Introduction
It is a common scenario: you are eating your "five-a-day", getting to the gym when you can, and yet you still feel inexplicably "off". Perhaps it is a persistent case of bloating after every meal, a lingering brain fog that makes your morning commute feel like walking through treacle, or a sudden flare-up of skin irritation that your usual creams cannot soothe. When these "mystery symptoms" arise, the conversation often turns toward the gut.
We now know that the gastrointestinal tract is far more than a simple processing pipe for food. It is a complex, living ecosystem known as the gut microbiome, home to trillions of microorganisms—bacteria, viruses, and fungi—that play a fundamental role in your immune system, your mood, and your metabolic health. The balance of these "good" and "bad" residents dictates how you feel on a daily basis.
In this article, we will explore the science of the microbiome and provide a practical, evidence-based roadmap on how to increase gut good bacteria. We will discuss the dietary shifts that actually work, the lifestyle factors that provide a foundation for growth, and how to identify when your symptoms might be linked to other systems, such as your thyroid. If you want to see the broader testing options we refer to, our thyroid blood tests collection is a useful place to start.
At Blue Horizon, we believe that health decisions should be made with a clear, broad view of your clinical context. Our approach follows a phased journey: we always recommend consulting your GP first to rule out underlying conditions, followed by a period of structured self-tracking of your symptoms and lifestyle. Only then, if you remain stuck or require a more detailed snapshot of your health, should you consider a private blood test to guide a more productive conversation with your medical professional. If you are new to the service, our how to get a blood test guide explains the process clearly.
Understanding the Gut Microbiome
The term "microbiome" describes the entire collection of microorganisms living in a specific environment. In the human gut, this community is incredibly dense; there are more bacterial cells in your body than there are human cells. For a long time, bacteria were viewed primarily as threats to be eliminated. However, we now understand that "good" bacteria are essential allies.
A healthy gut is generally defined by diversity. A diverse microbiome is like a thriving rainforest—resilient and capable of performing many different functions. These beneficial bacteria assist in breaking down complex carbohydrates (fibre), synthesising essential vitamins like B12 and K, and training your immune system to distinguish between friend and foe. For a broader explanation of why this ecosystem matters, you may also find our guide to what the gut microbiome is helpful.
When this balance is disrupted—a state known as dysbiosis—it can lead to a variety of symptoms. This imbalance might be caused by a course of antibiotics, a period of high stress, or a diet high in ultra-processed foods. Because the gut is connected to the brain via the vagus nerve (often called the gut-brain axis), the effects of dysbiosis are rarely confined to the stomach; they can manifest as irritability, fatigue, and even changes in sleep patterns.
Safety Note: While mild digestive changes are common, if you experience sudden or severe symptoms such as unexplained weight loss, blood in your stool, persistent vomiting, or severe abdominal pain, you must seek urgent medical attention from your GP, A&E, or by calling 999.
The Blue Horizon Method: A Phased Approach
Before jumping into complex protocols or testing, we recommend a calm and structured approach to your gut health.
Step 1: Consult Your GP
Your first port of call should always be your NHS GP. Symptoms like bloating, diarrhoea, or fatigue can overlap with many conditions, including Coeliac disease, Inflammatory Bowel Disease (IBD), or even simple vitamin deficiencies. It is vital to rule out these clinical causes before assuming your microbiome simply needs "rebalancing."
Step 2: Structured Self-Checking
If your GP has ruled out serious pathology but you still do not feel right, start a diary. For at least two weeks, track:
- Symptom timing: Does the bloating happen immediately after eating, or several hours later?
- Stool patterns: Use the Bristol Stool Chart to note consistency.
- Lifestyle factors: Note your sleep quality, stress levels, and exercise frequency.
- Dietary intake: Focus on your fibre intake and the variety of plants you eat.
Step 3: Targeted Action and Testing
Once you have a baseline of your symptoms and have addressed basic lifestyle factors, you may want to look closer. This is where a "snapshot" of your health can be useful. For example, gut health and thyroid function are closely linked; an underactive thyroid can slow down digestion (leading to constipation), while a healthy gut is required to convert thyroid hormones into their active form. If you want to understand the service behind these tests, our About Blue Horizon Blood Tests page gives a good overview.
How to Increase Gut Good Bacteria Through Diet
The most direct way to influence your microbiome is through the fuel you provide. Bacteria thrive on what we cannot digest ourselves.
Focus on Fibre and Prebiotics
Fibre is not just for keeping you "regular"; it is the primary food source for beneficial bacteria. Specifically, you want to focus on "prebiotics." These are types of fibre that pass through the small intestine undigested and ferment in the large intestine, feeding the "good guys."
Key prebiotic foods include:
- Alliums: Onions, garlic, and leeks contain inulin, a favourite of beneficial Bifidobacteria.
