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One Health: You & Me

Written by Sungmin Lee

Edited by Celina Tang, Jocelyn Tan, and Kyla Finlayson

Diving into our third pillar of One Health in our blog series, we will be exploring human health. Feel free to check out our blog posts on environmental health and animal health.

The One Health Diagram

WHO Definition of Health

The WHO defines human health as a “state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.”

However, there are criticisms of this definition of health. When was the last time you were completely healthy based on this very definition? A person is rarely in a state of complete physical, mental and social well-being. In short, health is very complex to define as humans each have our own unique view on health. Not only this, but there are countless ways to measure health using different criteria. This article will explore the various ways to investigate human health and the many aspects influencing human health definitions. Overall, after reading this article, readers should gain an appreciation on why human health is so complicated, and thus why a One Health approach is so desperately needed to tackle problems relating to human health.

Why is it difficult to define health? Why is health so complex?

There are countless factors that weigh into the complexities of defining health. Yet, there are common factors which can be made into categories. These include subjective experiences of health stemming from societal and individual perspectives, and how health measurements/definitions can differ based on various time intervals.

1. Subjective Experiences of Health

First, our internal beliefs might contradict what our medical tests indicate, and this may further conflict with our societal ideals. In clinical studies, researchers often use patient-reported outcomes. This method allows the patient’s view of health to dictate the results of a study. This is particularly evident in physician-patient interactions. Social stigma and ideals often influence what the patient reports and their definition of being healthy. Currently, it is almost impossible to standardize these responses, since each human is uniquely influenced and prioritizes the importance of various aspects of health very differently.

Again, society’s perception of health and social norms play a huge role in influencing an individual’s definition of health. Obesity is a prime example of this. It was observed in the US that social norms influence US children’s BMI growth. It was found that high obesity prevalence will lead to a continuous increase in children’s BMI due to increased socially acceptable mean BMI.

2. Time and its Influence on Health Measurements

Time is relative, and likewise health is measured differently based on which time periods it is evaluated in. For example, Current Health focuses narrowly on an individual’s current health. Lifetime Health, on the other hand, compares the health states, and its fluctuations experienced by person A and person B throughout their lifetimes. Lifetime Health takes into account both acute and fatal health states.

Intrinsic vs. Instrumental Value of Health

Health can be very tricky to define, but we do know that it is our most valuable asset. There are two ways to look at this value of health: the intrinsic and instrumental value. The intrinsic value of health is associated with personal satisfaction from the absence of disease.

The instrumental value of health highlights the functional value of a healthy individual. Being healthy allows us to work, sustain our livelihoods, play, and further our skills. Alternatively, being sick may perpetuate the cycle of poverty. For instance, a sick person may be unable to work, and consequently falls lower on the socioeconomic ladder due to medical costs, lost opportunities, and instability.

Therefore, intrinsic and instrumental value of health are interconnected and are two simple values that being healthy immediately provides.

Domains of Health

Figure outlining the various domains of health, which shows the different ways to measure health.

Health can be further classified into domains, both direct and indirect. These categories allow us to understand the broad nature of health and the uniqueness between each domain. The direct measurements of health such as vision, hearing pain, etc. outline the physiological and physical aspects of health. Indirect measurements of health are more functional and related to the aforementioned instrumental value of health. The purpose of using domains of health is to help us classify the vast categories that health encompasses, and allows us to organize the various aspects of health into two distinct, manageable domains.

Why do we try to put a monetary value on health?

Economists and government officials regularly try to place financial value on health outcomes. Examples of such measurements include GDP loss due to individuals too ill to work, health stock, and annual percentage of government budgets allocated to healthcare. Placing a monetary amount on human health is a common strategy because the effectiveness of health promotion strategies can be easily compared, and can be closely monitored. Understanding that placing a financial value on health allows the government to discern possible policies and budget allocation to support population health is important. This is yet another way we try to conceptualize and measure health!


Human health is a fundamental One Health pillar. Nonetheless, out of the three main pillars, human health, animal health and ecosystem health, none can be defined in a straightforward manner. It is important to appreciate the interconnectedness and complexity of each pillar in One Health and view them separately from the conventional method of studying most physical sciences. One Health affords us the luxury of exploring all relevant aspects of health. As such, understanding human health in a One Health context is imperative, since human health is very complex by nature. While studying human health from a purely clinical/biological perspective works, human health encompasses so much more. One must explore the various aspects of human health to understand what health is and how to improve healthcare outcomes both at an individual level and at a community wide level.



Most content is derived from OH3300A content on Human Health created by Dr. Stephanie Frisbee.

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