IBS--Free at Last!

What If I've Tested Negative for Lactose Malabsorption?

If you've tested negative for lactose intolerance, how does that fit into the FODMAPS picture?

First of all, let's review the test for lactose intolerance. The patient consumes a known amount of lactose. If the lactose is poorly digested and absorbed in the small intestine, it continues "down the line" to the large intestine, where it is fermented by the resident bacteria. They produce hydrogen gas as they ferment the lactose. Some of this gas is absorbed into the patients blood stream, where it travels to the lungs and is exhaled. If there is a sharp rise in the amount of hydrogen exhaled after the patient consumes the lactose, that is considered "positive" for lactose malabsorption. One thing to keep in mind is the fact that approximately 20% of us are not colonized by hydrogen-producing bacteria; instead, our resident bacteria many produce other types of gas such as methane or hydrogen sulfide (bad breath, anyone?).  Lactose-malabsorbing individuals in this category will falsely test negative for lactose intolerance on a hydrogen breath test alone, but might be positive if tested for both hydrogen and methane exhalation. The results of the lactose test really need to be viewed together with the patient's history of symptoms after consuming lactose, both during the test and at other times.

If someone has tested negative for lactose malabsorption AND doesn't particularly have a history of symptoms after ingesting milk products, it is pretty safe to say that individual is not lactose-intolerant.

However, even adults who tolerate lactose well in general do have limits to how much lactose they can handle. Because the effects of FODMAPS carbohydrates are additive, excessive lactose intake could put you over the top, and contribute to symptoms mostly caused by the other FODMAPS.

How much lactose is "excessive"? The answer to that question varies from one person to the next, but to put things in perspective, check out these generalizations about the lactose content of milk products:

Fluid milk: 11-14 grams per cup

Lactose-free milk: 0 grams per cup

Evaporated milk: 24 grams per cup

Yogurt: 5 grams per cup

Ice cream: 12 grams per cup

Butter: trace per 1 tsp

Most cheeses: 0-2 grams per ounce

Whey protein concentrate: varies

Whey protein isolate: trace per serving

To learn more about lactose intolerance and the FODMAPS elimination diet, visit www.ibsfree.net

What happens to the gas and fatty acids produced by bacteria in the gut?

A reader understands that colonic bacteria ferment sugars and complex carbohydrates in the gut. She wonders what happens to the gas and acids that are produced? Could they build up in the blood stream and cause illness?

The short answer is: No. Unlikely to build up in the blood stream of a person with normal respiratory health or to cause harm. The body has many ways get rid of or use up these normal products of fermentation.

The gases that results from fermentation have several possible fates. 

• Some of the bacteria in the colon actually feed on the gases produced in the first round of fermentation. Most of the gases produced are used up that way, provided the right bacteria are present.
• Some of the gas is expelled as flatus (farts).
• Some is absorbed into the blood stream. The gas that is absorbed in the blood stream is carried through the veins to the lungs. It is then exhaled in the breath.

In a person with normal respiratory health, it seems unlikely that gases produced by bacterial fermentation in the gut could build up in the blood or body tissues.

Different colonic bacteria produce different gases during fermentation. Interestingly, studies have shown that IBS patients who exhale methane gas (because they are colonized by methane-producing bacteria) tend to have constipation-predominant IBS. Some people are colonized by bacteria that produce hydrogen sulfide (rotten egg smell). This is pure speculation, but...I have been wondering if one could control bad breath with a FODMAPS elimination diet! Hmmm.

The short chain fatty acids produced during fermentation are actually the preferred energy source for the cells that line the gut, so most are "burned up" right on the spot.  Note that these are FATTY acids, not what you typically think of as tissue damaging acids, such as hydrochloric acid. Although chemically defined as acids, fatty acids do not have a low pH, as do even mild acids like acetic acid (vinegar). Fatty acids are the building blocks of food fat and fatty tissue. It seems unlikely that fatty acids produced in the gut would be capable of causing any harmful effects.

Buy IBS--Free at Last!