A recent action by the National Advertising Division (NAD), a self regulatory arm of the Better Business Bureau, addresses the level of proof necessary to support “natural” and “satiety” claims involving competing experts and a variety of scientific data in dispute. The Proctor & Gamble Company (P&G) successfully challenged three claims made by GlaxoSmithKline Consumer Healthcare, LLC (GSK) for its Benefiber Original and Benefiber Healthy Shape products. GSK disagreed with the case outcome, appealing NAD’s findings and recommendations to the National Advertising Review Board (NARB). Beyond the NAD’s specific findings, the decision also provides useful insight into how NAD evaluates health benefit and related claims and analyzes the corresponding scientific evidence and other substantiation. The outcome of the NARB appeal will likely shed further light on how the claims substantiation issues involved should be addressed by advertisers in the future.