Dr. John Gannage, MD

Dr. John Gannage, MD Dr. John Gannage is a Leader in Integrative Medicine to Restore Health and Prevent Disease

MARKHAM INTEGRATIVE MEDICINE is a clinic specializing in Integrative Medicine (integrating conventional and complementary/functional medicine) located in the City of Markham’s heritage district. DR. JOHN GANNAGE, MD is a leading provider of Integrative Medicine, offering health services as a licensed medical doctor to the Greater Toronto Area since 1992.

09/19/2025

Feeling exhausted, gaining weight without explanation, or struggling with brain fog, mood swings, or thinning hair? These may all be signs of thyroid dysfunction.

The thyroid is your body’s metabolic engine, and when it’s out of balance, everything slows down like your energy, your focus, even your mental health. The problem? Standard thyroid labs often miss what’s really going on.

In functional medicine, we go deeper. Beyond TSH, we look at free T3, free T4, reverse T3, and antibodies. We ask whether your thyroid is producing hormones properly, if they’re being converted efficiently, and if your cells are actually using them. We also consider root causes like nutrition, gut health, stress, toxins, and hidden food sensitivities.

The good news? There are real, natural ways to support thyroid healing.

If your labs look “fine” but you don’t feel fine, it’s time to dig deeper. Book a consultation and let’s uncover the root cause so you can get your energy, clarity, and quality of life back.

If you’ve been searching for answers, you already know how confusing Mast Cell Activation Syndrome can be. The truth is,...
09/17/2025

If you’ve been searching for answers, you already know how confusing Mast Cell Activation Syndrome can be. The truth is, even though MCAS isn’t new, it’s still a relatively newly recognized condition in medicine and that makes it harder to navigate.

Most doctors aren’t trained to connect the dots between symptoms that span multiple systems: gut issues, skin rashes, brain fog, respiratory flares, cardiovascular changes. Instead, patients get sent to specialist after specialist, each treating one piece of the puzzle without seeing the bigger picture.

On top of that, diagnostic criteria for MCAS are still evolving, and in conventional medicine the focus is often on symptom suppression rather than asking why the mast cells are overactive in the first place.

That’s where functional medicine comes in. By taking time to look deeper at gut health, toxins, stress, infections, hormones we can uncover root causes and work toward true healing instead of temporary relief.

If you suspect MCAS may be behind your symptoms, book a consultation below. Together, we’ll connect the dots and create a plan that finally makes sense.

From seasonal sniffles to food sensitivities, rates of allergies have exploded in just a few decades. And it’s not just ...
09/15/2025

From seasonal sniffles to food sensitivities, rates of allergies have exploded in just a few decades. And it’s not just genetics or “better testing.” The truth is, our modern environment is quietly reshaping the way our immune systems function.

Everyday exposures to pesticides, plastics, heavy metals, and hormone-disrupting chemicals are creating chronic inflammation and hormonal imbalance. Add in stress, gut damage, and processed foods and you’ve got the perfect storm for rising sensitivities.

Here’s the good news: you’re not powerless. By lowering your toxic load, repairing gut health, supporting natural detox pathways, and restoring hormone balance, it’s possible to calm immune overreactions and reduce allergic symptoms.

Allergies aren’t just an inconvenience, they’re a signal. When we listen to that signal and address the root causes, real healing becomes possible.

Ready to get to the root of your allergies and start feeling better? Book a consultation today.

Managing histamine intolerance doesn’t just come down to what you eat, it’s also about how you prep, store, and cook you...
09/10/2025

Managing histamine intolerance doesn’t just come down to what you eat, it’s also about how you prep, store, and cook your food.

Long cooking times, poor storage, or even reheating can all increase histamine levels and trigger symptoms. The good news is that simple shifts, like using an Instant Pot, freezing meals properly, or choosing airtight containers, can make a big difference in how your body responds.

Your kitchen habits can either help or hinder your healing. By being mindful of food prep methods, you can lower histamine load, preserve nutrients, and feel more in control of your health.

Want to know which approach works best for your body? Book a consultation to create a personalized nutrition plan that supports your healing.

09/09/2025

Gluten is often thought of as only a concern for those with celiac disease, but the truth is, it can impact many people beyond that.

For those with celiac disease, gluten triggers an autoimmune response that damages the small intestine, leading to nutrient malabsorption, inflammation, anemia, skin issues, and even brain fog.

But even if you don’t have celiac disease, removing gluten may still be beneficial especially if you’re dealing with autoimmune conditions. That’s because gluten itself can be pro-inflammatory, disrupt the gut lining, and aggravate symptoms both inside and outside the digestive tract.

If you’ve been struggling with unexplained symptoms or an autoimmune condition, it may be worth exploring how gluten is affecting your health.

Ready to get to the root of your symptoms? Book a consultation below.

