Probiotics: A Complete Guide
What are probiotics?
Probiotics are live microorganisms that are consumed through food supplements or fermented foods. The World Health Organization (WHO) defined probiotics in 2001 as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host."
Probiotics occur naturally in many fermented foods that have been consumed for centuries across various cultures. These include:
- Yogurt — one of the best-known probiotic foods, made by fermenting milk with lactic acid bacteria
- Kefir — a fermented dairy product containing a diverse microbial community
- Sauerkraut — fermented cabbage, particularly popular in Central and Eastern Europe, including Estonia
- Kimchi — a traditional Korean fermented vegetable dish
- Kombucha — fermented sweetened tea
- Miso and tempeh — fermented soy products
In Estonia, fermented foods have been a natural part of the cuisine for generations: sauerkraut, kefir, sour cream, and buttermilk are familiar to everyone. Probiotic food supplements offer these microorganisms in a concentrated form.
How do probiotics work?
The human digestive tract contains trillions of microorganisms, collectively referred to as the gut microbiota or microbiome. This complex ecosystem consists of bacteria, fungi, viruses, and other microorganisms.
Probiotics are live microorganisms that, after oral ingestion, pass through the stomach and reach the intestine. There, they temporarily or persistently colonise the intestinal mucosa and become part of the gut microbial community.
The composition of gut microbiota is unique to each individual and is influenced by multiple factors: diet, age, living environment, antibiotic use, and other circumstances. Probiotic microorganisms add diversity to the intestinal microbial community.
It is important to note that the European Food Safety Authority (EFSA) has not approved general health claims for probiotics as a category. This means it is not permitted to state that probiotics "improve digestion", "strengthen the immune system", or "reduce bloating" in marketing.
Common strains
Probiotic microorganisms are classified into different genera and species. Each strain is unique and they cannot be substituted for one another. Here is an overview of the most common ones:
Lactobacillus
Lactobacillus is a genus of lactic acid bacteria found naturally in the human digestive tract and in many fermented foods.
- Lactobacillus acidophilus — one of the most widely studied lactic acid bacteria, found in yogurt and other fermented dairy products
- Lactobacillus rhamnosus — an extensively studied strain used in many food supplements
- Lactobacillus plantarum — common in fermented vegetables such as sauerkraut
- Lactobacillus casei — found in cheese and other fermented foods
- Lactobacillus reuteri — occurs naturally in the human digestive tract
Bifidobacterium
Bifidobacterium is another major genus of probiotic bacteria, present in the human gut from birth.
- Bifidobacterium longum — one of the most prevalent bifidobacteria in the adult intestine
- Bifidobacterium lactis (also known as B. animalis subsp. lactis) — widely used in food supplements and fermented dairy products
- Bifidobacterium breve — found naturally in the infant gut
- Bifidobacterium bifidum — one of the first bifidobacteria to be discovered
Saccharomyces boulardii
Saccharomyces boulardii is a probiotic yeast that differs from bacterial probiotics. It is temperature-resistant and widely used in food supplements. As a yeast rather than a bacterium, it is not affected by antibiotics.
Forms available
Probiotics are available in several different forms:
Capsules
The most common supplement form. Capsules protect microorganisms from stomach acid and are convenient to carry. Some capsules are enteric-coated, meaning they dissolve only in the intestine.
Powder
Powdered probiotics can be mixed into water, smoothies, or food. This form allows flexible dosing and is suitable for those who prefer not to swallow capsules.
Liquid form
Liquid probiotics contain live microorganisms in a liquid carrier. These may require refrigeration.
Food-based sources
Fermented foods such as yogurt, kefir, sauerkraut, and kimchi naturally contain probiotic microorganisms.
CFU — what does it mean?
CFU (Colony Forming Units) is the unit of measure used to express the content of a probiotic. It indicates the number of viable microorganisms per dose. Supplements commonly contain between 1 billion and 100 billion CFU per serving.
A higher CFU count does not automatically mean a better product — what matters is the specific strain and its quantity.
Stability and storage
Probiotics fall into two categories based on storage requirements:
- Freeze-dried (lyophilised) — these are dried under special conditions and are stable at room temperature. Look for "shelf-stable" or "stable at room temperature" on the label.
- Refrigerated — these require cold storage (2-8 °C) to keep the microorganisms alive. Always check the packaging instructions.
How to take probiotics
How to take probiotics depends on the specific product and strain. Here are general guidelines:
- Always follow the instructions on the packaging — different products may require different methods of consumption
- With or without food — some probiotics are recommended to be taken with food, others on an empty stomach. This depends on the specific strain and product composition
- Consistency — probiotics are typically taken daily
- Water temperature — if mixing powder into liquid, use room-temperature or cool water, not hot, as high temperatures can damage live microorganisms
Storage
- Check the label for storage conditions — some products require refrigeration
- Keep probiotics in a dry place, away from direct sunlight
- Close the packaging properly after each use
- Pay attention to the expiry date — the number of viable microorganisms may decrease over time
Who uses probiotic supplements?
Probiotics are food supplements used by various people for different reasons:
- People interested in their microbiome — those who wish to add diversity to their gut microbial community
- Travellers — travelling, especially to exotic countries, means encountering new microorganisms. Some travellers bring probiotics along
- After a course of antibiotics — antibiotics affect the gut microbial community by eliminating both harmful and beneficial bacteria. Some people take probiotics after an antibiotic course to add diversity back to their microbial community
- Older adults — gut microbial composition changes with age
- Athletes — physically active individuals who pay attention to their nutrition and supplementation
Estonian context
In Estonia, fermented foods have a long-standing tradition. Sauerkraut, kefir, buttermilk, and homemade yogurt have been an integral part of Estonian cuisine. Probiotic food supplements offer a concentrated form of the same types of microorganisms found in traditional fermented foods.
Frequently Asked Questions
What are CFUs and why do they matter?
CFU (Colony Forming Units) is the unit of measure indicating the number of viable microorganisms in a supplement. Different products contain varying amounts of CFUs (typically 1 to 100 billion per serving). A higher number does not necessarily mean a better product — what matters is the specific strain and its concentration.
Do probiotics need to be refrigerated?
This depends on the product. Some probiotics are freeze-dried (lyophilised) and stable at room temperature. Others require cold storage. Always check the packaging instructions for the specific product.
What is the difference between prebiotics and probiotics?
Probiotics are live microorganisms. Prebiotics are non-digestible fibres (such as inulin, FOS) that serve as nourishment for gut microorganisms. These are two different concepts, although they are often mentioned together. Some products contain both — these are called synbiotics.
Can probiotics be taken alongside antibiotics?
Antibiotics destroy bacteria, including probiotic bacteria. If you wish to take probiotics during an antibiotic course, consult your doctor. A time gap between taking the probiotic and the antibiotic is generally suggested.
Are probiotics suitable for children?
Children's food supplements should always be discussed with a paediatrician. There are probiotic products specifically designed for children available on the market. Always follow the age restrictions and dosage instructions.
Are probiotics safe?
Probiotics are generally well tolerated. Some people may experience mild discomfort at the start of use, which usually subsides. If you have an immune deficiency or a serious illness, consult your doctor before taking probiotics.
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