Lactic Acid Bacteria

Lactic acid bacteria are kissin' cousins to probiotic bacteria - so much so that many people confuse the two.

Most (but not all) probiotics are lactic acid bacteria (commonly referred to as LAB).

Most LAB are not probiotic - but they are good for you.

So LAB are good and probiotics are even better!

A probiotic is a live micro-organism which when administered in adequate amounts confer a health benefit on the host (World Health Organization definition.)

LAB don't confer a defined health benefit - they just good for you in a general sort of way.

They are found mostly on the skin of healthy fruit and vegetables. In a vegetable such as tomato they are found in greatest concentration at the stem scar end1 - maybe we need to rethink our tendency to cut that piece out. If the surface of fruit or vegetables is disinfected then the LAB are killed.

The Science

Lactic acid bacteria are a group of Gram positive bacteria which convert carbohydrates to lactic acid without using oxygen.

Some of this large family produce only lactic acid whilst others also produce acetic acid, ethyl alcohol and carbon dioxide.

It is this carbon dioxide that causes the large holes in cheeses such as Emmenthal and Gruyere.

So our efforts to make food germ free and attractive actually reduces the amount of LAB that we consume.

Now when plants begin to decompose the LAB increase greatly - they just love the acidic conditions created.

So when we ferment or culture foods, the LAB in the plant or dairy product makes lactic acid as they "digest" their food. Lactic acid helps preserves things so these bacteria have been used in fermentation and the preservation of food for centuries.

Yogurt, cheeses, sauerkraut and sausages are some of the foods that use lactic acid bacteria in their preservation. LAB stop bad bacteria from spoiling the food.

The wonderful thing about fermentation is that it a "live" process. As the process evolves over time different micro-organisms increase and decrease. It is the changing pH level (acidity) that governs this process.

For example, when making sauerkraut the first bacteria will be members of the klebsiella family. As the sauerkraut becomes more acidic, the leuconostoc family increase and become the predominant bacteria, until finally the lactobacillus reign.

All of these lactic acid bacteria were originally living on (or in) the cabbage leaves. Fermentation increases their numbers enormously.

The sequential populations of different lactic acid bacteria each reach concentrations of 10 8to 10 9 colony forming units per gram. (1) This is the sort of level of probiotic bacteria that you will find in a good supplement.

So one gram of sauerkraut will give you as many good bacteria as a supplement but they will not all be probiotic bacteria. (But they will be good for you.)

If you eat cooked cabbage all the LAB will have been destroyed.

If you eat coleslaw (raw cabbage) then you would eat some LAB but not as many as in fermented cabbage.

I can't get my tastebuds to embrace sauerkraut (I'm a sweet tooth!) so I eat coleslaw on a very regular basis.

You can increase your daily intake of lactic acid bacteria by eating fruit and vegetables in their raw state. Try to ensure they have been grown in such a way that you don't have to peel everything. When I buy commercially grown apples, I peel them because I know they have been sprayed so many times. When I pick apples from our own trees, I eat them not only unpeeled but unwashed.

If you want to get in to fermenting some of your own foods, then my favorite book is Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods by Sandor Katz. Sandor has the ability to make everything from sauerkraut to miso to kombucha sound "doable" even for fermentation novices.


My Recommended Probiotics



1. ZdenkaSamish, Etinger-Tulczynska R , Miriam Bick. The Microflora Within the Tissue of Fruits and Vegetables. Journal of Food Science Volume 28 Issue 3, Pages 259 - 266.

2. Vethachai Plengvidhya, Fredrick Breidt Jr., Zhongjing Lu, and Henry P. Fleming. DNA Fingerprinting of Lactic Acid Bacteria in Sauerkraut Fermentations. Applied and Environmental Microbiology, December 2007, p. 7697-7702, Vol. 73, No. 23 0099-2240/07/$08.00+0 doi:10.1128/AEM.01342-07.