Live probiotics are living microorganisms that, when consumed in adequate amounts, may offer a health benefit. The term “probiotic” is derived from the Latin “pro” and the Greek “bios,” meaning “for life.” This definition from the Food and Agriculture Organization (FAO) and World Health Organization (WHO) highlights that the microbes must be alive to be effective. These beneficial organisms, primarily bacteria and some yeasts, support the microbial communities already in your body.
Mechanisms of Action in the Body
For probiotics to function, they must endure the stomach’s acidic environment to reach the intestines. One primary mechanism is competition with pathogenic bacteria. Probiotics compete for nutrients and physical space to attach to the intestinal lining, a process known as competitive exclusion. By occupying these adhesion sites, they make it more difficult for pathogens to multiply.
These beneficial microbes also contribute to the health of the gut environment. Some probiotics produce antimicrobial substances, such as bacteriocins and organic acids, which inhibit the growth of harmful organisms. This action helps to modulate the composition of the gut microbiota. A balanced microbiota is associated with positive health outcomes.
Probiotics also interact directly with the host’s body. They can strengthen the integrity of the intestinal barrier, which prevents unwanted substances from passing into the bloodstream. Probiotics can also modulate the immune system, as a large portion of immune cells are located in the gut, and they interact with these cells to influence immune responses.
Common Sources of Live Probiotics
Live probiotics can be obtained from foods and dietary supplements. Fermented foods are a primary natural source, containing live microorganisms from the fermentation process. Yogurt is a well-known source, often containing strains like Lactobacillus bulgaricus and Streptococcus thermophilus. To ensure the product contains live bacteria, look for labels stating “live and active cultures.”
Other fermented foods rich in probiotics include:
- Kefir, a fermented milk drink with a wider variety of bacteria and yeasts than yogurt
- Sauerkraut (fermented cabbage) and kimchi (a traditional Korean dish)
- Kombucha, a fermented tea
- Miso, a fermented soybean paste
Processes like pasteurization involve heat that can kill these beneficial bacteria, so choosing unpasteurized versions is necessary to get the probiotic benefit.
Probiotic dietary supplements offer a more concentrated and targeted way to consume specific strains. These are available in various forms, including capsules, powders, and liquids. When choosing a supplement, the label lists the specific genus, species, and strains, such as Bifidobacterium or Lactobacillus. This allows for selecting products with strains researched for specific effects.
Strain Specificity and Health Implications
A key concept in understanding probiotics is that their effects are highly specific to the strain. Just as there are different breeds of dogs, there are countless strains of bacteria, and they are not interchangeable. The scientific name of a probiotic consists of its genus (e.g., Lactobacillus), species (e.g., rhamnosus), and a specific strain designation (e.g., GG). This detail is important because health benefits are linked to these exact strains.
For example, the strain Lactobacillus rhamnosus GG (LGG) is one of the most extensively studied probiotics. Research has associated LGG with managing certain types of diarrhea, including that caused by antibiotics. It is thought to work by restoring the natural balance of gut microbes and has also been investigated for its role in supporting immune system function.
Another well-researched strain is Bifidobacterium animalis subspecies lactis BB-12 (BB-12). Clinical studies have linked this strain to improved bowel regularity, especially in adults who experience infrequent bowel movements. BB-12 has also been shown to support a healthy immune response by increasing the body’s resistance to common respiratory infections.
Ensuring Viability and Effectiveness
For probiotics to provide a benefit, they must be alive and in sufficient numbers when consumed. The quantity of live microbes in a product is measured in Colony Forming Units (CFUs). While a higher CFU count might seem better, the dose must be adequate and supported by research for a specific health effect. An effective dose can range from millions to billions of CFUs, as the appropriate amount is strain-dependent.
Proper storage is a factor in maintaining the viability of these microorganisms. Many probiotic products, especially fermented foods like yogurt and kefir, require refrigeration to keep the bacteria alive. Probiotic supplements may also have specific storage instructions. Exposure to heat, moisture, and light can reduce the number of live bacteria, diminishing the product’s effectiveness.
Pay close attention to expiration or “use by” dates. The number of viable bacteria in a probiotic product naturally declines over time. The CFU count listed on a label refers to the quantity at the time of manufacture, and this number will decrease throughout the product’s shelf life. Consuming probiotics before their expiration date helps ensure you ingest a sufficient number of live organisms.