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 However, product information and weblinks may be out of date.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.

Saturday, April 29, 2006

Molecules of Lactose - the Teeny Tiny Truth

Let's take a nostalgic stroll back to high school chemistry. Yeah, I'm getting all misty eyed too. But if you ever learned the concept of gram molecular weight and Avogadro's Number, that's where it first came up. (If not, you're special and you don't need to read this but you already know the answer.)

Avogadro's number is 6.022∙1023. That's a really really really huge number. Written out in full it reads: 602,200,000,000,000,000,000,000. The number is important because that's how many molecules exist in a mole of any substance. A "mole" is short for gram molecular weight.

The molecular weight of a molecule is the weight of N0 such molecules. The molecular weight of a molecule is equal to the sum of the atomic weights of its constituting atoms.

So what's the molecular weight of lactose? (Aha. This suddenly gets relevant.) Lactose's chemical formula is C12H22O11. I'll do the math for you. A mole of lactose molecules weights about 342 grams.

Now one gram is a tiny amount. There are 454 grams in a pound, 28.375 grams in an ounce. An eight ounce glass of milk has 12 grams of lactose. If you held an ounce of lactose in your hand, you couldn't even feel that it was there. Yet that one gram still contains 1,760,233,918,128,654,970,766 molecules of lactose. Rounded, that's 1.76•1021 molecules. (6.022∙1023 / 342)

That's why I tell people with lactose intolerance not to get worried about a few molecules of lactose. Or even a few billion. A few molecules can't hurt you. Your system wouldn't even recognize them.

Those with dairy protein allergies need to be a bit more careful, but similar math applies. Proteins are far heavier than lactose. They can weight a million times more. And even nanograms of protein can set off a reaction. A nanogram is one billionth of a gram. Even a million billion is small next to Avogardo's number, though. If you divide 1.76•1021 by a million billion, you're still left with 1.76•106 or 1,760,000. Almost two million protein molecules are needed at the very least to set out a reaction in the most sensitive person. The real minimum is probably larger than this.

Caution is definitely the byword for those who are anaphylactic to milk. For the rest of us, just remember a few molecules are the same as none at all.

Bookmark and Share

No comments: