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 . 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 .
It activates natural killer (NK) cells and enhances their cytotoxic activity .
2) L. lactis May Alleviate Allergies
It significantly attenuates atopic esophageal and bronchoalveolar eosinophilic inflammation in mice .
Oral treatment of newborn pigs with L. lactis significantly reduced the subsequent frequency of allergy, by dampening the Th-2 immune response .
3) May be Beneficial in IBD
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 .
It reduced inflammatory cytokine production and nitric oxide expression in mice with colitis .
4) Beneficial for the Skin
L. lactis increased sebum content, thereby potentially reinforcing the skin barrier in healthy young women .
L. lactis strain maintained skin hydration and improved subjective skin elasticity in middle-aged Japanese women .
5) Exhibits Antioxidant Properties
6) May Lower Blood Pressure
L. lactis reduces blood pressure, LDL cholesterol and triglyceride contents in hypertensive rats .
Milk fermented by L. lactis exhibits systolic and diastolic blood pressure- and heart-rate-lowering effect in rats with hypertension .
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 .
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 .
8) May Combat Cancer
L. lactis inhibits the proliferation of lung cancer cells, colorectal cancer cells, gastric carcinoma cells and breast cancer cells .
The cytoplasmic fraction of L. lactis inhibits human stomach cancer cell proliferation and induces cancer cell death .
- Decreases IL-4 in allergy [15, 34, 19] and increases IL-4 in infection .
- Decreases IL-8 [22, 24], IL-13 , and IL-18 .
- Can both increase [22, 35] and decrease IL-6 .
- Increases IL-10 [22, 11, 35] and IL-12 .
- Decreases IFN-γ  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 .
- Decreases NO  and iNOS  in inflammation [a study where iNOS was increased: 36].
- Decreases MIP-2 .
- Decreases IgE [15, 19] and increases IgA, IgG , and IgG2 .
- Decreases NOD-1, NOD-2, TLR-4 , CCL11 (eotaxin-1), CCL17 (TARC)  and COX-2 .
- Inhibits the activity of angiotensin I-converting enzyme (ACE) .
L. lactis is mostly nonpathogenic in humans, however, a number of cases of infection with L. lactis have been reported over the years .
Probiotics should be avoided in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms, where they may cause infections.