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Chapter 1
Introduction
This introductory chapter will discuss the basics of probiotics and what makes a good probiotic, and will provide some valuable tips on how to evaluate scientific studies for useful, practical information.
FREQUENTLY ASKED QUESTIONS
What are probiotics?
Probiotics are microorganisms (small, single-celled living organisms) that are ingested to benefit health and help fight diseases. Probiotics are either bacteria or yeasts.
Do bacteria and yeasts cause infections?
Indeed, disease-causing bacteria or yeasts (pathogens) can cause infections such as skin infections or pneumonia. Most other microorganisms are not harmful. Some microbes can even help maintain normal body functions and fight infections and diseases.
When are probiotics useful?
Probiotics can be helpful to prevent diarrhea while traveling or when taking antibiotics. Probiotics are useful for a wide variety of illnesses besides diarrhea. For chronic conditions, probiotics can be safely taken daily for years.
Are probiotics different from antibiotics?
Probiotics are living organisms taken for improving health. Antibiotics are substances that kill microorganisms. Antibiotics are “wonder drugs” for fighting infections, but they can have adverse effects (such as diarrhea, rashes, or allergic reactions). Some bacteria that cause infections have become resistant to treatment with common antibiotics. That leaves two choices: develop new antibiotics or come up with a different approach. Probiotics are that new approach.
Many different probiotic products are on the market today. Not all probiotic products or probiotic strains are the same. The types of bacteria or yeasts found in probiotic products may appear to be similar, but only some strains have been shown to be effective. This book will discuss the most effective strains so an informed choice can be made.
How do you know if a probiotic is really effective?
Marketing claims for probiotics are very diverse. Only those claims supported by well-conducted scientific studies should be trusted. Later in this chapter, we will discuss how to evaluate scientific studies.
Are probiotics regulated by the U.S. Food and Drug Administration (FDA) as are prescription drugs?
Yes and no. Yes, the FDA does keep track of probiotics as “dietary supplements,” but no, the degree of oversight for effectiveness and safety is not as high as it is for prescription drugs. How this affects the consumer will be discussed in this chapter.
Where do you find probiotic products?
Since 1994, probiotics can be sold in the United States “over the counter” (without the need for a prescription) as “dietary supplements.” Probiotic products can be found in pharmacies, as well as in some supermarkets and other stores (organic foods stores, supplement stores, and health food stores), or can be purchased on the Internet from many probiotics or health food Web sites. In many other countries, probiotics have been sold over the counter for many years.
Is “Acidophilus” a probiotic?
Yes, this is an example of one type of probiotic.
WHAT ARE PROBIOTICS?
Probiotic literally means “for life.” Probiotics are small, singlecelled, living organisms (microorganisms) that are ingested to benefit health and help fight diseases. Generally, probiotics are bacteria or yeasts. A wide array of different probiotics exists (see Figure 1.1), but most are bacteria of the Lactobacillus, Bifidobacterium, Enterococcus, or Escherichia genera or are yeasts of the genus Saccharomyces.
Do probiotics contain living bacteria?
Yes, and that is a good thing. There are billions of bacteria in the body helping in the digestion of food, producing vitamins, stimulating the immune system, and fighting infections. Most bacteria found in the human body are beneficial.
How are probiotics named? Just as larger organisms are. We humans are formally named Homo sapiens, for example. Microorganisms are referred to by their genus name, followed by a species name, which may be followed by a strain name. A genus group lumps together similar types of microbes (similar to a large family or clan). The species defines a narrower group (like members of a family with the same last name). Strains narrow it down to identical type organisms (much as people are identified by their first name). So, instead of identifying an individual by “Joe Smith of the Gardner clan,” a microorganism would be named “Gardner smith strain Joe.” An example is Lactobacillus casei strain Shirota. The genus and species names should be italicized.
The Gram stain is a useful way to characterize different types of bacteria. Bacteria either take up the purple stain (gram-positive) or not (gram-negative), and this is an easy first step in identifying bacteria. Streptococcus pneumoniae is an example of a gram-positive pathogen. Escherichia coli is gram-negative. The Gram stain appearances of these pathogens are shown in Figure 1.2.
FIGURE 1.1. Examples of some current probiotic products are shown. Source: Photograph by Lynne V. McFarland.
