Prof David Allison on healthspan, nutrition and how we can overcome the challenge of testing the efficacy of longevity interventions.
Hevolution Foundation recently released the second edition of its Global Healthspan Report, offering one of the most comprehensive assessments to date of the science, technology, investments and policies shaping how long people live in good health. Drawing on global surveys, investment analyses, expert interviews and an extensive review of emerging research, the 2025 report shifts the conversation from defining healthspan to accelerating its progress.
Longevity.Technology: The new Global Healthspan Report examines where meaningful advances have already been made and what the field must do next to translate promising science into real-world impact. As part of the development of the report, we spoke with Professor David Allison, Chief of Nutrition at Baylor College of Medicine, one of the world’s leading experts in obesity and nutrition, about progress in healthspan science, biomarkers and the role of nutrition in longevity.
Reflecting broadly on the progress made in healthspan at the “human applied level” to date, Dr Allison says the greatest impact so far has come from the treatment and prevention of disease.
“We’ve dramatically reduced infectious disease through vaccines, sanitation, treated water and hygiene,” he explains. “And we have effective medical treatments: stents, bypass surgeries, cancer surgeries. Survival from cancer is up even though cancer incidence isn’t dramatically down, so treatment has made the difference. We’ve also reduced smoking and improved nutrition. Then we have statins, antihypertensives, antidiabetic drugs and now successful anti-obesity drugs – all reducing mortality.”
Limited progress so far
However, Allison questions whether any of this is an example of slowing aging – a key tenet of the healthspan movement.
“There’s ongoing debate about whether ‘aging’ is fundamentally distinct from the accumulation of damage and diseases,” he says. “For example: if we treat hypertension, prevent a heart attack and extend someone’s life, have we truly slowed aging? That’s debatable.”
Allison says the next big step is to develop interventions based on the concept of slowing overall aging.
“I’m talking about gerotherapeutic agents or procedures adapted from mice that prolong median and maximum lifespan, not just treat or prevent a single disease,” he explains. “We have many promising findings in mice, and some are being translated into humans, but we don’t yet have overwhelming, clear evidence in humans.”
Addressing the translation challenge directly, Allison says the hardest part is conducting compelling research that can provide evidence for the healthspan-boosting effects of interventions.
“Ideally, you’d study tens of thousands of people, broadly representative across sex, race, geography and age – from early adulthood through older adulthood,” he adds. “That alone requires enormous numbers and is prohibitive in terms of time and cost. Even Hevolution would struggle to fund that, and no one wants to wait decades for results.”
Nutrition’s role in healthspan
Allison’s primary area of research, nutrition, is regarded one of the key pillars of longevity, but proving dietary benefits faces the same challenges as other potential interventions.
“Over the past 150 years, we’ve made food supplies adequate so people aren’t dying of poisoning, nutritional deficiencies, or starvation,” he says. “But beyond those foundational issues, there’s very little clear evidence that specific dietary elements meaningfully affect lifespan. I won’t say none exist, but strong, convincing evidence – especially from randomized human trials – is rare.”
“Blueberries for cognition, dark chocolate, polyphenols, protein levels. All interesting, sometimes plausible, but often questionable in terms of demonstrable benefits – especially if your standard is randomized controlled human trials.”
Allison acknowledges the best evidence for healthspan-boosting nutrition comes from whole dietary patterns like the Mediterranean diet.
“Even that evidence isn’t perfect, but it’s reasonably compelling,” he says. “That doesn’t mean other diets couldn’t be just as good. For example, some researchers advocate for a Nordic diet, and my group is working on a ‘Hoosier diet’ – foods consistent with Midwestern US culture but aiming for Mediterranean-level health outcomes.”
The idea is that the Mediterranean diet is simply an approach that could potentially be applied anywhere in the world, using an adapted local diet.
“It could improve adherence and is more respectful,” say Allison. “I enjoy Mediterranean foods myself, but telling everyone in rural Alabama or Indiana that they need to start eating octopus and extra virgin olive oil isn’t realistic. People may prefer foods aligned with their culture and local agriculture – corn, soybeans, peanuts, pecans, lean pork tenderloin and so on. There’s no reason those can’t form the basis of an equally healthy diet.”
“But again, to prove the benefits of diet change, we either need to accept a standard of evidence that combines animal studies, observational human data and shorter-term human trials – or we need more and better randomized controlled trials. Probably both.”
Proving healthspan benefits
To help overcome the challenge of proving whether healthspan interventions actually work or not, Allison suggests two key areas of progress that could make a difference.
“First, I think we need greater acceptance of research that isn’t strictly hypothesis-driven in the traditional mechanistic sense,” he says. “For example, testing across species can be framed as a hypothesis, but often we simply need the data – not because we deeply understand the mechanism, but because knowing the outcome is crucial.”
Allison’s second wish is an all-too familiar one for those in the longevity field.
“We need intermediary biomarkers we can trust,” he says. “Maybe that’s a pipe dream, but if measures like methylation status, senescent cell burden, or mitochondrial function could reliably indicate improvements in healthspan or lifespan, then that would dramatically accelerate research.”
So how close does Allison believe we are to having biomarkers that will allow researchers to run better trials and get truly actionable information?
“If your standard is definitive evidence from large human studies, we’re far from having that,” he says. “But if we can show, for example, that a treatment reduces mortality over five years in humans and moves a biomarker, and that in animals moving that same biomarker also improves lifespan across species, then that starts to be compelling.”
