Lactose intolerance is the inability to digest significant amounts of lactose, which is the predominant sugar of milk. Fifty million American adults are lactose intolerant. Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African-American, Jewish, Native American and Mexican-American adults, and 90 percent of Asian-American adults are lactose intolerant. The condition is least common among persons of Northern European descent.
Lactose intolerance results from a shortage of the enzyme lactase, normally produced by the cells that line the small intestine. Lactase breaks down milk sugar into simpler forms that can then be absorbed into the bloodstream. When there is not enough lactase to digest the amount of lactose consumed, although not usually dangerous, the results can be distressing.
Some causes of lactose intolerance are well-known. For instance, certain digestive diseases and injuries to the small intestine can reduce the amount of enzymes produced. In rare cases, children are born without the ability to produce lactase.
For most people, lactase deficiency is a condition that develops naturally and over time. After the age of two, the body begins to produce less lactase. The reasons for this are unclear and under study.
Common symptoms are nausea, cramps, bloating, gas and diarrhea, which can begin between about 30 minutes to two hours after eating or drinking foods containing lactose. Many people who have never been diagnosed as lactose intolerant, or "lactase deficient," may notice that milk and other dairy products cause problems that do not occur when eating other foods. The severity of symptoms varies, depending on the amount of lactose each individual can tolerate.
The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance test, the hydrogen breath test and the stool acidity test. A doctor can tell you where to go for these tests, which are performed on an outpatient basis at a hospital or clinic.
Fortunately, lactose intolerance is relatively easy to treat. No known way exists to increase the amount of lactase enzyme the body can make, but symptoms can be controlled through diet.
Small children born with lactase deficiency should not be fed foods containing lactose. Most older children and adults need not avoid lactose completely, but individuals differ in the amounts of lactose they can tolerate. For example, one person may suffer symptoms after drinking a small glass of milk, while another can drink one glass, but not two. Others may be able to manage ice cream and aged cheeses, such as cheddar and Swiss, but not other dairy products. Dietary control of the problem depends on each person's knowing, through trial and error, how much milk sugar and what forms of it his or her body can handle.
For those who react to very small amounts of lactose or have trouble limiting their intake of foods that contain lactose, lactase additives are available from drug stores without a prescription. One form is a liquid for use with milk. A few drops are added to a quart of milk, and after 24 hours in the refrigerator, the lactose content is reduced by 70 percent. The process works faster if the milk is heated first, and adding a double amount of lactase liquid produces milk that is 90 percent lactose free. A more recent development is a lactase tablet that helps people digest solid foods that contain lactose. One to three tablets are taken just before a meal or snack.
At somewhat higher cost, shoppers can buy lactose-reduced milk at most supermarkets. The milk contains all of the other nutrients found in regular milk and remains fresh for about the same length of time.
Calcium and Milk
Milk and other dairy products are a major source of nutrients in the basic American diet. The most important of these nutrients is calcium. Calcium is needed for the growth and repair of bones throughout life. In the middle and later years, a shortage of calcium may lead to thin fragile bones that break easily (a condition called osteoporosis). A concern for both children and adults with lactose intolerance is how to get enough calcium in a diet that includes little or no milk.
The RDA (recommended dietary allowance) for calcium for pregnant women and nursing mothers is 1,200 to 1,500 mg/day; for men, 1,000 mg/day; for adolescents and young adults 1,200-1,500 mg/day; and for postmenopausal women 1,000 to 1,500 mg of calcium per day. Therefore, it is important to make sure that each day's diet includes enough calcium, even if the diet does not contain dairy products. Quite a few foods are high in calcium and low in lactose. Many green vegetables, and fish with soft, edible bones are excellent examples.
Recent research has shown that yogurt may be a very good source of calcium for many lactose intolerant people, although it is fairly high in lactose. There is evidence that the bacterial cultures used in making yogurt produce the lactase required for proper digestion.
Although milk and foods made from milk are the only noteworthy natural sources, lactose is often added to prepared foods. It is important for people with very low tolerance for lactose to know about the many foods that may contain lactose, even in small amounts. Grocery items that may contain lactose include:
- bread and other baked goods
- processed breakfast cereals
- instant potatoes, soups and breakfast drinks
- lunch meats (other than kosher)
- salad dressings
- candies and other snacks
- mixes for pancakes, biscuits, cookies, etc.
Some so-called non-dairy products, such as powdered coffee creamer and whipped toppings, also may include ingredients that are derived from milk and therefore, contain lactose. Read food labels with care, looking not only for milk and lactose among the contents, but also for such words as whey, curds, milk byproducts, dry milk solids and nonfat dry milk powder. If any of these are listed on a label, the item contains lactose.
Use of Lactaid
The lactose-intolerant individual may well benefit from commercially available lactase (LactAid, Lactase). When added to whole or skim, fresh, canned or reconstituted dry milk, cream, or infant formula, it reduces the lactose to glucose and galactose. The liquid form (a yeast-derived ß-D-galactosidase in a glycerol carrier) calls for four or five drops per quart of milk. After shaking or mixing, the milk is refrigerated for 24 hours, during which time, 70 percent of the lactose is hydrolyzed.
For someone who cannot tolerate even that small amount of lactose, add twice the amount of enzyme; this will reduce the lactose by more than 90 percent. This treated milk, which has an unchanged shelf life, can be used for drinking, cooking, baking, and making cheese, yogurt and formula. The only change in taste is a slight increase in sweetness, due to sweeter monosaccharides. Hydrolysis adds a trace to the caloric and carbohydrate value of the milk, but diabetics should be aware of the higher content of rapidly absorbed simple sugars.
Tablet and capsule forms of commercial lactase are also available. One or two of these, taken with milk products, usually allow the lactose-intolerant individual to consume the equivalent of a serving of milk without developing symptoms. Alternatively, contents of the capsule form can be sprinkled on lactose-containing foods at the table.
Are tests needed to diagnose lactose intolerance?
What treatment will you be recommending?
What lactose aid do you recommend?
Should calcium supplements be taken? How much?
The following may help prevent or reduce the symptoms associated with lactose intolerance:
- Gastric discomfort may be less if you drink milk with meals instead of alone.
- Eat low-lactose cheddar or Swiss cheese.
- Eat yogurt with active, live culture.
- Pretreat milk yourself with over-the-counter lactose formulas, such as Dairy Ease and Lactaid. Adding the liquid form to milk and then letting it refrigerate for 24 hours can hydrolyze up to 99 percent of the lactose.
If you suspect that you are lactose intolerant, the best approach to the problem is to avoid dairy foods, yet, it must be understood that lactose intolerance is sometimes a temporary condition. It can occur as a result of such illnesses as inflammatory bowel disease, a parasitic infection or even a stomach flu, all of which can induce a short-lived deficiency of the enzyme lactase needed for the digestion of lactose. Taking certain medications, such as various antibiotics, can sometimes also bring on temporary lactose intolerance by causing a short-term lactase deficiency. Whatever the mechanism, the fact that lactose intolerance can be a passing condition in some individuals could make the advice to avoid milk products a more limited solution than often necessary.