If you are skeptical about Functional Medicine, good.

I mean that without irony.

Skepticism is the appropriate starting place for any medical idea — including this one. No one should accept a clinical approach simply because someone has attached the words functional, integrative, natural, or even evidence-based to it. Medicine deserves more scrutiny than that. We should be asking whether something makes biological sense, whether there is evidence to support it, how strong that evidence is, what the risks are, and whether acting on that information actually changes outcomes.

I would apply exactly the same standard to Functional Medicine.

There is, however, a fairly common misunderstanding about what Functional Medicine actually is. It is sometimes portrayed as alternative medicine, supplement medicine, unusual laboratory testing, or a search for obscure causes that conventional physicians have somehow missed. There are certainly practitioners operating under the Functional Medicine label who do those things. But none of them really defines Functional Medicine.

For me, Functional Medicine begins with a much simpler question: Why is this particular person ill in this particular way?

That sounds obvious. It represents a significant change in how we organize our thinking about chronic disease.

"It is much more important to know what sort of patient has a disease than what sort of disease a patient has."
— William Osler, MD

What a Diagnosis Tells Us

A diagnosis is one of the most powerful tools in medicine. If I determine that someone has rheumatoid arthritis, type 2 diabetes, psoriasis, inflammatory bowel disease, hypertension, or migraine, that diagnosis immediately connects the patient to an enormous body of medical knowledge.

It tells me how this patient is similar to other people who share the same diagnosis.

From studying thousands — sometimes millions — of people, we learn the natural history of the disease, which complications tend to occur, which laboratory abnormalities matter, which treatments work on average, and which interventions reduce the likelihood of bad outcomes. That accumulated knowledge is one of the great accomplishments of modern medicine, and Functional Medicine would be foolish to discard it.

But there is another question that the diagnosis does not completely answer.

Why did this person develop the disease?

Why did it appear at this particular point in life? Why does one patient with psoriasis have relatively mild skin disease while another develops extensive inflammation and psoriatic arthritis? Why does one person with type 2 diabetes have profound insulin resistance while another has relatively modest insulin resistance but declining pancreatic beta-cell function? Why do two patients with the same autoimmune diagnosis respond very differently to the same treatment?

A diagnosis tells us a great deal about how you are similar to other people with your disease. Functional Medicine is interested in the other side of that equation: what makes your case unique.

That does not mean your disease is completely unique. It means the particular combination of factors that allowed the disease to emerge — and that continues to influence its expression — may be quite different from the combination operating in someone else.

I think we need both kinds of information. I want everything the medical literature can tell me about the population of people who share your diagnosis. And then I want to bring that information back to the individual sitting in front of me.

That is where Functional Medicine begins to become interesting.

The Same Diagnosis Does Not Necessarily Mean the Same Biology

Take type 2 diabetes as a relatively straightforward example.

Two patients may both meet exactly the same diagnostic criteria. One may have substantial visceral adiposity, fatty liver, and severe insulin resistance. Another may be relatively lean but have limited pancreatic beta-cell reserve. A third may have gained 40 pounds over several years while becoming increasingly sedentary, sleeping poorly, and eating a diet dominated by refined carbohydrates. A fourth may have several of these processes occurring simultaneously.

They all have diabetes, and the diagnosis is correct. But the physiology that brought each person to that diagnosis is not identical.

The same principle becomes even more important in complex chronic illnesses — autoimmunity, chronic inflammatory disorders, fatigue syndromes, metabolic disease, neuroimmune illness. Genetics, previous infections, diet, body composition, sleep, physical activity, medications, environmental exposures, gastrointestinal function, stress physiology, immune regulation, and the sequence of events that preceded the illness may all matter.

This is increasingly consistent with the way modern biology understands disease. Network medicine views many disease states not as the failure of one isolated molecule but as disturbances arising within interacting biological networks. Barabási, Gulbahce, and Loscalzo described this framework in Nature Reviews Genetics, noting that disease phenotypes commonly reflect interacting pathobiological processes rather than a single abnormality.[1] López-Otín and Kroemer's work on the Hallmarks of Health describes health as something actively maintained through barrier integrity, homeostasis, biological rhythms, stress responses, resilience, repair, and regeneration — interconnected processes where disruption in one area influences several others.[2]

None of that proves Functional Medicine. But it does tell us that thinking about the human organism as an interconnected biological system is not an alternative concept.

It is modern biology.

The Body Does Not Know About Medical Specialties

Medicine has to divide the body into specialties. There is simply too much knowledge for any one person to master all of it. Cardiology, gastroenterology, endocrinology, neurology, rheumatology, psychiatry, dermatology — specialization allows people to develop extraordinary expertise, and that expertise saves lives.

