“TOOur bodies are unique, and so is the food you need. This is a fundamental principle of personalized nutrition (PN), as the UK’s leading advocate, health science company Zoe, explains. Since its launch in April 2022, 130,000 people have subscribed to the service, which uses a prick blood test, stool sample and wearable continuous glucose monitor (CGM) to recommend “smarter food” (at one point there was a waiting list of 250,000). Choices for your body.”
Like other companies working in this field, Zoe has all the hallmarks of serious science. Advisors to the US equivalent Levels include many respected scientists, including Robert Lustig, famous for sounding the alarm about the harms of refined carbohydrates such as sugar. Zoe is led by King’s College London scientist Tim Spector, who claims it was “created with world-leading science”.
The problem with the personalized nutrition industry is that it is still a young field of research and there is not yet good enough evidence in this field to believe that we have found valuable new interventions that are more useful than standard recommendations. The Food Standards Agency’s report last year spoke for many experts when it concluded that “the benefits of PN appear somewhat marginal compared to what is currently understood”, although it noted that “glucose monitoring and gut microbiome analysis could become more robust and actionable”. about healthy eating.”
One major problem is that personalization only goes so far and relies heavily on a few key biomarkers. Use the use of CGMs. These allow users to see blood sugar fluctuations, and especially post-meal peaks, in near real time. Zoe’s theory was summarized by Spector: “If you’re experiencing more than one spike in a day, your average glucose level will rise. We know that increases your risk of diabetes and heart disease. So if you can see which foods or meals produce the biggest increases, the idea is to change your diet to make them more likely.” You can edit it to make it flat.
However, most scientists are not convinced that nondiabetic CGM users can glean useful health information from them. “Glucose in a person without diabetes is a very small part of your overall metabolic health, let alone overall health,” says Nicola Guess, an academic dietitian and researcher at the University of Oxford who specializes in dietary prevention and management of type 2 diabetes. “There is a lot of inter-individual variability, and one person may have the same average blood sugar level despite having more and larger peaks than another.” Doctors can accurately diagnose diabetes or pre-diabetes with a standard fasting or HbA1c blood test. On the contrary, Guess says: “Data from CGM have no such diagnostic value”; Zoe also accepts this.
Another problem is that much of the findings of personalized nutrition research are based on analysis of mountains of data collected by users. This can be affected by diet, blood sugar levels, weight, etc. It causes many relationships to emerge between them. But these “cross-sectional” studies can only find associations, not causality. So the existence of an association between larger spikes and higher average blood sugar levels, even in healthy people, tells us nothing about causality. Higher spikes may be the result rather than the cause of an underlying metabolic problem. If that were the case, keeping spikes low would be addressing the signal of the problem, not the cause.
Worse, according to Guess, cross-sectional studies on very large data sets will inevitably produce false positives: associations that are statistically significant but actually random, “like buying an iPhone on Tuesday is associated with Crohn’s risk.”
Given these scientific limitations, Shivani Misra, a diabetes researcher and consultant at Imperial College London, says she sees no evidence for the theory that healthy people should try to flatten their blood sugar curves. He decries what he calls the “glucose-centricity” promoted by CGMs, which he sees as “so one-sidedly focused on one measure of metabolism” when there are “so many other inputs that we are not capturing.” “I think people are considering glucose as a marker because we have the technology to measure it,” Guess says. Personalized nutrition often starts with what we can measure, not what is most important to our health.
TThe usefulness of stool analysis is also controversial. Again, the basic premise behind the test is reasonable. Even James Kinross, who studies colorectal surgery at Imperial College London, acknowledges that “the microbiome is highly personalized and is probably the most important determinant of our response to different disease risks or different medications.” But like many other experts, he believes we don’t yet know enough about what a healthy microbiome looks like. The best advice for nourishing a healthy gut microbiome is to eat plenty of unprocessed foods, especially fibrous plants, and minimize intake of broad-spectrum antibiotics.
Most importantly, there is no such thing as good and bad bacteria, period. A bacterium may have a good effect on one person and a bad effect on another. Take your example Escherichia coli, most of which are found in the intestine. This is a genre with a lot of variation. Jacques Ravel, professor of microbiology and immunology at the University of Maryland, explains: “There are some. to parcel these will give you massive diarrhea, and some of them are very important for your health.” So a test for this has no clinical validity, meaning “there’s absolutely no clear way to tell how this maps to health or unhealthy.”
