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In home microbiome tests won't say shit about your gut health

With the recent advances, and subsequent price drops, in the technologies used to sequence gut bacteria, tests originally designed for laboratory investigations are increasingly marketed to the general public. Admittedly, it was a no-brainer for many tech start-ups to market ‘in home microbiome testing’ to the public, given the enthusiasm for the gut microbiome in both the scientific and lay community.

In home microbiome testing is increasingly offered by a number of tech start-ups, including uBiome and Atlas. Despite some unique claims of ‘patented precision sequencing’, most tests follow a stock standard format claiming to provide actionable results about your gut health, which can help with the diagnosis and management of certain diseases. But the question on the minds of many is, are these claims truly warranted and are these tests worth the considerable financial outlay?

Let's begin by understanding these tests...

With most of the commercially available products, people receive a kit in the mail, in which various faecal samples and swabs are collected. These are then returned to the company, where complex genomic analysis is performed to estimate the relative abundance of specific gut bacteria. A report is then produced and return to the customer. In many cases, companies also accompany this rather static information with links to certain diseases, which even include diseases outside of the gastrointestinal tract such as cardiovascular disease and Parkinson’s disease. Other companies will also include dietary recommendations and even specific ‘microbiome-directed dietary plans’.

It is this aspect of these tests that make scientists particularly concerned, with the enthusiasm for these tests extending far beyond what science currently tells us. It is certainly true that we are discovering more about the microbiome and its role in disease, at a rate that feels exponential! However, given our inability to truly manipulate the microbiome, much of the current literature about the microbiome and disease risk remains correlative at best.

This means that our ability to draw causative conclusions regarding an individual’s microbiome and their risk of disease is extremely premature.

This leap between correlation and causation is something that has been somewhat brushed over by many start-ups offering microbiome testing to the general public. Careful study of company websites reveals an excessive use of vague terminology such as ‘may’ and ‘could’, demonstrating that there just is not enough evidence to entirely support the claims many of these tests are making. This also highlights an important ethical dilemma, which once again has not been subject to the level of scrutiny of other ‘disease predictors’ such as personalised genetic tests.

Consequences of consumer misinterpretation… a cause for concern

Platforms such as AncestryDNA and 23andMe provide genetic testing services to the public, underpinned by claims of personalised risk prediction and disease susceptibility information. Recently, 23andMe was ordered to immediately cease all marketing, with the FDA stating the test is not analytically or clinically validated. Regulatory agencies feared that overstated results and inadequate quality control measures could result in unnecessary actions by their customers in a bid to prevent certain diseases. This was a devastating blow for 23andMe, however it highlights that even in a field underpinned by a solid evidence base, the risks of a customer misinterpreting their results is simply too high. In the case of microbiome testing in which similar claims are being made, the consequences have not been adequately appreciated and the moral obligation to provide accurate information appears to have been overrun by the provision of overinflated results.

Professor Robert Knight, a microbiome research expert and cofounder of the American Gut project (University of California, San Diego), says that what people can realistically expect to learn from these new commercial tests is more along the lines of a snapshot of how a person’s microbiome compares to others, and the presence of specific gut infections.

Many microbiome tests provide personalised diet plans tailored to your gut bacteria, but in reality, a diet rich in fruit and vegetables is the simplest way to improve gut health.

Another key downfall for many of these tests is their lacking appreciation for the heterogeneity in the microbiome, both between individuals and within individuals. The microbiome is extremely malleable and will change in response small dietary changes and lifestyle factors. With a single, once-off test, the influence of these factors is not properly incorporated or adjusted for, producing inaccurate results. Some companies such as Thryve, do offer monthly microbiome testing subscriptions in which machine learning provides an overview of the dynamic changes occurring in a person’s gut. Although this is a step in the right direction, this approach fails to address the fact that there is still a lot we do not know about the microbiome. In fact, the ‘ideal’ microbiome still remains elusive with many seemingly healthy people displaying vast differences their microbiome composition.

This has the distinct possibility to encourage people to adopt numerous approaches to ‘improve’ their microbiome, despite there being no reason to do so.

The consequences of microbiome testing are where the true problems lie, with reports of some individuals taking drastic measures to improve their microbiome. Of particular concern is a new trend for in-home faecal transplants, in which ‘healthy’ stool is used to transplant ‘good’ bacteria into a recipient’s bowel. Although faecal transplantation is an effective treatment for some gut infections, it must be performed by a highly specialised physician. DIY faecal transplantation is regrettably an increasingly popular trend, with over 4000 ‘how-to’ videos on YouTube. The core issue with this approach is that it is inherently dangerous, with risks of bowel injury and disease transmission. However, it once again raises the question of what is the ‘ideal microbiome’, with people often selecting friends and family members as donors, without any information about their microbiome.

Personalised dieting for your gut bacteria

Although seemingly less dangerous, many commercially available microbiome test results are also accompanied by a personalised diet plan, based on the unique composition of a person’s gut bacteria. Many of these plans come equipped with probiotic formulations and prebiotic approaches in a bid to enhance the composition of a person’s microbiome and mitigate disease risk. While these may not have any obvious dangers, they are based on scarce evidence as we still do not know what microbial composition is best to prevent certain diseases. Furthermore, probiotic supplementation in an otherwise healthy person is probably not going to do anything apart from put dollars in the pockets of probiotic companies.

Take home message

These tests were inevitably going to transition from the laboratory to peoples’ homes. In some ways, it is an encouraging move towards engaging the general community with science. However, it appears that the commercial interest of these start-up companies is pushing the capabilities and claims of these tests to a level that is far beyond the science, praying on peoples’ increasing need to have control over their health status and our society’s quest for more personalised health information. At the end of the day, the best and most simple way to promote gut health (which is what all the hype around the microbiome is really about) is to eat a healthy diet, rich in fruits, vegetables and other plant-based foods; and I think we all need to ask ourselves if we really need to pay for a poo test to tell us this.

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