The most famous of all probiotics – L. bulgaricus, now reclassified as L. delbrueckii, has long been known to promote wellbeing and longevity. Find out how this probiotic can boosts your immunity and combat infections.

What is Lactobacillus delbrueckii?

Lactobacillus delbrueckii  is a species of lactic acid bacteria that is widely used in dairy fermentation (R).

Previously known as L. bulgaricus and L. lactis, these probiotics were shown to have highly similar DNA to L. delbrueckii, and have since been considered to be subspecies of L. delbrueckii (R).

L. delbrueckii  ssp. bulgaricus was discovered more than a century ago in 1905, as a result of a study into the unusual longevity of mountain villagers in Bulgaria (and was thus at the time named L. bulgaricus) (R).

In 1912, the New York Times wrote an article about the use of fermented yogurts with L. delbrueckii  ssp. bulgaricus in Bulgaria titled “Metchnikoff Confirmed in His Theory of Long Life” (R).

Today, L. delbrueckii  ssp. bulgaricus is one of the economically most important lactic acid bacteria and is used worldwide in the production of yogurt (R).

Health Benefits of L. delbrueckii

1) L. delbrueckii  Boosts Immunity

L. delbrueckii  Stimulates Th1 Immunity

L. delbrueckii  stimulates the production of inflammatory cytokines and induces macrophage activation and Th1 differentiation in blood cells from healthy volunteers (R).

L. delbrueckii  Combats Bacterial and Viral Infections

The intake of yogurt fermented with L. delbrueckii  ssp. bulgaricus increases the activity of natural killer cells and reduces the risk of catching the common cold in elderly (R).

L. delbrueckii  increases survival in mice infected with Listeria monocytogenes (R).

Similarly, L. delbrueckii  ssp. bulgaricus increases survival in mice infected with Klebsiella pneumoniae and L. monocytogenes (R).

Yogurt fermented with L. delbrueckii  ssp. bulgaricus helps mice fight the influenza virus by increasing natural killer cell activity, and increasing anti-influenza virus antibodies (R).

L. delbrueckii  Prevents the Aging of the Immune System

L. delbrueckii  ssp. bulgaricus could favor the maintenance of an adequate immune response in the elderly, mainly by slowing the aging of the T-cell subpopulations and increasing the number of immature T cells which are potential responders to new antigens (R).

2) L. delbrueckii  May Reduce Inflammation

L. delbrueckii  ssp. lactis was shown to possess anti-inflammatory effects (R).

Skimmed milk with L. delbrueckii  ssp. bulgaricus inhibits the secretion of proinflammatory cytokines produced by accessory white blood cells (R).

Both live bacteria and isolated L.  delbrueckii DNA were shown to be efficacious in attenuating intestinal inflammation (R).

L. delbrueckii  May Alleviate Atopic Dermatitis

Oral intake of heat-killed L. delbrueckii  ssp. bulgaricus inhibited the development of atopic dermatitis and the elevation of inflammation markers in mice (R).

3) L. delbrueckii  May Alleviate Arthritis

Oral intake of skimmed milk fermented with L. delbrueckii  ssp. bulgaricus markedly inhibits the development of arthritis in mice (R).

4) L. delbrueckii  Combats Allergies

L. delbrueckii  ssp. bulgaricus degrades the allergenic whey protein β-lactoglobulin and inhibits IgE binding in allergic patients (R).

5) L. delbrueckii  is Beneficial for the GI Tract

L. delbrueckii  May Beneficially Modify the Gut Microbiota

L. delbrueckii  increases the number of beneficial Bifidobacteria in mice(R).

L. delbrueckii  May Protect from Infection-Caused Intestinal Damage

L. delbrueckii  ssp. lactis ameliorates mucosal barrier destruction caused by Salmonella typhimurium infection in human GI cells (R).

L. delbrueckii  May Ameliorate Antibiotic-Induced Microbiota Dysfunction

L. delbrueckii  microcapsules relieve intestinal tissue damage in mice and ameliorate antibiotic-induced intestinal microbiota dysfunction (R).

C. difficile is one of the main causes of antibiotic-associated diarrhea, and L. delbrueckii  ssp. bulgaricus was shown to inhibit C. difficile-mediated GI cell toxicity (R).

L. delbrueckii  May Ameliorate Intestinal Inflammation

L. delbrueckii  ssp. lactis has anti-inflammatory properties in acute intestinal inflammation in mice (R).

L. delbrueckii  ssp. bulgaricus ameliorates colitis in mice (R).

L. delbrueckii ssp.  bulgaricus pretreatment protects newborn rats infected with E. sakazakii from developing necrotizing enterocolitis, resulting in improved survival (R).

L. delbrueckii  Combats H. pylori

L. delbrueckii  ssp. bulgaricus inhibits H. pylori in the laboratory (R).

L. delbrueckii  ssp. bulgaricus, together with Streptococcus thermophiles, improves H. pylori eradication rates in infected patients (R).

6) L. delbrueckii  May Combat Cancer

A lysozyme lysate from L. delbrueckii  ssp. bulgaricus has shown antitumor activity in mice and human cells (R).

L. delbrueckii  ssp. bulgaricus was found to inhibit intestinal carcinogenesis in rats, ear-duct tumors in rats, and tracheal carcinogenesis in hamsters (R). This probiotic was also reported to inhibit the growth of sarcoma (R), leukemia, plasmacytoma, adenocarcinoma, melanosarcoma, and spontaneous tumors in mice (R).


In infections:

  • L. delbrueckii, in many cases, induces the production of inflammatory cytokines IL-12, TNF-α, and IFN-γ (R,R,R,R), and increases NK cell activity (R,R, R).
  • This probiotic also increases IL-1 production (R,R), and in some cases IL-6, and may mediate endogenous pyrogenic activity (fever) (R).
  • L.delbrueckii  increases IgA and IgG(1) (R,R).
  • L. delbrueckii  increases antimicrobial peptide hBD-2 (R).

In inflammation:

  • However, it was also shown that, in mice with arthritis, L. delbrueckii  inhibits secretion of IFN-γ, IL-6, TNF-α and the chemokine MCP-1 by accessory cells (R).
  • In some cases, L. delbrueckii  also increases IL-10 (R,R), and decreased pro-inflammatory IL-8 (R).
  • In inflamed tissues, L. delbrueckii  reduced IL-6 levels and serum amyloid A (R), decreased the production of TGF-β, and IL-12 and caused an expansion of CD4+Foxp3+ regulatory T cells (R).
  • Isolated L. delbrueckii  DNA was shown to be as efficacious in attenuating intestinal inflammation as the treatment with live bacteria (R).

In allergies:

  • L. delbrueckii  degrades the allergenic whey protein β-lactoglobulin and inhibits IgE binding (R).


L. delbrueckii  is considered safe, but should be avoided in immunocompromised individuals, people with organ failure, and dysfunctional gut barrier, where probiotics may lead to infection.

About the Author

Biljana Novkovic - PHD (ECOLOGICAL GENETICS) - Writer at Selfhacked

Dr. Biljana Novkovic, PhD


Biljana received her PhD from Hokkaido University.

Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science & health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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