DAO might not be a household name, but if you struggle with histamine intolerance, it’s one you’ll want to know.Diamine ...
09/08/2025

DAO might not be a household name, but if you struggle with histamine intolerance, it’s one you’ll want to know.

Diamine oxidase (DAO) is the primary enzyme responsible for breaking down dietary histamine. When DAO levels are low, or its activity is blocked, histamine builds up in the body leading to symptoms like migraines, digestive issues, fatigue, skin flare-ups, and more.

Because most DAO is made in the gut, factors like leaky gut, poor gut health, genetics, certain medications, and even hormone imbalances can all interfere with DAO activity. The result? More histamine than your body can handle.

The good news: supporting DAO levels through gut health, nutrition, and in some cases supplementation, can help restore balance.

If you’re experiencing unexplained symptoms that sound like histamine intolerance, it could be a sign your DAO needs support.

Book a consultation to get to the root of what’s driving your symptoms and learn how to rebalance histamine for better health.

An “about me” post, but told through the words of my patients.If you’re new here, I’m Dr. John Gannage, founder of Markh...
09/03/2025

An “about me” post, but told through the words of my patients.

If you’re new here, I’m Dr. John Gannage, founder of Markham Integrative Medicine. For over 30 years, I’ve dedicated my practice to rethinking how we prevent and treat chronic disease.

My work focuses on integrative approaches to health like nutrition, detoxification, mast cell activation, and histamine intolerance. I also have a special focus on biomedical therapies for children and families navigating developmental challenges, including autism.

At the heart of it all is patient-centered care and I think my patients say it best. Swipe through to read their stories.

If you’re ready to experience a more personalized approach to your health, I’d love to work with you.

Book a consultation today.

09/02/2025

Leaky gut is real and it could be the missing link behind symptoms like bloating, brain fog, fatigue, food sensitivities, joint pain, or even skin issues.

When the gut lining is damaged, it stops acting like a protective filter and starts letting toxins, bacteria, and undigested food into the bloodstream. The result? Your immune system goes on high alert, creating inflammation that shows up all over the body.

Processed foods, gluten, alcohol, stress, gut infections, or even certain medications can all play a role. The good news: with the right testing and a structured gut repair protocol, healing is possible.

Ready to get to the root of your symptoms? Book a consultation with Dr. Arvind Tuteja below to start your gut healing journey.

Many children are told they “just have allergies” or “it’s anxiety” when the real issue may be mast cells gone haywire. ...
09/01/2025

Many children are told they “just have allergies” or “it’s anxiety” when the real issue may be mast cells gone haywire. Mast cell activation can cause skin flares, gut troubles, mood swings, fatigue, congestion, and more especially in kids who are more sensitive to everyday triggers like food, stress, or even temperature changes.

The challenge? Standard tests often miss it in children. That’s why a functional medicine approach can make such a difference by looking at the whole picture: diet, gut health, environmental exposures, stress, and gentle mast cell stabilizers to calm symptoms.

With the right support, families can move beyond endless allergy tests and start finding real relief.

Thinking your child might be dealing with more than “just allergies”? Read the full blog below to dive deeper or book a consultation and let’s uncover what’s really going on.

08/29/2025

Vitamin D isn’t just about bone health or immunity, it's a key player in mast cell regulation.

Even without other triggers (like gluten, mold, or stress), being deficient in vitamin D can activate mast cells and worsen symptoms. Levels naturally peak after summer sun and drop by February, especially if you live in the northeast.

The solution? Don’t guess, test. Check your vitamin D, supplement if needed, and work with your practitioner to stay repleted, not depleted.

Wondering if vitamin D deficiency could be affecting your mast cells? Book a consultation to get personalized guidance.

Struggling with histamine intolerance? The DAO enzyme may be the missing piece. DAO is your body’s main tool for breakin...
08/27/2025

Struggling with histamine intolerance? The DAO enzyme may be the missing piece. DAO is your body’s main tool for breaking down histamine from food, but gut issues, genetics, hormones, and even drinks like alcohol or tea can block its activity.

The result? Histamine buildup and frustrating symptoms. The right nutrients and gut support can help restore balance.

If this sounds familiar, let’s take a closer look together. Book your appointment today below.

08/27/2025

Hormonal birth control can be an important tool for many reasons, whether it’s managing painful periods, skin issues, or contraception. But what’s often overlooked are the nutrient depletions it can cause.

Long-term use has been linked to lower levels of vitamins like B6, B12, and B9. These nutrients are essential for red blood cell production, energy metabolism, nerve health, and brain function. Birth control may also alter the gut microbiome, further impacting overall wellness.

If you’re currently using hormonal birth control, it’s worth checking your nutrient status, especially B12, and supporting your body with the right diet and lifestyle strategies.

If you want to know more about how birth control might be affecting your health, book an appointment and let’s take a closer look together.

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Markham, ON
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