Lactose: truth or intolerances.

"I know hundreds of people who have spent years and thousands of dollars on tests looking for ulcers or spastic bowels, and who have been told they're crazy,' says David Jacobs, a Washington, D.C., internist who is certified in nutrition, allergy, and immunology.

"I tell them to lay off all dairy products for two weeks. The results are usually so striking that it changes their lives."

Most of the people Jacobs is talking about have lactose intolerance. Their bodies no longer produce lactase, the enzyme that digests milk sugar, or lactose.

"The most common symptoms are abdominal pain, bloating, gas, and diarrhea,' says Jacobs. But some also have bad breath, headaches, and a lack of energy."

While most people have heard of lactose intolerance, many have hazy-or wrong-information about how it should be diagnosed and treated. Here are six myths about this surprisingly common problem.

1. Most adults are lactose intolerant and cannot drink a glass of milk without experiencing symptoms.

Roughly 70 percent of the world's population begins losing the ability to make lactase after they've been weaned.(1) That means some school-aged children suffer as much as adults.

However, says Dennis Savaiano of the University of Minnesota, "only one-fifth to one-third of those [lactase-deficient] people have symptoms after drinking a single glass of milk."

That's because the friendly bacteria in our large intestines gobble up at least some of the lactose our enzymes can't digest. it's only when people consume too much lactose for their bacteria to handle that gas, cramps, and diarrhea set in.

On the other hand, one-fifth to one-third of 70 percent of the world's adults is a lot of people-as many as one out of every four.

2. A lactose tolerance test is the best way to diagnose the condition.

Wrong. In a standard lactose tolerance test, physicians ask people to drink a beverage containing about as much lactose (50 grams) as they'd get in four glasses of milk. If a blood test shows that very little sugar was absorbed, the person flunks" the test and is diagnosed as lactose intolerant.

This unrealistically huge load of lactose causes symptoms in 75 to 96 percent of lactase-deficient people.(1) But no more than a third of them have symptoms after drinking one glass of milk. And only half have symptoms after 20 grams of lactose-almost as much as in two glasses of milk.

"A lactose tolerance test is a waste of money because it's too imprecise," says Jacobs, who instead advises people to avoid dairy products for two weeks. That also catches the people who can't tolerate other components of milk.

For example, in some studies milk has mysteriously caused bloating and diarrhea even in people who can digest lactose.(2) It may be a sensitivity to the protein in milk," speculates Lindsay Allen of the University of Connecticut.

3. People who are lactose intolerant should avoid all dairy products.

Not necessarily. Milk has more lactose than cheese, ice cream, and a number of other dairy products (see "Lactose from Most to Least"). While the exquisitely sensitive person may have symptoms after eating a hot dog made with a little dry milk, others may only get into trouble after drinking two glasses of milk.

Symptoms also depend on what else is in the milk or the meal. Fat, sugar, other food, or anything else that slows the transit of food through the digestive tract makes it easier for your resident bacteria to handle the lactose load.

"People get fewer symptoms if they drink milk with a meal, if they drink whole rather than skim milk, or chocolate rather than unflavored milk," says Savaiano. (Don't take that as a recommendation, though.)

4. Lactose intolerant people can digest fermented dairy products, like buttermilk, yogurt, and acidophilus milk.

Yogurt, yes. Frozen yogurt, buttermilk, and acidophilus, no.

Those handy little bacteria that turn milk into yogurt, Streptococcus thermophilus and Lactobacillus bulgaricus, can actually digest some of the milk's lactose as the milk is fermented and stored. (The bulgaricus eat the most.) What's more, the yogurt bugs digest much of the remaining lactose once they're in your small intestine.(3) Talk about convenient.

But that can't happen unless the bacteria survive the acid in your stomach (fortunately, yogurt is a good buffer) and reach the small intestine intact.(4) There, your bile acids break them open, releasing lactose-digesting enzymes into the gut, says Minnesota's Savaiano.

Freezing destroys much of the enzymes' activity, though.(4) "Three years ago, we tested all the frozen yogurts on the market in the Twin Cities,' says Savaiano. "None had significant enzyme activity."

And labels that claim that the frozen yogurt contains active cultures" are no guarantee. They don't say how much," he points out.

Still, lactose malabsorbers suffer less discomfort with frozen yogurt than with milk.(4) That's probably because frozen yogurt's sugar, protein, and (sometimes) fat slow its movement through your gut.

As for buttermilk, it's fermented either by Sireptococcus lactis or by a combination of two other streptococci. Unlike the bacteria in yogurt, these microbes can digest lactose only if it has phosphorus added to it.

