A taste of health

We’ve all heard the adage, “An apple a day keeps the doctor away.” But despite the common-sense connection between diet and health, until recently, nutrition hasn’t been a core focus of modern medicine.

Today, that’s quickly changing as researchers discover new links between what we eat and our physical and mental health. Increasingly, scientists are recognizing that food can be a potent preventive and therapeutic tool, affecting everything from heart health to psychiatric symptoms.

“Despite all our drugs and devices and spending more on health care, Americans’ health is not as good as that in most developed countries,” said Christopher Gardner, PhD, the Rehnborg Farquhar Professor and a professor of medicine.

“The power of food, which is so basic and less expensive, is becoming clearer and clearer.”

Gardner is one of the Stanford Medicine researchers who are at the forefront of unearthing how diet affects well-being, paving the way for nutrition to become an integral component of medical education and patient care.

When Shebani Sethi, MD, was a resident training at an obesity clinic, she encountered a 31-year-old patient who needed help losing weight for medical reasons. The woman also had schizophrenia that had not responded to multiple medications or to electroconvulsive therapy. The physician overseeing her care prescribed a ketogenic diet — one high in fat, moderate in protein and low in carbohydrates.

The patient lost weight, as intended. But Sethi observed another outcome: Her psychiatric symptoms also improved. “She saw major reductions in her hallucinations and delusions, and that really intrigued me,” said Sethi, a Stanford Medicine clinical associate professor of psychiatry and behavioral sciences.

As a medical student and resident training in psychiatry and obesity medicine, she often saw patients struggling with physical ailments such as diabetes and hypertension, along with mental health problems, such as treatment-resistant depression or schizophrenia. Sethi observed that the issues were treated largely in isolation. “To me, it made sense to address both simultaneously and collaboratively so patients have better outcomes,” she said.

In 2015, while still a resident, Sethi coined the term “metabolic psychiatry” and founded the nation’s first clinical research program in metabolic psychiatry at Stanford Medicine. The discipline focuses on exploring how disruptions in the body’s process of converting food into energy, known as metabolism, contribute to mental illness.

Research has linked psychiatric conditions including depression, bipolar disorder and schizophrenia to metabolic dysfunction, such as insulin resistance and mitochondrial abnormalities. Metabolic psychiatry offers a way to shift how these disorders are understood and new avenues for treatment, such as diet and medications that address metabolic issues.

Sethi’s most recent research, published in Psychiatric Research in March 2024, provided preliminary evidence that the effect she observed in her patient with schizophrenia was not an anomaly.

Sethi and her team recruited 21 participants, including five with schizophrenia and 16 with bipolar disorder, who were either overweight or had a metabolic condition, such as insulin resistance or high cholesterol. Each followed a keto diet that prioritized high-fat foods including nuts, cream and oils and avoided high-carb options including starchy fruits, bread, pasta and sugar.

“This was the first clinical trial done since 1965 with a ketogenic diet in both bipolar illness and schizophrenia, and the outcomes are quite encouraging and worthy of further exploration.”

Shebani Sethi, clinical associate professor of psychiatry and behavioral sciences

After four months, participants who stuck to the diet experienced significant weight loss, a 27% drop in a measure of insulin resistance and a 36% drop in fat located deep in the abdomen. Their mental health improved, too: Patients with schizophrenia showed a 32% reduction in the intensity of their psychiatric symptoms. Among all participants, the severity of mental illnesses improved by an average of 31%, as measured by the Clinical Global Impression scale, a tool clinicians use to track patients’ psychiatric conditions. Life satisfaction also jumped by 17%, and sleep quality improved by 19%.

“This was the first clinical trial done since 1965 with a ketogenic diet in both bipolar illness and schizophrenia, and the outcomes are quite encouraging and worthy of further exploration,” Sethi said. The reason the diet may help, she noted, is likely that it leads the body to use fat instead of sugar as fuel, producing chemicals known as ketones. Many patients with psychiatric conditions show signs of struggling to efficiently process sugar in the brain, according to Sethi. Ketones can serve as a more efficient energy source that “circumvents the pathway where we’re seeing metabolic deficits,” she said, improving cognitive function.

