Personalized nutrition apps could provide valuable data to people trying to eat healthier, though more research must be done to show effectiveness.
As a type 2 diabetic, Michael Snyder has long been interested in how blood sugar levels vary from one person to another in response to the same food, and whether a more personalized approach to nutrition could help tackle the rapidly cascading levels of diabetes and obesity in much of the western world.
Eight years ago, Snyder, who directs the Center for Genomics and Personalized Medicine at Stanford University, decided to put his theories to the test. In the 2000s continuous glucose monitoring, or CGM, had begun to revolutionize the lives of diabetics, both type 1 and type 2. Using spherical sensors which sit on the upper arm or abdomen – with tiny wires that pierce the skin – the technology allowed patients to gain real-time updates on their blood sugar levels, transmitted directly to their phone.
It gave Snyder an idea for his research at Stanford. Applying the same technology to a group of apparently healthy people, and looking for ‘spikes’ or sudden surges in blood sugar known as hyperglycemia, could provide a means of observing how their bodies reacted to an array of foods.
“We discovered that different foods spike people differently,” he says. “Some people spike to pasta, others to bread, others to bananas, and so on. It’s very personalized and our feeling was that building programs around these devices could be extremely powerful for better managing people’s glucose.”
Unbeknown to Snyder at the time, thousands of miles away, a group of Israeli scientists at the Weizmann Institute of Science were doing exactly the same experiments. In 2015, they published a landmark paper which used CGM to track the blood sugar levels of 800 people over several days, showing that the biological response to identical foods can vary wildly. Like Snyder, they theorized that giving people a greater understanding of their own glucose responses, so they spend more time in the normal range, may reduce the prevalence of type 2 diabetes.
The commercial potential of such apps is clear, but the underlying science continues to generate intriguing findings.
“At the moment 33 percent of the U.S. population is pre-diabetic, and 70 percent of those pre-diabetics will become diabetic,” says Snyder. “Those numbers are going up, so it’s pretty clear we need to do something about it.”
Fast forward to 2022,and both teams have converted their ideas into subscription-based dietary apps which use artificial intelligence to offer data-informed nutritional and lifestyle recommendations. Snyder’s spinoff, January AI, combines CGM information with heart rate, sleep, and activity data to advise on foods to avoid and the best times to exercise. DayTwo–a start-up which utilizes the findings of Weizmann Institute of Science–obtains microbiome information by sequencing stool samples, and combines this with blood glucose data to rate ‘good’ and ‘bad’ foods for a particular person.
“CGMs can be used to devise personalized diets,” says Eran Elinav, an immunology professor and microbiota researcher at the Weizmann Institute of Science in addition to serving as a scientific consultant for DayTwo. “However, this process can be cumbersome. Therefore, in our lab we created an algorithm, based on data acquired from a big cohort of people, which can accurately predict post-meal glucose responses on a personal basis.”
The commercial potential of such apps is clear. DayTwo, who market their product to corporate employers and health insurers rather than individual consumers, recently raised $37 million in funding. But the underlying science continues to generate intriguing findings.
Last year, Elinav and colleagues published a study on 225 individuals with pre-diabetes which found that they achieved better blood sugar control when they followed a personalized diet based on DayTwo’s recommendations, compared to a Mediterranean diet. The journal Cell just released a new paper from Snyder’s group which shows that different types of fibre benefit people in different ways.
“The idea is you hear different fibres are good for you,” says Snyder. “But if you look at fibres they’re all over the map—it’s like saying all animals are the same. The responses are very individual. For a lot of people [a type of fibre called] arabinoxylan clearly reduced cholesterol while the fibre inulin had no effect. But in some people, it was the complete opposite.”
Eight years ago, Stanford's Michael Snyder began studying how continuous glucose monitors could be used by patients to gain real-time updates on their blood sugar levels, transmitted directly to their phone.
The Snyder Lab, Stanford Medicine
Because of studies like these, interest in precision nutrition approaches has exploded in recent years. In January, the National Institutes of Health announced that they are spending $170 million on a five year, multi-center initiative which aims to develop algorithms based on a whole range of data sources from blood sugar to sleep, exercise, stress, microbiome and even genomic information which can help predict which diets are most suitable for a particular individual.
“There's so many different factors which influence what you put into your mouth but also what happens to different types of nutrients and how that ultimately affects your health, which means you can’t have a one-size-fits-all set of nutritional guidelines for everyone,” says Bruce Y. Lee, professor of health policy and management at the City University of New York Graduate School of Public Health.
With the falling costs of genomic sequencing, other precision nutrition clinical trials are choosing to look at whether our genomes alone can yield key information about what our diets should look like, an emerging field of research known as nutrigenomics.
