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Lion’s Mane mushroom and the title “One Mushroom. Two Patients.” for a Dr. Kara Fitzgerald blog on targeted Lion’s Mane formulations.

One Mushroom, Two Patients: A Practitioner’s Case for Targeted Lion’s Mane Formulation

There’s a question worth asking every time you prescribe Lion’s Mane: which patient are you prescribing it for? Most integrative practitioners already use Lion’s Mane, but few consider the variables. Raw material, preparation type, extract, and dose all affect therapeutic outcomes. To confound matters further, the market positioning of Lion’s Mane tends to be a poor reflection of both tradition and clinical research. The clearest example is that it gets labeled as a nootropic, something anyone might use for sharper thinking. That framing attracts consumers, but it does not hold up in clinic.

A woman looking out a sunlit window surrounded by imagery representing fertility, mitochondria, and reproductive health, illustrating a holistic approach to fertility preservation beyond egg freezing.

Fertility Preservation Beyond Egg Freezing

A 31-year-old patient sits across from me and says, “My friends are all freezing their eggs. Should I be doing that too?” It is a question I hear constantly. And while oocyte cryopreservation is a legitimate tool for specific situations, the way it is being marketed has created a damaging assumption: that fertility is a fixed, steadily declining resource that technology must eventually rescue.

Older woman lifting a dumbbell with muscle anatomy illustration behind her, representing strength training and healthy aging.

Why Muscle Strength Is the #1 Predictor of Healthy Aging

There’s one metric that consistently predicts how well we age, and it’s finally showing up in the conversations that matter. It’s not blood pressure, cholesterol, or BMI. It’s muscle strength. Muscle health plays a central role in healthy aging, influencing mobility, quality of life, and metabolic health. Yet historically, strength has been viewed primarily through the lens of fitness or performance rather than as a core clinical target.

illustrated overlays of muscle fibers, a brain, and cellular structures, alongside protein-rich foods and supplements (capsules, powder, fish, chicken), representing the connection between nutrition, muscle health, and aging.

How to Overcome Muscle Anabolic Resistance: Key Nutrients for Healthy Aging

No doubt our regular readers and listeners will have noticed that muscle is having a moment in the healthy aging conversation. In this article, I want to tease out the potential contribution of some additional interventions that we can think about clinically to support muscle health – the amino acid leucine, its derivative HMB (beta-hydroxy-beta-methylbutyrate), vitamin D and urolithin A.

Beyond fiber quantity: the role of fiber diversity in shaping the gut microbiome

Beyond fiber quantity: the role of fiber diversity in shaping the gut microbiome

More than 90% of women and 97% of men in the US fall short of recommended fiber intake. The standard American diet lacks the overall fiber content that each of us need to maintain health. But, this gap is not only about quantity; there’s also a significant gap in fiber diversity. There is evidence that fiber quality and diversity are critical because different types of fiber are metabolized by different gut bacteria, producing a variety of short-chain fatty acids (SCFAs) and downstream effects on gastrointestinal and metabolic health.

Is Creatine Safe?

Is Creatine Safe? What Clinicians Need to Know About Side Effects, Dosing, and Longevity Benefits

If you’re still skeptical about incorporating creatine into your clinical practice, or even into your own supplement stack, this second part of our blog series may help you make that final decision. I understand the hesitation. The internet is saturated with both legitimate concerns and anecdotal horror stories about creatine use (and misuse). Extreme water retention, hair loss, and gastrointestinal distress are frequent talking points.

Heat and Light as Medicine: What Research Shows About Infrared Therapy, Cardiometabolic Health, and Longevity

Heat and Light as Medicine: What Research Shows About Infrared Therapy, Cardiometabolic Health, and Longevity

Functional medicine often focuses on nutrition, exercise, and stress management as the foundational pillars of health. But what other powerful environmental inputs could be leveraged with greater precision? What if heat and light could be used as biological inputs in a way that is measurable and clinically relevant?

