When a dietary change does not work out, it is tempting to blame the advice itself. Yet the change may also be a part of the problem. Increasing fibre intake can be beneficial for health, but suddenly adding large amounts of beans, whole grains, and seeds may cause bloating, gas, or abdominal discomfort. Many fibres are fermented by gut bacteria, producing gas as a by-product. The effect depends on the type and quantity of fibre, the foods eaten alongside it and individual digestive characteristics. A gradual increase may therefore be easier to tolerate than a complete dietary overhaul overnight.
However, the speed and scale of a dietary change are only a part of the explanation. Even when two people eat the same food in similar quantities, their bodies do not necessarily process it in exactly the same way.
One reason lies in the gut microbiome, the community of microorganisms living in our digestive tract. These microbes help break down certain components of food that our own digestive enzymes cannot fully process, including some types of fibre. Different people have different microbial communities, influenced by factors such as diet, medication and environment. As a result, the same meal can provide different microbes with different opportunities to produce substances that affect digestion and other bodily processes. The microbiome can also change in response to diet, although this does not mean that every unpleasant reaction is caused by gut bacteria, or that there is one ideal microbiome for everyone.
The study provides a useful reminder that people can differ biologically even when those differences are not immediately visible. However, there is an important distinction: finding a genetic association with a metabolic trait does not automatically tell us how a person should eat.
Beyond the gut, our bodies differ in how they absorb, transport, and use nutrients. Genetics contribute to these differences. Genes provide instructions for making proteins, including enzymes that help the body transform molecules from one form into another. Variations in these instructions can influence how efficiently particular metabolic processes work and the concentrations of certain substances in the blood. In other words, metabolism is not a single, identical process shared by everyone.
This was explored in a large study published in Nature in 2026. Led by researchers affiliated with the University of Tartu in Estonia, the study used data from the Estonian Biobank and UK Biobank, to investigate how genetic differences relate to hundreds of metabolic traits measured in blood. These included different types of fats and cholesterol-related particles, amino acids, and other small molecules involved in the body’s functions.
The study provides a useful reminder that people can differ biologically even when those differences are not immediately visible. However, there is an important distinction: finding a genetic association with a metabolic trait does not automatically tell us how a person should eat. Nor did this study directly test how different people respond to particular foods or diets. Instead, it helps researchers understand the genetic influences on metabolism, providing a foundation for further research into why nutritional responses vary.
Genetics and gut microbes are not the whole story, either. The quantity of food, the composition of a meal, physical activity, sleep, medication, and existing health conditions can all influence how the body responds. Someone who feels uncomfortable after introducing more whole foods may not be reacting negatively to healthy eating itself. The problem could be the amount, the particular foods chosen, the speed of the change, or a combination of factors. Equally, a person’s immediate digestive comfort does not necessarily reveal whether a diet is beneficial for their long-term health.
Does this mean universal dietary recommendations are inadequate? Not necessarily. Recommendations to eat a varied diet, consume sufficient fibre, and limit excessive intake of certain nutrients are based on evidence about health across populations. They provide a useful starting point, even if they cannot predict every individual’s experience. A recommendation can be beneficial on average without producing identical effects in every person.
The challenge is distinguishing between general principles supported by evidence and the assumption that one specific eating pattern must work equally well for everyone.
Social media often turns nutrition into a collection of rules, encouraging people to maximise a nutrient or eliminate a food without considering the wider context. But health is not a competition to consume the most fibre or protein, nor does feeling different from someone else mean that something is wrong with your body.
Perhaps the most useful approach is to treat dietary advice as a starting point rather than a rigid formula. Make changes gradually, pay attention to how you feel, and consider the overall quality of your diet rather than judging individual foods in isolation. Persistent or severe symptoms deserve appropriate medical advice rather than simply being attributed to adaptation. Nutrition science can offer valuable general guidance while recognising that individual bodies are not identical. Eating well is about understanding how to apply sound principles in ways that support health in real life.
This article was written by Emma Nahkor as part of the Local Journalism Initiative.
