remarked that if experimental study does not demonstrate a meaningful effect, nothing of interest has really been demonstrated. This raises the question, What is a meaningful magnitude of effect? She asked members of the workshop audience whether they considered an intervention that decreases absences from school by half a day per year enough of a magnitude of effect to consider the intervention worthwhile. Few audience members nodded yes. Yet, that is exactly the magnitude of effect demonstrated in a study on hand-washing by children—and it was enough of an effect to justify a national hand-washing campaign by the Centers for Disease Control and Prevention. Using the same end point—missed school days—Leyer et al. (2009) showed that a 6-month course of L. acidophilus NCFM/B. animalis Bi-07 probiotic resulted in more than 1 fewer missed school days per child. That is double the effect of hand-washing, Sanders noted. “Sometimes in the probiotic field we kind of beat ourselves up because we don’t have these overwhelmingly huge magnitudes of effect,” she said. “But maybe we don’t need them.”

Yet another major scientific challenge is that not all studies demonstrate the same effects. Mixed results reflect the considerable individual-level variation in microbiota that has been demonstrated many times (Candela et al., 2010). They also reflect the prevalence of underpowered, small-N probiotic studies. An underpowered study providing no evidence of an effect is very different from a sufficiently powered study providing evidence of no effect. Sanders said, “We need to be able to distinguish that and possibly quit running underpowered studies.”

In addition to these scientific challenges, Sanders suggested that new regulatory challenges may end up discouraging future probiotic research. In October 2010, FDA issued a guidance on determining when human research studies require Investigational New Drug (IND) applications (FDA, 2010). Sanders interpreted the guidance to mean that any human study on the cure, treatment, mitigation, or prevention of disease or on the structure or function of the body is a drug study and therefore can only be conducted with an IND. “If it’s ever finalized in this form,” she said, “it will have a chilling effect on research” in probiotics.

In conclusion, Sanders touched on another regulatory challenge that would be explored in depth by subsequent workshop speakers (see Chapter 6), that is, the current regulatory framework for product claims. Probiotic products sitting side by side on the store shelf can be very different regarding both content and scientific evidence for safety and efficacy, but allowable information on claims doesn’t enable consumers and health care professionals to differentiate among products. Sanders mentioned Proctor and Gamble’s Align. The claim is that Align builds and supports a healthy digestive system, but the scientific evidence is for improved symptoms associated with irritable bowel syndrome (O’Mahony et al., 2005; Whorwell

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