L. lactis is a commonly used probiotic whose health benefits we are just beginning to understand. This bacterium boosts the immune system, may combat allergies, hypertension, and IBD, and has beneficial effects on the skin.

What is L. lactis?

Lactococcus lactis is a lactic acid producing Gram-positive bacterium used extensively in the production of buttermilk, cheese, pickled vegetables, and other fermented products.

L. lactis is often studied as a genetically modified organism for the treatment of animal [1, 2, 3, 4, 5, 6] and human diseases [7]. Its health benefits as a probiotic, however, are less known and researched.

Note that this post is about Lactococcus lactis. For more information about Lactobacillus lactis check out the post about L. delbrueckii.

Health Benefits of L. lactis

1) Boosts Immunity

Yogurt fermented with L. lactis activates plasmacytoid dendritic cells (pDC), that are important for both innate and adaptive immune responses [8, 9], and lowers the risk of the common cold in human subjects [8].

It activates natural killer (NK) cells and enhances their cytotoxic activity [10].

It improves resistance against pneumococcal infection by improving pathogen lung clearance, reduces lung injuries and increases survival of infected mice [11, 12].

L. lactis-fed mice have drastically improved survival rate, reduced weight loss, and reduced lung damage when infected by murine parainfluenza virus (mPIV1) [9] the influenza virus (H1N1) [13].

Kefir-isolated L. lactis protect cells from C. difficile toxins [14].

2) L. lactis May Alleviate Allergies

Both live and heat-killed L. lactis ameliorate the allergic response in mice [15, 16, 17].

It decreases the Th2 response [16] and induces a Th1-polarizing program in dendritic cells in mice [17].

It significantly attenuates atopic esophageal and bronchoalveolar eosinophilic inflammation in mice [18].

Ethanol can increase allergic responses. L. lactis was shown to restore oral tolerance in mice, by reducing local and systemic allergic outcomes such as IL-4 and IgE [19].

Oral treatment of newborn pigs with L. lactis significantly reduced the subsequent frequency of allergy, by dampening the Th-2 immune response [20].

3) May be Beneficial in IBD

Soy milk fermented with L. lactis exhibits anti-inflammatory effects and prevents IBD in mice [21, 22].

Administration of heat-killed L. lactis suppressed IBD symptoms, such as shortening of colon length, damage to the colon mucosa, and spleen enlargement in mice [23].

It reduced inflammatory cytokine production and nitric oxide expression in mice with colitis [24].

4) Beneficial for the Skin

L. lactis increased sebum content, thereby potentially reinforcing the skin barrier in healthy young women [25].

L. lactis strain maintained skin hydration and improved subjective skin elasticity in middle-aged Japanese women [26].

5) Exhibits Antioxidant Properties

Exopolysaccharide (EPS) of L. lactis increased catalase, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity, and decreased malondialdehyde (MDA) levels in mice [27].

6) May Lower Blood Pressure

L. lactis reduces blood pressure, LDL cholesterol and triglyceride contents in hypertensive rats [28].

Milk fermented by L. lactis exhibits systolic and diastolic blood pressure- and heart-rate-lowering effect in rats with hypertension [29].

7) May be Beneficial in Aging

Long-term oral intake of L. lactis suppressed the reduction of bone density and body weight in senescence-accelerated mice [30].

L. lactis May Prevent Age-Related Hearing Loss

Intake of heat-killed L. lactis altered the intestinal flora, affected plasma metabolite levels, including fatty acid levels, and slowed down age-related hearing loss in mice, by inhibiting the loss of neurons and hair cells in mouse inner ear [31].

8) May Combat Cancer

L. lactis inhibits the proliferation of lung cancer cells, colorectal cancer cells, gastric carcinoma cells and breast cancer cells [32].

The cytoplasmic fraction of L. lactis inhibits human stomach cancer cell proliferation and induces cancer cell death [33].


  • Decreases IL-4 in allergy [15, 34, 19] and increases IL-4 in infection [11].
  • Decreases IL-8 [22, 24], IL-13 [16], and IL-18 [32].
  • Can both increase [22, 35] and decrease IL-6 [24].
  • Increases IL-10 [22, 11, 35] and IL-12 [35].
  • Decreases IFN-γ [24] in inflammation and increases IFN-γ in allergy and infection [15, 35, 8].
  • Decreases  TNF-α in inflammation [24, 32]  and increases TNF-α in infection and anti-tumor response [36, 11, 35].
  • Can increase Tregs bearing surface TGF-β [22].
  • Decreases NO [32] and iNOS [24] in inflammation [a study where iNOS was increased: 36].
  • Decreases MIP-2 [24].
  • Decreases IgE [15, 19] and increases IgA, IgG [11], and IgG2 [15].
  • Decreases NOD-1, NOD-2, TLR-4 [15], CCL11 (eotaxin-1), CCL17 (TARC) [16] and COX-2 [32].
  • Inhibits the activity of angiotensin I-converting enzyme (ACE) [29].


L. lactis is mostly nonpathogenic in humans, however, a number of cases of infection with L. lactis have been reported over the years [37].

Some strains of L. lactis increase biogenic amines putrescine and tyramine [38].

Probiotics should be avoided in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms, where they may cause infections.

Buy L. lactis

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About the Author

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

Dr. Biljana Novkovic, PhD

PhD (Ecological Genetics)

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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