But "our bodies have no system to [add phosphorus to] lactose," says Savaiano. So buttermilk causes no fewer symptoms than ordinary milk.(5)

Nor is a lactase-deficient person better off with acidophilus milk.(5) The Lactobacillus acidophilus bacteria do not digest the milk's lactose either because manufacturers use frozen starter cultures or because, unlike yogurt's bacteria, most L. acidophilus don't get broken up by bile acids, says Savaiano.

5. If you can't absorb lactose, you can't absorb the calcium in milk either.

Wrong again. Calcium, riboflavin, protein, vitamins A and C, copper, and zinc--essentially all nutrients that have been studied-we absorbed just as well by people who don't have lactase.(6)

6. Once you lose the ability to digest milk, it will never come back, no matter how much you drink.

Yes and no. it's possible that, over time, the more milk you drink, the fewer problems you'll have digesting it. But that's not because your body starts making more lactase. Animal studies suggest that it's the bacteria in your intestines that rise to the occasion.(7)

"Parents needn't worry that feeding their children too little milk causes lactase deficiency," says Edwina Murray of the Massachusetts institute of Technology. People either have the gene to continue making lactase as an adult or they don't-how much milk they drink is irrelevant.(6)

in fact, what's surprising is not that 70 percent of the world doesn't have the gene to digest milk sugar, but that 30 percent does. "Geneticists are fascinated by this adaptation, which probably took place 5,000 to 10,000 years ago," says Savaiano.

Only people whose ancestors came from three areas--Northern Europe, the Middle East, and Central Africa--have the gene. "These were the places milk of animals was first used as food for adults," says Savaiano. "That people in those places got this genetic adaptation is absolutely amazing."

TIPS FOR THE INTOLERANT

1. If you're troubled by gas, bloating, or diarrhea, try avoiding all dairy products for two weeks. "Watch out for hidden sources of milk, such as cream sauces, creamed soups, and salad dressings," cautions Washington, D.C., physician David Jacobs. And remember (who could forget?) that plenty of foods other than dairy products can cause gas and bloating (see 'Out of Gas?" March 1991).

2. if your two-week trial leads to a drastic drop in symptoms, start experimenting to see if you can tolerate cheese, yogurt, or other dairy products. "It can take two or three days before you get symptoms, though," says Jacobs. So space out the trials.

3. The symptoms of lactose intolerance can be temporary. Antibiotics, a stomach virus, or a parasitic infection can wipe out the lactosedigesting bacteria in your colon. With time, the bacteria-md your ability to drink a glass of milk without symptoms-should return.

4. Try a lactose-reduced milk like Lactaid. Manufacturers add enough lactase to digest 70 percent of the lactose in these milks.

If you still get symptoms after drinking lactose-reduced milk, you can add more lactase (several companies sell the enzyme). Better yet, you can take lactase in a capsule along with the milk (or any other dairy product). For more information, call Lactaid at 800-257-8650, Dairy Ease at 800-446-6267, or Lactrase at 800-558-5114.

6. For a more convenient, cheaper alternative, try drinking your milk in smaller quantities and with meals.

7. If you can't tolerate any dairy products, make sure you're getting enough calcium from foods like tofu, broccoli, kale, salmon-with-the-bones, or, if necessary, from a calcium supplement.

1 J. Dairy Sci. 70: 397, 1987.
2 Am. J. Clin. Nutr. 45:1457,1987.
3 N. Eng. J Med 310:1,1984.
4 Am. J. Clin. Nutr. 45:432,1987.
5 Am. J Clin. Nutr. 40: 1219, 1984.
6 Am. J Clin. Nutr. 48:1126,1988.
7 J. Nutr. 109: 856, 1979.
  Lactose
    from Most to Least
  The numbers vary largely because the ingredients
vary Add milk solids to your milk, yogurt, or processed
cheese, for example, and you add more
lactose And yogurt s bacteria keep digestng its lactose
during storage ... and even after you eat it
Product                                   Lactose
                                          (grams)
Whey, dry  (1 oz.)                         19-21
Milk, acidophilus skim  (1 cup)              11
Yogurt, whole milk  (1 cup)                10-12
Milk  (1 cup)                               9-14
Buttermilk  (1 cup)                         9-12
ice milk (3/4 cup)                           8
Yogurt, lowfat (1 cup)                      5-19
Velveeta cheese (1 1/2 oz.)                  4
fee cream (3/4 cup)                         3-8
Orange sherbet (3/4 cup)                    1-2
Half-and-Half, cream, or sour
cream (2 Tb.)                                1
Most hard cheeses  (1 1/2 oz.)               1
American, pasteurized processed (1 1/2 oz.) 0-6
Ricotta cheese (1/2 cup)                    0-6
Cottage cheese, creamed (1/2 cup)           0-4
Cream cheese (1 1/2 oz.)                    0-1
Butter or margarine (1 Tb.)                  0