Perspectives · Individualised medicine

N-of-1 trials and citizen science

How do you know that the expensive supplement you have purchased, or the new diet, is actually helping your health?

By Dr Cindy de Villiers · Originally published 2019 · Reviewed and lightly edited July 2026 · General information, not medical advice

Seen the latest on mushroom extracts or fish collagen? Big promises, big prices, all “scientifically validated.” I won't even mention the diet wars. How do you know if an intervention that is “backed by the latest research” will actually work for you? This is something I have been pondering from both a personal and a clinical perspective. Saturated fat may clog your arteries, but dairy may prevent certain cancers in some people. What is going on in science? And what is N-of-1 citizen science tracking anyway?

The promise of science

Science. The word itself evokes the promise of truth, of researchers pursuing effective treatments for the scourges of life. Science has been defined as “a system of knowledge covering general truths … as obtained and tested through scientific method,” while the scientific method is the “pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses.”

Ah, the promise of science and the secrets of life. Where else would a bright-eyed girl look but to medical school? How wonderful was the promise of science, and the guidance of learned teachers into the world of molecules and life — science and medicine that had respectively proven the world was round and that consumption was caused by a microbe named Mycobacterium tuberculosis.

How scientific discoveries are announced

After being peer-reviewed by a panel of scientists, most research is published in academic journals. Once accepted, a paper often forms the basis of further hypotheses and argument. Journals are then rated for relevance — the impact factor — based on how often their papers are cited by others. The published literature provides a vast body of information, which I search almost every day when trying to answer a question such as: do mushroom extracts improve brain health?

So why do you need to be your own researcher?

Let's look at a number of considerations, starting with the process of publishing medical research.

Published research

I would posit that most scientists are of good intent. They are generally employed by academic institutions, such as universities, or by industrial producers, with the intention of researching particular hypotheses or producing cures. University researchers are usually required to publish a certain number of papers every year. Universities may also be partnered with industry and receive considerable funding from those organisations. The institutions can then pay their researchers, publish more papers, gain further academic credence, and enrol more students. Sweet — maybe. And many medical-journal publishers are for-profit businesses that charge a considerable sum to read each paper, limiting access to researchers inside academic institutions.

The next consideration is bias. To suggest that bias is fully excluded from scientific methodology would be naïve. Even researchers acknowledge that “our talent for jumping to conclusions makes it all too easy to find false patterns in randomness, to ignore alternative explanations … to ceaselessly lead ourselves astray without realising it.” We all need to admit that there is bias in science, and in ourselves.

Then there is funding and kudos: direct funding by organisations with a financial interest in the outcome, and the personal cost to those scientists brave enough to go against the prevailing understanding — some would say dogma. Think of Galileo; and yes, it still happens today, albeit in a different guise. The editor of The Lancet, one of the oldest and most prestigious medical journals, has written: “The case against science is straightforward: much of the scientific literature, perhaps half, may simply be untrue. Afflicted by studies with small sample sizes, tiny effects, invalid exploratory analyses, and flagrant conflicts of interest … science has taken a turn towards darkness.”

The reading

It has been said that if you read two clinical papers per day, by the end of the year you will be years behind in your reading. Most doctors also have limited training in interpreting the statistics; trial teams often have their own statistician analysing a vast amount of data, and it is not always practical to review that analysis thoroughly. So doctors generally take advice from guidelines and organised education — which are themselves compiled by professional organisations consisting of doctors and industry, relying in turn on specialists who cannot personally go through all the material in even their own field. While the days of the pharmaceutical rep are all but over, pharmaceutical and supplement companies still spend heavily on marketing through value-added online services.

Types of studies

Without going into too much detail: clinical studies look at the effect of an intervention such as a pharmaceutical, while epidemiological studies research patterns in populations. Epidemiological studies compare lifestyle, exposures, and diet against the risk of disease — for example, does eating vegetables prevent memory loss? There are numerous hurdles. They are often based on questionnaires (participants need to be truthful and have good memories), and the results can mislead: people who eat more vegetables also tend to exercise more, so is it the exercise, not the vegetables, protecting memory? Researchers adjust for these confounders, but what about the confounders we don't yet know about?

A clinical study is easily applied to something foreign to the body — Exenatide for diabetes, say. Whether magnesium is useful for sleep is less clear-cut. Why?

Applicability

With both types of study, groups rather than individuals are studied. Taking the Exenatide example, it has been calculated that four people need to take the drug for one person to benefit. This is the Number Needed to Treat. So how do you know whether you are one of the three who do not respond? And how do you know that a change you notice is due to the intervention, rather than some other effect — you started going to bed earlier as well as taking the magnesium?

Applying this methodology to well-being and chronic conditions also ignores the fact that humans are not genetically identical and present with a myriad of environmental factors affecting how their genes are expressed. Epidemiological studies in particular need to be interpreted with care, so as not to “result in more harm than good.” It is not unreasonable to suggest that spinning a wheel would sometimes produce an intervention for the individual as useful as one drawn from a study. As medicine moves from treating mainly acute illness and injury towards “unexplained” chronic disease and unwellness, an alternative model of inquiry is needed.

Taking back science, and democratising health

If the science of health and well-being is so conflicted, how does an individual and their practitioner move forward? N-of-1 trials — in which there is only one person being studied — are gaining interest as possibly “the ultimate strategy for individualising medicine.”

What if this were taken further? Consider a method in which the individual is both the scientist and the subject. (My apologies to all researchers now shuddering at the heresy.) My countering argument is this: if we are all biased, and if science has taken a “turn towards darkness,” then part of the way forward is citizen science.

Technology might give an individual access to clinical experience — standing on the shoulders of the giants who have gone before — alongside their own data. Specific outcome measures are now trackable with available technology and can be analysed against interventions the person chooses, based on known physiological pathways, clinical experience, clinical trials, and population studies. This is already being undertaken; recent examples include work at Swarthmore College and the Salk Institute's circadian research.

Why track your own health data?

Without discounting the placebo effect, and as Matthew Walker, author of Why We Sleep, put it: “One practice known to convert a healthy new habit into a permanent way of life is exposure to your own data.”

While almost any health metric is trackable — weight, resting heart rate, fasting blood glucose, mood, even what level of Sudoku you can finish — one overall indicator, heart rate variability (HRV), is now reasonably accessible and accurate. HRV can potentially be used to assess nutritional and lifestyle influences on health, and it not only correlates with ageing but is studied as a marker of health and well-being. That is exciting for this nerdy practitioner.

I am looking to reclaim the promise of science and the exploration of life. Medicine is changing, and new tools are beginning to bypass the roadblocks that separate people from their own data and the outcomes they seek. Used thoughtfully, and in partnership with a clinician who knows you, that shift is a genuine opportunity to answer the only question that ever really mattered — not “does this work on average,” but “does this work for me?”

A note on reading this in 2026: the argument stands, but self-tracking has moved on considerably since this was written, and no device or metric replaces an assessment by a clinician who knows your history. The specific tools mentioned are illustrative, not recommendations.