Gut health has become an increasingly prominent topic in nutrition and wellness. An optimally functioning gut supports digestion, immunity, metabolism, and even cognitive and emotional health. However, alongside this surge in awareness has come a parallel rise in the marketing of supplements, particularly probiotics and prebiotics, often promoted as essential tools for optimising gut function.
While supplements can serve a purpose in specific clinical contexts, they are not always required. For the majority of individuals, they are not the most effective first step. Instead, a diverse and balanced diet, rich in whole foods, remains the most evidence-based and sustainable way to support gut health.
The gut microbiome
The gut microbiome refers to the trillions of microorganisms residing in the digestive tract. They include primarily bacteria, but also fungi, protozoans, and even viruses. These microbes play a critical role in a number of physiological functions, including:
- Digesting dietary fibre and producing short-chain fatty acids (SCFAs)
- Modulating the immune system
- Protecting against pathogenic organisms
- Synthesising certain vitamins, such as B12 and K2
Microbial diversity is considered a marker of gut health. Diet plays a central role in shaping this diversity, making nutrition a powerful tool for modulating gut health.
Supplements: When are they useful?
Probiotics
The global probiotics market is expected to surpass £60 billion by 2030. It is important to note that their impact depends on various factors, including:
- The specific strain(s) used
- The viability of those strains when ingested
- The individual’s baseline microbiome composition
- The duration and context of use (e.g., post-antibiotic treatment or IBS management)
While probiotics can be beneficial under the guidance of a registered health professional, they are not essential for most individuals seeking to maintain or improve general gut health. They can be useful as part of a holistic management plan for individuals with symptoms related to microbiome dysbiosis.
Multivitamins and specific vitamins and minerals
A number of different vitamins and minerals play a role in supporting gut health. Multivitamins or specific vitamins/ minerals can be a helpful tool for individuals with reduced dietary intake, increased nutrient needs, or diagnosed deficiencies. Examples include dietary deficiency, during pregnancy, recovery from illness, or in cases of restricted diets. They offer a convenient way to bridge nutritional gaps when whole food sources are limited or impractical. However, for most, a varied and balanced diet rich in a wide variety of plant foods, whole grains, proteins, and healthy fats remains the gold standard. Whole foods provide not only essential vitamins and minerals but also fibre, antioxidants, and synergistic compounds that supplements can’t fully replicate.
That said, one notable exception in the UK is vitamin D. Due to limited sunlight exposure, especially during autumn and winter, it’s recommended that everyone in the UK take a daily 10 mcg vitamin D supplement to support bone health, immune function, and overall wellbeing. Even with a nutritious diet, it’s difficult to obtain sufficient vitamin D from food alone, making supplementation a practical and evidence-based choice for most people living in the UK.
Food first: The power of whole foods
Whole foods contain a complex matrix of micronutrients, fibre, and bioactive compounds that support the microbiome far more holistically than isolated supplements. They provide the substrates needed for beneficial bacteria to thrive and promote the production of short chain fatty acids (SCFAs), which are key for maintaining the health of the gut lining.
Key food components to consider include:
Prebiotics
Defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP) as:
“A substrate that is selectively utilised by host microorganisms conferring a health benefit.”
Prebiotics are non-digestible fibres that stimulate the growth of beneficial gut bacteria. Common dietary sources include:
- Chicory root
- Jerusalem artichokes
- Onion
- Garlic
- Legumes
- Asparagus
Probiotics
Defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP) as:
“Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”
While probiotic supplements must meet stringent criteria to be effective, some foods naturally contain live, beneficial bacteria. However, not all fermented foods qualify as probiotics.
Fermented foods
Defined by ISAPP as:
“Foods made through desired microbial growth and enzymatic conversions of food components.”
Examples include:
- Live yoghurt with active cultures
- Kefir
- Sauerkraut
- Kimchi
- Tempeh
- Miso
- Kombucha
Though many fermented foods are not formally classified as probiotics, regular inclusion in the diet has been shown to enhance microbial diversity and modulate immune responses.
Microbiome diversity: The importance of colour
A simple but powerful recommendation for supporting gut health is to ‘eat the rainbow.’ Colourful plant foods provide polyphenols and antioxidants, which act as both fuel and signalling molecules for different microbial species.
Each colour is associated with distinct health-promoting compounds:
- Red and purple (e.g., berries, red cabbage, beetroot): Rich in anthocyanins, which support anti-inflammatory bacterial strains.
- Orange and yellow (e.g., carrots, sweet potatoes, squash): Contain carotenoids, linked to immune regulation and SCFA production.
- Green (e.g., broccoli, kale, spinach): Provide chlorophyll, folate, and glucosinolates with detoxifying and anti-inflammatory effects.
- White and brown (e.g., garlic, onions, mushrooms, oats): High in prebiotic fibres and polyphenols that promote Bifidobacteria and Lactobacilli.
Consuming a wide variety of plant foods, ideally 30 or more per week, has been associated with significantly greater microbial diversity, according to findings from the American Gut Project.
Practical ways to support gut health
For most individuals, the following strategies can meaningfully enhance gut function and microbial diversity:
- Prioritise plant diversity: Aim for a range of vegetables, fruits, legumes, whole grains, nuts, and seeds each week. The variety is more impactful than quantity.
- Increase fibre gradually: Build up to 25–30g of fibre per day from both soluble (e.g., oats, lentils) and insoluble (e.g., whole wheat, bran) sources to avoid bloating or discomfort.
- Include fermented foods regularly: Incorporate small daily portions of live yoghurt, kefir, or traditionally fermented vegetables.
- Limit ultra-processed foods: Highly processed products tend to be low in fibre and high in additives, emulsifiers, and sugars, all of which may negatively impact the gut lining and microbiota composition.
- Hydrate and manage stress: Good hydration supports digestion and nutrient absorption, while chronic stress can alter microbial balance and increase gut permeability.
When supplements may be appropriate
In certain situations, supplements can be helpful, particularly when guided by a qualified health practitioner. These scenarios may include:
- Following antibiotic use
- Diagnosed gastrointestinal conditions (e.g., IBS, IBD, SIBO)
- Specific immune or skin disorders
- Travel-related gut disturbances
In these instances, strain specificity and dose matter. Always choose clinically validated strains backed by research and seek advice before starting any new product.
Final thoughts
Supplements have a place in targeted gut health strategies. They are not a panacea, nor are they necessary for everyone. For most individuals, a nutrient-dense, fibre-rich, and colourful whole food diet remains the most effective and evidence-based way to support long-term gut health. By embracing food-first principles, we not only nourish ourselves but also create the right conditions for a thriving and diverse microbial community.
Disclaimer
This post is not a substitute for professional medical advice, diagnosis or treatment. For individual nutrition or medical advice, please consult individually with a registered dietitian, registered nutritionist or registered medical practitioner.
Author: Dr Rebecca Healey, MBBS, MSc, RNutr, mBANT, DOccMed
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