The field is expanding quickly. In another pilot study, published in February 2025 and led by researchers at the University of Edinburgh, scientists asked people with bipolar disorder — regardless of whether they had a metabolic condition — to follow a keto diet for six to eight weeks. Participants saw their weight and blood pressure fall. The researchers also noted that higher levels of ketones were linked to higher mood and energy levels and to lower impulsivity and anxiety. Sethi is aware of more than 10 other studies around the world exploring the effects of a keto diet on various mental health conditions.

In March 2025, Sethi and her team launched a randomized clinical trial to evaluate the effects of a keto diet on around 120 people with bipolar disorder, schizophrenia and major depressive disorder, some but not all of whom are diagnosed with metabolic dysfunction. The study, which is expected to be completed in 2028, will assess changes in well-being, quality of life, cognitive function and severity of symptoms, along with detailed measures of metabolic function.

Despite promising findings to date, Sethi doesn’t recommend that patients switch to a keto diet independently. “It’s not safe to do it on your own, especially when you’re taking medications or have health conditions such as psychiatric illness or diabetes,” Sethi said. “You need to be followed by someone who has expertise.”

Still, Sethi said everyone’s mental health would benefit from a more nutritious diet, including eating fewer refined carbohydrates and ultra-processed foods. “It may not move the needle on psychiatric symptoms, but these things are going to be helpful — there’s no question,” she said.

In the fall of 2021, Gardner received a call from Louie Psihoyos, the director of a Netflix documentary series called You Are What You Eat. He asked if Gardner wanted to oversee a research study that would be featured on the show. Funding was available, and the filmmaker promised his team would recruit participants. But Gardner had to agree to two criteria: evaluate a vegan diet and study identical twins.

“Wow, this is cool!” Gardner thought at the time. He had spent decades researching the effects of specific foods and supplements, as well as popular diets, such as Atkins, vegetarianism and the Mediterranean diet. So he jumped at the opportunity to evaluate a strictly plant-based diet, especially in identical twins. For the director, this approach was mainly a tactic to attract viewers; for Gardner, it added scientific rigor.

First, he decided to explore whether eating a vegan diet would improve heart health. To find out, Gardner and his team conducted a randomized controlled trial with 22 pairs of identical twins without cardiovascular disease who’d been eating standard American fare. All participants were asked to follow a healthy diet for eight weeks that prioritized vegetables, legumes, fruits and whole grains and avoided sugars and refined starches. One twin in each pair, however, avoided meat, dairy and other animal products.

The study, published in JAMA Network Open in 2023, found that the twins who ate a vegan diet had larger drops in low-density lipoprotein cholesterol (sometimes called “bad” cholesterol), fasting insulin level and weight, on average, than their siblings. These improvements are linked to a lower risk of heart attacks and cardiovascular disease.

“The conclusion wasn’t that the world should go vegan — I don’t think that’s practical for a lot of people. But when clinicians are advising patients, they can feel a little more confident that this diet has multiple benefits.”

Christopher Gardner, professor of medicine

Next, Gardner and his team wanted to know whether eating a plant-based diet slows down physical aging. In a parallel analysis published in BMC Medicine in 2024, they observed that the twins who followed a vegan diet showed differences in DNA methylation, a chemical process that affects how genes are expressed, and the length of telomeres, protective caps at the ends of chromosomes.

This suggested that the twins who ate a plant-based diet were aging significantly more slowly on a cellular level than the omnivorous twins. “In just eight weeks, vegans improved their biological age,” Gardner said, “They were metabolically healthier.”

Gardner’s approach reflects a shift in nutrition research, from a focus on individual nutrients to specific foods and now to dietary patterns. Plant-based diets have such a positive effect, he said, because they’re higher in fiber, antioxidants, certain vitamins and minerals, and unsaturated fat, and they’re lower in saturated fat and cholesterol, as well as the hormones and antibiotics often found in animal products. But going vegan alone isn’t enough: “This was a healthy vegan diet — not French fries, Oreos and Coke,” Gardner said.

You don’t have to avoid meat entirely to benefit from eating more vegetables, fruits, legumes, nuts and seeds. Americans, who eat more meat than residents of almost every other country, could cut back considerably, and Gardner pointed out that any increase in plant-based foods is likely to have some positive effect.

