Can a Light Really Be Called “Healthy”?
Starting with a Common Label: Defining the Boundaries for Judging Healthy Lighting
Author | Lawrence Lin
GLGA Chairman | GLG Board Member | IWBI WELL Light Concept Advisor | LRS Founder & CEO
At exhibitions, I often come across labels such as “healthy lighting,” “sleep lighting,” and “eye-care lighting.” Someone may point to a spectrum graph and ask me: “The peaks have been reduced and the spectrum has been filled in—does that prove it is healthy?” My answer is usually not the most popular one: this only shows that the product has certain optical characteristics; it does not, by itself, prove a health outcome.
A light source can be measured, and a period of light exposure can be designed; but “health” is the result of the interaction between people, light, space, time, and activity. What we really need to do is not give a lighting product a permanently valid “healthy” label, but ensure that light serves specific people in the right way, at the right time.
1 | First, Separate the Three Levels
The first level concerns the characteristics of the light source or luminaire, such as spectral power distribution, luminous flux, correlated colour temperature, colour rendering, light distribution, and temporal light modulation. These characteristics answer the question: “What kind of light does this product emit?”
The second level is light exposure within a space—for example, how much light the eyes actually receive at a particular location, from a particular direction, and during a particular period. It answers the question: “What is the person actually receiving here?” The results will differ depending on factors such as whether the same luminaire is installed higher, positioned farther from the person, or whether the person’s orientation changes.
Only at the third level do we consider the person’s response, including whether they can see clearly, whether they feel comfortable, whether alertness and sleep rhythms are affected, and what their experience is over long-term use. These responses can be influenced by age, daily routines, previous light exposure, medication, and individual differences.
Confusing these three levels is at the root of many marketing debates. Product specifications can support design, but they cannot bypass the spatial and human levels and be directly translated into health outcomes.
2 | “Integrative Lighting” Is More Accurate Than “Healthy Lighting”
The CIE uses the term “integrative lighting,” which is commonly translated into Chinese as “综合照明” or “整合照明.” It emphasizes considering both the visual and non-visual effects of light, while taking into account people’s physiological and psychological needs together with energy consumption, environmental factors, and building conditions. It is neither light therapy nor an approach focused solely on optimizing a single circadian metric.
This is also why I prefer to talk about “health-oriented lighting design” rather than casually applying the label “healthy” to an individual product. Good lighting should first enable people to see clearly, remain comfortable over extended periods, and move around safely. On that foundation, we can then consider whether people receive sufficient circadian stimulation during the day and whether unnecessary disruption is avoided at night.
3 | A Simple On-Site Check
Suppose a desk lamp is marketed as full-spectrum, low-blue-light, and free from visible flicker. Once we place it in an office, we still need to ask:
Is the illuminance on the work surface sufficient? Is the screen creating reflections? How much light exposure is reaching the eyes? Is the same lighting setting being used during the day and at night? For someone who spends long periods looking downward, are their eyes even receiving the portion of the light that the product claims to provide?
These questions do not diminish the value of the product. On the contrary, they put the product back into the real world. Only when we consider the actual context does a set of specifications begin to become evidence for lighting design.
4 | What We Can Say Today — and What We Cannot
What we can say today: A product may meet clearly defined optical, visual-comfort, or electrical performance requirements. Under specified distances, viewing directions, and dimming conditions, it can provide measurable and repeatable light exposure.
What we cannot say: Temperature, “full spectrum,” a single-point measurement, or a spectrum graph alone is not enough to claim that a product can treat insomnia, improve immunity, or be suitable for everyone.
5 | Three Things We Can Do Today
- When you see a “healthy” lighting claim, first ask whether it refers to a product characteristic, spatial light exposure, or a human outcome.
- Ask suppliers to provide the measurement conditions, rather than presenting only a string of attractive numbers.
- In project specifications, clearly define the visual, circadian, control, and verification objectives together.
Evidence label: Established consensus.
The visual and non-visual effects of light should be considered together; product specifications cannot substitute for human outcomes.
References
- CIE, Integrative Lighting — Terminology Definition：https://cie.co.at/eilvterm/17-29-028
- CIE PS 001:2024：https://cie.co.at/publications/cie-position-statement-integrative-lighting-recommending-proper-light-proper-time-3rd
- CIE S 026:2018：https://www.cie.co.at/publications/cie-system-metrology-optical-radiation-iprgc-influenced-responses-light-0
In the next article, we start with the eye: beyond helping us see, it also quietly keeps time for the body.
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