When was the last time you felt truly well? Not simply free of illness, but consistently energetic, mentally clear, well-rested, and comfortable in your body?
For many people, the first signs that something is changing are subtle. They begin feeling tired in the afternoon, notice their sleep isn't as restorative, experience unexplained bloating, or find it harder to concentrate. These changes may not point to a diagnosable disease, and routine bloodwork may appear normal. Yet they can still be worth investigating.
This is where the conversation about integrative functional medicine vs. conventional medicine for preventive care becomes especially relevant. Both approaches have important roles in maintaining health, but they can differ in how they investigate symptoms, interpret findings, and develop treatment plans.
At Jyzen in Mill Valley, California, Chief Medical Officer Dr. Beth McDougall has spent nearly 30 years practicing integrative and functional medicine. Her approach is grounded in a belief that paying attention to changes in how someone feels and functions can help identify opportunities to improve health before more significant problems develop.
"Typically, there is a path from absolute perfect health to a medical illness where your body starts to give you subtle warning signs along the way," she explains. "It's so much easier to course correct if you actually pay attention to that subtle deviation."
What Is the Difference Between Functional Medicine and Conventional Medicine?
Conventional medicine uses evidence-based screening, diagnostic testing, medications, procedures, and specialist care to prevent, identify, and treat illness. Preventive services such as blood pressure monitoring, cholesterol assessment, cancer screening, and diabetes screening are fundamental parts of conventional primary care.
Functional medicine takes a more systems-oriented approach, examining how factors such as nutrition, metabolism, hormonal function, sleep, stress, environmental exposures, and lifestyle may contribute to a person's health. Rather than evaluating symptoms in isolation, practitioners often look for relationships between different bodily systems.
These approaches overlap considerably. A skilled conventional primary care physician may provide highly personalized preventive care, just as an integrative physician may prescribe medication, order conventional diagnostic tests, or refer patients to specialists.
The meaningful difference often lies in the clinical emphasis, the time devoted to investigation, and the breadth of factors considered.
For Dr. McDougall, one of the most important distinctions is her willingness to investigate symptoms that might otherwise be considered too mild or nonspecific to warrant extensive evaluation.
"If someone starts feeling fatigued in the afternoon, or their mental clarity begins to slip, or their sleep is no longer as sound, I pay attention to that," she says. "I try to figure out why."
Her goal is to understand what has changed and whether there is an identifiable, treatable reason behind it.
Why Normal Lab Results Don't Always Tell the Whole Story
One of the most common frustrations patients describe is feeling unwell despite being told that their laboratory results are normal.
Laboratory reference ranges are important tools. They help clinicians recognize patterns associated with disease, but a result falling within a reference interval does not necessarily explain a person's symptoms or rule out every possible health concern.
Dr. McDougall considers laboratory findings alongside the patient's medical history, family history, symptoms, lifestyle, and previous results. She is particularly interested in changes over time that might help explain a decline in how someone feels.
An Example: Investigating Possible Thyroid Dysfunction
Consider a patient who experiences persistent morning fatigue, constipation, dry skin, hair thinning, and difficulty concentrating. Their thyroid-stimulating hormone (TSH) level is 4.3 mIU/L, a value that may fall near the upper end of some laboratories' reference ranges.
Dr. McDougall would want to investigate further, especially if the patient has a family history of thyroid disease.
"To me, that might be too high of a TSH for that individual," she explains.
Rather than relying on a single laboratory value, an appropriate evaluation may include reviewing free thyroid hormone levels, considering thyroid antibodies when indicated, repeating testing, and investigating other possible causes of the symptoms.
A mildly elevated or high-normal TSH does not automatically establish hypothyroidism or mean that thyroid medication is needed. Treatment decisions depend on the full clinical picture, and evidence for treating mild subclinical hypothyroidism is mixed.
The broader lesson is that a laboratory result is one piece of information. Understanding what it means requires clinical judgment and attention to the individual.
