What Kind of Diet Does Your Body Need? From Nutritional Epidemiology to Precision Health
Interview with Professor Tianying Wu
Reporter: Jessica Jialin Jiang
We eat, drink, and sleep every day. These ordinary habits may be connected to our health in ways that are far more complicated than we realize. Why can the same food affect different people differently? Could the temperature of what we eat and drink be related to sleep and mental health? And in the future, could each of us have a truly personalized diet designed for our own body?
To explore these questions, we interviewed Dr. Tianying Wu, a professor of epidemiology at San Diego State University’s School of Public Health. Her research focuses on nutrition, lifestyle, chronic disease, and aging, with the goal of finding more precise ways to promote healthy aging.
From Medicine to Nutritional Epidemiology
Dr. Wu’s academic background spans medicine, nutrition, and epidemiology. She received medical training as an undergraduate, later earned a Ph.D. in nutritional biochemistry and a master’s degree in epidemiology, and completed postdoctoral research in molecular nutritional epidemiology at the Harvard School of Public Health.
Today, much of her research centers on a question that affects everyone: How do our everyday diet and lifestyle influence disease and aging?
Unlike clinical research that focuses on individual patients, nutritional epidemiology looks at entire populations. Researchers analyze the diets, lifestyles, and health outcomes of large groups of people to identify patterns.
But discovering who is more likely to develop a disease is only the first step.
Dr. Wu explained that epidemiology can reveal associations between lifestyle factors and disease, while molecular biology can help researchers understand the mechanisms behind those associations. Scientists might investigate what is happening inside the body at the level of cells, metabolism, or mitochondria.
By combining these approaches, researchers can address two important questions: What is happening, and why is it happening?
When a Glass of Ice Water Becomes a Research Question
One of Dr. Wu’s recent areas of research comes directly from everyday life: Could the temperature of our food and drinks affect our health?
The idea was partly inspired by her observations of different cultures.
She noticed that iced drinks and cold foods are much more common in the United States than in China and some other Asian countries. At the same time, sleep, mental health, and gastrointestinal health have become major areas of concern in public health.
These observations led her to wonder whether the temperature of food and beverages might be related to certain health outcomes.
Her research on this topic attracted attention from more than twenty media outlets after publication.
The research also revealed an interesting pattern: associations between hot or cold food consumption and health may not be exactly the same among Asian and White populations.
According to Dr. Wu, both biological and cultural factors could contribute to these differences. Populations may differ in areas such as gut microbiota, blood circulation, and sensitivity to cold. At the same time, people grow up with different dietary traditions and habits.
This raises another interesting question: when people immigrate to a new country and gradually adopt the local lifestyle, are those new dietary habits equally suitable for their bodies?
For now, much of this research identifies associations rather than proving cause and effect, so further studies are still needed.
How Could the Gut Affect Sleep and Mood?
In recent years, the gut–brain axis has become an increasingly important area of medical and public health research.
In simple terms, the gut and the brain are not completely separate systems. What we eat affects our digestive system, and the gut communicates with the brain through complex biological pathways. As a result, diet may also be connected to sleep and mental health.
When asked what foods might help people sleep better, Dr. Wu did not recommend a particular “sleep food.”
Rather than searching for a single “magic” food, she emphasized the importance of an overall healthy lifestyle. For example, avoiding excessive nighttime eating, limiting cold foods and drinks that may interfere with the body’s transition to a resting state, and getting adequate daytime sunlight may help support a healthy circadian rhythm and sleep.
During sleep, the body needs to gradually enter a relaxed state. Under normal conditions, cortisol levels decrease at night while melatonin levels rise, helping the body transition from daytime activity to nighttime rest.
So rather than asking only, “What should I eat before bed?” a more useful question may be whether our overall daily habits support the body’s natural rhythms.
Association Does Not Mean Causation
During the interview, Dr. Wu emphasized one of the most important principles in scientific research: association does not necessarily mean causation.
Suppose a study finds that people with a certain dietary habit also tend to have poorer sleep. That does not automatically mean the dietary habit caused their sleep problems. Many other factors—such as age, exercise, stress, income, and other eating habits—could also play a role.
One way researchers can investigate causation more closely is through randomized intervention studies. For example, participants could be randomly divided into groups, with one group changing a particular lifestyle behavior while another continues its usual routine. Researchers could then compare their health outcomes.
Long-term studies are another valuable approach.
Dr. Wu gave the example of following students from ninth grade through college while continuously recording changes in their lifestyles and health. Researchers could then better determine whether a lifestyle change occurred before a particular health problem developed.
Some longitudinal studies continue for ten or even twenty years.
Scientific knowledge becomes stronger through repeated observation, testing, and years of accumulated evidence.
In the Future, Everyone May Have a Personalized “Healthy Diet”
If the same food can affect people differently, should everyone really receive the same nutritional advice?
That is exactly the question precision nutrition aims to address.
Dr. Wu believes strongly in the future of this field. She expects dietary recommendations to move increasingly away from a “one-size-fits-all” approach.
A person’s genetics, gut microbiome, metabolism, lifestyle, and existing health conditions may all affect how the body responds to food. For example, a healthy person, someone with obesity, and a smoker may not benefit from exactly the same dietary recommendations.
Even when we eat may matter alongside what we eat.
Dr. Wu explained that some of her research suggests the relationship between food and inflammation may vary according to season and individual characteristics. For example, associations between red meat consumption and inflammation may differ by season and by whether a person smokes.
This means that future public health research may need to move beyond simply asking:
“Is this food healthy?”
Instead, researchers may ask:
“For whom, at what time, and under what circumstances is this food appropriate?”
Good Research Questions Can Begin with Everyday Life
For students interested in medicine, public health, or scientific research, Dr. Wu’s advice goes beyond studying textbooks.
She encourages young people to experience the real world, travel, and observe.
When visiting another country or region, students can pay attention to what people eat, how they live, and which health conditions are common. They can then ask: Why do these differences exist? Could they be connected to environment, culture, diet, or lifestyle?
In her view, one of the most important skills in research is the ability to ask good questions.
And valuable scientific questions do not always begin in a laboratory. Many begin by carefully observing ordinary life.
This way of thinking has also influenced Dr. Wu’s own research. She explained that some ideas from traditional Chinese medicine and long-term observations of health have inspired scientific hypotheses in her work. Traditional observations cannot replace modern scientific testing, but they can provide a starting point for new questions that can then be examined through modern epidemiological and biomedical methods.
Making Health Advice Truly Personal
When asked what impact she most hopes her research will have in the future, Dr. Wu returned to one central idea: precision.
She hopes science will eventually help different people find diets and lifestyles that truly fit their individual needs, rather than asking everyone to follow exactly the same recommendations.
She is particularly interested in developing health recommendations that are more appropriate for Asian immigrants, taking into account both cultural backgrounds and individual biological differences. With her familiarity with Asian culture and her scientific experience in the United States, she hopes to help answer these cross-cultural health questions.
At the end of the interview, Dr. Wu also discussed how her faith influences the way she thinks about science and health. As a Christian, she views nature and the human body as following underlying patterns, including the cycle of day and night and the body’s circadian rhythms. To her, one purpose of scientific research is to discover and better understand these patterns and use that knowledge to improve human health.
From a glass of ice water to the complex connections between the gut and the brain, and from cultural differences in eating habits to a future in which each person may receive personalized nutritional guidance, Dr. Wu’s research reminds us that many important scientific questions can be found in the most ordinary parts of daily life.
Observe the world, ask questions, and use science to search for answers. Perhaps that is one of the most fascinating parts of research.
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