What is lactose? What is lactase?

Dr. Savaiano: “Lactose is the sugar found in dairy products. Lactase is the enzyme that digests lactose. Lactases are found in all mammals, particularly during infancy, and are also found in bacteria in the gastrointestinal (GI) tract.”

What is lactose intolerance? 

Dr. Savaiano: “Most of the world’s population has a large capacity to digest lactose when they’re infants. But once they’re weaned, and they mature, there’s a genetic reduction in the amount of lactase that the intestinal tract produces. If these individuals consume too much lactose, they could have symptoms of intolerance. Typical symptoms of lactose intolerance are flatulence, stomach rumbling, and in rare instances, short term diarrhea. Once the lactose has exited the GI tract, the symptoms end. Symptoms of lactose intolerance depend on several factors including dose of lactose, GI transit and regular milk consumption, which adapts the GI bacteria.”

Should those with lactose intolerance avoid dairy products?

Dr. Savaiano: “Not at all, in fact, that’s the wrong strategy. Although it seems intuitive, it’s actually inappropriate. Lactose intolerance depends on dose, so if one drinks a small amount of milk, or has a small amount of dairy food, the small dose will almost certainly be tolerated.

Regarding dose, drinking one cup of milk (8 ounces) or less usually does not cause symptoms. But those who have symptoms with this amount should try one-half cup. Soft cheeses and ice cream are better tolerated than milk. Hard cheeses have almost no lactose and should be well tolerated. Yogurt is also well tolerated due to the bacterial lactase in the product. Products with a lot of whey (and thus, lactose) such as “frozen yogurt” (which really isn’t yogurt) are often poorly tolerated.

Regarding transit, always drink milk and eat dairy foods with a meal. This slows transit, dramatically improving digestion and tolerance.

Regular milk drinkers (one to three small servings per day) have much better tolerance because they have adapted their intestinal bacteria to improve digestion of lactose.”

Sarah: “Those with lactose intolerance don’t need to abstain from dairy. There are many solutions that can keep dairy foods in the diet. This includes looking for lactose-free options (Guess what?! It’s still dairy, but just has the lactose removed!),  seek out products naturally low in lactose like low-fat cottage cheese, Swiss and mozzarella cheese and Greek yogurt, and start with small amounts of dairy and gradually increase over a few days or weeks. Keep in mind that lactose intolerance is different for every person and one person may be able to tolerate some foods others cannot.”

Is there a test for lactose intolerance?

Dr. Savaiano: “There is a very good test, called the breath hydrogen test, but it’s used primarily in research settings, not in clinical settings. Most physicians will simply use an exclusion diet – if you avoid lactose and don’t have symptoms, they will assume you’re lactose intolerant. However, if you want a more definitive test, your university hospital may be able to do a hydrogen test to determine if you are a lactose maldigester and subject to potentially having intolerance symptoms.”

Is lactose intolerance the same as milk allergy?

Dr. Savaiano: “No, they’re very different – they have different mechanisms. Milk allergy is quite rare. The typical symptoms for milk allergy (a true allergic response) often include skin rash. There could be some GI symptoms as well, whereas lactose intolerance is defined clearly by flatulence, stomach distention and diarrhea.”

Sarah: “Lactose intolerance is often misunderstood and is commonly confused with a milk allergy. A milk allergy is a food allergy, which is an overreaction of the immune system to a specific food protein. It can trigger an allergic reaction that may include a range of symptoms from moderate (rashes and itching) to severe (trouble breathing, wheezing, etc.).

Lactose intolerance has nothing to do with the immune system. Those with lactose intolerance are missing the enzyme lactase, which breaks down lactose, a sugar found in milk and dairy products. As a result, individuals who are lactose intolerant have difficulty digesting these foods and may experience an array of gastrointestinal symptoms such as cramps, bloating and diarrhea. While it can cause great discomfort, it is not life-threatening.”

Is lactose intolerance a common problem?

Dr. Savaiano: “About three-quarters of the world’s population has the potential for lactose intolerance, and about one-fourth of the U.S. population. Lactose intolerance is a genetic trait – it’s not an environmental trait. It’s a trait that is actually recessive, but most common among the world’s population.”