When Symptoms Persist: Looking Beyond the Initial Workup
Some patients seek integrative care after months or years of unexplained symptoms. They may have visited multiple specialists, undergone standard testing, and still lack a clear understanding of what is affecting their health.
Dr. McDougall frequently works with patients experiencing complex combinations of fatigue, brain fog, gastrointestinal complaints, and other persistent symptoms. Her approach begins with a detailed history intended to identify patterns, exposures, risk factors, and possible explanations that deserve further evaluation.
Chronic Fatigue and Tick-Borne Illness
For someone experiencing significant fatigue and cognitive difficulties, one possibility Dr. McDougall considers is a history of tick exposure.
Depending on the person's symptoms, exposure history, and other clinical findings, appropriate testing for Lyme disease or other tick-borne infections may be warranted.
These illnesses can sometimes present with symptoms that overlap with other conditions, making a careful differential diagnosis essential. However, persistent fatigue or brain fog alone does not establish a tick-borne infection, and testing must be interpreted using validated methods.
The value of taking a comprehensive history is that it can reveal information that changes which diagnoses should be considered.
Environmental Exposures and Unexplained Symptoms
Dr. McDougall also asks patients about their living and working environments when symptoms suggest that environmental factors may be contributing.
For example, someone with worsening asthma, sinus congestion, and allergic symptoms may have experienced significant dampness or mold exposure in a building.
Mold exposure is associated with respiratory symptoms, allergies, and asthma exacerbations in susceptible individuals. A clinical evaluation may include reviewing exposure history and considering appropriate allergy or pulmonary testing.
It is also important to distinguish established effects of mold exposure from less-validated diagnostic and treatment claims. Urine mycotoxin testing, for example, is not recommended by the CDC for diagnosing illness related to indoor mold exposure.
For Dr. McDougall, these examples illustrate why understanding a patient's broader circumstances matters. A comprehensive evaluation should consider the potential influence of medical, environmental, and lifestyle factors without assuming that every symptom has a single underlying cause.
What Does Functional Medicine Look at for Preventive Care?
Dr. McDougall believes that understanding a person's current health and future risk factors can create opportunities for earlier intervention.
Her preventive evaluations may extend beyond a routine physical, with testing selected according to a patient's history, symptoms, age, family history, and individual health goals.
Metabolic Health and Cardiovascular Risk
Metabolic health is a major focus of preventive medicine at Jyzen.
Blood glucose regulation, insulin resistance, blood pressure, cholesterol, body composition, and physical fitness can provide valuable information about cardiovascular and metabolic risk.
"Metabolic dysfunction underlies so many of the diseases we're concerned about as we age," Dr. McDougall explains.
Insulin resistance and other metabolic abnormalities are associated with increased risks of type 2 diabetes and cardiovascular disease, while metabolic health also intersects with several other chronic conditions.
Depending on the individual, evaluation may include fasting glucose, hemoglobin A1c, lipid testing, and additional metabolic markers. Advanced cardiovascular assessment or imaging may be considered in selected patients, particularly when family history or other risk factors warrant further investigation.
Dr. McDougall is interested in coronary imaging technologies such as Cleerly, which analyzes coronary CT angiography images to characterize plaque. These tools can provide additional information in appropriate clinical circumstances, although they are not recommended as routine screening for every healthy adult.
The goal is to identify meaningful risk factors and translate them into a practical prevention strategy.
Bone Density and Fracture Risk
Bone health is another area where Dr. McDougall encourages patients to think ahead.
Bone loss often progresses without noticeable symptoms, and many people don't discover they have reduced bone density until later in life.
She is interested in assessments that evaluate skeletal health, including bone density and technologies designed to provide information about bone strength or fragility.
Established osteoporosis screening recommendations support testing women aged 65 and older, as well as younger postmenopausal women at increased fracture risk. Earlier evaluation may also be appropriate for people with particular medical conditions or risk factors.
When decreased bone density or elevated fracture risk is identified, interventions such as resistance training, adequate nutrition, and, when indicated, medical treatment may help preserve bone health and reduce future fracture risk.
