November 2, 1995
Media Contact: Debbie Bangledorf
Phone: (410) 955-4948
Shortly after weaning, many children slowly lose at least some of their tolerance for lactose, the natural sugar in milk and other dairy foods. Some develop gas and diarrhea and parents may ban these foods to prevent trouble.
Now, new research from the Johns Hopkins Children's Center affirms for kids what is already suspected among adults: yogurt is okay.
In a study reported in the November issue of The Journal of Clinical Nutrition, children with symptoms of lactose intolerance experienced fewer side effects when they ate yogurt than when they drank milk.
Specifically, when children ate yogurt containing the live active bacteria Lactobacillus bulgaricus and Streptococcus thermophilus -- two organisms traditionally used to make yogurt -- they suffered less pain and discomfort than when they consumed milk or even pasteurized yogurt that does not contain live cultures.
"Studies in adults suggest that the live active cultures produce the enzyme lactase, which hydrolyzes, or breaks down lactose," says Jose Saavedra, M.D., director of pediatric nutritional support at the Children's Center. "While that is true to some extent in children, our study suggests that in kids, the rate at which lactose reaches the colon may also play a role."
The density of yogurt, he says, is likely to delay gastric emptying from the stomach to the small bowel. As a result, lactose is delivered slowly to the colon, where fermentation begins and gas forms.
Lactose is the principal carbohydrate of mammalian milk. In most mammals, including the majority of humans, intestinal lactase levels are at their highest immediately after birth and decrease with weaning until low levels are present in adults, says pediatric gastroenterologist, Jay Perman, M.D.
When children and adults lose the ability to absorb lactose in the small bowel (called malabsorption), bacteria in the colon will feed on it, producing gas and short chain fatty acids. For some, production of gases -- hydrogen, for example -- leads to symptoms (or lactose intolerance). In the Hopkins study, 14 children experienced an average of 50 percent fewer symptoms when they ate yogurt with live cultures, compared to milk or pasteurized yogurt. And when the yogurt-eating children did have symptoms, they were more likely to rate them as mild or moderate, rather than severe.
The children received typical servings (12 g) of milk, pasteurized yogurt and yogurt containing active live culture. The yogurts were made from the same milk used in the study, and prepared and supplied by the Dannon Company, Inc., Minster, Ohio. Children consumed milk or yogurt every other day over a five-day period following an overnight fast. A standard hamburger meal was the only other food eaten on those days. Symptoms and breath hydrogen levels, a common indicator of malabsorption, were measured at regular intervals.
"Breath hydrogen levels were nearly double and rose almost twice as fast in children who drank milk," says Saavedra. "At that time, children were most likely to rate their symptoms as severe."
Some people never develop lactose malabsorption symptoms while others battle them only temporarily, such as after the onset of irritable bowel syndrome or diarrhea. Most people avoid the symptoms by ingesting over-the-counter products that contain the enzyme lactase or by avoiding foods that contain lactose.
Lactose has limited sweetness relative to other sugars and its solubility and crystallization enhance its use in the candy and confection industries. Its browning properties also make it useful in the manufacture of baked products. In addition, lactose is often present in commercially made non-dairy products such as breads, cereals, breakfast drinks, salad dressings and cake mixes and it is found in some prescription and over the counter drugs because of its tablet forming properties.
Other authors of the study are Michele A. Shermak, M.D., Teri L. Jackson, R.N., S. Huang, Ph.D., and Theodore M. Bayless M.D. This study was partially supported by a grant from the National Yogurt Association. The authors express their gratitude to Richard Gottal for his technical support.
The Johns Hopkins Children's Center is the children's hospital of The Johns Hopkins Medical Institutions. Maryland's only comprehensive acute-care hospital for children, the Center, with its 193-bed hospital and more than 40 divisions and services, treats 7,000 inpatients and more than 90,000 outpatients annually.