Why Everyone's Gut Microbiome Is Different: The Science of Personalised Nutrition

Why Everyone’s Gut Microbiome Is Different: The Science of Personalised Nutrition

Why microbial communities vary between people, what gut testing can and cannot reveal, and how personalised nutrition builds on healthy eating fundamentals.

Two people can eat the same meal yet experience different glucose, triglyceride, appetite or digestive responses. That does not mean nutrition principles no longer matter. It means a response is shaped by the food, the person and the circumstances—including health, sleep, activity, medications and, potentially, the gut microbiome.

Microbiome science is helping researchers explore this variation. It is also revealing why there is no single ‘perfect’ microbial profile and why one stool test cannot yet prescribe an ideal diet.

Key Takeaways

· The gut microbiota differs markedly between people, including healthy people, and each person’s community can remain recognisably their own over time.

· Early life, habitual diet, geography, household, age, health, medicines and other exposures all contribute; none determines the microbiome alone.

· Microbial diversity can be useful in research, but a higher diversity score is not a universal measure of better health.

· Stool samples provide valuable information, but they do not capture every microbial community or activity along the digestive tract.

· Personalised nutrition is promising, yet the microbiome is only one input alongside clinical history, metabolic health, preferences and lifestyle.

· For most people, varied whole foods, fibre-rich plants, regular movement and sustainable habits remain a sound foundation.

Microbiota and Microbiome: What Is the Difference?

Gut microbiota describes the microorganisms living in the digestive tract, including bacteria, archaea, fungi and viruses. Gut microbiome is often used more broadly for those organisms, their genes and the environment in which they interact. In everyday writing, the terms are sometimes used interchangeably.

These communities help transform food components that human enzymes cannot fully digest. They can produce short-chain fatty acids and modify bile acids and other compounds. Their effects depend on the organism, its strain, its neighbours, the available food and the host—so labels such as ‘good’ and ‘bad’ bacteria are often too simple.

Why Is Everyone’s Gut Microbiome Different?

Early life

Microbial communities develop rapidly in infancy. Birth circumstances, feeding, household contacts, environment, antibiotics and many other exposures can influence this early development. These are associations and influences, not a fixed destiny for lifelong health.

Diet and food culture

Habitual diet helps determine which substrates reach the large intestine. Fibres, resistant starches and other compounds differ across vegetables, fruit, legumes, whole grains, nuts and seeds. Food traditions, availability, preparation methods and eating patterns therefore matter alongside nutrient totals.

Explore Food Diversity Explained, Why Dietary Diversity Matters More Than Superfoods and The Food Matrix Explained.

Place, people and lifestyle

Geography, household members, pets, travel, physical activity, sleep, stress and social routines can all coincide with microbial differences. Because these factors overlap, a study can identify an association without proving that one factor caused it.

Health, age and medicines

Illness and ageing can coincide with changes in diet, mobility, physiology and medication use. Antibiotics can substantially disturb gut communities, although recovery differs between people and treatments. Antibiotics should still be taken when clinically needed and exactly as prescribed.

Unique Does Not Mean Random

The Human Microbiome Project found striking differences between healthy individuals, while samples from the same person were generally more similar over time than samples from different people. The microbiome is therefore both personal and dynamic: short-term fluctuations can occur within an ecosystem that remains recognisably individual.

Different species can also perform overlapping functions. Two people may have different microbial names on a report yet share some metabolic capabilities. Researchers increasingly examine genes, pathways and metabolites as well as a list of organisms.

Why ‘More Diversity’ Is Not a Complete Health Score

Within-sample diversity—often called alpha diversity—counts and compares the organisms detected in a sample. Lower diversity has been associated with some conditions, but the meaning depends on the body site, age, population, health context and method used.

A single diversity number cannot show which organisms are present, what they are doing or whether their activities suit that person. Some healthy microbial communities are less diverse, and greater diversity is not automatically beneficial. Function, stability and clinical context matter.

For a practical discussion, read Microbiome Diversity Explained.