Hormonal Health Through Different Life Stages
Hormonal changes can influence sleep, energy, mood, body composition, and overall quality of life.
For women in their 40s and 50s, Dr. McDougall pays particular attention to the menopausal transition. She considers symptoms, menstrual history, sleep, metabolic health, and other factors that may influence how a woman experiences this stage of life.
Hormone testing can be useful in selected circumstances, particularly when a specific endocrine disorder is suspected. However, routine hormone panels are not always necessary to diagnose perimenopause, since hormone concentrations naturally fluctuate during this transition.
Her broader approach focuses on helping women maintain their health, understand symptoms, and make informed decisions about available treatment options.
Digestive Health and the Microbiome
Dr. McDougall also considers digestive health an important part of the overall picture.
Persistent bloating, irregular bowel habits, abdominal discomfort, and changes in digestion deserve an appropriate medical evaluation rather than being dismissed as normal.
Growing research continues to explore the relationships between the gut microbiome, metabolism, immune function, and disease. However, commercial microbiome testing is still evolving, and many results do not yet have well-established clinical interpretations.
Dr. McDougall's interest in the microbiome is part of her broader emphasis on the relationships between bodily systems. At the same time, evidence-based colorectal cancer screening remains essential, with screening generally recommended beginning at age 45 for adults at average risk and earlier for certain higher-risk individuals.
Is More Testing Always Better for Prevention?
One of the defining features of Dr. McDougall's clinical philosophy is her interest in gathering detailed information before significant health problems develop.
She believes that identifying meaningful changes early can create opportunities to intervene through lifestyle changes, targeted treatment, or additional medical evaluation.
However, comprehensive care does not necessarily mean ordering every available test.
Testing offers the greatest value when results are accurate, clinically meaningful, and likely to influence care. Unnecessary testing can produce false positives, incidental findings, additional costs, and treatments that may not improve health.
This is particularly important in preventive medicine, where many patients feel relatively well and the potential benefits of screening must be weighed against the possibility of harm.
At Jyzen, the objective is to use clinical history, appropriate testing, and physician interpretation to develop an individualized understanding of health rather than simply accumulating more data.
As Dr. McDougall puts it, "It's what you measure and what you do with what you find that is so critical."
Where Conventional Medicine Excels and Why Functional Medicine Should Complement It
Despite the differences in approach, Dr. McDougall does not believe patients should have to choose between functional and conventional medicine.
She has tremendous respect for the expertise of medical specialists and the diagnostic and treatment capabilities available through conventional healthcare.
Cardiologists, neurologists, endocrinologists, gastroenterologists, surgeons, and other specialists bring deep knowledge of their respective fields. Advanced imaging, emergency care, surgical interventions, and evidence-based medications are indispensable when patients need them.
"I love the fact that we have medical specialists that we can refer to," Dr. McDougall says.
Where integrative medicine can add value, she believes, is in maintaining perspective on the whole person, especially when multiple medical conditions or specialists are involved.
The Integrative Physician as a Care Coordinator
Dr. McDougall describes her role with complex patients as that of a quarterback.
A patient might be working with a cardiologist for cardiovascular concerns, an endocrinologist for thyroid disease, and a gastroenterologist for digestive symptoms. Each specialist provides expertise in a particular area, while an integrative physician may help coordinate information and consider how the patient's health concerns interact.
"Sometimes people lose the forest for the trees if they're strictly seeing medical specialists," she explains. "I'm the one who's incorporating all of that and keeping the big picture."
This collaborative approach can also help patients discuss nutrition, physical activity, sleep, stress management, and supportive care alongside conventional treatment.
Any supplements or complementary treatments must be evaluated for safety, particularly when patients take prescription medications or receive treatments such as chemotherapy.
There are also practical limitations to consider. Many integrative evaluations, specialized tests, and treatments are not covered by insurance, creating additional out-of-pocket expenses. Patients should understand the evidence supporting a proposed test or treatment, its cost, and whether it is likely to change their care.