“The conclusion wasn’t that the world should go vegan — I don’t think that’s practical for a lot of people,” he said. “But when clinicians are advising patients, they can feel a little more confident that this diet has multiple benefits.”

Gardner became a vegetarian in 1983 and has been vegan for 15 years. “Every once in a while, if there’s a cookie, I don’t ask if there’s dairy in it,” he said. “I’m a pretty healthy 65-year-old.”

Around a decade ago, when Michelle Hauser, MD, was a postdoctoral research fellow at Stanford Medicine, she joined a task force to improve how medical students learn about nutrition. As was the norm at medical schools, the required curriculum included sparse lectures on the topic, largely focused on biochemistry, and student feedback was negative. “They had trouble seeing the connection to medicine,” said Hauser, a clinical associate professor of surgery and of medicine.

This wasn’t the first time she encountered skepticism about the role of nutrition in medicine. Throughout her medical education, she observed a defeatist sentiment among doctors about patients considering nutrition in their care: “People won’t eat healthy. Don’t waste your time. Just prescribe medicines.” 

Hauser wasn’t buying it. She had trained as a chef at Le Cordon Blue and spent time in the kitchen of Chez Panisse, a Bay Area restaurant known for its focus on farm-to-table cuisine, then taught sold-out classes in healthy cooking. She knew that diet and other lifestyle changes were critical for promoting well-being. The only way to get people to eat nutritious meals, she believed, was to make them delicious.

“It’s not that people don’t want to eat healthy food,” she said. “People don’t want to eat food that doesn’t taste good.” 

In January 2017, while still a postdoc, Hauser launched an elective course in culinary medicine, which combines evidence-based nutrition and culinary skills to help providers guide patients toward healthier diets. 

“Our patients come to us thinking we know about nutrition, but so much of our medical training isn’t focused on that. We need to understand the mechanics of how things work, but we’re missing an important tool if we’re not trying to translate that into material we can talk to patients about.”

Michelle Hauser, clinical associate professor in the Department of Surgery

She secured a small grant and donated her time to develop the curriculum, which includes eight sessions on topics including sautéing, roasting and healthy breakfasts.

Medical and physician assistant students cook and share a wholesome meal, then absorb a lesson on nutritional topics such as healthy proteins, fiber and techniques for counseling patients. They also participate in a discussion board where they practice advising a hypothetical patient on dietary changes.

Hauser said the course, which remains popular, transforms students’ own diets, as well as their ability to offer clinical guidance. Surveys comparing students who took the class to those wait-listed have shown a significant difference in knowledge, attitudes and behaviors about cooking and nutrition, she said. 

“Students get the importance of nutrition when they’re doing it hands-on instead of just learning about it in lectures,” Hauser said. “It’s much more effective.” 

In December 2019, Hauser collaborated with the American College of Lifestyle Medicine, where she later became president-elect, to publish a culinary medicine curriculum based on her course. It’s free online at stan.md/CulinaryMedEd and has been downloaded more than 12,000 times by people in more than 100 countries. 

Hauser is publishing a second edition in October 2025 that includes videos of knife skills and recipe preparation and shares  nutrition information. She said she hopes the curriculum makes it easier for medical schools and health professional education programs to teach culinary medicine, even if they lack specialized instructors or kitchen facilities. 

With the American College of Lifestyle Medicine, Hauser has also launched a free website, stan.md/CulinaryMed, that translates course materials for the general public and includes educational handouts. In addition, she’s developing a training course for health professionals that will be the basis of a board certification exam in culinary medicine.

Hauser is heartened to see that interest in culinary medicine is growing but, for her, change can’t come fast enough. “Our patients come to us thinking we know about nutrition, but so much of our medical training isn’t focused on that,” she said.

“We need to understand the mechanics of how things work, but we’re missing an important tool if we’re not trying to translate that into material we can talk to patients about.”

Janice Owens took pride in cooking recipes passed down through generations — fried chicken, corn bread, mac and cheese, potato salad. But after years of too much fried food and not enough fruits and vegetables, her health was suffering. Owens, 62, lives in Castro Valley, California, and was struggling with high blood pressure and depression. Severe arthritis made movement painful, and she could make it only a short distance with her walker before taking a break.

