Kefir remains a popular fermented milk beverage, despite the increasingly competitive beverage market. Many people drink kefir for its alleged health benefits, according to a 2007 report in the “Nestle Nutrition Workshop Series.” The bacteria in kefir produce lactic acid by fermenting lactose. Kefir contains many kinds of enzymes that underlie this process. Talk to your doctor before ingesting large amounts of kefir.

What Kefir Enzymes Do

Casein plays a critical role in turning milk into kefir. Nearly 80 percent of the protein in milk comes from four members of the casein family, according to January 2009 review in the “Journal of Chromatography.” These substances include alpha-casein, kappa-casein and two types of beta-casein. A study published in the January 2010 issue of the “Journal of Dairy Science” showed that the enzymes present in kefir break down milk caseins. The resulting substances -- known as peptides -- have a broad range of health-promoting effects. They can, for example, bolster your immune system.

Lmm-Protease-Lh and Hmm-Protease-Lh

Manufacturers often use Lactobacillus helveticus to ferment dairy products such as cheese and kefir. This bacteria improves the flavor of cheddar cheese, according to an October 2010 review in the “Journal of Dairy Science.” The enzymes mediating these effects remain unknown. A study presented in the September 2008 edition of “Bioresource Technology” purified Lactobacillus helveticus samples to identify the enzymes present in the bacteria 45. The scientists found two unique substances known as Lmm-protease-Lh and Hmm-protease-Lh. The identification of these enzymes could allow the production of amino acids from the proteins contained in meat, fish and whey.

Cell-Wall-Bound Proteinase

Dairy producers use lactic starters such as bacteria from the Lactobacillus family to manufacture yogurt and kefir 4. These substances break down the casein in milk and begin the conversion of milk to fermented products 1. An enzyme from the cell-wall-bound proteinase group mediates this process. Another member of this family might appear in kefir. An investigation published in the June 2006 issue of “Biotechnology and Biotechnological Equipment” tested this hypothesis in Lactobacillus kefir -- a strain commonly found in kefir. The researchers identified at least one cell-wall-bound proteinase based on its ability to break down beta-casein and not alpha-casein.

Phosphatidylinositol 3-Kinases

It remains unknown how kefir achieves its alleged health effects. Byproducts of kefir -- known as kefiran -- lower blood pressure, according to a 2004 report in “Biofactors.” Kefir itself might enhance athletic performance. An experiment described in the November 2002 edition of “Cytotechnology” looked at kefir’s effect on glucose uptake 8. The researchers exposed cultured muscle cells to kefir during a single testing session. This treatment increased the uptake of glucose -- an effect known to enhance athletic abilities. Kefir-induced activation of phosphatidylinositol 3-kinase appeared to mediate this effect. This family of enzymes plays an important role in cell growth.