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Tests for Lactose Intolerance


Thumbing through the medical literature, I've come across descriptions of at least 18 separate and distinct tests for LI. Each has had a place and purpose, if only as part of medical research. Only three of them are ever used in the U.S., however, one just on babies. Europeans use variants on one additional one that is never seen in the states. (If you need to know about all 18, check out chapter 13 in my book, Milk Is Not for Every Body).


The Hydrogen Breath Test (HBT)

The HBT is the best around, simple, direct, and non-invasive (meaning no needles). It works because your breath normally never contains hydrogen gas. You find it there only when the bacteria in your colon ferment carbohydrates, exactly what happens when a load of undigested lactose hits.

Testing is typically done first thing in the morning after a 12-hour fast. You'll likely be asked to blow into a small mouthpiece connected to a laminated foil bag that resembles a pillow-shaped mylar balloon (although several variations may be found).

That first bag is set aside to be used as a baseline. You then drink a solution of lactose in water, although some doctors use milk itself. The amount of lactose may range from 10 to 50 grams: The larger amounts will identify a greater number of people as LI but will also cause more symptoms in those who are sensitive. (Be prepared. You may feel quite ill during and after.)

It takes time for the lactose to reach the colon and for the bacteria to build up a supply of hydrogen in the breath. Various labs will take further breath samples at intervals of 15-60 minutes and for up to two to six hours. Longer is usually better, and the use of milk requires a longer test.

While the test itself is so simple that it can be done almost anywhere, the collected samples are usually shipped off to a specialized laboratory that can afford the several thousand dollars needed to purchase the analyzer. Don't bother to ask for exact results. All that matters is whether you are over a certain threshold. How high doesn't matter and doesn't even relate to how bad your symptoms will be.

This test is extremely accurate. It can be even be used on very young children. But it does have a few flaws.

People on antibiotics should not take it because the antibiotics may knock out the very bacteria which would otherwise produce the hydrogen. Using aspirin before the test may create a misleading rise in hydrogen. Smoking will do the same. A certain percentage of the population don't even have the right kind of bacteria to make hydrogen.

The test is also used to discover other conditions, including bacterial overgrowth in the intestines and rapid transit. Other sugars, including glucose, fructose, sorbital and lactulose, may be used in place of the lactose. You need to talk with your doctor about these if you get a reaction that is not attributed to lactose intolerance. A good article on the test is available here. [Warning: contains java.]

In any case, unless something disqualifies you, in the U.S. the HBT is the one you want.


The Blood Glucose Test (BGT)

OK, let's say that for some reason you can't take the HBT. What then? The next best test is the BGT.

It works in almost the same way as the HBT. You drink your lactose and then get tested every little while. The big difference is that this test requires a blood sample instead of a breath sample.

The BGT works like this. If you digest lactose, then you'll see a big jump in your blood sugar count. If you don't digest lactose, no jump. The doctors call this a flatline. If it goes up, then you are not lactose intolerant. If nothing happens, then you are LI. Confusing? It sure is.

So two big disadvantages. It's invasive and it's indirect. And it's not as accurate as the HBT. On the good side, the BGT is still probably 95% accurate and it should be available absolutely everywhere and anywhere.

However, if, like me, you're old enough that you got tested when the BGT was the only test around, and you're not positive whether you're really LI or not, you may want to get yourself retested using the HBT, just to doublecheck the results.


The Ethanol Test

When lactose is digested, it is broken down into two simpler sugars, glucose and galactose. Galactose is extremely uncommon in nature. If it were to appear in your blood stream, then for sure you can digest lactose. So why not use it as your test marker?

That's exactly what a lot of doctors in Europe do. (They sometimes combine this with the BGT as well.) The Ethanol test is still an indirect test for LI, but it's extremely accurate and needs just one blood sample, a mere 40 minutes after drinking the lactose load.

So why don't doctors in the states use it? Because you have to drink a small amount of ethanol, the alcohol in beer, to do the test. Nobody seems to mind this in Europe; they use the test even on children (with a smaller amount of alcohol, of course.) In the puritanical U.S., alcohol and testing don't mix. Not even research physicians mention it. But doctors in Europe have had excellent results with it for the past twenty years.


LI Tests for Children

The HBT is by far the best test for children. What kid wants to be stuck with needles for six hours? It can be done on infants as young as six months (even three months for some hospitalized youngsters). The one problem with it is that prolonged diarrhea can disrupt the bacteria, and so the test is not reliably accurate until the intestines have had a few days to recover.

Babies up to six months have their own test, making use of the one thing they produce in large quantities: stool. The stool test works because 1) only carbohydrates produce acidic stools in young children, and 2) the only carbohydrate in breast milk or a milk-based formula is lactose. The test is so simple it can be performed right at the bedside.

Two problems, though. One is that the stool test is not all that accurate as a diagnostic tool. The other is that it won't work on children who are already being fed on soy or other non-milk formulas. But it should give your doctor an indication of what to do next.


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