The ASPIRE-DNA clinical trial at Imperial College London is aiming to see whether particular genetic variants can be used to classify individuals into two groups, those who are more glucose sensitive to fat and those who are more sensitive to carbohydrates. By following a tailored diet based on these sensitivities, the trial aims to see whether it can prevent people with pre-diabetes from developing the disease.
But while much hope is riding on these trials, even precision nutrition advocates caution that the field remains in the very earliest of stages. Lars-Oliver Klotz, professor of nutrigenomics at Friedrich-Schiller-University in Jena, Germany, says that while the overall goal is to identify means of avoiding nutrition-related diseases, genomic data alone is unlikely to be sufficient to prevent obesity and type 2 diabetes.
“Genome data is rather simple to acquire these days as sequencing techniques have dramatically advanced in recent years,” he says. “However, the predictive value of just genome sequencing is too low in the case of obesity and prediabetes.”
Others say that while genomic data can yield useful information in terms of how different people metabolize different types of fat and specific nutrients such as B vitamins, there is a need for more research before it can be utilized in an algorithm for making dietary recommendations.
“I think it’s a little early,” says Eileen Gibney, a professor at University College Dublin. “We’ve identified a limited number of gene-nutrient interactions so far, but we need more randomized control trials of people with different genetic profiles on the same diet, to see whether they respond differently, and if that can be explained by their genetic differences.”
Some start-ups have already come unstuck for promising too much, or pushing recommendations which are not based on scientifically rigorous trials. The world of precision nutrition apps was dubbed a ‘Wild West’ by some commentators after the founders of uBiome – a start-up which offered nutritional recommendations based on information obtained from sequencing stool samples –were charged with fraud last year. The weight-loss app Noom, which was valued at $3.7 billion in May 2021, has been criticized on Twitter by a number of users who claimed that its recommendations have led to them developed eating disorders.
With precision nutrition apps marketing their technology at healthy individuals, question marks have also been raised about the value which can be gained through non-diabetics monitoring their blood sugar through CGM. While some small studies have found that wearing a CGM can make overweight or obese individuals more motivated to exercise, there is still a lack of conclusive evidence showing that this translates to improved health.
However, independent researchers remain intrigued by the technology, and say that the wealth of data generated through such apps could be used to help further stratify the different types of people who become at risk of developing type 2 diabetes.
“CGM not only enables a longer sampling time for capturing glucose levels, but will also capture lifestyle factors,” says Robert Wagner, a diabetes researcher at University Hospital Düsseldorf. “It is probable that it can be used to identify many clusters of prediabetic metabolism and predict the risk of diabetes and its complications, but maybe also specific cardiometabolic risk constellations. However, we still don’t know which forms of diabetes can be prevented by such approaches and how feasible and long-lasting such self-feedback dietary modifications are.”
Snyder himself has now been wearing a CGM for eight years, and he credits the insights it provides with helping him to manage his own diabetes. “My CGM still gives me novel insights into what foods and behaviors affect my glucose levels,” he says.
He is now looking to run clinical trials with his group at Stanford to see whether following a precision nutrition approach based on CGM and microbiome data, combined with other health information, can be used to reverse signs of pre-diabetes. If it proves successful, January AI may look to incorporate microbiome data in future.
“Ultimately, what I want to do is be able take people’s poop samples, maybe a blood draw, and say, ‘Alright, based on these parameters, this is what I think is going to spike you,’ and then have a CGM to test that out,” he says. “Getting very predictive about this, so right from the get go, you can have people better manage their health and then use the glucose monitor to help follow that.”
Dr. Robert Montgomery, almost one year post-transplant, at a vineyard in Casablanca, Chile, August 2019.
Having spent my working life as a transplant surgeon, it is the ultimate irony that I have now become a heart transplant patient. I knew this was a possibility since 1987, when I was 27 years old and I received a phone call from my sister-in-law telling me that my 35-year-old brother, Rich, had just died suddenly while water skiing.
Living from one heartbeat to the next I knew I had to get it right and nail my life—and in that regard my disease was a blessing.
After his autopsy, dots were connected and it was clear that the mysterious heart disease my father had died from when I was 15 years old was genetic. I was evaluated and it was clear that I too had inherited cardiomyopathy, a progressive weakening condition of the heart muscle that often leads to dangerous rhythm disturbances and sudden death. My doctors urged me to have a newly developed device called an implantable cardioverter-defibrillator (ICD) surgically placed in my abdomen and chest to monitor and shock my heart back into normal rhythm should I have a sudden cardiac arrest.
They also told me I was the first surgeon in the world to undergo an ICD implant and that having one of these devices would not be compatible with the life of a surgeon and I should change careers to something less rigorous. With the support of a mentor and armed with what the British refer to as my "bloody-mindedness," I refused to give up this dream of becoming a transplant surgeon. I completed my surgical training and embarked on my career.
