Introduction
In an era when the pursuit of longevity is gaining increasing prominence, the intricate relationship between food and aging becomes paramount. Dr. Zhaoli Dai-Keller, a distinguished nutritional epidemiologist and lecturer at the School of Population Health at The University of New South Wales (UNSW), also known as UNSW Sydney, has dedicated her career to unraveling the dietary secrets of centenarians and translating those insights into actionable steps for healthier aging. With a focus on disease prevention, food policy, research integrity, and health disparities, her research spans diverse cultures and populations, illuminating the profound impact food choices have on our journey through life as we age.
Known affectionately as Joy, Dr. Dai-Keller has led multiple projects using population-based cohorts, nationally representative survey data, and electronic health records in Singapore, the US, and Australia. These studies focus on diet and other modifiable risk factors for the development of chronic conditions associated with aging. This insightful interview delves into her groundbreaking work, focusing on the dietary habits of the world’s oldest people and their influence on chronic disease prevention, as well as the evolving role of nutrition in healthcare settings.
Throughout the interview, we address a broad spectrum of topics, examining the dietary patterns of centenarians, the role of nutrition in preventing chronic diseases, and the challenges and opportunities facing an aging population. As a result of evidence-based information gathered from the rural landscapes of longevity to the complexities of hospital food services, Dr. Dai-Keller offers practical wisdom and guidance for fostering a longer and more vibrant life through mindful eating.
CFAM: What initially inspired you to focus on nutritional epidemiology, especially concerning aging? Can you share any significant challenges you’ve faced in your career and how you overcame them? Looking back, what achievements are you most proud of, and how do you hope your work will influence the field of aging and nutrition in the future?
Dr. Dai-Keller: I am Chinese, and we believe that food is medicine (in Chinese: 医食同源). Keeping this as my lifestyle principle started when I was young. As an undergraduate, I developed my passion for studying food and nutrition and earned my doctoral degree in nutritional epidemiology. As an academic and a nutritional epidemiologist, I have been quite fortunate to research food/nutrition, health, and aging in older people after receiving my PhD and have led many cohort studies of the roles of diet and nutrition play in musculoskeletal disorders, cardiovascular diseases, mental health disorders, and longevity in Asia, the US, Australia, and beyond.
I have faced many challenges, especially moving around three continents in the last decade. Public health and nutrition research is not generally well-funded, so I have encountered a lot of setbacks. I am sure I will continue to encounter various challenges in this field. But I always remind myself that doing the things I am passionate about will eventually pay off.
Some of my future projects include understanding perceived healthy eating and the challenges older people in the community face when accessing nutritious fiber-rich foods, such as fresh fruits and vegetables. I also plan to co-develop personalized interventions that help older people to adopt healthy eating habits that are appropriate for their socioeconomic and cultural backgrounds. I will explore the experiences, feasibilities, and barriers reported by patients, clinicians, and dietitians with regard to their experience of hospital food service and food quality in order to identify opportunities for intervention. The goals of these projects are to implement effective dietary interventions to improve healthy eating and enjoyment for older people in e community and hospital settings.
Centenarian Diets & Longevity
CFAM: Dr. Dai-Keller, based on your study of centenarians, A systematic review of diet and medication use among centenarians and near-centenarians worldwide (GeroScience, July 2024), you emphasize the importance of following diverse, low-salt diet. Could you explain how these dietary patterns specifically contribute to longevity and what key physiological mechanisms are involved? Among the various nutrients and food groups you’ve researched, which do you find most crucial for promoting a longer healthspan? What actionable advice can you provide younger generations with varying cultural dietary backgrounds to help them incorporate these longevity-enhancing practices into their lifestyles?
Dr. Dai-Keller: Our systematic review [ a rigorous research method that analyzes multiple studies using predefined criteria to answer a specific research question.] on centenarians diverse dietary pattern emphasizes a balanced diet of macronutrients, with an average of 59.6 percent (range: 57 to 65 percent) carbohydrates, 18.5 percent (range: 12 to 32 percent) protein, and 29.3 percent (range: 27 to 31 percent) fat intakes. While the diets are culturally diverse, they all highlight the consumption of staple foods, especially whole grains, root vegetables, fruit, green leafy vegetables, and proteins primarily sourced from poultry, fish, and legumes, but rarely red meat intake.
