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Health Benefits of Yogurt Probiotics (L. delbrueckii)

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:
L. delbrueckii

The most famous of all probiotics – L. bulgaricus, now reclassified as L. delbrueckii – has long been believed to promote wellbeing and longevity. Read on to learn more about the research on this common probiotic supplement.

What is Lactobacillus delbrueckii?

Lactobacillus delbrueckii is a species of lactic acid bacteria that is widely used in dairy fermentation [1].

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 [2].

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) [3].

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” [4].

Today, L. delbrueckii ssp. bulgaricus is one of the economically most important lactic acid bacteria and is used worldwide in the production of yogurt [1].

Health Benefits of L. delbrueckii

L. delbrueckii probiotic supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.

Possibly Effective For

1) H. pylori Infection

L. delbrueckii ssp. bulgaricus, together with Streptococcus thermophilus, improved H. pylori eradication rates in 292 infected patients. This result suggests a role for L. delbrueckii probiotics alongside conventional therapy for H. pylori infection [5].

L. delbrueckii ssp. bulgaricus inhibited H. pylori in the laboratory [6].

Insufficient Evidence For

The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of L. delbrueckii for any of the below-listed uses. Remember to speak with a doctor before taking L. delbrueckii probiotic supplements, and never use them in place of something your doctor recommends or prescribes.

2) Gestational Diabetes

In a study of 64 pregnant women with gestational diabetes, L. delbrueckii reduced weight gain and fasting blood sugar compared to the placebo [7].

3) Immunity

Bacterial and Viral Infections

The intake of yogurt fermented with L. delbrueckii ssp. bulgaricus increased the activity of natural killer cells and reduced the rate of common cold infections in 142 elderly volunteers [8].

L. delbrueckii increased survival in mice infected with Listeria monocytogenes [9].

Similarly, L. delbrueckii ssp. bulgaricus increased survival in mice infected with Klebsiella pneumoniae and L. monocytogenes [10].

Yogurt fermented with L. delbrueckii ssp. bulgaricus helped mice fight the influenza virus by increasing natural killer cell activity and increasing anti-influenza virus antibodies [11].

Aging of the Immune System

L. delbrueckii ssp. bulgaricus maintained the immune response in 61 elderly subjects, 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 [12].

Th1 Immunity

L. delbrueckii stimulated the production of inflammatory cytokines and induced macrophage activation and Th1 differentiation in blood cells from healthy volunteers [13].

Animal & Cell Research (Lacking Evidence)

No clinical evidence supports the use of L. delbrueckii probiotics for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.

4) Inflammation

L. delbrueckii ssp. lactis is believed to possess anti-inflammatory effects [14].

Skimmed milk with L. delbrueckii ssp. bulgaricus inhibits the secretion of proinflammatory cytokines produced by accessory white blood cells [15].

Both live bacteria and isolated L. delbrueckii DNA were shown to be efficacious in attenuating intestinal inflammation [12].

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 [16].

5) Arthritis

Oral intake of skimmed milk fermented with L. delbrueckii ssp. bulgaricus markedly inhibits the development of arthritis in mice [17].

6) Allergies

L. delbrueckii ssp. bulgaricus degraded the allergenic whey protein β-lactoglobulin and inhibited IgE binding in blood drawn from allergic patients [18].

7) Gut Health

Gut Microbiota

L. delbrueckii increased the number of beneficial Bifidobacteria in mice [19].

L. delbrueckii microcapsules relieved intestinal tissue damage in mice and ameliorated antibiotic-induced intestinal microbiota dysfunction [19].

C. difficile is one of the main causes of antibiotic-associated diarrhea and L. delbrueckii ssp. bulgaricus inhibited C. difficile-mediated GI cell toxicity on direct exposure [20].

Infection-Caused Intestinal Damage

L. delbrueckii ssp. lactis repaired mucosal barrier destruction caused by Salmonella typhimurium infection in human GI cells [21].

Intestinal Inflammation

L. delbrueckii ssp. lactis had anti-inflammatory properties in acute intestinal inflammation in mice [22].

L. delbrueckii ssp. bulgaricus ameliorated colitis in mice [23].

L. delbrueckii ssp. bulgaricus pretreatment protected newborn rats infected with E. sakazakii from developing necrotizing enterocolitis, resulting in improved survival [24].

Cancer Research

A lysozyme lysate from L. delbrueckii ssp. bulgaricus has shown antitumor activity in mice and human cells [10].

L. delbrueckii ssp. bulgaricus was found to inhibit intestinal carcinogenesis in rats, ear-duct tumors in rats, and tracheal carcinogenesis in hamsters [25]. This probiotic was also reported to inhibit the growth of sarcoma [26], leukemia, plasmacytoma, adenocarcinoma, melanosarcoma, and spontaneous tumors in mice [27].

The relevance of these studies to human cancer therapies is unknown.

Mechanism of Effect

In cells and animals, researchers have observed a number of potential mechanisms of effect for L. delbrueckii. These are compiled below.

In infections:

  • L. delbrueckii, in many cases, induced the production of inflammatory cytokines IL-12, TNF-α, and IFN-γ [28, 13, 29, 30], and increased NK cell activity [11, 31, 30].
  • This probiotic also increased IL-1 production [32, 10], and in some cases IL-6, and may mediate endogenous pyrogenic activity (fever) [33].
  • Increased IgA and IgG(1) [11, 19].
  • Increased antimicrobial peptide HBD-2 [12].

In inflammation:

  • In mice with arthritis, L. delbrueckii inhibited secretion of IFN-γ, IL-6, TNF-α and the chemokine MCP-1 by accessory cells [15].
  • In some cases, L. delbrueckii also increased IL-10 [9, 22], and decreased proinflammatory IL-8 [12].
  • In inflamed tissues, L. delbrueckii reduced IL-6 levels and serum amyloid A [16], decreased the production of TGF-β, and IL-12 and caused an expansion of CD4+Foxp3+ regulatory T cells [14].
  • Isolated L. delbrueckii DNA attenuated intestinal inflammation as effectively as treatment with live bacteria [12].

In allergies:

  • L. delbrueckii degraded the allergenic whey protein β-lactoglobulin and inhibited IgE binding [18].


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.

To avoid adverse effects or unexpected interactions, talk to your doctor before starting L. delbrueckii probiotics.

About the Author

Biljana Novkovic

Biljana Novkovic

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 and 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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