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Newer Knowledge of Dairy Foods
Other
Specific Health Benefits of Cultured and Culture-Containing Dairy Foods
Interest in the health benefits of cultured (fermented) dairy foods dates back to the early 1900s, when Elias Metchnikoff, in his book called The Prolongation of Life , associated intake of large quantities of Bulgarian fermented milk with a long life. Today, researchers are investigating the therapeutic role of probiotic bacteria (i.e., beneficial bacterial cultures such as Lactobacillus and Bifidobacterium ) in dairy foods. The following are some of the potential health benefits associated with intake of cultured dairy foods.
- Improved Tolerance to Milk. A number of studies have demonstrated that intake of yogurt enhances lactose digestion in individuals with low intestinal levels of lactase, the enzyme necessary to digest lactose or milk's sugar (i.e., a condition called lactase nonpersistence). The lower lactose content of some cultured dairy foods compared to milk may contribute to the beneficial effect of these foods for individuals who have difficulty digesting lactose. The beneficial effect may also be explained by the ability of the starter cultures used in the manufacture of yogurt with live, active cultures to produce the enzyme lactase, which digests the lactose in yogurt. Yogurts with live active cultures can be identified by the National Yogurt Association's "Live and Active Culture" seal. Only yogurts meeting specific requirements (i.e., at least 10 million organisms per gram at the time of purchase) may carry this seal. Yogurt without live cultures, unfermented or sweet acidophilus milk, and cultured buttermilk are tolerated about the same as milk by individuals with lactase nonpersistence. Intake of cultured dairy foods such as yogurt may also improve tolerance to milk in individuals with cow's milk allergy/sensitivity (as well as help prevent allergies to other foods).
- Intestinal Health. Yogurt with specific strains of live active cultures has been demonstrated to help maintain the normal intestinal microflora balance and suppress harmful bacteria in the intestine. A particular strain of bacteria used in yogurt, Lactobacillus strain GG, aids in treatment and prevention of antibiotic-associated diarrhea, traveler's diarrhea, and acute diarrhea in children. In adults, this particular strain of Lactobacillus has been shown to stimulate bowel function by altering the microflora and suppressing fermentation in the intestine. Yogurt with Lactobacillus gasseri may be beneficial for older adults with "atophic gastritis," a condition that predisposes to intestinal infections and constipation.
- Protection Against Ulcers. Specific strains of Lactobacillus acidophilus may protect against stomach ulcers by suppressing the growth of Helicobacter pylori , a known ulcer-inducing bacteria.
- Cholesterol Lowering. The blood cholesterol lowering effect of fermented milk was demonstrated more than 30 years ago during studies conducted with Maasai tribesmen in Africa. While some more recent studies support a hypocholesterolemic effect of cultured dairy foods, the data are conflicting. Different strains of lactic bacteria in cultured dairy foods appear to have different effects on blood cholesterol levels. In a study of older adults, intake of about 1 cup of yogurt with live cultures per day for one year prevented an increase in blood total and low-density lipoprotein (LDL) cholesterol levels.
- Anti-cancer Effects. The possibility that lactic acid bacteria in cultured dairy foods may protect against certain cancers such as colorectal cancer, and possibly breast cancer, has been investigated. Studies indicate that specific bacterial strains of Lactobacillus reduce the growth of cancer cells and the activity of fecal carcinogenic enzymes implicated in the development of colon cancer. In laboratory animals, intake of yogurt has been shown to reduce colorectal tumors. However, additional research is necessary to confirm an anticarcinogenic effect of cultured dairy foods such as yogurt in humans.
- Enhanced Immunity. Intake of yogurt may improve some of the body's immune defense responses. When adults consumed 1 cup of yogurt with live cultures per day for one year, allergic symptoms decreased. Further studies are necessary to confirm this beneficial effect of yogurt on the immune system.
Many studies investigating the role of cultured dairy foods in reducing the risk of chronic diseases and clinical conditions appear promising. However, much additional research using specific strains of probiotic cultures is required to substantiate the health benefits of cultured dairy foods beyond their nutritional value in humans.
References
Kosikowski, F.V., and V.V. Mistry. Cheese and Fermented Milk Foods. Vol. I. Origins and Principles . 3rd edition. Brooktondale, N.Y.: F.V. Kosikowski and Associates, 1997.
Salminen, S., and A.V. Wright (Eds.). Lactic Acid Bacteria. Microbiology and Functional Aspects . 2nd ed. New York: Marcel Dekker, Inc., 1998.
Miller, G.D., J.K. Jarvis, and L.D. McBean. Handbook of Dairy Foods and Nutrition . 2nd edition. Boca Raton, Fla.: CRC Press, 1999.
Tannock, G.W. (Ed.). Probiotics. A Critical Review . Wymondham, U.K.: Horizon Scientific Press, 1999.
Kolars, J.C., M.D. Levitt, M. Aouji, and D.A. Savaiano. Yogurt -- an autodigesting source of lactose. N. Engl. J. Med. 310 : 1, 1984.
Salminen, S. Functional dairy foods with Lactobacillus strain GG. Nutr. Rev. 54(suppl) : 99, 1996.
Michetti, P., G. Dorta, P.H. Wiesel, D. Brassart, E. Verdu, M. Herranz, C. Felley, N. Porta, M. Rouvet, A.L. Blum, and I. Corthesy-Theulaz. Effect of whey-based culture supernatant of Lactobacillus acidophilus (johnsonii) La1 on Helicobacter pylori infection in humans. Digestion 60(3) : 203, 1999.
Anderson, J.W., and S.E. Gilliland. Effect of fermented milk (yogurt) containing Lactobacillus acidophilus L1 on serum cholesterol in hypercholesterolemic humans. J. Am. Coll. Nutr. 18 : 43, 1999.
Pearce, J. Effects of milk and fermented dairy products on the blood cholesterol content and profile of mammals in relation to coronary heart disease. Int. Dairy J. 6 : 661, 1996.
Taylor, G.R.J., and C.M. Williams. Effects of probiotics and prebiotics on blood lipids. Br. J. Nutr. 80(suppl. 2) : 225s, 1998.
Wollowski, I., S.-T. Ji, A.T. Bakalinsky, C. Neudecker, and B.L. Pool-Zobel. Bacteria used for the production of yogurt inactivate carcinogens and prevent DNA damage in the colon of rats. J. Nutr. 129 : 77, 1999.
Van de Water, J., C.L. Keen, and M.E. Gershwin. The influence of chronic yogurt consumption on immunity. J. Nutr. 129(Suppl) : 1492s, 1999.
Pelto, L., S.J. Salminen, and E. Isolauri. Lactobacillus GG modulates milk-induced immune inflammatory response in milk hypersensitive adults. Nutr. Today 31(suppl) : 45, 1996.
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