How Helping Older Dolphins Unlocked A Secret To Healthy Aging

How Helping Older Dolphins Unlocked A Secret To Healthy Aging

Did you know that 1 in 3 older dolphins develops the same aging-associated conditions as humans? While continually helping to improve the health of older Navy dolphins living in San Diego Bay, veterinarians found that some dolphins had elevated cholesterol, insulin resistance, chronic inflammation, and fatty liver disease – just like some of us.

Creatine Benefits Beyond Muscle: Emerging Research on Brain Health, Metabolism, and Longevity

Creatine Benefits Beyond Muscle: Emerging Research on Brain Health, Metabolism, and Longevity

Creatine has been around for decades. I leaned on it big time in my early career days (both as a physician and a competitive cyclist). I lectured on it in my second year of medical school. And as an athlete, I had firsthand experience of creatine’s most common side effect – water retention. I saw visible changes in my face and swelling in my ankles as I loaded on creatine before a big athletic event, dropping the dose afterwards. Even so, creatine has consistently demonstrated an excellent safety profile when used appropriately. What excites me now is its potential to benefit other areas, such as brain and cardiovascular health, and its validation by the latest research. In this 2-part article, we explore the latest research on creatine’s health benefits, clinical uses, dosing strategies, and potential side effects. Take a read; you may be surprised by some of the findings! ~DrKF

Urolithin A for mitochondria and immune health

Human Clinical Evidence Supporting High-Dose Urolithin A for Mitochondrial and Immune Function

Age-related declines in muscle function, immune resilience, and cellular energy are closely linked to mitochondrial dysfunction, making mitochondrial-targeted interventions a key focus of aging research. In this context, recent placebo-controlled human trials show that a Urolithin A dose of 1000 mg produces broader and more pronounced effects on mitochondrial gene expression, muscle performance, and immune markers than lower doses.

Ovarian Rejuvenation & AI: How Aging Science Is Accelerating

Ovarian Rejuvenation & AI: How Aging Science Is Accelerating

How close are we to ovarian rejuvenation and what role will AI play in getting us there? In this conversation, reproductive biologist and aging researcher Dr. Vittorio Sebastiano joins Dr. Kara Fitzgerald to explore how rapidly advancing technologies are transforming geroscience and regenerative medicine.

GLP-1 and Gut Microbiome Dysbiosis

From Promise to Paradox: GLP-1 Agonists May Offset Their Own Benefits Through Gut Microbiome Dysbiosis

In recent years, glucagon-like peptide-1 receptor agonists (GLP-1 RAs) use has increased 700% in the general population and over one quarter of those diagnosed with diabetes are on these medications.

The FxMed Moments That “Broke the Internet” in 2025

The FxMed Moments That “Broke the Internet” in 2025

Happy holidays, everyone! As you enjoy the festive season, I wanted to take a moment to reflect on some of the highlights from this past year here at Dr. Kara Fitzgerald. One of the biggest was certainly our virtual Functional Medicine is Longevity Medicine™ Masterclass.

Targeting Immune Aging: New Findings from the MitoImmune Study on Urolithin A (Mitopure®)

Can Mitopure®, and its active ingredient Urolithin A, support an aging immune system? As we recognize immune aging as a primary driver of age-related disease, this question has taken on new clinical importance. The newly published MitoImmune study in Nature Aging provides the first rigorous clinical evidence to address this question. Conducted by researchers from Timeline, the Buck Institute for Research on Aging, and the lab of Professor.

AI in Functional & Longevity Medicine: 2025 Practitioner Insights

How Are Functional Medicine Practitioners Using AI? Access DrKF’s Report

An excellent colleague of mine recently had an unpleasant experience when she discovered that every single citation in an article she’d generated using AI and sent over as a potential guest post appeared fine on first glance, but was completely fabricated. Not one existed. Thankfully, our team caught it very quickly and never would have approved it for publication without checking. But I’ll admit: I understand the temptation. Most of us are balancing a dozen spinning plates. If AI can lighten the load, who wouldn’t be leaning in?

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