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My old website can be found at

For quick offline reference, you can purchase Planet Lactose: The Best of the Blog as an ebook on or or or a whole lot of other places that Smashwords is suppose to distribute the book to. 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.

Thursday, September 27, 2007

Fermented Food Isn't Cultured Food

It's nice of people to want to help those of us with lactose intolerance. It would be even nicer if they knew what the heck they were talking about first. Never take any advice from an article on the internet without checking it first.

An Indian website,, published an article by Harmanpreet Kaur extolling the virtues of probiotics.

Nothing wrong there. It's just the point gets lost in the fine details.

Any fermented product contains probiotic bacteria, which are good bacteria.

Well, no. Not at all true. Fermentation, historically, is far more associated with yeast than with bacteria. That kind of fermentation happens when yeast convert sugar to alcohol. Beer, wine, cider, and other regional alcoholic beverages are fermented and none of them contain probiotic bacteria.

In fact, there are dozens of fermented foods that are part of just about every culture. The Wikipedia article on fermentation contains a long list. Some of them might have probiotic bacteria in them, but that's a coincidence.

What you want to look for are cultured products. Cultured products do have bacteria in them, and these bacteria may have probiotic properties. The distinction is a fine one: bacteria do fermentation. But instead of converting sugar to alcohol, this different fermentation process produces acids.

Some of the most familiar acids are produced this way. Vinegar is acetic acid, and it is made by bacterial fermentation. Cheese is made by acid curdling the casein protein.

And then there's pyruvate. Glucose is the most important sugar in the world, at least to humans. All carbohydrates, including all complex sugars, eventually break down in the process of digestion and metabolism into the simple sugar glucose. Glucose is the energy source that the body runs on.

In glucose metabolism, a molecule of glucose breaks down into two molecules of pyruvic acid. Lactic acid fermentation breaks down the pyruvate into lactic acid.

Bacteria can also do the same sort of fermentation of lactose (which is a chemical combination of the simple sugars glucose and galactose) into lactic acid. Lactic acid sours milk, and gives yogurt and other forms of sour milk such as koumiss, kefir, and leban their distinct flavor. Breaking down the lactose also makes these naturally low-lactose milk products, which is one reason they are so well tolerated by those with lactose intolerance.

It's these lactic acid bacteria, like Lactobacillus bulgaricus, the bacteria that is in all yogurt, that has the useful probiotic properties. The fact that they also ferment lactose is secondary.

In short, not all fermented products are alike. Take warning: fermented foods - like the Indian foods dosa, idli and uttapam that Kaur mentions - may be good for you or not, but the fact that they are fermented does not mean that they have beneficial probiotic bacteria. They don't.

And it helps to know some of these basic facts about food if you are lactose intolerant or have any reason to avoid certain foods or ingredients. Knowledge is power. Lack of knowledge, in the famous quote, and you'll be a eunuch all your life.

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