Functional medicine is a field of medicine that employs assessment and intervention to improve physiological, emotional/cognitive, and physical function. In this context, function is the "kind of action or activity proper to a person, thing, or institution."(1) Functional medicine is science-based health care that demands a systematic, patient-centered approach to understanding the underlying web of physiological factors and effects that influence health and the progression of disease. It incorporates the functional principles that exist in many conventional and alternative practices but focuses, as a special core competence, on the principles of molecular medicine and modern nutritional biochemistry with an emphasis on clinical application.

As the field of functional medicine evolves, so do the useful metaphors for explaining and illustrating to both patients and professional colleagues the principles and methodologies of this field. In what follows, I address the key principles, processes, and metaphors for explaining balanced, dynamic health according to a functional perspective, and explore how these processes, when dysfunctional, lead to the conditions traditionally identified as disease.


Biochemical Individuality Based on Genetic and Environmental Uniqueness
According to a functional medicine perspective, patient care presumes that each person is a unique individual with a singular genetic structure. Our purpose as functional medicine practitioners is to elicit and understand our patients’ uniqueness, including their experiences. These experiences are the context of the complex processes where environment merges with their genetic inheritance. We have seen with great anticipation the evolution of thinking and instrumentation that has brought us closer to describing the probabilities and possibilities inherent in our inherited DNA templates.(2) We have come to understand that our DNA does set boundaries on individual performance. However, as the deterministic model of genetics breaks down, research has demonstrated a plasticity to genetic induction not appreciated earlier.(3) Important to functional medicine practitioners is the idea that lifestyle translates into quantifiable effects on health through the energetics of our biochemistry and genetics. These effects can lead to disease. As we more fully understand the web-like relationships between environment and genetic responses, we can develop individual programs that reliably reflect the unique needs of our patients.(4)

Patient-Centered versus Disease-Centered
The individual—not the disease—is the target of treatment. Functional medicine views disease not as an enemy (not even as independent realities) with which to grapple, but as a manifestation of the breakdown of mechanisms that maintain control, resilience, and balance.(5) Dysfunction and disease are rarely organ-specific. Rather, they are an altered systemic physiological malfunction that requires an integrated model of therapeutic intervention. Functional medicine focuses on the interaction between the host and his or her internal and external environment and the processes that can go awry in this relationship. Findings in molecular medicine research have caused a revolution based on the discovery that modifiers of gene expression are not only produced inside the body by different organs, they also exist as agents of change within the diet and environment.

The patient-centered biographic model is a key feature of functional medicine. An early spokesman for this concept was Leo Galland, MD, who wrote:

"Disease is a dynamic event in the life of an individual, determined by disharmonies, imbalances and pernicious influences. The goal of diagnosis is not to identify the disease entity, which has no independent reality, but to characterize the disharmonies of the particular case, so that they can be corrected."(6)

This approach to diagnosis emphasizes the functional pathogenesis of disease in individual patients. It may complement or replace the convention of differential diagnosis, in which diseases are treated as distinct entities existing independently of the patients they inhabit. Patient-centered diagnosis focuses on knowing the mediators, triggers, and antecedents of disease (illustrated below) in each individual patient.

Dynamic Balance of Internal and External Factors
Important to the functional medicine practitioner is the idea that lifestyle translates into quantifiable effects on health and disease through the energetics of our biochemistry and genetics. Different activities and emotions; such as eating, exercising or not exercising, joy, pain, and love, for example; are integral to inducing the homeodynamic mix of molecules that, through the masking and unmasking of chromosome sites, lead to the sum of experiences that our patients identify as their lives. Jeffrey Bland, PhD, describes this balance as follows:

"Environment modifies not only the expression of inducible genes but also post-translational cellular function. After the genes have been expressed and their message has been translated into the manufacture of protein and other cellular materials, the structure and function of these substances can be further altered as a consequence of processes such as oxidation or glycation. Both of these post-translational influences can further alter cellular function in such a way as to be associated with unhealthy aging.

The combination of the environmental effects on both gene expression and post-translational modification of cellular materials gives rise to symptoms of aging that are well recognized in clinical medicine. For example, individuals who smoke heavily appear to age faster, and they have higher risk of age-related diseases such as cancer and heart disease. Individuals who consume excessive alcohol also appear to age more quickly, and they have increased risk to liver and heart-related problems. Individuals who consume poor quality diets that are excessive in calories and low in essential nutrients show the signs of over-consumptive under-nutrition with obesity, poor health patterns, and more prevalent age-related diseases. These examples demonstrate how environment and lifestyle influence gene expression and post-translational modification of cellular function. Medicine has focused principally on the diagnosis of these diseases once they occur, and physicians have historically placed less emphasis on understanding genetic susceptibilities and gene expression modifiers."(7)

Web-like Connections of Physiological Factors
Sidney Baker, MD, explains that "people do not get sick from diseases, but rather diseases reflect a disruption in the dynamic balance between themselves and their environment."(8)
Fundamental to functional medicine is a profound awareness of web-like interactions among all systems—interactions that have been artificially singularized by disease taxonomy. Robert Heinlein describes the dilemma as follows:

"The greatest crisis facing us is a crisis in the organization and accessibility of human knowledge. We own an enormous ‘encyclopedia’ which isn’t even arranged alphabetically. Our ‘file cards’ are spilled on the floor. The answers we want may be buried in the heap."

