As the slogan “Make America Great Again” continues to shape political messaging in the United States, Health and Human Services Secretary Robert F. Kennedy Jr. is attempting to attach a new public health mission to it—"Make America Healthy Again." During a two-day visit to California last week, Kennedy mixed politics, science and public health reform while calling for a national “moonshot” on microbiome research, an emerging field that scientists believe could transform cancer treatment and prevention.

Speaking at the City of Hope in Duarte recently, Kennedy addressed researchers from the National Cancer Institute, the National Institutes of Health, and major cancer centers across America. The event, titled The Next Frontier of Cancer Prevention and Care: The Microbiome, focused on how tiny organisms living inside the human gut may affect cancer risk, immunity and response to treatment.

“The scientific community has an advocate now in this administration,” Kennedy told the gathering while urging the US government to make microbiome science a national priority.

The microbiome refers to trillions of bacteria, viruses and fungi that live mainly in the human digestive system. Scientists increasingly believe these microscopic organisms play a critical role in health. Several recent studies published in journals such as Nature Reviews Cancer and Cell suggest gut bacteria may influence how patients respond to immunotherapy, one of the most advanced forms of cancer treatment currently available.

Researchers have already observed striking lab-level findings. In some experiments, mice with healthier gut bacteria showed stronger immune attacks against tumours. In another widely discussed study from laboratories in Chicago and Paris, cancer patients who received certain antibiotics before immunotherapy were found to have poor treatment outcomes because the drugs disrupted beneficial gut microbes.

That growing evidence is pushing governments and drug companies to rethink cancer prevention itself.

Kennedy’s visit also carried a political undertone. His “Take Back Your Health” tour comes as the Trump administration intensifies its messaging around chronic diseases, addiction, and healthcare costs. America continues to face alarming public health numbers. According to the US Centers for Disease Control and Prevention, six in ten American adults live with at least one chronic disease, while drug overdose deaths and homelessness remain deeply linked in several urban regions.

At the symposium, Jay Bhattacharya, cancer immunologist Giorgio Trinchieri, and microbiome expert Marcel van den Brink joined discussions on future therapies that may one day personalise cancer care through gut bacterial analysis.

City of Hope CEO Robert Stone said partnerships between governments, hospitals, and scientists would determine whether these breakthroughs actually reach ordinary patients.

“The advances that help patients live longer and better lives depend on sustained research, strong partnerships and a shared focus on making the best cancer care available to more people,” Stone said.

A day later in downtown Los Angeles, Kennedy met county officials and addiction recovery experts alongside senior adviser Kathryn Burgum. Discussions were centred on homelessness, mental illness, and substance abuse treatment using what officials described as "outcome-based care"—a model that rewards successful recovery instead of the number of medical services billed.

Los Angeles County Supervisor Kathryn Barger said addiction and homelessness could not be solved without cooperation between federal and local authorities.

For many public health experts, however, the real test lies beyond slogans and conference halls. Microbiome science remains promising but still experimental. Large human trials are ongoing, costs remain high, and researchers are still trying to understand why gut bacteria behave differently from person to person.

Yet Kennedy’s California visit has placed one thing firmly into public debate: whether America’s next healthcare revolution may begin not in a hospital ward, but deep inside the human gut.