How Scientists Study the Gut Microbiome

· 16S rRNA sequencing estimates bacterial and archaeal groups but usually offers limited species- and strain-level resolution.

· Shotgun metagenomic sequencing captures a wider set of microbial genes and can estimate functional potential, although potential is not the same as activity.

· Metatranscriptomics, proteomics and metabolomics investigate gene expression, proteins and metabolites.

· Repeated samples help distinguish a lasting pattern from a short-lived fluctuation.

· Diet records, clinical measures and medication data help researchers interpret microbial findings.

Most large human studies use stool because it is practical to collect. Stool mainly reflects organisms in the intestinal contents and differs from microbes attached to the gut lining or living elsewhere along the tract. Collection, storage, sequencing and analysis methods can also change the result.

Why People Can Respond Differently to the Same Meal

In the PREDICT 1 study, adults showed substantial variation in blood glucose, triglyceride and insulin responses to identical meals. Meal composition mattered, but person-specific factors also contributed. The microbiome explained part of the variation in some outcomes—not all of it.

Timing, previous meals, sleep, activity, body composition, insulin sensitivity, genetics and measurement error can all influence a post-meal response. It is therefore inaccurate to attribute every individual difference to gut microbes.

What Personalised Nutrition Can—and Cannot—Do

Personalised nutrition aims to tailor advice using information such as health goals, clinical history, dietary intake, biomarkers, metabolism, genetics, lifestyle, preferences and sometimes the microbiome. Machine-learning models can combine many inputs and identify patterns that simpler approaches may miss.

The challenge is translation. A model can perform well in the population that trained it yet work less well elsewhere. Researchers must test whether recommendations are reproducible, practical, safe and better than established care over meaningful periods—not merely whether an algorithm can fit existing data.

Personalisation should refine sound nutrition principles, not replace them. A useful plan must still be nutritionally adequate, culturally appropriate, affordable and sustainable.

Should You Buy a Commercial Microbiome Test?

A consumer test may describe organisms detected in a stool sample, but it cannot currently provide a complete map of the digestive tract or diagnose most gut conditions. Results can vary with the sample, laboratory method, reference database and timing.

An international expert consensus published in 2025 concluded that evidence for the clinical usefulness of routine microbiome testing remains scarce. Be cautious when a report claims to identify a perfect diet, promises to ‘rebalance’ the microbiome, diagnoses disease or recommends stopping treatment.

Persistent pain, bleeding, unexplained weight loss, fever, anaemia, ongoing diarrhoea or major changes in bowel habits warrant medical assessment rather than a consumer microbiome report. A GP or Accredited Practising Dietitian can help interpret symptoms and dietary needs.

A Practical, Evidence-Informed Approach

1. Build variety across the week with vegetables, fruit, legumes, whole grains, nuts and seeds as suitable for you.

2. Increase fibre gradually and drink enough fluid; a sudden large increase can worsen symptoms for some people.

3. Choose a pattern you can maintain rather than chasing one ‘microbiome superfood’.

4. Include fermented foods if enjoyed and tolerated, but remember that not every fermented food contains live microbes at the point of eating.

5. Move regularly, prioritise sleep and take prescribed medicines as directed.

6. Seek individual advice for allergies, coeliac disease, inflammatory bowel disease, IBS, pregnancy or another medical condition.

See Why Whole Foods Feed Both Your Gut and Brain, Why Gut Health Is About More Than Digestion and The Complete Guide to Gut Biotics.

Where Bone Broth Fits

Bone broth is not automatically a probiotic or prebiotic, and it is not a treatment for an unhealthy microbiome. Its practical role is culinary: it can provide a savoury base for soups, stews, legumes, whole grains and vegetable-rich meals. Check the nutrition information panel because protein and sodium vary by product and serving.

· Shop Broth & Co bone broth collection

· Shop Broth & Co Wellness Nutrition

Frequently Asked Questions

Is there one ideal gut microbiome?

No universal microbial recipe has been established. Healthy people can have very different communities, and function may matter as much as the organisms detected.