The problem comes when we unconsciously begin to imagine that biology is organized the same way.

It isn't.

"You cannot understand a system by looking at its parts in isolation."
— Fritjof Capra, The Web of Life

The gastrointestinal tract communicates continuously with the immune system. The immune system communicates with the nervous system. The nervous system influences endocrine function. Hormones influence metabolism. Metabolism influences immune behavior. Sleep influences glucose regulation, appetite, autonomic tone, cognition, immune activity, and blood pressure. Skeletal muscle is not simply something that moves us around — it is a metabolically and hormonally active organ. Adipose tissue is not simply stored energy — it participates in endocrine and inflammatory signaling.

The categories are ours. The connections belong to biology.

Functional Medicine is largely an attempt to take those connections seriously when trying to understand chronic illness.

So How Does Functional Medicine Actually Work?

For me, one of the most important tools in Functional Medicine is not an unusual laboratory test.

It is a good history.

I want to understand what happened over time, because chronic illness rarely appears out of nowhere. What was your health like before this began? What changed? Was there an infection, pregnancy, surgery, medication change, period of extraordinary stress, significant weight change, gastrointestinal illness, occupational exposure, or change in sleep or diet that preceded the deterioration?

Sometimes there is an obvious turning point. Often there isn't. More commonly, a pattern emerges only after we construct the timeline.

Then I want to understand the physiology. How well is the person regulating glucose? What is happening metabolically? Is there evidence of excessive inflammatory signaling? How is the gastrointestinal system functioning? What about sleep, circadian rhythm, autonomic regulation, body composition, physical conditioning, nutritional status, environmental exposures, and immune regulation?

The point is not to identify how many abnormalities we can discover. That is actually one of the places where Functional Medicine can go badly wrong. If I order an enormous number of tests, identify 37 things outside an arbitrary reference range, and prescribe something for every one of them, I have not practiced systems medicine. I may simply have created a more expensive version of fragmented medicine.

What I am really looking for are the high-leverage points.

If three or four disturbances can explain much of what I am seeing downstream, those are far more interesting to me than a collection of isolated abnormalities. The goal is to construct the simplest biological model that adequately explains the patient, and then test that model by seeing what happens when we intervene.

What About the "Root Cause"?

Functional Medicine is frequently described as medicine that searches for the root cause. I understand the appeal of that phrase, and sometimes there really is one dominant cause. If someone is profoundly iron deficient because of an occult gastrointestinal bleed, finding the source of that blood loss is far more important than repeatedly giving iron.

But most chronic disease is more complicated than a single root.

I tend to think in terms of drivers and maintaining factors.

Imagine a patient with autoimmune disease who also has poor sleep, insulin resistance, significant psychological stress, altered gastrointestinal function, nutritional inadequacy, a history of infection, and an important environmental exposure. Which one is the root cause?

That may not even be the right question.

A more useful question is: Which factors are meaningfully contributing to the disease process now, how are they interacting, and which of them can we actually change?

That view is less satisfying if what we want is a single villain. But it is much closer to how complex biological systems actually behave.

Why Food, Sleep, Movement, and Stress Matter So Much

Another misconception is that Functional Medicine places unusual emphasis on diet, exercise, sleep, and stress because these are somehow more "natural."

That is not why they matter.

They matter because they are enormous physiological inputs.

"Let food be thy medicine and medicine be thy food."
— Hippocrates

The Diabetes Prevention Program is a useful example. More than 3,200 people at high risk for type 2 diabetes were randomized to placebo, metformin, or an intensive lifestyle intervention. Over an average follow-up of 2.8 years, lifestyle intervention reduced the incidence of diabetes by 58 percent compared with placebo. Metformin reduced it by 31 percent.[3] That finding was published in The New England Journal of Medicine. There is nothing alternative about it.

It simply demonstrates something we sometimes forget: changing the conditions in which a disease is developing can change the trajectory of the disease.

Food is information entering the system several times every day. Physical activity changes metabolic function, vascular biology, mitochondrial signaling, and insulin sensitivity. Sleep affects virtually every regulatory system we have. Chronic stress alters autonomic, endocrine, immune, and behavioral physiology.

These things are not adjuncts to biology.

They are biology.

What About Supplements and Advanced Testing?

Supplements can be useful, but supplements are not Functional Medicine.

Sometimes we are correcting a deficiency. Sometimes a nutrient or botanical has evidence for a particular effect. Sometimes we are using a nutrient therapeutically at doses beyond what food ordinarily provides. There should still be a reason. I want to be able to answer: what are we trying to accomplish, and why do we believe this will help?