- Legumes: Lentils, chickpeas, and beans provide a slow-release fuel source for the gut.
- Whole Grains: Oats and barley contain beta-glucans, which support immune health.
- Vegetables: Asparagus, Jerusalem artichokes, and slightly under-ripe bananas are excellent sources.
Introduce Probiotics
While prebiotics are the "fuel," probiotics are the "passengers"—living microorganisms that, when consumed in adequate amounts, provide a health benefit. Rather than relying solely on supplements, which can sometimes lead to an overgrowth of a single strain, we recommend incorporating fermented foods into your daily routine.
- Live Yogurt: Look for "live and active cultures." Avoid versions with high added sugar, as sugar can feed less desirable bacteria.
- Kefir: A fermented milk drink that often contains a wider variety of bacterial strains than yogurt.
- Sauerkraut and Kimchi: Fermented cabbage dishes that provide both probiotics and fibre.
- Miso and Tempeh: Fermented soy products that are staples in Japanese and Indonesian diets.
The Power of Diversity: "Eat the Rainbow"
One of the most robust findings in gut science is that people who eat more than 30 different types of plants per week have significantly more diverse microbiomes than those who eat fewer than ten. This does not mean 30 different meals; it means counting every nut, seed, herb, spice, fruit, and vegetable. A sprinkle of mixed seeds on your porridge or a handful of fresh coriander in a curry all count toward this goal.
Lifestyle Factors That Support Gut Health
Your gut bacteria are sensitive to your environment. You can have a perfect diet, but if your lifestyle is chaotic, your microbiome may still struggle.
Prioritise Sleep
There is a bidirectional relationship between the gut and sleep. Lack of sleep (fewer than seven hours for most adults) can increase stress hormones, which in turn can alter the permeability of the gut lining and change the composition of your bacteria. Aim for consistent wake-up and wind-down times to keep your "internal clock" and your gut bacteria in sync.
Manage Stress and Cortisol
Chronic stress is a major disruptor of gut health. When you are stressed, your body produces cortisol. High levels of cortisol can slow down digestion and reduce the blood flow to the gut, making it harder for "good" bacteria to thrive.
At Blue Horizon, we include a Cortisol marker in our thyroid testing tiers (Bronze, Silver, Gold, and Platinum) because we recognise that your stress response is inextricably linked to your metabolic and hormonal health. If you want to see the most comprehensive version of that profile, our Thyroid Premium Platinum test page shows the full panel.
Hydration and Movement
Water is essential for the mucosal lining of the gut and for moving fibre through your system. Dehydration can lead to constipation, which allows "bad" bacteria to linger longer in the colon.
Similarly, regular moderate exercise has been shown to increase the production of short-chain fatty acids (SCFAs), which are anti-inflammatory compounds produced by your gut bacteria that help protect the gut lining and boost overall health. If you are interested in the gut-focused side of testing, our Gut Health collection brings those options together in one place.
The Connection Between Gut Health and the Thyroid
For many people, "gut issues" are actually symptoms of a different system being out of balance. The thyroid gland, a small butterfly-shaped gland in your neck, acts as the master controller of your metabolism.
If your thyroid is sluggish (hypothyroidism), every process in your body slows down, including your gut transit time. This can lead to constipation and an overgrowth of bacteria. Conversely, we need a healthy gut to help convert the storage hormone (Thyroxine or T4) into the active hormone (Triiodothyronine or T3) that our cells can actually use.
If you have improved your diet and lifestyle but still suffer from bloating, fatigue, and weight changes, it may be worth investigating your thyroid function to see if it is contributing to your symptoms. For more detail on the markers and how they fit together, our guide to interpreting thyroid test results is a useful next read.
Blue Horizon Thyroid Testing Tiers
We offer a range of premium thyroid tests that allow you to see the "bigger picture." Unlike standard tests that might only look at one marker, our panels include cofactors like Magnesium and Cortisol.
- Bronze Thyroid: This is our focused starting point. it includes the base thyroid markers: TSH (Thyroid Stimulating Hormone—the brain's signal to the thyroid), Free T4 (the storage hormone), and Free T3 (the active hormone). Crucially, it also includes Magnesium (essential for muscle relaxation in the gut) and Cortisol (the stress marker).
- Silver Thyroid: Everything in the Bronze tier, plus Thyroid Peroxidase Antibodies (TPOAb) and Thyroglobulin Antibodies (TgAb). These markers help identify if an autoimmune process is affecting your thyroid, which is often linked to gut health.
- Gold Thyroid: Our most popular comprehensive snapshot. It includes everything in Silver, plus a check of your vitamins and minerals: Ferritin (iron stores), Folate, Active Vitamin B12, Vitamin D, and CRP (C-Reactive Protein—a marker of systemic inflammation).
