Do Probiotics Survive Stomach Acid?

If you're looking to support your health, you've likely come across the topic of probiotics – and you're not alone: With the growing recognition of the role probiotics play in supporting systemic health, supplemental probiotics have quickly become one of the top-selling dietary supplements on the market. But how do you know if probiotics are working? This article will discuss how to supplement probiotics effectively to maximize their health benefits and survival through the digestive tract.

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What Are Probiotics?

Probiotics are live microorganisms, including bacteria and yeasts, that confer a health benefit to the host when consumed in adequate amounts. They are classified by their genus, species, and strain. For example: Lactobacillus (genus) rhamnosus (species) GG (strain). 

The primary sources of probiotics are diet and supplements. Dietary supplements contain seven main genera of microbes: 

• Lactobacillus
• Bifidobacterium
• Saccharomyces
• Streptococcus
• Enterococcus
• Escherichia
• Bacillus

Probiotics alter the composition of the microbiome, the community of microorganisms residing in or on the human body. The gut microbiome is the collection of microorganisms that colonize the gastrointestinal (GI) tract and has been found to influence human health by their roles in: 

• Regulating digestion and metabolism
• Producing nutrients, neurotransmitters, enzymes, and short-chain fatty acids
• Inhibiting the growth of pathogenic organisms
• Modulating immune function
• Communicating with the nervous system

Probiotics combat dysbiosis (an imbalance in the microbiome) and are beneficial in treating and preventing a range of human diseases, including: 

• Chronic inflammation
• Obesity
• Constipation
• Antibiotic-associated diarrhea (AAD)
• Irritable bowel syndrome (IBS)
• Urogenital infections, such as bacterial vaginosis (BV)
• Viral infections
• Anxiety and depression

The Challenge of Stomach Acid

Stomach acid, also called gastric acid, is a highly acidic digestive secretion produced by the stomach's lining. Hydrochloric acid, produced by parietal cells, is the main constituent responsible for gastric acid's acidic quality. (17)

Acidity is measured on a pH scale ranging from 0 to 14. The lower the pH level, the more acidic a substance is. Stomach acid has a pH of 1.5-2.5. Acid aids digestion because it helps break down food so important nutrients can be absorbed into circulation. It also acts as a natural antimicrobial substance and one of the body's first-line defenses against infectious pathogens entering the body through the mouth. (17)

Mechanisms of Probiotic Survival

Stomach acid's broad antimicrobial nature poses a barrier to probiotic efficacy. It does not differentiate between "good" and "bad" bugs. Probiotics' survivability is a critical factor in their efficacy. Therefore, one of the main concerns of oral probiotics is whether they are effective if they must travel through the stomach. 

The stomach harbors its own distinct microbiota composed of acid-resistant bacterial strains. Studies using culturing methods have identified Lactobacillus and Bifidobacterium as two of the most predominant bacterial genera in the stomach. These bacteria demonstrate remarkable resilience to the harsh conditions of the upper digestive tract, including exposure to stomach acid and bile acids, which are significant threats to probiotic viability. Their ability to thrive in such an acidic environment underscores their potential as effective probiotics capable of surviving the journey through the stomach to confer their health benefits in the intestines. (12) 

Spore-forming probiotics, particularly those of the Bacillus genus, have been used for medical purposes in humans since the 1960s. Spores are dormant, or inactive, bacterial lifeforms. Bacterial spores are highly resistant to environmental stressors, such as heat and acid, increasing their likelihood to survive the acid environment of the stomach. Once they travel into the more hospitable environment of the lower digestive tract, bacterial spores can germinate into vegetative cells and become metabolically active. (20) 

Strategies have been developed to enhance the survival rate of non-spore-forming probiotics as they pass through the stomach. These include microencapsulation techniques, which involve coating the probiotic cells with a protective layer of polysaccharides, proteins, or fats. Probiotic encapsulation improves the supplement's shelf life and shields it from stomach acid during GI transit. 

Probiotics Most Likely to Survive Stomach Acid

Lactobacilli are lactic acid bacteria; they produce lactic acid as a main byproduct of their metabolic activity. This explains their natural resiliency to high-acidity environments, including the stomach and vagina. Lactobacillus rhamnosus GG has been demonstrated to survive passage through the GI tract and acidic environments (pH 2.5) for up to four hours. Lactobacillus casei Shirota is another probiotic proven to survive transit through the GI tract. 

