You may have noticed lately that the dairy department of your grocery store has become overrun with yogurts labeled “active” or “probiotic”, referring to the beneficial bacteria that allegedly improve your digestive system.

The World Health Organization suggests we define probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host”. (That's us, the host. I adore yogurt, but it reminds me a little too much of Aliens.) Yogurt is produced by introducing lactic acid bacteria into milk, which is then fermented, during which the bacteria convert the natural sugars in milk (lactose) into lactic acid. The increased acidity causes milk proteins to thicken, and the lactic acid gives it its tang.

Strains of the genera Lactobacillus and Bifidobacterium are two principal kinds of probiotic bacteria, lactobacillus being one of the primary bacteria used to make regular yogurt, so really the only difference is that it’s a slightly different strain of lactobacillus in one vs. the other. The thing about probiotics is there are so many strains of bacteria – even when they are in the same species, they have different probiotic functions. To keep tabs on each one, particularly when there is such a wide variety of factors, would be difficult, so there is a tendency to generalize about 'probiotic' effects, assuming that any body of research on specific probiotic strains can be applied to any product marketed as a probiotic.

The rationale behind probiotics is that they are intended to assist the body's naturally occurring gut flora to reestablish themselves. They are sometimes recommended after a course of antibiotics. Maintenance of a healthy gut flora is, however, dependent on many factors, especially the quality of food intake. Dairy products are the most common vehicle for probiotics because they protect the bacteria from being broken down by stomach acids, enabling them to make it through the digestive system to the intestinal tract intact. They also provide compounds known as prebiotics that feed the probiotics, but I won’t even get into all that.

Lactobacillus is present in the gastrointestinal tract, where they are symbiotic and make up a small portion of the gut flora, and change the PH of your colon. Your intestinal tract is home to approximately 100 trillion – that’s like a bajillion – microorganisms, consisting of over 400 known bacterial species, and many that have not even been identified yet, because they can't be cultured.

There is no question that yogurt is good for you – it’s very high in calcium and protein, and usually low in fat. I far prefer low fat (and even full-fat) yogurts to the fat-free varieties, which are overly sweet and usually gelatin-thickened. For the ultimate in fro-yo, strain plain yogurt in a cheesecloth or coffee strainer set in a colander for a few hours, sweeten with honey, add some vanilla and put it in an ice cream maker. Ultra-creamy with a fraction of the fat of ice cream, and more health benefits. It’s also ideal for those with lactose intolerance, because the lactose has already been digested. And believe it or not, yogurt is easy to make yourself.

Making your own yogurt is much like making your own sourdough, but far easier – once you have the starter going, you can make your next batch using a bit of the last, and so on. But to begin, you’ll need a small container of the best plain yogurt you can find, making sure it contains active cultures. I use Bles-Wold yogurt from Sunterra market or Vital Green Farms from the Calgary Farmer’s Market. Start with 2 1/2 cups of milk. I haven’t experimented with soy milk, but regular milk (whole, 2% or 1%, not skim) and goat’s milk (which will produce a tangier yogurt) work very well. Bring it to a simmer in a saucepan, then turn down the heat and simmer for 2 minutes. Pour the scalded milk into a bowl, through a strainer or cheesecloth if you have acquired any brown bits around the edge, and cool until you can hold your finger in the milk and count to 10.

The ratio of milk to (plain) yogurt is 2 1/2 cups to 1 rounded tablespoon. Place the yogurt in a small dish and add some of the milk to it to warm it up, then whisk it back into the milk. Pour into a glass jar (glass holds heat well), wrap in a towel or sweater and put in a warm place for about 6 hours or overnight. Ideally, you want to keep it undisturbed at about 110 degrees for 6-8 hours, but mine has not been that hot and still works. The best way I’ve found to keep it warm is to put the jar in one of those small coolers that isn’t good for much more than a 6-pack, fill it halfway with warmish water and put the lid back on. In the morning you should end up with a lovely jar of fresh yogurt.

Julie is a best selling cookbook author, food writer, cooking instructor and the food and nutrition columnist on the Calgary Eyeopener on CBC radio. She lives in Calgary with her husband and two-year-old son, Willem. Watch for her new cooking show, It's Just Food, with co-host Ned Bell, to air on Access TV and CLT stations across Canada this fall. For recipes and daily ramblings visit her blog at juliewashere.blogspot.com.