Lactose digestion from yogurt: influence of a meal and additional lactose

Article Abstract:

Lactose is a sugar that is naturally present in dairy products such as milk and yogurt. In the small intestine, lactose is normally broken down into glucose and galactose by an enzyme called lactase. Humans have a limited ability to digest lactose, and lactase deficiency is not uncommon in adults. Lactase deficiency results in a condition called lactose intolerance. People who have lactase deficiency cannot digest foods that contain lactose, or they have a limited ability to digest them. In these individuals, eating foods containing lactose causes symptoms of abdominal cramps, diarrhea and gas. Previous studies have shown that people who have lactase deficiency are better able to digest the lactose present in yogurt than the lactose in milk. This is because yogurt contains bacteria (used in the fermentation process) that make an enzyme called beta-galactosidase (beta-gal) that can digest lactose. To evaluate the ability of beta-gal to digest lactose present in yogurt and lactose from other sources, 22 people with lactase deficiency were examined. Each subject consumed 10 different test meals containing yogurt, milk and different amounts of added lactose. Since the amount of hydrogen present in a person's breath increases when lactose is eaten and not digested, lactose digestion was evaluated by measuring breath hydrogen as well as by assessing symptoms. The test meals containing yogurt were better tolerated (produced fewer and less severe symptoms of gas and diarrhea) than those containing milk. When additional lactose was included along with the yogurt, the beta-gal enzyme in the yogurt did not improve the digestion of the added lactose. It is concluded that symptoms of lactase deficiency are minimal when yogurt is eaten by itself or with a meal. However, when additional lactose from other food sources is present, symptoms of lactase deficiency will increase and are related to the amount of lactose consumed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Lactose

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Relative effectiveness of milks with reduced amounts of lactose in alleviating milk intolerance

Article Abstract:

Lactase is an enzyme located in the small intestine that is responsible for digesting the lactose (sugar) that is present in milk. Many adults cannot drink milk because they do not make enough lactase to digest the milk. This is called milk intolerance or lactose intolerance, and it causes symptoms of gas, intestinal cramps, and diarrhea. People with lactose intolerance can often digest yogurt and milk products that do not contain large amounts of lactose. Special milk products that contain only small amounts of lactose (called lactose-modified products) have been developed and tested in people who have milk intolerance. However, the exact amount of lactose that can be consumed by people with lactose intolerance has not been determined. Therefore, a study was performed to determine how much lactose can be consumed by people who have milk intolerance. The study included six adults with milk intolerance who drank four different milk preparations: whole milk; milk with 50 percent of the lactose removed; milk with 80 percent of the lactose removed; and milk with 95 percent of the lactose removed. Five of the six subjects had symptoms of gas, cramps or diarrhea after drinking the whole milk. Only one of the six subjects had these symptoms after drinking the milk with 50 percent or 80 percent of the lactose removed. None of the subjects had symptoms after drinking the milk with 95 percent of the lactose removed. It is concluded that reducing the amount of lactose in whole milk by 50 percent is adequate to relieve the symptoms of milk intolerance in most people who cannot digest lactose. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment

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Strains and species of lactic acid bacteria in fermented milks (yogurts): effect on in vivo lactose digestion

Article Abstract:

Lactose intolerance, the inability to digest lactose, is caused by a deficiency of beta-galactosidase (beta-gal, an enzyme that converts lactose to glucose and galactose). People who are deficient in beta-gal cannot tolerate milk because milk contains lactose. However, these people can tolerate yogurt, even though it contains lactose, because yogurt is fermented with bacteria that have the beta-gal enzyme (lactic acid bacteria). Streptococcus thermophilus and Lactobacillus bulgaricus are lactic acid bacteria that are commonly found in yogurts. A study was performed to evaluate the ability of lactose-intolerant individuals to digest yogurts and fermented milks prepared with different strains of lactic acid bacteria. The subjects consumed seven different yogurts and four different fermented milks prepared with different strains of lactic acid bacteria. The ability to digest the yogurt or fermented milk was determined by measuring the amount of hydrogen given off in the subject's breath. The amount of hydrogen in the breath increases when lactose cannot be digested. All seven yogurts dramatically improved lactose digestion. Also, the fermented milks containing Lactobacillus bulgaricus or Streptococcus thermophilus greatly improved lactose digestion. These results indicate that adding lactic acid bacteria to fermented milk and yogurt increases the ability of lactose-intolerant individuals to digest lactose. Heat treatment or pasteurization of dairy products, to increase shelf life, will destroy lactic acid bacteria and reduce the ability to digest lactose in certain individuals. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Lactic acid, Fermented milk, Cultured milk

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