Three key notions, first articulated by Leo Galland, MD, help illustrate and organize the web-like thinking that is essential to the success of the functional medicine practitioner. The antecedents of our patients’ dysfunction nest within their biological terrain and genetic susceptibilities. The patient’s dynamic balance has constant perturbations that require adaptation. However, sometimes a force of change such as allergens, xenobiotics, drugs, endotoxins, and emotional stress are strong enough to create a dysfunctional response; Dr. Galland labels these forces triggers. The patient’s response to a trigger consists of complex, web-like effects on the biologic system known as mediators. For example, cytokines, prostanoids, leukotrienes, and lipid peroxides are mediators that cause an inflammatory response.

As futuristic as it may seem, the next step in diagnosis and treatment protocols can incorporate an assessment of the unique risk factors present by virtue of the patient’s DNA interacting with the end-products of his or her lifestyle, diet, environment, and thoughts. For example, we know that the byproducts of tobacco smoke interact with cellular gene structures in the lungs to induce translational molecules. The presence or absence of these molecules affects the detoxifying function of patients’ liver cells. In turn, these cells arbitrate the development of breast cancer. This research regarding the polymorphic expression of inherited detoxification capabilities helps explain contradictions regarding the connection between smoking and breast cancer. The phenotypic expression of breast cancer is controlled by the genetic susceptibility of the patient experiencing the tobacco smoke, which helps define this susceptibility.

This genetotrophic disease and susceptibility model dates back to Roger Williams, PhD,(9) who discovered many of the B vitamins. The year prior, Linus Pauling published pivotal research demonstrating that genetically controlled translational molecules control form and function in sickle cell disease. Today we see clinical applications that decrease sickle cell crisis flowing from the understandings evolved from this model.(10) Rich literature exists on the genetics and epidemiology of aging and chronic illness as well. (11) A model allowing for modifiable factors for achieving healthy aging has been reported by Evans and Rosenberg from their Tuft’s Medical School study on aging.(12)

Health as a Positive Vitality—Not Merely the Absence of Disease
Today medicine is at a crossroads. Although medicine has successfully contributed to the evolution of the science of disease diagnosis and treatment during the past four decades, it has not been as successful in promoting healthy aging. A majority of the aging baby boomer population expects that they will never retire and will continue to engage in multiple activities, travel the world, be physically active, meet exciting new challenges, and be available as catalysts for social change as they grow into their 70s and 80s. This is not a health as the absence of disease model, but rather health as a positive, achievable vitality model.

Fries (Stanford University Medical School researcher in the processes of aging) explains that much of the loss of function associated with disease among older individuals is a consequence of the progressive loss of "organ reserve."(13) When we are young, there is a reserve of organ function beyond that which is necessary for the baseline requirements of most organ systems. As we age, however, we lose organ reserve; stresses that we could have once accommodated now exceed our resilience, which results in health crises. Fries emphasizes that organ reserve is related to biological age. As we lose organ reserve, our biological age increases, making us more susceptible to disease. We can modify how quickly we lose organ reserve and undergo biological aging through changes in lifestyle, environment, and nutrition. It is now recognized that 75 percent of our health and life expectancy after age 40 is modifiable on the basis of such choices. (14),(15)



1. The Random House Dictionary of the English Language. New York: Random House, Inc; 1969.
2. Bishop JE, Waldholz M. Genome. New York: Simon and Schuster; 1990.
3. Hesketh JE, Partridge K. Gene cloning: studies of nutritional regulation of gene expression. Proc Nutri Soc. 1996;55:575-581.
4. Motulsky, AG. Nutrition and genetic susceptibility to common diseases. Am J Clin Nutr. 1992;5S:1244-1245.
5. Baker SM. Detoxification and Healing. New Canaan, Conn: Keats Publishing, Inc; 1987.
6. Galland L. Medicine in Different Perspective: A Biographical Approach to Illnesses can erase the False Distinction between Science and Humanism in Medicine. 133 E 73 St. New York, NY 10021.
7. Bland JS. The use of complementary medicine for healthy aging. Alt Therapies. 1998;4(4):42-48.
8. Baker SM. Detoxification and Healing. New Canaan, Conn: Keats Publishing, Inc; 1987:173.
9. Williams R. The concept of genetotrophic disease. Lancet. 1950;1:287-289.
10. Perrine SP, Olivieri NF, Faller DV, Vichinsky EP, Dover GJ, Ginder GD. Butyrate derivatives. New agents for stimulating fetal globin production in the B-globin disorders. Am J Ped Hematol/Oncol. 1994;16(1):67-71.
11. Fries J, Crapo LM. Vitality and Aging. San Francisco, Calif: W.H. Freeman & Co; 1981.
12. Evans W, Rosenberg IH. Biomarkers. The 10 keys to Prolonging Vitality. New York: Fireside; 1991.
13. Fries JF. Aging, natural death, and the compression of morbidity. NEJM. 1980;303:130.
14. Murray CJL, Lopez AD. Alternative projections of mortality by cause 1990-2020: global burden of disease study. Lancet. 1997;349:1498-1504.
15. Bland JS. The use of complementary medicine for healthy aging. Alt Therapies. 1998;4(4):42.

Author's Bio: 

This definition is part of a series that covers the topic of Alternative Medicine. The Official Guide to Alternative Medicine is Dr. Z, Peter Zeischegg. Dr. Z’s current clinical and consulting work centers on alternative therapies without drugs and surgery, with emphasis on improving and balancing brain function.

Additional resources on Alternative Health can be found at:

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Dr. Z, Peter Zeischegg, The Official Guide to Alternative Medicine