- Platinum Thyroid: This is the most extensive profile available. It adds Reverse T3, HbA1c (a long-term blood sugar marker), and a full Iron Panel. This requires a professional blood draw due to the complexity of the markers. If you want to compare the options side by side, the thyroid blood tests collection is the best place to review them.
Practicalities of Testing
For all our thyroid tests, we generally recommend a 9am sample. This ensures consistency, as hormone levels naturally fluctuate throughout the day. Bronze, Silver, and Gold tiers can be completed at home via a fingerprick or a Tasso device, or at a clinic. Platinum always requires a professional nurse or clinic visit.
Once you receive your results, they are presented in a clear report. However, these results are not a diagnosis. They are designed to be taken to your GP or endocrinologist to help you have a much more informed and targeted conversation about your health journey. If you want a deeper look at how the service is set up, our FAQs page answers common questions about ordering and results.
Practical Scenarios: When to Look Deeper
To help you decide if you need to take further steps, consider these common real-world situations:
- Scenario A: You have increased your fibre and started eating fermented foods, but you still feel exhausted and your hair is thinning. In this case, checking a broader panel like our Gold Thyroid may reveal that your Vitamin D or B12 levels are low, or that your thyroid is not functioning optimally despite your dietary efforts.
- Scenario B: You are under immense pressure at work and your digestion has become erratic, with frequent bouts of "nervous stomach." A test that includes Cortisol, like our Bronze Thyroid, might confirm that your stress response is impacting your gut, suggesting that meditation or lifestyle changes are as important as your diet.
- Scenario C: You have been told by your GP that your TSH is "normal," but you still suffer from chronic constipation and brain fog. A more detailed tier that includes Free T3 and Reverse T3 can provide a more nuanced view of how your body is actually using thyroid hormone, which you can then discuss with a specialist.
How to Maintain Your Progress
Improving your gut health is not a "quick fix" or a 30-day detox; it is a long-term commitment to your internal ecosystem.
- Consistency over Perfection: It is better to eat 20–25 plants every week consistently than to eat 30 for one week and then return to ultra-processed foods the next.
- Be Cautious with Supplements: While probiotics in pill form can be helpful for some, they should not replace a diverse diet. Always speak to a healthcare professional before starting new supplements, especially if you have a medical condition or are pregnant.
- Listen to Your Body: Use your diary to notice patterns. If a certain "healthy" food like onions consistently causes severe discomfort, it is okay to reduce it while you work on other areas of your gut health.
- Work with Professionals: If you are making significant changes to your diet, or if you have a history of eating disorders or complex medical needs, seek the support of a registered dietitian or your GP.
Summary
Increasing your "good" gut bacteria is a journey of nourishment and patience. By focusing on a wide variety of plant foods, incorporating fermented options, and supporting your body with adequate sleep and stress management, you can create an environment where your microbiome—and you—can thrive.
Remember the Blue Horizon Method: rule out serious issues with your GP first, track your own patterns, and then use targeted testing if you need to see the bigger picture. Whether it is checking your cortisol levels or ensuring your thyroid is supporting your metabolism, having the right data can turn a frustrating "mystery" into a manageable plan. If you want to compare the broader approach to gut testing, the gut microbiome test page is a good next step.
For more information on our range of tests, you can view the current thyroid testing page.
FAQ
How long does it take to increase good gut bacteria?
While your microbiome can begin to shift within just a few days of a major dietary change, it generally takes several weeks to months of consistent habits to see a significant and stable change in your gut health and symptoms. Resilience is built over time through repeated exposure to diverse plant foods and healthy lifestyle choices.
Can antibiotics permanently destroy my gut bacteria?
Antibiotics are life-saving medications, but they do act like a "forest fire" in the gut, clearing out both good and bad bacteria. While a single course rarely causes permanent damage, frequent use can reduce diversity. You can support recovery by focusing on prebiotic and fermented foods during and after your course of treatment. For more background on how gut bacteria support the body, our guide to what gut bacteria do is worth reading.
Is it better to take a probiotic supplement or eat fermented foods?
For most people, fermented foods (like kefir, kimchi, and live yogurt) are superior because they provide a wider variety of bacterial strains along with the nutrients in the food itself. Supplements can be useful for specific clinical conditions, but they should be used under professional guidance to avoid imbalances.
Why does Blue Horizon include Cortisol in thyroid tests?
We include Cortisol because the "gut-brain-thyroid" connection is inseparable. Stress (Cortisol) directly impacts both your thyroid function and your gut health. By measuring Cortisol alongside thyroid markers, we help you and your GP see if stress is a primary driver behind your digestive or metabolic symptoms.
