Lactose Intolerance

For many people in the world, the slogan “Got milk?” quickly translates into “Got a bathroom nearby?”

Lactose intolerance—the inability to digest the naturally occurring sugar in milk—produces symptoms of gas, cramping, bloating, and diarrhea roughly two hours after someone with the condition consumes a food or beverage that contains lactose, also called milk sugar.

Lactose Intolerance Defined
Alisa Fleming, author of Go Dairy Free: The Guide and Cookbook for Milk Allergies, Lactose Intolerance, and Casein-Free Living, says, “Lactose is the primary carbohydrate in milk products. During the digestion process, lactose is broken down into two sugars called glucose and galactose. This step occurs in the small intestine with the assistance of an enzyme known as lactase. Many people have or develop a shortage of lactase and therefore are unable to properly digest some or all of the lactose they consume. The unabsorbed lactose passes into the colon where the ‘party’ ensues. This lactase deficiency and any resulting gastrointestinal symptoms are what we typically refer to as lactose intolerance.”

According to the National Institute of Diabetes and Digestive and Kidney Diseases, some 30 million to 50 million Americans (up to 80% of African Americans and American Indians and 90% to 100% of Asian Americans) are lactose intolerant. The condition is seen least in people of northern European descent.

Some researchers peg the failure to digest lactose in adulthood as the norm rather than the exception. For example, biology tells us that humans and other mammals normally have lactase present in the digestive tract right after birth, when milk is the mainstay of the diet. This enzyme gradually declines after weaning.

Over the millennia, certain populations have experienced a mutation— actually an evolutionary adaptation—by which lactase continues to be present later in life. This typically occurs in societies where fresh milk and dairy products are among the most abundant foods and eating these foods without pain or peril has been necessary to survival. (Think Denmark, for example, where per capita consumption of dairy products is more than 500 pounds per year vs. China where per capita consumption is less than 30 pounds annually.)

This natural tendency to lose lactase after toddlerhood explains why many people are lactose intolerant. This condition is called primary lactose intolerance. It can develop as early as the age of 5 and worsens with increasing age.

Lactose intolerance doesn’t necessarily demand the vigilant avoidance of certain foods as do other allergies or intolerances. A person with gluten intolerance, for example, must strictly avoid gluten. But if you are lactose intolerant, you may be able to tolerate a certain amount of lactose in your diet. And since milk and milk products contain many essential nutrients not as readily available in other foods, you don’t want to eliminate those foods entirely if you can partake of them comfortably at some level.

The trick is to determine on an individual basis how much lactose may be too much for you. “Some people may have a complete loss of lactase activity, but many will retain 10% to 30% of their initial level of the enzyme activity. This may allow for digestion of very low levels of lactose,” says Fleming.

Primary lactose intolerance is the most common type, while there are two other forms: “Secondary lactose intolerance typically occurs temporarily after a stomach flu or in cases of celiac disease, irritable bowel disease, and chemotherapy for cancer of the gastrointestinal tract,” says Melvin B. Heyman, MD, chief of pediatric gastroenterology, hepatology, and nutrition at the University of California, San Francisco Children’s Hospital. “The other is congenital lactose intolerance. This is a metabolic disorder in which an infant is born without any lactase.”

A Definitive Diagnosis
The simplest and least expensive way to diagnosis lactose intolerance, according to Jeannie Gazzaniga-Moloo, PhD, RD, a Roseville, California-based spokesperson for the American Dietetic Association, “is to go on a lactose-free diet for a week. Then add a small amount of lactose-containing food—milk, for example—into your diet and see if the symptoms return.”

Since symptoms such as gas, bloating, and diarrhea are common to numerous conditions, some folks feel better taking a definitive test. There are three available.

The lactose tolerance test begins with a 24-hour fast. At the end of this fast, blood is drawn and the glucose level measured. Then a lactose-rich beverage that contains about 50 grams of the milk sugar—or the equivalent of four glasses of milk—is consumed. Blood is drawn over the next two to three hours to check glucose levels.

Normally, says Fleming, “When lactose reaches the digestive system, the lactase enzyme breaks it down into glucose and galactose. The liver then changes the galactose into more glucose, which in turn enters the bloodstream and raises the blood glucose level. If lactose is incompletely broken down, then the blood glucose level does not rise as it should, and a diagnosis of lactose intolerance may be confirmed.”

The hydrogen breath test measures the amount of hydrogen gas present in your breath. In those who are lactose intolerant, bacteria naturally present in the colon ferment undigested lactose, and hydrogen is one of the by-products.
To prepare for this test, Heyman says, “I recommend that you do not take any antibiotics for two weeks prior. Then eat just meat and rice the day before. An increase in the amount of breath hydrogen indicates that lactose isn’t being digested properly.”

