They are undeniably the functional ingredient of the decade. Dubbed friendly or good bacteria, probiotics rose from obscurity to almost ubiquity on yoghurt labels, and appear in new and unprecedented categories that are wildly successful.

Synonymous with health and regularity, their scientific names on food Nutrition Facts panels in today's 'microbe-phobic' society is truly a testament to the power of strategic positioning and clever marketing. Probiotics actually changed the standard of the yoghurt product category.

Sales of yoghurt, the mother of all probiotic foods, doubled to $13.7 billion in 2008 (from $6.8 billion in 2003) and is forecasted to double again by 2013 (Euromonitor). Japan leads the fray with per capita consumption at around 8.7lb, followed by Europe with 4.7lb and the US with just 1.8 lb.

Not all foods have been successful with probiotics. When Kraft Foods launched LiveActive branded probiotic cheese, the target audience simply did not 'get' probiotics in cheese and was unwilling to support the premium pricing for health benefits in a product it chose for pleasure. Swiss confectioner Barry Callebaut's probiotic chocolate, with up to four times the dosage of live probiotic bacteria in dairy, also failed to impress consumers.

Similarly, ice cream with probiotics failed, but frozen yoghurt has been wildly successful and has spawned a number of retail outlets for consumers seeking their daily dosage (like coffee).

Gum and mints — for oral health and breath freshening — appear ideal for probiotics. Just look at sugar-free gum, which rapidly became the industry standard and accounts for half of the US $19.6 billion global chewing-gum market in 2008. The category fit is reflected by the popularity of Swedish probiotics producer BioGaia's Probiotic Chewing Gum with Lactobacillus reuteri. Redmond, Washington, based Nutraceutix incorporated three probiotic strains in a mint to combat oral thrush, dental caries and bad breath.

Probiotic products are only successful when the consumer can notice a difference. "An effective probiotic will show an effect on digestion in a day or two at the most," says Dave Tabaczynski, founder, Mass Probiotics (Boston, Massachusetts). "Manufacturers now have an ingredient with a palpable benefit for consumers." Effectiveness depends on the dosing, prebiotic enhancement and storage conditions. Three billion cfu of live bacteria are needed daily because of our increasing reliance on processed foods, which are generally pasteurized and doused with preservatives to prevent bacterial and yeast spoilage.

Probiotics is the biggest success story of any functional ingredient, and consumers will further change how manufacturers confer unique health benefits of 'live' bacteria in foods.