A diet like this would be high in dietary fiber, phytochemicals, and antioxidants. Minimal red meat intake reduces saturated fats and trimethylamine N-oxide (TMAO), a dietary byproduct formed by gut bacteria during digestion linked to cardiovascular disease and cancers. Overall, the physiological mechanisms by which the health benefits of such a diet align with commonly acceptable aging theories include reduced oxidative stress, inflammation, and cellular damage in the DNA, leading to a reduction in the systemic disorders created by aging diseases and phenotypes.
From my research, I have found that it is crucial for diets promoting healthspan to be mainly plant-based, to include whole grains, some fruits, vegetables, nuts, and legumes, or a diet mostly plant-based to promote healthspan, to be rich in dietary fiber. Fiber plays a crucial role in digestion, reducing constipation, and promoting a healthy gut microbiome that affects cognition and cardiovascular and musculoskeletal functions. This is the same dietary advice I would give the younger generations, although calcium and protein intake are also vitally important for bone and muscle growth and development. Hence, dairy products, especially fermented dairy products such as yogurts, are good sources of protein because they contain gut-friendly microbes such as those containing lactobacillus and bifidobacterium. Also, for the younger generations, we emphasize that animal sources of protein should come from poultry, fish, and a moderate intake of red meat, with a minimal intake of processed meat, which contains high levels of sodium, nitrates, and nitrites.
We reviewed the health habits of centenarians. These 4 things could lead to a longer life. (UNSW Newsroom August 2024)
The health habits of Centenarians! (Joy Drive, Podcast)
Medication Use & Preventive Health
CFAM: Your research suggests that centenarians typically use fewer medications. What does this indicate about their approach to health and to disease prevention? How should this insight influence the medical community’s approach to health management and preventive care, particularly when prescribing for the elderly? Considering the risks of polypharmacy, what specific changes would you advocate in prescribing practices for older adults?
Dr. Dai-Keller: We have found that centenarians, on average, use fewer than five medications simultaneously. This shows that those with extreme longevity generally have fewer health conditions or have delayed onset of those conditions until they reach their nineties. Linking this finding to their healthy lifestyles, such as diet, and their healthy lipid and metabolic profiles, along with low smoking or drinking, good sleep, and their living environment, suggests that, in addition to the pharmacological treatments prescribed to older people, the medical community should implement lifestyle medicine to manage their existing health conditions or as a prevention strategy before the onset of disease development. In this situation, we advocate no medical treatments but underscore the importance of necessary medications and appropriate doses in disease management. These plans should be monitored periodically to adjust for taking only the most essential and appropriate medications to avoid unnecessary polypharmacy [describe the simultaneous use of multiple medicines by a patient for their conditions], which puts older adults at risk of falls, cognitive impairment, and hospitalization as a result of harmful drug interactions. Clear communication with older patients or their caregivers is also essential to inform them of the benefits and risks of the treatments so that they can be part of the decision-making and management of their health conditions.
Sleep, Longevity & Modern Challenges
Sleep quality is a significant factor in your studies of longevity. Could you discuss how sleep quality and duration impact the health outcomes of older adults? Based on your observations of centenarians, what recommendations can you offer to improve sleep habits? Additionally, are there any dietary or nutritional interventions that you believe could enhance sleep quality in aging populations?
Dr. Dai-Keller: Sleep quality and quantity affect our immune system, stress hormones, and cardiometabolic functions, including obesity, high blood pressure, and diabetes.
Good sleep, including both quality (less wake time and sufficient deep sleep) and duration ( 7 to 8 hours per night), is associated with extended years of good health and reduced risks of chronic diseases. For example, In a study of three European cohorts, individuals without sleep disturbance were projected to live six additional years in good health and three more years without chronic diseases between the ages of 50 and 75 as compared to those with severe sleep disturbance. Moreover, sleep satisfaction was found to modulate the link between occupational stress and metabolic syndrome or BMI, while both long (> 8 hours) and short (< 7 hours) sleep durations were associated with an increased risk of death.
Recommendations to improve good sleep habits include maintaining a regular sleep routine, creating a restful environment, including suitable temperature, exercising regularly, and managing stress. Eating should be finished at least four hours before sleep time, liquids no less than two hours before sleep time, and (depending on the individual’s caffeine metabolism) caffeinated beverages should be avoided for at least ten to twelve hours before sleep time. The evidence relating to foods that may be particularly beneficial to improving sleep quality is less convincing.
