Because of spam, I personally moderate all comments left on my blog. However, because of health issues, I will not be able to do so in the future.

If you have a personal question about LI or any related topic you can send me an email at I will try to respond.

Otherwise, this blog is now a legacy site, meaning that I am not updating it any longer. The basic information about LI is still sound. However, product information and weblinks may be out of date.

In addition, my old website, Planet Lactose, has been taken down because of the age of the information. Unfortunately, that means links to the site on this blog will no longer work.

For quick offline reference, you can purchase Planet Lactose: The Best of the Blog as an ebook on or Almost 100,000 words on LI, allergies, milk products, milk-free products, and the genetics of intolerance, along with large helpings of the weirdness that is the Net.

Sunday, March 15, 2009

Science Whiz Kids Whiff on LI Answer

If there's one thing I've got to be rooting for, it's a team of math-science whiz kids. A neat article by Anne W. Semmes in the Greenwich Citizen talked about a test competition featuring a group of "rising science and math stars [getting ready] for the March 21 Northeast Science Bowl's grueling 12-hour 'Jeopardy style' competition hosted at the UConn School of Engineering at Storrs."

One of the questions in their trial was on chemistry:

"For individuals who are 'Lactose Intolerant,' the reason for their gastric distress is the production of methane, or acetic acid and nitrogen, or lactic acid and carbon monoxide or acetic acid and methane?"

"Lactic acid and carbon dioxide," one boy fired off.

Oops. Bad answer. In fact, it's the worst answer of the four possibilities.

As I've explained many times, undigested lactose that reaches the colon is fermented by bacteria that naturally live there. The result of the fermentation are a number of gases and what are called short-chain fatty acids. And those cause the distress.

The double jeopardy question therefore is: which gases and which fatty acids?

For an excruciatingly technical answer, let's turn to a technical article, Colonic Fermentation May Play a Role in Lactose Intolerance in Humans by Tao He et al. American Society for Nutrition J. Nutr. 136:58-63, January 2006.
During colonic fermentation, lactose is first hydrolyzed to glucose and galactose, which are subsequently fermented, leading to the production of a series of intermediate (e.g., lactate, formate and succinate) and end-product metabolites [i.e., acetate, propionate, and butyrate, gases (H2, CO2 and CH4), and biomass].

First the gases. They are H2, hydrogen, CO2, carbon dioxide, and CH4, methane. Not carbon monoxide, CO. Carbon dioxide is the common gas exhaled by the body in every breath. Carbon monoxide is deadly. I hope that no chemistry student would ever confuse the two.

Part two are the fatty acids. Technically, the list of metabolites He's team found are salts of acids. And lactate is the salt of the fatty acid that is lactic acid. However, lactate is not just one of the six salts. It is an intermediate product, not an end product. It's the end products that give us the distress. Butyric acid, from butyrate, is probably what causes the distinctive awful smell of gas produced by lactose intolerance, although propionic acid and acetic acid are also both smelly. Lactic acid isn't, which should be a giveaway.

So which of the remaining three anwers is correct? Let's take them one at a time.

Methane? Methane is a correct as one of the gases, but no fatty acid is listed.

Acetic acid and nitrogen? Acetic acid is a correct fatty acid but nitrogen is not one of the correct gases.

Acetic acid and methane? Both are part of the total picture so this has to be the answer the judges were looking for.

Remember that these are high school students. No disgrace in not knowing every answer to unusual chemical problems. I'm pretty sure most doctors would get this question wrong as well. Give the team a few more years and who knows how much they'll know.

What a pleasant antidote to the vast amount of ignorance on the internet.

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