Do Fermented Milk Products Play a Role in Immune Function?

The development and maintenance of the immune system depend largely on healthy gut microbiota. As fermented and probiotic milk products are a source of beneficial live microorganisms that can improve gut microbiota, a number of studies have investigated the role of these products in immune regulation. To date, the available evidence suggests that fermented milk products may enhance immune functions.

main humaine tenant des cellules microscopiques de virus et de bactéries cancéreuses comme métaphore de la maladie pathogène


  • Fermented milk products such as yogurt may promote cellular immune functions.
  • Both regular and probiotic yogurt appear to have favourable effects on immune function.

The evidence

A randomized controlled trial by Meyer et al. evaluated whether yogurt consumption had stimulating effects on the immune system. Thirty-three healthy women aged 22 to 29 years were randomized to either a conventional or a probiotic yogurt. The subjects consumed 100 g per day of the respective products for 2 weeks, and the amount was increased to 200 g for the subsequent 2 weeks. It was found that both products enhanced cellular immune functions, but there was no significant difference between them.1

In another randomized controlled trial, the effect of the dietary deprivation of fermented foods on the immune system was assessed. The study consisted of 20 healthy adult volunteers aged 23 to 43 years who regularly consumed yogurt and/or cheese (at least 5 servings per week) and other fermented products (at least 3 servings per week). They were instructed not to consume any fermented products for 2 weeks. Following this restriction, the participants were randomized to the daily consumption of 200 mL of either regular or probiotic yogurt for 2 weeks.2

  • The deprivation of fermented foods was associated with a fall in innate immune response.
  • Both the regular and probiotic yogurt counteracted the adverse immunological effect.
  • The probiotic yogurt was more effective than the regular yogurt at counteracting the fall in immune response.

Marcos et al. conducted a prospective randomized controlled trial to investigate the effect of milk fermented with yogurt cultures plus Lactobacillus casei on the immune system of individuals under academic examination stress. The participants were 155 healthy university students aged 18 to 23 years. For 6 weeks, they were assigned to either 1 daily glass of semi-skimmed milk or 2 daily servings of 100 mL of the fermented milk product. The results indicated that the fermented milk product may modulate immune response among individuals under academic examination stress.3

In addition to human studies, several animal models have been used to examine the immunomodulatory effect of milk products. In a 2012 study, it was observed that a cheese-containing diet modulated immune responses in mice.4 Another study suggested that a fermented milk product with 2 probiotics and a prebiotic may have a beneficial effect on the humoral and cell-mediated immunity of host animals.5

Potential mechanisms

Fermented milk products contain large quantities of beneficial bacteria such as lactic acid bacteria, which may enhance both innate and adaptive immunity. The immunomodulatory activity of lactic acid bacteria includes the activation of the systemic and secretory immune response via the coordination of interactions between the microbiota, epithelial cells and immune cells.6

Milk and milk products contain bioactive peptides that have been shown to increase the activity of immune system cells. Evidence suggests that these peptides assist in the proliferation of lymphocytes, the functioning of natural killer cells, the synthesis of antibodies and the production of cytokines.7 It has been demonstrated that both conventional and probiotic yogurt may stimulate cytokine production and promote higher alertness of the immune system.8

Lactoferrin, an iron-binding glycoprotein found in milk and milk products, is an immune modulator and has antimicrobial and antioxidant properties. It influences innate and adaptive immunity by modulating the migration, maturation and functions of immune cells.9


Evidence on the immunological properties of milk products comes principally from studies on fermented milk products. These studies indicate that both conventional and probiotic fermented milk products such as yogurt may strengthen the immune system.

Further research from randomized controlled trials is needed to determine whether conventional and probiotic fermented milk products have different effects. Additional studies are also needed to investigate the potential benefits of different types of milk products.

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