The same skepticism that applies to medications should apply to supplements. Is there evidence of benefit? What is the quality of that evidence? What are the risks? Are there drug interactions? Does the person still need it six months from now?

A cupboard full of supplements is not evidence of sophisticated Functional Medicine. Sometimes it is evidence that we have lost the plot.

The same principle applies to advanced testing. Some of it can be extremely useful. Some is interesting but not yet clinically actionable. Some commercial testing has moved considerably faster than the science needed to interpret it. Before ordering a test, I want to know whether the assay is reliable, whether the result means what we think it means, and most importantly, whether knowing it is likely to change what I do.

Being able to measure something and knowing what to do with that measurement are two different things.

Does Functional Medicine Have Evidence?

This deserves a careful answer, because it is easy for both supporters and critics to overstate their case.

There is substantial evidence for many of the things used within Functional Medicine: nutrition, physical activity, weight reduction, treatment of nutritional deficiencies, sleep optimization, smoking cessation, stress management, and metabolic interventions. There is considerably less research evaluating Functional Medicine as a complete model of care.

One well-known study from Cleveland Clinic compared patients seen at their Center for Functional Medicine with patients receiving conventional family health center care. After statistical matching, Functional Medicine patients showed greater improvement in patient-reported physical health at six months.[4] The finding is interesting. The study was observational. The authors appropriately described it as hypothesis-generating.

A randomized controlled trial published in 2024 found that Functional Medicine health coaching improved adherence to an elimination diet and several patient-reported outcomes compared with a self-guided approach.[5] That tells us something useful about one component of care. It does not prove the entire model.

"The greatest obstacle to discovery is not ignorance — it is the illusion of knowledge."
— Daniel Boorstin

I am comfortable with that uncertainty. Functional Medicine does not need to be defended as though it were a belief system. It needs to be studied. Some of its ideas will hold up very well. Some will need to be modified. Some probably will not survive careful investigation and should be abandoned when the evidence tells us to abandon them.

That is not a failure of Functional Medicine.

That is how medicine is supposed to work.

Where I Think Functional Medicine Adds Something Important

The real value of Functional Medicine is not that it has discovered an entirely different human body.

It hasn't.

The value is in how we organize the questions.

Your diagnosis gives us access to everything medicine has learned from people who resemble you. Then we ask a second set of questions about the person who has the diagnosis. What happened before the illness? What biological systems have become dysregulated? What vulnerabilities existed beforehand? What continues to drive the process? What remains resilient? What is modifiable? And where might a relatively small intervention produce a disproportionately large improvement?

In other words, I am interested in both the disease and the person who has the disease.

I do not see those as competing approaches.

If I have pneumonia, I want someone to diagnose the pneumonia and determine whether I need antibiotics. If I am having a heart attack, I want modern cardiology. If I have cancer, I want the best oncologic diagnosis and treatment available.

But if I have accumulated several chronic conditions over twenty years — weight increasing, sleep deteriorating, glucose regulation worsening, fatigue deepening, gastrointestinal function declining, inflammatory problems emerging — I also want someone to stand far enough back from the individual diagnoses to ask whether these things might be connected.

That is the space Functional Medicine is trying to occupy.

It is not an alternative to good medicine. At its best, it is an attempt to make good medicine more complete — by asking not only what disease does this person have, but why is this disease appearing in this person, in this way, at this time?

"The good physician treats the disease; the great physician treats the patient who has the disease."
— William Osler, MD

If you are still skeptical, good.

The answer is not to believe me. The answer is to keep asking whether the model explains what we actually see, whether the biology holds together, whether the evidence supports what we are doing, and, ultimately, whether the patient gets better.

That is the standard that matters.

If you'd like to explore whether this approach makes sense for your situation, we'd be glad to talk. You can reach us at JustBeWell.info or by phone at (320) 347-1212.

-Dr. Sult

References

1. Barabási AL, Gulbahce N, Loscalzo J. Network medicine: a network-based approach to human disease. Nature Reviews Genetics. 2011;12(1):56-68.
2. López-Otín C, Kroemer G. Hallmarks of Health. Cell. 2021;184(1):33-63.
3. Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine. 2002;346(6):393-403.
4. Beidelschies M, et al. Association of the Functional Medicine model of care with patient-reported health-related quality-of-life outcomes. JAMA Network Open. 2019;2(10):e1914017.
5. D'Adamo CR, et al. Functional Medicine health coaching improved elimination diet compliance and patient-reported health outcomes. Medicine. 2024;103(8):e37148.