The third test measures stool acidity. Bacteria in the colon ferment undigested lactose to lactic acid, which can be detected in a stool sample.

Cutting Back on Lactose
The remedy for lactose intolerance sounds simple: Avoid or limit lactose, depending on individual tolerance. In practice, however, that can be difficult because lactose is found in many foods in addition to milk and dairy products—for example, some boxed, canned, frozen, and prepared foods such as breads, cereals, lunch meats, salad dressings, and mixes for baked goods.

Another perplexing issue is that not all dairy foods contain the same amount of lactose. For example, an 8-ounce serving of cow’s milk contains 9 to 12 grams, depending on how it’s manufactured and whether it’s whole, low fat, or skim milk. Lactose-reduced milk supplies 0 to less than 2 grams of lactose per serving. Ice cream, on the other hand, provides around 6 grams per half-cup serving, while cultured milk products such as yogurt contain 5 grams per 8-ounce cup. However, yogurt that contains live cultures is generally fine for those intolerant to lactose due to yogurt’s digestion-boosting bacteria.

Cheese is tricky. “The lactose percentages don’t just vary by the type of cheese but also by how the cheese is manufactured,” says Fleming. “Hard and soft ripened cheeses that are produced via traditional methods are often better tolerated than are milk, as the fermentation processes and higher fat content contribute to lower lactose levels. Plus, the traditional aging of cheese (for more than two years) reduces the lactose content to near 0.

“However, modern processes used in the production of most cheeses today rarely assist in lactose reduction and typically involve minimal aging,” she says. “Cheeses that often are moderately high in lactose are lower fat soft cheeses, including ricotta, feta, and cottage cheese. Also, highly processed cheeses [eg, Velveeta] are often very high in lactose and best avoided by the lactose intolerant.”

Drinking in Enough Nutrition
Milk and dairy products are good sources of the bone-building mineral calcium. Leaving this food group out of the diet means fishing for other sources, such as canned salmon with the bones, dark-green vegetables (except spinach, chard, and beet greens), tofu processed with calcium sulfate, okra, sesame seeds, turnip greens, soybeans, figs, tempeh, almond butter, broccoli, and fortified soy milk. Today, several brands of orange juice, breakfast cereals, and breakfast bars have added calcium, too. In fact, one serving of these fortified foods can offer as much calcium as a glass of milk (about 300 milligrams). Adult men and women require 1,000 milligrams of calcium daily.

Dairy products are also a good source of riboflavin, potassium, and vitamin D. Lean meats, poultry, fish, grains, broccoli, turnip greens, asparagus, and spinach contain riboflavin, while many fruits and vegetables such as citrus, tomatoes, melons, and leafy greens are potent sources of potassium. Vitamin D is delivered in small amounts in whole eggs, liver, salmon, and fortified margarine, and sunlight also triggers vitamin D production in the skin.

Shopping and Cooking Tips
The key to avoiding lactose-containing foods or finding those with a low lactose content, says Heyman, is reading food labels. This can sometimes take some real supermarket sleuthing. “For example, some nondairy creamers contain lactose,” says Moloo. “That’s why it’s important to check the ingredient listing on a product.”

Look for milk and lactose in the list of ingredients and also check for words such as whey, curds, milk by-products, dried milk, milk solids, and powdered milk. If any of these words are listed on a label, the product contains lactose.

Those with severe lactose intolerance also need to read labels on products other than foods. “Nutritional supplements and some medications can contain lactose,” says Fleming.

In the kitchen, there are many tasty ways to cook lactose free. Fleming shares a few of her favorites:

• Try milk alternatives. There are hundreds, so if you don’t like one, try another. Then experiment with them in cooking. For example, you don’t want to use a sweetened or vanilla-flavored milk in a savory dish like cream of mushroom soup. Many soy, rice, cashew, and oat milks are unsweetened. Hemp milk has a bitter taste, and this can affect the taste of a dish.

• In place of Parmesan cheese as a topping, try chopped olives. These add both flavor and salt. Toasted breadcrumbs, chopped sundried tomatoes, and chopped nuts will also add a burst of flavor as a topping.

• Missing the creaminess of rich heavy cream in a dish? Use coconut milk. Coconut milk will also whip, but soy milk won’t. Nut milk adds a creamy texture, and cashew is an especially good choice.

“Enjoy experimenting,” says Fleming. “Instead of being a chore, it can be a fun part of a lactose-free diet.”

— Carol M. Bareuther, RD