Moreover, Ravel published an article detailing several studies that questioned the accuracy of stool testing laboratories; some of these could not reliably identify bacteria in the gut; In a US study, some laboratories gave different results for the same sample.
“My view is that Zoe personalizes things that don’t matter,” Guess says. “The things that are killing people in the UK and around the world are LDL cholesterol and blood pressure.” It states data that Zoe did not measure.
The key hurdle to personalized nutrition is that in the scientific health world, you can either provide cutting-edge research or provide well-founded advice, but it’s hard to do both. Companies like Zoe are trying to get on both horses at the same time. On the one hand, Zoe is a research project that constantly analyzes its users’ data and searches for new insights. On the other hand, it already makes recommendations to users based on its ongoing studies.
Sarah Berry, an associate professor at King’s College London and Zoe’s chief scientist, puts the bullet in it. Zoe admits that “it’s fair to say it’s controversial and controversial” about her science, but that’s because “everything that comes out is always more controversial.” Still, he justifies Zoe’s “ahead of the curve” study by reasoning: “The more we wait until we have more RCTs [randomised control trials] and because of this connection beyond doubt of causality, I don’t think we’ll ever get to the point where we can give people actionable advice.”
Misra says you didn’t eat this. “There are well-designed studies that are game-changing, that are changing outcomes for people in really dramatic ways, that are cost-effective, and that are changing policy. I can give you countless examples.” One of them is research on low-calorie diets aimed at putting type 2 diabetes into remission. “This was a randomized controlled trial, a very high-impact study. “Within three years of this finding it has now become national policy and everyone will be able to access the mitigation programme.”
Zoe also blurs another important distinction. Healthcare providers are subject to a number of onerous legal restrictions. But Zoe currently operates as a wellness company, operating “without the regulation that applies to clinics and medical operations,” as Ravel puts it. So, at the front of the Insights report, the disclaimer sent to anyone who completed two weeks of monitoring of Zoe warns: “Your insights are not clinical test results… Please consult your physician before making any changes to your diet.”
Still, the entire program is designed to encourage diet change by gamifying eating, allowing users to achieve a Zoe score of over 75 out of 100 for their daily food intake. Its marketing is full of health claims, with its homepage imploring people to “Eat for your body and your health,” listing benefits like “Improved gut health,” “Achieve a healthy weight,” and “Improved overall health.”
KWhen I asked Berry so openly about the tension between giving advice and rejecting it, he told me he had to get back to me. Despite pressure on this issue, no such statement came. “Why aren’t regulators more interested in this?” asks Kinross. “I don’t understand this for the life of me.”
But Zoe claims it’s “scientifically proven to work.” This builds on the publication of the programme’s first peer-reviewed study this month. There were some positive but modest results: an average weight loss of 2.46 kg was significant but not very impressive after more than four months. However, there were no changes in various other biomarkers, including blood pressure, insulin, glucose, and postprandial triglycerides.
More importantly, the study compared Zoe participants to a control group without blind testing. They were given only standard nutritional advice and a helpline to call. It was entirely predictable that people who recorded every meal with Zoe for 18 weeks would eat healthier. The study group was also unrepresentative of the general population as a whole: 86% were women and the average body mass index was 34 (those over 30 were considered obese).
Guess has already published a blog detailing criticisms of the study; Kinross, for his part, says the experiment appears to have been designed to “create what I would call the science of marketing, which is enough science to convince the average person that this has value.”
When asked about the design of the experiment, Berry said, “If we wanted to test the effectiveness of Zoe scores alone, then we would need to match the method of distribution” so that both groups were using the same app. This will allow a study to “look at how the actual advice itself compares with standard care advice delivered in the same way.” But while Berry said that would be fine, the actual study was designed to test “the effectiveness of the Zoe program” as a package and compare it to “standard care” alone. This seems like a strange goal: if Zoe’s USP is personalization of advice, why design a study that doesn’t intentionally test these elements?
Consumers, meanwhile, are paying personalized nutrition companies to have their bodies monitored to an extent that Kinross finds “Orwellian.” Zoe charges a one-off penny payment of £300 and a monthly subscription of £24.99. “People don’t understand the value of the data they pay to give,” she says.
These are the problems for which personalized nutrition is a research project and people pay huge amounts of money to be guinea pigs.