Lactose Intolerance
What Is Lactose?
Lactose is actually two sugar molecules joined together: it is known as a disaccharide (di = two; saccharide = sugar). The digestive enzyme lactase splits lactose into its two constituent sugars: glucose and galactose. These are single sugars, called monosaccharides (mono = one; saccharide = sugar). Monosaccharides are small enough to be transported across the cells that line the digestive tract and into circulation, where they are an important source of energy for many body functions. The lactose molecule is too large to pass through the cells lining the digestive tract; lactase breaks it down into smaller pieces so that it can reach the circulation and be used as a source of energy for the body.
♦ Lactose is milk sugar.
♦ Lactose intolerance is caused by a lack of the enzyme required to digest lactose in the digestive tract.
♦ Lactose intolerance is not an allergy.
♦ Milk allergy is caused by an immunological reaction against the proteins in milk.
Table The milk-free diet: foods allowed and foods restricted
| Type of Food | Foods Allowed | Foods Restricted | |
| Milk and
Milk Products |
Soy beverages | All cow’s milk (whole, 2%, 1%, skim;
Lactaid, Lacteeze, or other lactose-free or lactose-reduced milk; acidophilus milk) |
|
| Soy-based infant formula | |||
| Casein hydrolysate formula | |||
| Rice Dream | |||
| Coconut milk | Milk from all animals (goat, sheep,
other) |
||
| Nut milks | |||
| Seed milks | • All milk derivatives (cream, half-and-
half, whipping cream, light cream, sour cream, ice cream) |
||
| Non-dairy creamers: | |||
| e.g., Coffee Rich
Potato-starch-based drinks |
|||
| • All milk products (buttermilk, yogurt,
quark, kefir, cheese of all types) |
|||
| (e.g., Darifree)
Clarified butter |
|||
| • Any manufactured product containing
ingredients indicating milk such as |
|||
| • Milk-free margarine | |||
| • Whey-free margarine | |||
| • Milk-free soybean cake | - Casein
- Caseinates -Whey - Lactose - Lactalbumin - Lactoglobulin -Milk solids |
||
| Breads and
Cereals |
• Breads and baked goods
made without milk or milk products |
• Baked products made with milk or
milk products such as breads, crackers, biscuits, muffins, pancakes |
|
| • French or Italian bread | • Cereals containing milk or milk solids | ||
| • Some whole-wheat bread | • Commercial baking mixes | ||
| • Some rye bread | • Any manufactured food containing
ingredients indicating that they were derived from milk |
||
| • Soda crackers | |||
| • Bagels | |||
| • Pasta without cheese or
milk-containing sauce |
|||
| • Plain cooked or ready-to-
eat cereals |
|||
| • All plain grains, flours,
and starches |
|||
| Legumes | • All plain legumes such as
dried beans, dried peas; lentils; dais |
• Any legume prepared with milk
such as |
|
| -Milk | |||
| • Milk-free; casein-free tofu | - Cream | ||
| • Peanut butter | - Cheese | ||
| • Soybeans | |||
| • Any soybean product free
from milk components |
|||
| Fruit | • All pure fruits and pure
fruit juices |
• Any fruit with cream, milk, or butter
as additional ingredients, toppings, or sauces |
|
| Meat
Poultry, and Fish |
• All fresh or frozen meat
poultry, or fish |
• Commercially prepared meat, poultry, or fish that is: | |
| • Processed meats made
without milk or milk products |
- Breaded
- Battered - Creamed • Commercially produced meat products containing milk ingredients such as meat loaf, hot dogs, cold cuts, sausages |
||
| Eggs | • Plain, boiled, fried, or
poached |
• Any egg dish containing milk ingredients
such as |
|
| • Omelette or scrambled made
without milk or cheese |
-Milk | ||
| - Cream | |||
| • Milk-free mayonnaise | - Cheese
- Commercial mayonnaise |
||
| Nuts and
Seeds |
• All plain nuts and seeds | • Nuts, seeds, and nut and seed
mixtures with coatings containing milk or lactose • Any nut or seed candies or confectioneries containing milk ingredients |
|
| Spices and
Herbs |
• All pure spices and herbs | • None | |
| Sweeteners | • All pure sugar, syrup, honey
• Sugar Twin |
• Sugar substitutes containing lactose | |
| Fats and Oils | • Clarified butter | • Cream | |
| • Pure vegetable oils | • Sour cream | ||
| • Milk-free margarines such as | • Cream cheese | ||
| - Fleischmann’s low
sodium, no salt |
• Whipped topping | ||
| • Butter | |||
| - Parkay Diet Spread | • Margarine containing whey or milk | ||
| - Canoleo margarine | • Salad dressings with milk or milk
products |
||
| - Real mayonnaise | |||
| - Nondairy dessert topping | |||
| - Shortening | |||
| -Lard | |||
| - Meat dripping | |||
| - Gravy made without milk |
What Is Lactase?
Lactase, the enzyme that digests lactose, is made within the epithelial cells lining the digestive tract. If these cells are damaged, they cannot produce enough lactase. As a result, lactose is incompletely broken down into glucose and galactose and some lactose remains intact. The undigested lactose remains in the intestines and eventually finds its way into the large bowel. Here millions of bacteria use any undigested food for their own nourishment, multiplying rapidly and producing a large number of by-products. Usually a variety of gases, organic acids, and other irritating chemicals result from the activity of these microorgansims. We feel the effects as excessive flatus, abdominal bloating, pain, loose stool, or diarrhea, and general distress in the lower intestines.
Lactose intolerance does not involve the immune system, and no antibodies are produced. Therefore, lactose intolerance is not an allergy.
Incidence of Lactase Deficiency
In Babies and Young Children
Virtually every baby has enough lactase to digest the lactose in its mother’s milk at birth. Lactase deficiency in infants is uncommon because lactose is the principal sugar in human milk and the baby needs lactase in order to digest lactose. Because lactose is so important to babies’ nutritional needs, they are usually born with enough of the enzyme to digest it. There is a medical condition known as congenital alactasia, or primary lactase deficiency, in which the baby is born without the ability to produce the enzyme, but this is an extremely rare event.
A temporary lactase deficiency can develop in babies when the inflammation associated with a bacterial or viral infection in the digestive tract damages the cells that produce the enzyme. This is known as secondary lactase deficiency, to distinguish it from primary congenital alactasia. Happily, in secondary lactose intolerance the cells rapidly return to normal when the infection clears up, and the usual level of lactase production is quickly reestablished.
In Older Children and Adults
Most adults lose some degree of lactase activity after puberty. In certain ethnic groups, such as the Oriental races, African blacks, persons of Middle Eastern origin, aboriginal peoples of North and South America and the Arctic, and people from the Mediterranean region, lactose intolerance may be as high as 80% of the population. In contrast, only about 20% of people of northern European origin lose the ability to produce lactase. In most cases, complete loss of lactase does not occur, but these people produce the enzyme at such a low level that consumption of large quantities of milk and milk products with normal levels of lactose leads to the uncomfortable symptoms of lactose intolerance.
Secondary lactase deficiency can occur in adults as well as children. Bacterial and viral infections, and sometimes the use of strong drugs and medications taken by mouth, such as antibiotics, may damage the fragile epithelial cells in the digestive tract. If lactose was tolerated prior to the epithelial damage, regular lactase activity will resume as soon as the cells return to normal.
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