Light and Your Health

  • September 7, 2022
  • 2 minutes read

In densely populated and urbanised Singapore, we are never completely without light. How does this affect the way our bodies function?

Light plays a vital role in regulating our circadian rhythms, which are driven by our biological clock. The circadian biological clock is controlled by a part of the brain called the suprachiasmatic nucleus (SCN), a group of cells in the hypothalamus that respond to light and dark signals. From the optic nerve of the eye, light travels to the SCN, signalling the internal clock that it is time to be awake. In the morning, with light exposure, the SCN sends signals to raise the body temperature and produce hormones like cortisol.

The SCN also responds to light by delaying the release of other hormones like melatonin, which promotes sleep. Irregular sleep schedules or travelling to a place with a different time zone puts us in conflict with our natural sleep patterns, and can affect our ability to think and perform well.

Our bodies depend on natural sunlight in other ways as well. Regular exposure to sunlight increases serotonin levels in the body, keeping us active and alert. Sunlight contains the full spectrum of light, consisting of radio, microwave, infrared, visible, ultraviolet (UV), X-rays and gamma rays. Of these, visible and UV rays have been found to benefit the body.

Although UV rays release a compound, nitric oxide, that lowers blood pressure, prolonged exposure to it can cause premature skin ageing and damage the body’s immune system. In fact, according to medical journal The Lancet, indoor workers who had three to nine times less solar UV exposure were found to have lower levels of vitamin D. Vitamin D promotes bone growth and helps prevent conditions ranging from breast cancer to depression.

Exposing yourself to the sun in safe amounts, therefore, is not only beneficial, but necessary for the body. On the other hand, we are also heavily exposed to artificial light that can have adverse effects on the body.

There is growing concern that constant exposure to light when it’s dark disrupts our circadian rhythm. Artificial light at night suppresses the production of melatonin, resulting in delayed or broken sleep.

Other findings show that the glare from computers or smartphones at night can lead to weight gain. This is because the blue light they emit acts as a wake-up call for the brain and signals to the body clock that it’s time to get up, and replenish energy stores that have been used up during the night.

“A small amount of blue light is not likely to have much effect on sleep or health,” says Professor Jim Horne, former head of sleep research at Loughborough University. “But the brain is more sensitive to blue light than any other colour, and it does tend to affect the body clock more than other light colour.”

Therefore, be sure to keep your bedroom as dark as possible, and consider stopping the use of electronic devices right before bed.

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