The origins of yogurt lie in the isolated Caucasus mountains of Russia, but to-day this milk product has a prominent place in the dairy case of most grocery stores. Yogurt was one of the first foods that was promoted widely because of its possible health benefits. In 1908 E. Metchnikov wrote in his book 'The Prolongation of Life' that the secret to longevity that he found in the Russian mountains was the yogurt that the people were making and eating. Since that time, many people have questioned the scientific validity of this conclusion, but the advent of probiotics has changed that. There is a growing body of evidence that probiotics or foods that contain live bacteria are good for the health.

Today yogurt is strictly defined as a milk product produced by the action of two bacteria - Streptoccus thermophilus and Lactobacillus bulgaricus. In addition, yogurt now may contain bifido bacteria and sometimes lactobacillus casei. The first two are needed to convert milk to yogurt and the later two are being added because of their health promoting properties.

To be truly effective it is important that the bacteria in yogurt are alive when consumed. Proper production, packaging, storage, shipping and refrigeration are necessary to ensure this. Although no standards exist, it is generally agreed that to be effective yogurt should contain 100 to 1000 million live bacteria per ml. Why so many?

The stomach is the first line of defence of the body against possible disease organisms. The low pH (or high acidity) of the stomach kills most foreign bacteria before they pass into the intestines. If this weren't so we would be sick more often. By consuming a very large number of bacteria in yogurt, some survive and pass through the stomach. However, the environment in the intestines is not friendly either. Our intestines are home to a wide variety of different bacteria; some of these bacteria are beneficial and some are not. The yogurt bacteria must compete with the normal intestinal bacteria for nutrients and sites to adhere to. Because the yogurt bacteria are foreign, they do not find adhesion sites along the intestinal wall and are quickly flushed through the intestines and are excreted in the feces.

Yogurt must be eaten regularly to be effective. This is not a ploy by yogurt makers to get us to buy more yogurt. This is the true. A steady supply of yogurt means that the yogurt bacteria are present in the intestines where they can benefit the host. Stop eating yogurt and very soon they are all eliminated.

Although yogurt is the best known probiotic there are other products on the market such as kefir, acidophilus milk and fermented vegetables that contain live bacteria. It is the bacteria that give these products their health promoting properties. They must be alive and they must be consumed in large numbers continuously to be effective.