Rural Living & Healthspan
CFAM: Many centenarians you studied reside in rural areas. What specific factors related to rural living contribute to their health and longevity? How do these factors differ from urban living conditions, especially in terms of diet, physical activity, and social connections? Can urban residents adopt any of these rural advantages to enhance their own healthspan, particularly through access to fresh and locally sourced foods?
Dr. Dai-Keller: The high prevalence of centenarians residing in rural areas aligns with the observation that regions with a high concentration of centenarians worldwide, called Blue Zones, are predominantly situated in remote islands, such as the Okinawa Prefecture in Japan; the Nuoro Province of Sardinia in Italy; the Nicoya Peninsula in Costa Rica; and Icaria in Greece. Rural living is remote from urban / business districts, with less life and work pressure; the environment offers fresh air, water, and green space. Centenarians living in rural environments or a blue zone usually form a friendly and supportive community where people connect and lean on one another. As a result, their diet is simpler, fresher, and home-cooked, with minimal processing. In addition, rural environments promote leisure activities in open spaces to connect and de-stress.
Urban residents can also adopt rural living styles. For example, take some time to follow natural hiking trails or go to beaches, lakes, or public parks. Contributing to local or home gardens to grow plants and, even better, fruits and vegetables can also help manage stress and connect with others in the community. And, of course, eating and sharing home-grown produce is a great way to sustain healthy dietary habits. If growing your own is not an option, going to the local farmers’ markets to shop for seasonal and fresh local produce and proteins is another way to connect with family or friends and promote healthy eating and social interactions with others.
Nutritional Interventions & Policy
CFAM: From your extensive research, what nutritional interventions have you identified as most effective for aging populations? How can these interventions be customized to accommodate the cultural and individual diversity of the population? What role should policymakers play in facilitating and promoting these interventions? How can technology and innovation help make them more accessible and practical for underserved communities?
Dr. Dai-Keller: Most of my research involves epidemiological studies or systematic reviews designed to generate evidence. Based on my findings, fiber-rich foods are the critical foundation for improving one’s dietary quality and reducing obesity, cardiovascular disease, hypertension, type 2 diabetes, and musculoskeletal pain.
A higher intake of whole grains, fruits, vegetables, nuts, and legumes would be the best way to prevent and manage age-related chronic conditions and ensure healthy aging. The recommendations for dietary fiber intake are, on average, 25 grams per day, with 2 to 3 servings of whole grain foods (including popcorn), five servings of fruits and vegetables, and 2 servings of nuts or legumes.
The good news for a fiber-rich diet is that it can be adapted to suit all cultures and ethnicities.
Policymakers should make fiber-rich food easily accessible, especially for low socio-economic groups and those living in rural or remote areas (except those living in the blue zones😊). They should work to increase health and nutrition literacy among older people as well as their families and carers to make them aware of the health benefits of fiber-rich foods, provide the skills they need to read food labels and teach cooking methods that alleviate older adults’ deteriorating physical and cognitive functions.
Grocery shopping apps may make it easier to shop for these foods, and health apps offer an accessible way to increase health literacy and food skills. Of course, for this to be effective, older people must have internet access and basic knowledge of how to download and use the apps. Here are some examples of ways to meet the dietary recommendations for fiber intake:
Hospital Food & Patient Outcomes
CFAM: Your research,” The association between patient-reported experiences with hospital food services and recovery outcomes – A population survey of patients from 75 public hospitals” ( Clinical Nutrition published by the European Society for Clinical Nutrition and Metabolism), examines the nutrition provided in hospital settings. What have you found are the essential changes needed in hospital food services to improve outcomes for patients, particularly the elderly? What challenges do hospitals face in implementing these improvements, and are there any successful models from other countries or healthcare systems from which we can learn?
Dr. Dai-Keller: My recent research involving hospital food service included a population-representative survey that provided feedback from 21,900 patients across 75 public hospitals in the State of New South Wales in Australia. Our findings show that among the 80 percent of patients who consumed hospital food (mean age: 60.6 years, Standard Deviation: 18.3; 53 percent females), satisfaction with the hospital food service was strongly linked to overall care satisfaction and recovery outcomes, including complications acquired in hospital and delayed discharge due to feeling unwell.