What followed were periods of stability punctuated by near-death experiences. I had a family, was productive in my work, and got on with life, knowing that this was a fragile situation that could turn on its head in a moment. In a way, it made my decisions about how to spend my time and focus my efforts more deliberate and purposeful. Living from one heartbeat to the next I knew I had to get it right and nail my life—and in that regard my disease was a blessing.
In 2017 while pursuing my passion for the outdoors in a remote part of Patagonia, I collapsed from bacterial pneumonia and sepsis. Unknowingly, I had brought in my lungs one of those super-bugs that you read about from the hospital where I worked. Several days into the trip, the bacteria entered my blood stream and brought me as close to death as a human can get.
I lay for nearly 3 weeks in a coma on a stretcher in a tiny hospital in Argentina, septic and in cardiogenic shock before stabilizing enough to be evaced to NYU Langone Hospital, where I was on staff. I awoke helpless, unable to walk, talk, or swallow food or drink. It was a long shot but I managed to recover completely from this episode; after 3 months, I returned to work and the operating room. My heart rebounded, but never back to where it had been.
Then, on the eve of my mother's funeral, I arrested while watching a Broadway show, and this time my ICD failed to revive me. There was prolonged CPR that broke my ribs and spine and a final shock that recaptured my heart. It was literally a show stopper and I awoke to a standing ovation from the New York theatre audience who were stunned by my modern recreation of the biblical story of Lazarus, or for the more hip among them, my real-life rendition of the resurrection of Jon Snow at the end of season 5 of Game of Thrones.
Against the advice of my doctors, I attended my mom's funeral and again tried to regain some sense of normalcy. We discussed a transplant at this point but, believe it or not, there is such a scarcity of organs I was not yet "sick enough" to get enough priority to receive a heart. I had more surgery to supercharge my ICD so it would be more likely to save my life the next time -- and there would be a next time, I knew.
As a transplant surgeon, I have been involved in some important innovations to expand the number of organs available for transplantation.
Months later in Matera, Italy, where I was attending a medical meeting, I developed what is referred to as ventricular tachycardia storm. I had 4 cardiac arrests over a 3-hour period. With the first one, I fell on to a stone floor and split my forehead open. When I arrived at the small hospital it seemed like Patagonia all over again. One of the first people I met was a Catholic priest who gave me the Last Rights.
I knew now was the moment and so with the help of one of my colleagues who was at the meeting with me and the compassion of the Italian doctors who supplied my friend with resuscitation medications and left my IV in place, I signed out of the hospital against medical advice and boarded a commercial flight back to New York. I was admitted to the NYU intensive care unit and received a heart transplant 3 weeks later.
Now, what I haven't said is that as a transplant surgeon, I have been involved in some important innovations to expand the number of organs available for transplantation. I came to NYU in 2016 to start a new Transplant Institute which included inaugurating a heart transplant program. We hired heart transplant surgeons, cardiologists, and put together a team that unbeknownst to me at the time, would save my life a year later.
It gets even more interesting. One of the innovations that I had been involved in from its inception in the 1990s was using organs from donors at risk for transmitting viruses like HIV and Hepatitis C (Hep C). We popularized new ways to detect these viruses in donors and ensure that the risk was minimized as much as possible so patients in need of a life-saving transplant could utilize these organs.
When the opioid crisis hit hard about four years ago, there were suddenly a lot of potential donors who were IV drug users and 25 percent of them were known to be infected with Hep C (which is spread by needles). In 2018, 49,000 people died in the U.S. from drug overdoses. There were many more donors with Hep C than potential recipients who had previously been exposed to Hep C, and so more than half of these otherwise perfectly good organs were being discarded. At the same time, a new class of drugs was being tested that could cure Hep C.
I was at Johns Hopkins at the time and our team developed a protocol for using these Hep C positive organs for Hep C negative recipients who were willing to take them, even knowing that they were likely to become infected with the virus. We would then treat them after the transplant with this new class of drugs and in all likelihood, cure them. I brought this protocol with me to NYU.
When my own time came, I accepted a Hep C heart from a donor who overdosed on heroin. I became infected with Hep C and it was then eliminated from my body with 2 months of anti-viral therapy. All along this unlikely journey, I was seemingly making decisions that would converge upon that moment in time when I would arise to catch the heart that was meant for me.
Dr. Montgomery with his wife Denyce Graves, September 2019.
(Courtesy Montgomery)
Today, I am almost exactly one year post-transplant, back to work, operating, traveling, enjoying the outdoors, and giving lectures. My heart disease is gone; gone when my heart was removed. Gone also is my ICD. I am no longer at risk for a sudden cardiac death. I traded all that for the life of a transplant patient, which has its own set of challenges, but I clearly traded up. It is cliché, I know, but I enjoy every moment of every day. It is a miracle I am still here.