Then, in December 2024, Owens’ doctor at Hayward Wellness, a primary care center in the Alameda Health System, referred her to Recipe4Health, a three-month program that sent her weekly deliveries of fresh produce through what was dubbed a “Food Farmacy.”

She also participated in a “Behavioral Pharmacy,” weekly group health coaching meetings led by a community organization called Open Source Wellness. Sessions covered topics such as deciphering food labels, healthy recipes, movement and stress reduction.

Owens learned to switch from white rice to brown, to sauté instead of deep fry, and to cut back on salt and instead use seasoning blends. She picked up stretches that helped with her arthritis, and her daily walks grew longer and less painful; sometimes, she even traded her walker for a cane. She started taking her blood pressure medication regularly, quit smoking and took up meditation. As a result, her blood pressure dropped, and her mood improved.

“It really kind of changed my life.”

Janice Owens, a participant in programs that included receiving weekly deliveries of fresh produce and learning tactics for improving her well-being

“It really kind of changed my life,” said Owens, who extended her participation in Recipe4Health for another three months.

“Produce prescriptions,” which subsidize access to healthy foods and nutrition education, are one pillar of Food as Medicine, a growing movement that promotes access to nutritious foods as a tool for improving health and treating disease.

Research from Lisa Goldman Rosas, PhD, a Stanford Medicine associate professor of medicine and of epidemiology and population health, offers evidence that the strategy works. Collaborating with Alameda County Health and the University of California, San Francisco, Rosas and her team studied more than 2,600 people who participated in Recipe4Health between 2020 to 2022. They published their findings in the American Journal of Preventive Medicine in November 2024.

Participants, who were referred to the program by providers at community health centers in Alameda County, California, all faced chronic nutrition-related conditions, and many were food insecure.

Participation in the Food Farmacy and Behavioral Pharmacy increased their intake of fruits and vegetables by about half a serving a day, the researchers found. “You might say, ‘That’s not much,’ but Recipe4Health was giving 16 servings a week, which is really not a lot,” Rosas said. “The fact that you saw participants increasing their produce consumption on a daily basis is quite encouraging.”

Food prescriptions boosted both physical and mental well-being, the researchers found. Whether participants enrolled in only the Food Farmacy or both the Food Farmacy and Behavioral Pharmacy, all reported marked improvements in loneliness, quality of life, and the number of days they felt physically or mentally unwell, on average. In addition, electronic health records showed that participants had lower levels on average of non-HDL cholesterol, which is linked to higher risk of heart disease, than a control group a year after the intervention.

“The fact that we saw benefits compared with a control group suggests that Food as Medicine really is contributing to improvements in health outcomes, which is quite promising.”

Lisa Goldman Rosas, associate professor of medicine and of epidemiology and population health

Participants who took part only in the Food Farmacy program also saw a significant drop in their HbA1c levels — a key indicator of diabetes risk — a year later, compared with a control group. Researchers didn’t see this effect in patients who also attended the Behavioral Pharmacy, which Rosas said might have been because that group had lower HbA1c levels before the program.

“The fact that we saw benefits compared with a control group suggests that Food as Medicine really is contributing to improvements in health outcomes, which is quite promising,” Rosas said.

The program also improved patients’ mental health, Rosas and her team concluded in a complementary article published in Health Services Research in January 2025. Based on surveys and interviews, they found that people who received produce deliveries and group health coaching saw improvements in symptoms of depression and anxiety. (Patients who didn’t have coaching improved only if they didn’t have clinical depression or anxiety before the program.)

Patients who joined the Behavioral Pharmacy generally had better physical and mental health outcomes. “Nutritional education or health coaching is a fundamental component to help participants take that produce the last mile,” Rosas said. “Otherwise, it can be kind of overwhelming.”

Rosas recently launched a broader evaluation of Recipe4Health, collecting more detailed data on participants’ diets and health outcomes. She and her team are also examining Food as Medicine initiatives targeting Latinas, patients with diabetes and cancer survivors. Her hope is that hard data will encourage providers to adopt the approach and insurers and lawmakers to offer coverage. — Contact Katia Savchuk at medmag@stanford.edu