or kill them with antibiotics. However, antibiotics don't work as well as they used to, and some bacteria survive all antibiotics. We now need Probiotics. The good friendly bacteria, or probiotics, promote the body's natural immunity, keep us healthy and help our digestion. They are very necessary and may keep the bad bacteria level lower. There are many types of good bacteria in our body that we need-acidophilus is one that you may have heard of. Inside each of us live vast numbers of beneficial bacteria which we need to have to stay in good health. Our gastrointestinal tract is home to more than 400 different species of bacteria weighing one and a half kilograms. This is a large quantity of working bacteria which perform very important functions in our body - from the mouth all the way down to the rectum. We live in harmony with them and they provide us with an excellent service if they are given a reasonable diet and kept in good health." (7)

Wilkipedia "Probiotics are dietary supplements containing potentially beneficial bacteria or yeasts. According to the currently adopted definition by FAO/WHO, probiotics are: ‘Live microorganisms which when administered in adequate amounts confer a health benefit on the host’. [1] Lactic acid bacteria (LAB) are the most common type of microbes used. LAB have been used in the food industry for many years, because they are able to convert sugars (including lactose) and other carbohydrates into lactic acid. This not only provides the characteristic sour taste of fermented dairy foods such as yogurt, by buffering the pH and creating fewer opportunities for spoilage organisms to grow, and lowering cholesterols in blood, hence creating huge health benefits on preventing gastrointestinal infections, hyperlipidemia, and hypertensions etc [2]. Strains of the genera Lactobacillus and Bifidobacterium, are the most widely used probiotic bacteria. [3] (8)

THE BARRON REPORT "One final note: start slowly. When you first start using a probiotic supplement, there is a chance that you will precipitate a die-off of bad bacteria in your intestinal tract. This can lead to gas, stomach rumblings, and cramping for up to three weeks." (9)