There was a stark difference in outcomes between English-speaking patients and those who do not speak English at home, underscoring significant disparities based on cultural and ethnic diversity. Patients who rated the hospital food service as “poor/very poor” were 2.7 times more likely to be dissatisfied with overall care and 1.9 times more likely to have delayed discharge. These risks increased to over 10 times and 3.2 times for non-English-speaking patients, respectively. Additionally, among patients aged 75 and older, a poor food experience was 4.5 times more likely to experience delayed discharge, indicating that the older the patient, the more significant the impact of their hospital food experience had on recovery.
Our study also identified key technical aspects of food service—such as correct food orders, timely delivery, taste, and uninterrupted meals–as crucial factors in patient satisfaction and recovery.
The challenges to both the quality of the food service and the quality of the food itself include cost and a broad awareness of meeting patients’ dietary needs if they are from other cultures in countries with diverse populations.
I am not aware of a particular model for improving hospital food service and diet quality because the ones that seemed better were in private rather than public hospitals.
However, based on our research, academia, other researchers, advocates, and patients are increasingly demanding and inquiring about investing in the development of patient-centered dietary algorithms to improve food intake and nutrition for older patients in hospitals and to consider patients’ cultural and ethnic backgrounds.
Given the growing global aging population, especially those from diverse cultural and ethnic backgrounds, it is vital to 1) review the nutritional adequacy of existing hospital food standards or guidelines, taking into account patients’ multiple cultural and ethnic backgrounds, and 2) understand the lived experience of patients, and reflection of dieticians and clinicians regarding the impact of hospital food service and food quality on patients’ satisfaction, malnutrition risk, and recovery outcomes.
The Future of Nutritional Epidemiology
Looking ahead, what aspects of nutritional epidemiology do you find most promising for advancing our understanding of aging and nutrition? What emerging technologies or methodologies are likely to transform this field? What advice would you offer to new researchers entering the field, particularly regarding the skills and perspectives necessary for success?
Dr. Dai-Keller: Researchers need to utilize similar aging epidemiological cohorts globally, including their aging outcomes, phenotypes, and biomarkers concerning nutrition in order to acquire data (IPD) meta-analysis to generate evidence on pooled results among eligible studies. These findings would be more robust and generalizable to broader populations from other regions and countries with diverse cultural and ethnic backgrounds.
Emerging technologies include app-based digital data to capture diet and nutrition intakes as well as other lifestyle habits and some health data, such as weight, body composition, blood pressure, and blood glucose levels. However, the technology is still not advanced enough to capture accurate dietary intake data.
The other emerging area is analysis of the microbiome, which reflects what we eat and how we live. With the advancement of the field, I cannot imagine why we won’t be able to identify personalized diets that achieve the health-desirable gut microbiome that makes people feel healthy, happy, and energetic.
I think that data analytic skills can enable students or those who are entering the field of nutrition research to link and analyze various data sources, and machine-learning techniques to develop personalized algorithms would allow the new generation to move the field of nutrition and aging forward and make it easier for lay people to adopt healthy dietary and lifestyle choices to improve their quality of life as they age.
Fact Sheet
- Your preferred pronouns: she/her
- The place you grew up in Guangzhou, China, a city that is famous for its food
- The place you currently call home: Sydney, Australia
- Job title: Assistant Professor
- As a child, you wanted to be a scientist who contributes to the world and humanity.
- One word you would use to describe our food system: needs to be greener
- Foodie hero: the late Athony Bourdain
- Your breakfast this morning: coffee; that’s it
- Favorite food: perfect croissant
- Favorite dessert: chocolate cheesecake
- Last meal on Earth: wagyu beef steak
- Your healthiest habit: eating celery as lunch or snacks
- Least healthy habit: Eating croissants
- Food As Medicine social media must follow: Food As Medicine Coalition
- Food newsletters, websites, or books you can’t stop reading: I need to create one myself.
- Your proudest “Food” moment: My perfectly baked challah at home
- Your favorite ingredient that heals: Peppermint tea
- If you were to bring a gift as a meal, what would it be? Pecan pie, the Southern style