As mentioned above, Bifidobacterium are also commonly used in supplemental probiotic blends due to their natural acid-resistant properties. Research demonstrates that, in particular, Bifidobacterium longum and Bifidobacterium animalis subsp. lactis BB-12 exhibit high acid tolerance. (29, 34) 

Bacillus coagulans is the most studied spore-forming probiotic. Other spore-formers commonly incorporated into oral probiotic supplements include Bacillus subtilis and Bacillus clausii. The fact that these probiotics colonize the GI tract and are effective in treating a range of GI-related symptoms and conditions supports the notion that they can survive stomach acid.

Best Ways to Take Probiotics

Many questions inevitably come up when deciding what probiotics to buy and how to take them. 

Timing and Dosage

Some manufacturers suggest taking probiotics on an empty stomach, while others recommend consuming them with food. When in doubt, follow the label instructions or the advice of your doctor. 

Recommendations for the timing of probiotic supplements may vary based on the type of probiotic supplement you're taking. For example, research indicates that Saccharomyces boulardii shows consistent viability whether taken with or without food. On the other hand, Lactobacillus and Bifidobacterium tend to survive better when taken with food or up to 30 minutes before a meal. (32)

Pairing probiotics with certain foods may enhance bacterial survival rates. Fats, for example, can buffer the stomach's acidic environment to a pH closer to 3 or 4, which appears optimal for the survival of Lactobacilli and Bifidobacteria. 

Sugars and carbohydrates also appear to enhance the survival of Lactobacilli in acidic environments.

Dosage will also affect probiotic efficacy. Probiotics are dosed per colony forming units (CFUs), which measure the number of viable cells per dose. Most probiotic supplements contain anywhere from 1 to 50 billion CFUs per dose. (27) 

The amount of probiotics you should take will depend on why you are taking them: some conditions respond to lower doses and others higher. Dosing should be guided based on what the clinical research says about your specific health concern. This website is a helpful resource that consolidates scientific evidence into clinically relevant probiotic dosing information. In general, common doses range from 5-10 billion CFUs daily for children and 10-20 billion CFUs daily for adults.

Formulation and Delivery Methods

Probiotic supplements are most commonly sold in capsule, powder, tablet, or liquid form. Patients who dislike or cannot swallow pills may benefit from mixing a powder in their food or beverage. (18) 

To ensure the safety of probiotic supplements, it is important to select high-quality, clinically tested products. Quality control measures, such as third-party testing, ensure that the product contains the stated amount of live bacteria and is free from contaminants.

Probiotics can also be obtained through food, just like our ancestors did before the development of dietary supplements. Fermented foods like yogurt, kefir, sauerkraut, and kimchi naturally contain probiotics. 

Enhancing Probiotic Survival and Efficacy

In addition to the considerations discussed above, the following tips will help enhance probiotic survival and efficacy:

• Select probiotic strains tailored to specific health conditions. Probiotics are strain- and disease-specific, meaning the choice of probiotic strain plays an important role in determining its effectiveness for targeted health treatments.
• Use synbiotics, which are probiotics combined with prebiotics. Synbiotics enhance the usefulness of probiotics by stimulating their growth and activity and improving their survival in the gut. 
• Support gut health with a healthy diet, regular exercise, managing stress, avoiding excessive alcohol consumption, and sleeping well. 

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Key Takeaways

• The survival of probiotics through stomach acid is a critical factor influencing their efficacy. Research highlights that specific probiotics, such as certain Lactobacillus, Bifidobacterium, and spore-forming Bacillus species, demonstrate superior acid resistance and higher survival rates. Optimal timing, dosage, and probiotic delivery methods will further enhance probiotic viability. 
• In addition to dietary and supplemental probiotics, gut health can be supported by eating a balanced diet, a healthy lifestyle, and prebiotic supplements.
• It is highly recommended that people make informed choices about probiotic supplementation, guided by evidence-based research and the advice of a healthcare professional, to ensure probiotic safety and maximize health benefits tailored to individual needs.