Since the amendment of the Occupational Health and Safety Act in 2013, every employer has been obliged to assess the risk of psychological stress. This poses major challenges for those responsible for occupational health and safety with regard to practical implementation (Bamberg & Mohr, 2016) as the legislature has left open how exactly the risk assessment is to be implemented. Recommendations on appropriate procedures such as those formulated in DIN EN ISO 10075-3 must be critically evaluated insofar as appropriate instruments are required not only to assess psychological stress but also to assess psychological strain. This can lead to biases, especially in surveys (Podsakoff, Mackenzie, Lee & Podsakoff, 2003; Specter, 2006). Physiological measures used in parallel with the survey instruments could provide a remedy here. With this work the appropriateness of the antioxidative potential (AOP) as an indicator of oxidative stress for the objective assessment of subjective stress should be examined. To this end, six studies were conducted in different settings. They were designed to investigate the relationship between AOP, subjective stress and diet. In none of the studies could the assumed effect pattern be completely confirmed. Rather, contrary directions of effects could be determined so that the findings must be described as inconsistent. Regardless of methodological limitations of the studies, the results highlight above all the high research demand that still exists in ...