Not All Probiotics Are Equal: Strain-by-Strain Guide

Not All Probiotics Are Equal: Strain-by-Strain Guide

The probiotic shelf at the pharmacy or health store is long and choosing can be overwhelming. Dozens of products promise "billions of good bacteria," but the most important question is: which bacteria exactly? This guide walks through the best-studied strains and their specific use cases.

Why Strain Matters More Than Count

Imagine buying a dog. "Dog" is like a probiotic genus (Lactobacillus). "Golden retriever" is the species. But the specific dog — its temperament, health, ability — is the strain. The same logic applies to probiotics.

A product containing 100 billion CFU of the wrong strain may be less effective than one containing 1 billion CFU of the right strain. What matters is not just quantity, but quality and suitability.

Lactobacillus rhamnosus GG: The Most Studied Strain

Also known as: LGG
Primary use: General digestive health support

L. rhamnosus GG is the world's most researched probiotic strain, with over 1,000 scientific publications. Key findings:

• Supports digestive tract balance
• Contributes to maintaining the gut barrier
• Well-documented safety profile across all age groups
• Good adhesion to the intestinal mucosa

LGG is well suited as an everyday probiotic for those looking to support general digestive health.

Saccharomyces boulardii: The Unique Yeast Probiotic

Type: Yeast (not a bacterium)
Primary use: Supporting digestion during antibiotic use

S. boulardii is unique because it is the only widely used yeast-based probiotic:

• Not affected by antibiotics — it is a yeast, not a bacterium
• Can be used simultaneously with antibiotics
• Does not permanently colonise the gut — clears within 3–5 days after cessation
• Typical dose: 250–500mg daily

Learn more in our article about Saccharomyces boulardii.

Bifidobacterium infantis 35624: The IBS Specialist

Also known as: B. infantis 35624 (Alflorex)
Primary use: Supporting relief of IBS symptoms

This strain has garnered special attention in IBS research:

• The Whorwell et al. (2006) study showed significantly improved IBS symptoms
• Affects bloating, abdominal pain, and bowel motility disturbances
• Optimal dose in studies: 1x10 to the power of 8 CFU (100 million) — interestingly, the lower dose worked better than the higher one

This underscores once more that with probiotics, "more" is not always "better."

Lactobacillus acidophilus NCFM: The General Digestive Supporter

Primary use: General digestive health, lactose tolerance

L. acidophilus NCFM is one of the oldest and most studied strains:

• Supports lactose breakdown in the intestine
• Good survivability in stomach acid
• Often combined with B. lactis Bi-07 for enhanced effect
• Extensive evidence base for safety and tolerability

Bifidobacterium longum BB536: The Immune Supporter

Primary use: Immune system support

B. longum BB536 is the most studied strain in Japan and has been in use for over 40 years:

• Research indicates support for immune function
• Particularly studied in the context of seasonal respiratory complaints
• Well-tolerated and stable

CFU Count: How Many Billions Do You Need?

CFU (colony forming units) counts vary enormously between products: from 1 billion to 100 billion and beyond. What science says:

Important: a higher CFU count does not automatically mean better results. The right strain at the right dose matters more than sheer numbers.

Multi-Strain vs Single-Strain Probiotics

Both approaches have their place:

Single-strain products:

• Better when you want a specific, research-backed effect
• Easier to dose
• Results are more predictable

Multi-strain products:

• May offer broader support
• Different strains can work synergistically
• Suitable for general well-being support

Practical Selection Guide

For digestive support:
→ L. rhamnosus GG (LGG) or L. acidophilus NCFM

Alongside antibiotic courses:
→ S. boulardii (the only strain unaffected by antibiotics)

For IBS symptoms:
→ B. infantis 35624

For immune support:
→ B. longum BB536 or a multi-strain combination

While travelling:
→ S. boulardii (shelf-stable, no refrigeration needed)

Summary

Probiotic selection should be strain-based, not just brand or price driven. L. rhamnosus GG is the most studied strain for general digestive health. S. boulardii is a unique yeast probiotic unaffected by antibiotics. B. infantis 35624 specialises in IBS symptoms. CFU count matters, but the right strain is more important than a big number.

Dietary supplements are not a substitute for a varied, balanced diet and healthy lifestyle.

References

• Whorwell, P.J., Altringer, L., Morel, J., Bond, Y., Charbonneau, D., O'Mahony, L., Kiely, B., Shanahan, F. & Quigley, E.M. (2006). Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. American Journal of Gastroenterology, 101(7), 1581-1590.

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