Sarah:  “It’s estimated that 10 percent of Americans are lactose intolerant, but because many are self-diagnosed, this percentage is probably much lower. Inaccurate self-diagnosis of lactose intolerance or misinformation about dairy may cause people to unnecessarily eliminate dairy from their diet and miss out on its key nutrients. This is why it is so important to visit your doctor or a registered dietitian if you think you may be lactose intolerant to ensure a proper and accurate diagnosis.”

If you are experiencing problems you think are associated with lactose intolerance, please visit your physician.

Listen to Dr. Savaiano discuss lactose intolerance.

//www.bestfoodfacts.org/document_center/download/Savaiano.mp3

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Does drinking milk and using other dairy products tend to cause allergies in children?

Dr. Taylor: “Milk allergies, yes of course. It is impossible to become allergic to milk if you are never exposed. The allergy is caused by drinking milk from a different species, i.e. cow’s milk.”

Why are we the only mammals that drink milk after we are weaned from our mothers?

Dr. Macrina: “The simple answer is: because we can. It is a food that’s available to us. During the hunter-gatherer times people consumed what was available. With the domestication of cattle, milk was another product that became available. Milk is a nutritious food – in addition to calcium, it contains a good amount of magnesium and potassium, two minerals that most people don’t consume in sufficient quantities. It also contains high-quality protein and some of the fatty acids in milk have health-promoting effects. If you’re trying to reduce fat intake, you can always opt for low fat or skim varieties.”

If you wish to learn more, or have questions, feel free to submit a question to the experts!

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According to Dr. MacDonald, dairy intolerance is a catch phrase to mean several things that can interfere with a person’s ability to consume milk or dairy products. When talking about dairy intolerance, people usually refer to two very different conditions.

Lactose intolerance: This occurs when the body is unable to convert lactose (milk sugar) due to the lack of a sufficient amount of the enzyme lactase in the intestine. Common symptoms include cramps, bloating and diarrhea.

According to a study from the American Academy of Pediatrics, lactose intolerance is rare in infants because the enzyme lactase is generally at its highest levels soon after birth and declines as people age. True lactose intolerance, where the body lacks the enzyme lactase, usually shows up in grade school and beyond.

Different people have varying levels of lactose intolerance. Dr. MacDonald notes that some with lactose intolerance can consume ice cream or cheese because of lower levels of lactose in those foods. In addition, some people may develop a temporary lactose intolerance after an intestinal illness, for example, or if lactose is eliminated from the diet after a long time. In both instances, the body would need time to begin making a sufficient level of lactase.

Milk allergy: Milk contains several proteins and sometimes the body’s immune system can have a reaction to a specific dairy protein. This is caused by the body reacting to a dairy protein. According to Dr. MacDonald, “this is an allergic reaction and not intolerance.”

Breastfeeding and Dairy Intolerance

One of our readers asked, “When my son was about 3 months, we learned he had a dairy intolerance, and because I was breast-feeding, I had to stop consuming dairy products. We slowly and carefully started introducing dairy products back into his diet around 9 months and he seems to be fine now with drinking whole milk and eating yogurt and cheese. Is it common for babies to outgrow this so quickly? And if so, why?” In answering our reader’s question, Dr. MacDonald cautions that it is not “really possible to know if the child was having a dairy intolerance at the time unless a specific test was done and the reaction documented.”

And because human milk is not directly created from the cow’s milk in a mother’s diet, Dr. MacDonald says it is unlikely that the milk proteins contained in the dairy products consumed by a mother find their way into the breast milk she produced for her newborn. In this case she says that, “There is not an easy answer, but it could be that the child’s reaction had nothing to do with the diet of the mother, and the fact that the child did better when she stopped consuming dairy was circumstantial. It would be more likely that the infant was reacting to something else and did not have a dairy intolerance at all, and therefore has not outgrown a dairy intolerance – and rather, never had it at all.”

The U.S.Centers for Disease Control and Prevention (CDC) estimates that four to six percent of children under the age of 18 suffer from a food allergy. Food allergies are the body’s immune response to certain proteins in foods. For many consumers, the allergy creates a mild reaction, but some food allergies (such as those to peanuts and shellfish) can be severe and should be managed with the direction of a doctor. If you suspect you or your child have a food allergy, talk to your doctor who can diagnose and help you effectively manage a food allergy.

If you’re a breastfeeding mom, have you had to adjust your diet to limit your newborn’s reaction to breast milk?

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