Redrawing therapeutic boundaries: microbiota and cancer.

The unexpected roles of the microbiota in cancer challenge explanations of carcinogenesis that focus on tumor-intrinsic properties. Most tumors contain bacteria and viruses, and the host's proximal and distal microbiota influence both cancer incidence and therapeutic responsiveness. Continuing the history of cancer-microbe research, these findings raise a key question: to what extent is the microbiota relevant for clinical oncology? We approach this by critically evaluating three issues: how the microbiota provides a predictive biomarker of cancer growth and therapeutic responsiveness, the microbiota's causal role(s) in cancer development, and how therapeutic manipulations of the microbiota improve patient outcomes in cancer. Clarifying the conceptual and empirical aspects of the cancer-associated microbiota can orient future research and guide its implementation in clinical oncology.

Reframing Nutritional Microbiota Studies To Reflect an Inherent Metabolic Flexibility of the Human Gut: a Narrative Review Focusing on High-Fat Diets.

There is a broad consensus in nutritional-microbiota research that high-fat (HF) diets are harmful to human health, at least in part through their modulation of the gut microbiota. However, various studies also support the inherent flexibility of the human gut and our microbiota's ability to adapt to a variety of food sources, suggesting a more nuanced picture. In this article, we first discuss some problems facing basic translational research and provide a different framework for thinking about diet and gut health in terms of metabolic flexibility. We then offer evidence that well-formulated HF diets, such as ketogenic diets, may provide healthful alternative fuel sources for the human gut. We place this in the context of cancer research, where this concern over HF diets is also expressed, and consider various potential objections concerning the effects of lipopolysaccharides, trimethylamine-N-oxide, and secondary bile acids on human gut health. We end by providing some general suggestions for how to improve research and clinical practice with respect to the gut microbiota when considering the framework of metabolic flexibility.

Can aging research generate a theory of health?

While aging research and policy aim to promote 'health' at all ages, there remains no convincing explanation of what this 'health' is. In this paper, I investigate whether we can find, implicit within the sciences of aging, a way to know what health is and how to measure it, i.e. a theory of health. To answer this, I start from scientific descriptions of aging and its modulators and then try to develop some generalizations about 'health' implicit within this research. After discussing some of the core aspects of aging and the ways in which certain models describe spatial and temporal features specific to both aging and healthy phenotypes, I then extract, explicate, and evaluate one potential construct of health in these models. This suggests a theory of health based on the landscape of optimized phenotypic trajectories. I conclude by considering why it matters for more candidate theories to be proposed and evaluated by philosophers and scientists alike.

The sciences of healthy aging await a theory of health.

Debates in fields studying the biological aspects of aging and longevity, such as biogerontology, are often split between 'anti-aging' approaches aimed largely at treating diseases and those focusing more on maintaining, promoting, and even enhancing health. However, it is far from clear what this 'health' is that would be maintained, promoted, or enhanced. Interestingly, what few have yet to fully reflect on is that there is still no theory of health within the health or aging sciences that would provide an integrative explanatory framework akin to other scientific theories. After clarifying why such a theory could be useful, I discuss five general features of medical theories that could be used to evaluate the utility of a given proposal. With these features in hand, I suggest that philosophers and scientists work together on analyzing actual medical research (experimental analysis), and the ways in which a theoretical construct of 'health' is being progressively identified and measured therein. I conclude by suggesting that research fields studying stress and aging might be particularly helpful in developing candidates for theory construction due to their broad scope, increasing specificity, and potential for providing integrative explanations.

The muddle of medicalization: pathologizing or medicalizing?

Medicalization appears to be an issue that is both ubiquitous and unquestionably problematic as it seems to signal at once a social and existential threat. This perception of medicalization, however, is nothing new. Since the first main writings in the 1960s and 1970s, it has consistently been used to describe inappropriate or abusive instances of medical authority. Yet, while this standard approach claims that medicalization is a growing problem, it assumes that there is simply one "medical model" and that the expanding realm of "the medical" can be more or less clearly delineated. Moreover, while intended to establish the reality of this growing threat, this research often requires making arbitrary or unjustified distinctions between different practices. To better clarify the concept of medicalization, I will focus more on capturing the variety of medical practices than on the sociological aspects of medical discourse. In doing so, I will explore the distinction between medicalization and pathologization, a distinction that is often overlooked and that brings with it many conceptual and practical implications. After defining these terms, I will use some examples to show that while pathologizing is closely tied to medicalizing, both can occur independently. I will then further develop this distinction in terms of the different individual and social effects of these practices.

Putting phenomenology in its place: some limits of a phenomenology of medicine.

Several philosophers have recently argued that phenomenology is well-suited to help understand the concepts of health, disease, and illness. The general claim is that by better analysing how illness appears to or is experienced by ill individuals--incorporating the first-person perspective--some limitations of what is seen as the currently dominant third-person or 'naturalistic' approaches to understand health and disease can be overcome. In this article, after discussing some of the main insights and benefits of the phenomenological approach, I develop three general critiques of it. First, I show that what is often referred to as naturalism tends to be misunderstood and/or misrepresented, resulting in straw-man arguments. Second, the concept of normality is often problematically employed such that some aspects of naturalism are actually presupposed by many phenomenologists of medicine. Third, several of the key phenomenological insights and concepts, e.g. having vs. being a body, the alienation of illness, the epistemic role of the first-person perspective, and the idea of health within illness, each bring with them new problems that limit their utility. While acknowledging the possible contributions of phenomenology, these criticisms point to some severe limitations of bringing phenomenological insights to bear on the problems facing philosophy of medicine that should be addressed if phenomenology is to add anything substantially new to its debates.

Escaping the Conceptual Analysis Straitjacket: Pathological Mechanisms and Canguilhem's Biological Philosophy.

This essay discusses four key criticisms recently leveled against the main attempts to use conceptual analysis to understand health and disease. First, it examines the weaknesses of these attempts and suggests a better way to proceed. Next, it briefly discusses another disease debate concerning pathological mechanisms and suggests that this approach could be more fruitful than that of conceptual analysis. The final section demonstrates how Georges Canguilhem's (1904-1995) biological philosophy of disease avoids some of the problems associated with conceptual analysis, and how he can contribute to both debates. Canguilhem's appeal to biological normativity is understood as contributing to a theoretical explanation, and a possible naturalization, of what is specific to healthy and pathological phenomena.