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    2. Lactose Intolerance, Milk Allergy- Interview - Top

    We hear a lot about babies having trouble digesting milk. InteliHealth spoke with David M Paige, M.D., professor, Maternal & Child Health, Johns Hopkins School of Public Health, about baby formulas, soy substitutes, and lactose intolerance in general. (Not incidentally, Dr. Paige was the founding father of the Women, Infants, and Children (WIC) Program, the federal program that supplies formula and other baby food products to low-income families.)

    InteliHealth: The soy formulas for infants who are allergic to milk - do they give babies everything they need?
    Dr. Paige: Yes. In order to meet the nutritional needs of the infant, formulas - whether based on milk or soy - must follow very strict standards set by the FDA and the American Academy of Pediatrics. But the term "milk allergy" has to be used advisedly; it tends to cover several different issues. A milk allergy means that someone has an adverse reaction to protein or other elements in milk. Lactose intolerance is an inability to digest lactose, the sugar in milk. Those who are lactose-intolerant lack sufficient amounts of an enzyme in the digestive tract, called lactase, that breaks down milk sugar.

    IH: Is lactose intolerance a disease?
    Dr. Paige: You need to distinguish between lactose intolerance that may occur secondarily to an intestinal insult in an infant and the mechanism that occurs in normal healthy older children and adults. Here in the United States, where so many are of western European extraction, we think of lactose intolerance almost as though it were a disease. But if you look at the mammalian world as a whole, although both human and animal babies drink mother's milk for a time, after infancy mammals usually lose the ability to digest lactose, and they go on to other foods. So-called lactose intolerance is the normal state of affairs in adults. But all baby mammals start out as "lactose-tolerant." One of the defining criteria for being a mammal, after all, is that as an infant it drinks mother's milk. True milk allergy to human milk or formula occurs in only 1 percent to 8 percent of all babies and is not related to lactose intolerance.

    IH: But we've all known babies who just couldn't tolerate milk. Aren't they lactose-intolerant?
    Dr. Paige: The great majority of these "lactose intolerant" babies are suffering from a temporary bout of diarrhea, most often caused by a viral infection. This virus, called a rotavirus, attacks and destroys the lactase in the baby's intestine, making milk temporarily indigestible. Once the rotavirus infection clears up, that baby can go back on milk. There is a serious condition in newborn infants, alactasia, in which the baby has no lactase activity at all, but fortunately this is extremely rare.

    IH: You mentioned people of western European extraction. Why are they able to tolerate lactose?
    Dr. Paige: Cultural geographers, geneticists, and anthropologists hypothesize that when early man migrated north from the African continent, the colder climate and shorter growing season in what is now Europe forced them to look for sources of food beyond the grains and meat they were used to. Those early Europeans with a genetic anomaly that allowed them to digest the lactose in raw milk had an evolutionary advantage in that part of the world. Today, about 90% of people of western European stock can digest milk. But don't forget that drinking fresh cow's milk is actually an aberration; it's we in the U.S. who've got things topsy-turvy. About 90% of Asians, 60% or 65% of African Americans and Eastern Europeans, 80-90% of Native Americans, and 60-80% of Latin American adults can't digest milk.

    IH: Are there other foods besides milk that contain lactose?
    Dr. Paige: Yes, and people need to read food labels carefully. Milk, if you remember the nursery rhyme, is made up of "curds and whey." Whey, the lactose-containing fraction of cow milk protein, is found in many foods. The curds, or other protein in milk, is used exclusively for infant formula and other adult formulas. This results in tons and tons of leftover whey. The leftover whey couldn't be poured down the drain because it stimulates sewer life, so scientists at the U.S. Department of Agriculture set out to find new uses for whey. They found, for instance, that it could be used in beer making. And now, whey - which happens to contain about 75% of the lactose - is turning up in all sorts of commercial foods, even in hot dogs. So if you are lactose-intolerant, read the labels and watch out for whey.

    IH: When does lactose intolerance usually make itself known to a person?
    Dr. Paige: In North Americans, it begins to surface around ages 8 to 12, when gas or looser stools begin to be associated with milk consumption. But it is not a smooth linear decline: the adverse reaction to milk will vary with how much milk is consumed, with other foods that are eaten along with milk, and with how much lactase is still being produced in the intestine.

    IH: Should people who are lactose-intolerant take pills that allow them to eat milk products?
    Dr. Paige: People should be encouraged to follow a diet that is culturally appropriate for them. Encouraging Asians in the United States to drink milk when this was not a traditional part of the diet may not be appropriate. Encouraging lactose-intolerant African Americans to abandon the consumption of "pot liquor," the calcium-rich water in which collard greens and other broad leafy greens were cooked, in favor of milk is neither respectful of the culture nor nutritionally appropriate. Individuals who have traditionally consumed milk and discover increasing intolerance in older age, and who wish to continue drinking milk, can consume a lactose-hydrolyzed milk.

    IH: Are there any new developments in baby formulas?
    Dr. Paige: Baby formulas continue to be refined in an attempt to make them as similar to human milk as possible. My advice is to accept no substitute - breastfeed your infant.

    Copyright The Johns Hopkins University, 1997. All rights reserved.
    - Updated: June 11, 2001

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