Scientists have long known that light stimulates alertness and helps to reset our circadian rhythms. But a study published in the Journal of Physiological Anthropology confirms that bright light early in the morning can also aid tryptophan levels.

Tryptophan is a precursor to serotonin which is itself a precursor to melatonin. The higher the tryptophan levels in your body, the better you will sleep.

Thirty-three people took part in the study, with half exposed to 30 minutes of 150 lux (equivalent to indoor light) at eye level and half exposed to 5000 lux (bright light – outdoor light in the morning can measure around 10,000 lux ) at eye level in the morning. Tryptophan was analyzed over the morning hours and was found to decrease in those receiving the lower light levels.

Modern work habits see most people go directly from home in the morning to an office, cutting out the bright light necessary to reset their circadian rhythm. Without adequate light (at least 1000 lux, but the higher the better), the 24-hour body clock will ‘drift’, adding about half an hour to its cycle each day. That means it may take you an extra half hour to get to sleep at night. 

For this reason, it’s important that people who work indoors get outside during the day (take your morning, lunch and afternoon breaks outdoors). Doing so can have a significant effect on your sleep, your mood and your energy.