For Dr. McDougall, the ideal is a healthcare team that combines the strengths of both approaches.
How Functional Medicine Approaches Healthy Aging in Your 30s, 40s, and 50s
What if you feel generally healthy and simply want to stay that way?
For Dr. McDougall, this is one of the most valuable times to think about prevention.
She begins by understanding the patient's current health, family history, lifestyle, symptoms, and long-term goals. Appropriate testing may help establish a baseline and identify risk factors that deserve attention.
But laboratory testing is only part of the picture. Much of the work of preventive medicine happens through the habits people build and maintain over time.
Building Strength and Cardiovascular Fitness
Maintaining lean muscle mass becomes increasingly important with age. Resistance training helps support strength, physical function, metabolic health, and bone health.
Dr. McDougall also encourages patients to develop cardiovascular fitness through a combination of aerobic activity and, when appropriate, higher-intensity exercise.
Steady aerobic training, including activities performed at a moderate intensity, can support cardiovascular and metabolic health. High-intensity interval training may provide additional improvements in cardiorespiratory fitness for individuals who can exercise safely at that level.
The right training program depends on a person's current fitness, medical history, and physical capacity.
Eating for Your Individual Needs
Nutrition is another cornerstone of Dr. McDougall's approach.
Rather than prescribing one diet for everyone, she considers the person's metabolic health, activity level, body composition, medical conditions, and stage of life.
Someone who spends most of the workday sitting may have different nutritional needs from someone who is physically active throughout the day. A woman navigating perimenopause may also have different priorities from someone in their early 30s.
The emphasis is on developing a sustainable pattern of eating that supports adequate nutrition, metabolic health, and long-term well-being.
Sleep, Stress, and Social Connection
Dr. McDougall also emphasizes that healthy aging involves more than exercise and food.
Consistent, restorative sleep supports cognitive function, metabolic regulation, and overall health. Meditation and mindfulness practices can help people manage stress, while spending time outdoors and maintaining meaningful social relationships contribute to well-being.
Wearable technologies can offer useful information about sleep and activity patterns, although consumer sleep measurements should not be treated as diagnostic assessments.
These habits may seem simple, but their cumulative effects can be substantial.
Dr. McDougall encourages patients to establish them before health challenges make lifestyle changes more difficult.
Is Functional Medicine Better Than Conventional Medicine for Preventive Care?
The answer depends on what you're looking for, your health history, and the specific care being offered.
Conventional preventive medicine provides essential, evidence-based services that have been shown to improve health outcomes, including vaccinations, cardiovascular risk management, and appropriate cancer screening.
Functional and integrative medicine may offer a more expansive evaluation of symptoms, lifestyle, and interactions between different systems, particularly for people seeking a deeper understanding of persistent concerns or personalized health goals.
Neither approach should replace sound clinical judgment. More testing, additional supplements, or treatment of every borderline laboratory result does not automatically translate into better health.
For Dr. McDougall, the most effective approach combines careful investigation with collaboration, appropriate diagnostics, and individualized care.
The ultimate goal is to help patients understand their health more fully and take meaningful action when opportunities for improvement arise.
A More Proactive Approach to Preventive Health at Jyzen
At Jyzen, we believe preventive care should begin with understanding the individual.
Our physicians combine integrative and functional medicine with advanced diagnostic capabilities, individualized treatment planning, and a focus on the lifestyle factors that shape long-term health.
Whether you're experiencing subtle changes in energy, sleep, or metabolism, navigating a new stage of life, or simply interested in understanding your health more deeply, an individualized medical evaluation can help identify appropriate next steps.
As Dr. McDougall explains, maintaining health requires paying attention to changes, understanding what they mean, and making informed decisions about how to respond.
Interested in a more personalized approach to preventive medicine? Explore care at Jyzen in Mill Valley, California, and schedule an appointment with one of our physicians to discuss your health concerns and long-term goals.