The Health Effects of Cultured Milk Products with Viable and Non-viable Bacteria

In food regulations, the viability of bacteria is emphasised in food standards and regulations for yoghurt and fermented milks. Non-viable cultured milks have longer shelf-life and easier storage which favour the technology, but it has been claimed that only dairy products with viable microorganisms have beneficial health effects. In the case of lactose tolerance by lactase-deficient subjects, viable and non-viable cultured milks show similar effects. In the case of treatment of acute gastro-enteritis some probiotics show clinical efficacy in shortening the duration of diarrhoea both in viable and non-viable form. Saccharomyces boulardii is required in a viable form for the treatment of candidiasis whilst lactic acid bacteria show efficacy both in the viable and non-viable form. Stimulation of the human immune system by oral administration of fermented milks or probiotic cultures has been observed with viable bacteria only. Effects in faecal bacterial enzyme activities are observed following consumption of viable bacteria only. All health benefits reported for fermented milks have been documented using viable bacteria and data on non-viable preparations is often limited. Future work should focus on controlled blinded studies to further clarify the differences.