Functional medicine: Focusing on imbalances in core metabolic processes

Could screening patients for cytokine markers help direct interventions to prevent quality-of-life deterioration? What evidence is there that a patient’s ­methylenetetrahydrofolate reductase (MTHFR) genotype and baseline folate level can determine whether folate therapy will be needed to prevent stroke?

Favorable findings in these areas and others—eg, that specific probiotics benefit those with various gastrointestinal, respiratory, and lipid disorders—are strengthening support for the clinical approach of functional medicine (FM), which focuses on core functional processes: assimilation, defense and repair, energy, biotransformation and elimination, transport, communication, and structural integrity.

In this article, we describe the paradigm of FM, review its origins, and present the evidence base of selected topics: diagnostic testing, nutrition and supplements, probiotics, and chelation. As FM’s popularity increases, a better understanding of it will help us educate our patients on this approach and implement some of its evidence-backed practices. In preparing this review we used keyword searches of PubMed, Embase, Web of Science, Cochrane Library, University of Florida Health Science Center Library eJournals, the Institute for Functional Medicine website,¹ and Lifestyle Medicine textbook.²

The core of functional medicine

Complementary and alternative medicine (CAM) refers to medical practices diverging from standards of care and not generally taught at US medical schools or available at US hospitals.³ Integrative Medicine encompasses evidence-informed CAM, conventional Western medicine, and whole systems like FM.⁴

FM aims to identify root causes of disease, emphasizing function as a dynamic process that can move back and forth on a continuum between health and disorder.^5,6 There are 7 defining characteristics of FM: (1) patient centered vs disease centered; (2) systems biology approach acknowledging web-like interconnections of physiologic factors; (3) dynamic balance of gene–­environment interactions; (4) personalized care based on biochemical individuality; (5) promotion of organ reserve and sustained health span; (6) health as a positive vitality—not merely the absence of disease; and (7) function vs pathology focused.⁵

The concept of FM is not new. Its origins can be traced to the 19th century. Jeffrey Bland, PhD, credits the term’s first use to Sir Willoughby F. Wade, MD, in an 1871 Lancet editorial, “Clinical lecture on functional medicine.” Bland formulated the FM paradigm and in 1991 founded the Institute for Functional Medicine (the Institute), its main educational and certifying organization.⁷ The Institute certifies masters- or doctorate-prepared health professionals from both conventional and complementary health fields who complete 7 courses (Applying FM in Clinical Practice, Gastrointestinal, Environmental Health, Immune, Hormone, Cardiometabolic, and Bioenergetics), present 1 case report, and pass a written exam. In a retrospective cohort study, researchers found that the FM model was associated with greater improvements in patient-reported, health-related quality of life (QOL) compared with usual care.⁸

Clinical model

FM uses a comprehensive yet practical matrix for obtaining patient histories and for guiding diagnostic testing.⁹ Tools that support ­history-taking include a timeline; weeklong dietary survey; daily activity log; exercise, sleep and self-care questionnaires; and an environmental risk assessment. Instead of a review of symptoms arranged by organ system as is typical with conventional Western medicine, FM assesses the balance of core functional processes: assimilation, defense and repair, energy, biotransformation and elimination, transport, communication, and structural integrity.

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