• The Gram stain was invented in 1884 by a Danish physician, Christian Gram
• Gram-positive microbes take up a crystal violet iodine stain, and the purple color cannot be washed out with alcohol
• Gram-negative microbes take up the stain, but alcohol wash removes the purple color
• The reason for the differential staining is due to fundamental differences between gram-positive and gram-negative cell walls
FIGURE 1.2. Gram stains of two different types of bacteria: On the left, Streptococcus pneumoniae, a gram-positive (purple stained) bacterium, and on the right, Escherichia coli, a gram-negative (red stained) bacterium. Source: Photograph by Lynne V. McFarland.
Probiotics are not antibiotics, chemicals, genetically altered foods, or artificial substances. They are living organisms that usually were first found in humans and then tested for their ability to fight or prevent disease. Probiotics are available in capsules, tablets, or a variety of food products. The probiotics sold in capsules usually are freezedried (lyophilized), which helps maintain their viability (number of living organisms) for extended periods of time. Some probiotics sold in capsules are heat-dried, liquid cultures of the probiotic, but the heating process used in the manufacturing of the product can kill the microbe and eliminate its probiotic benefit. Probiotics may be added to milk or other beverages. One example of a popular method for providing high probiotic activity is a yogurt containing living probiotic bacteria.
HISTORY OF PROBIOTICS
Probiotics are not something new invented in a laboratory. Microorganisms have been used for many centuries to preserve foods, although only in the previous century has the science of this process been understood. Early populations did not know that when they added a small amount of yogurt to the previous day’s batch of milk and kept it in a warm place overnight they were seeding and propagating Lactobacillus bulgaricus and other lactic acid bacteria to coagulate milk protein. They knew only that the final product tasted good and lasted longer than raw milk. Other fermented foods have long been popular because of their taste and improved storage. For example, sauerkraut and kimchi result from bacterial action on cabbage (plus other vegetables for kimchi). Milk fermented by lactic acidproducing bacteria has long been thought to have more beneficial effects on health than milk itself. The heavy consumption of kefir by populations in the mountainous Caucasus region between the Black and Caspian seas has been associated with longevity, as has yogurt use in Bulgaria. Elie Metchnikoff (1845-1916), a Russian scientist, is credited with calling attention to the health benefits of yogurt. His hypothesis was that lactic acid bacteria in the yogurts counteract the harmful putrifying bacteria in the intestines. He associated the longevity of the Bulgarians and those from the Caucasus region with regular yogurt use and claimed to have improved his own ill health with sour milk fermented with lactic acid bacteria from Bulgaria. He credited his long life (71 years, long by the standards of his time) to ample amounts of yogurt in his diet, and his views were widely accepted at the time.1
In the early 1960s the term probiotic began to be applied to microbes used for medicinal purposes. A more recent and widely accepted definition is “defined, live microorganisms administered in adequate amounts, which confer a beneficial physiological effect on the host.”2 The use of probiotics has long remained popular in Europe and parts of Asia, but until recent years was uncommon in the United States. Today, probiotics are used worldwide, and the discovery of new, more effective probiotic microorganisms will serve to expand their medical applications. Nevertheless, few of the 1290 articles published on probiotics since 1990 are targeted for the general public. We hope this book will fill this gap.
MEDICAL CONDITIONS FOR PROBIOTICS
Not all diseases or conditions can be effectively treated with probiotics. Typically, diseases that respond best are those involving a disruption of normal microbial flora. The normal flora has a beneficial function, called “colonization resistance,” that discourages pathogenic organisms from colonizing the body.3 But this protective mechanism can be disrupted if the normal flora is disturbed by surgery, antibiotics, or other medications. Probiotic treatment can act as a substitute for these disturbed bacteria, or probiotics can produce substances that combat pathogenic bacteria and then work to restore the normal protective microflora.
What is normal microflora? Humans are normally host to billions of bacteria (see Figure 1.3). These bacteria help maintain many normal functions. A count of all the human cells would reveal that only about 10 percent make up the body structure, while 90 percent are bacteria normally carried in or on the body. Most normal microflora is found in the gastrointestinal tract. There are millions of bacteria in the mouth, not very many in the stomach, and billions in the small and large intestines. All those bacteria are called “normal microflora.” What is the function of normal microflora? Normal microflora has many important functions including helping to digest food, producing some vitamins, stimulating immune responses, and helping move food through the gastrointestinal tract. Normal flora also acts to protect against invasion by the ever-present, disease-causing bacteria we are exposed to. This defense mechanism is called “colonization resistance” because the layers of normal bacteria help form a ba...
