Tone Henriksen is Science Advisor of the Good Light Group, and co-author of the scientific article on the effect of blue-blocking glasses on melatonin onset during pregnancy.
All life is adapted to the natural light-dark cycle produced by the 24-hour rotation of the earth. Even before we are born, we get a time-cue from the outer environment from our mother’s night hormone melatonin. Melatonin passes freely over the placenta and seems to be important for a healthy pregnancy in several ways. The hormone of darkness plays an important role for the placenta – the organ securing oxygen and nutrition to the fetus. Melatonin is a strong free radical scavenger and has neuroprotective function for the growing fetus. Nevertheless, melatonin protection is not part of the general advice to pregnant women – yet.
Recent evidence suggests a simple way of protecting pregnant women and fetus from melatonin shortage, without the need to stay in real darkness. As it turns out, all light is not equal when it comes to suppressing the darkness hormone melatonin. To the brain-, light containing high portions of blue frequencies is interpreted as daylight. Natural morning and mid-day sunlight have a high portion of blue. In 2014, Shuji Nakamura won the Nobel Prize in Physics for inventing blue emitting LED diodes-, which was necessary for making white and bright indoor lighting, similar to sunlight. However, in the natural condition, the sun sets in the evening.
Image a camping bon-fire, far away from electric lighting. No blue light there, and melatonin production in the brain starts fine-tuned and synchronized to the internal circadian rhythm and natural environment. This is a nice scenario but, except during holidays, hardly a practical advice to pregnant women. Could blue-blocking (BB) glasses work as well? Randi Liset and co-authors in Bergen, Norway, conducted the first trial testing the melatonin protective effects of amber glasses (99% blue-blocking) as compared to grey control glasses (approximately 50% blue-blocking) for healthy pregnant women in the third trimester (N=60) A randomized controlled trial on the effects of blue-blocking glasses compared to partial blue-blockers on sleep outcomes in the third trimester of pregnancy - PMC (nih.gov)
Both groups wore the glasses for three hours prior to their preferred bedtime. After two weeks, the BB-glasses group had 43 minutes earlier melatonin onset and the control group 11 minutes earlier melatonin onset than at baseline. The adjusted difference of 28 minutes was highly significant. The superiority of the near 100% blue-blocking over the partially blue-blocking control condition was clear. This shows the need for blocking as much blue light as possible in the evening for optimal protection of the rise of your melatonin. These glasses seem an easy way to effectively lower melanopic lux levels in the evening.
Other studies have shown that more daylight during the daytime increases the capacity of producing melatonin the following night. Follow-up studies combining daytime light exposure and evening blue-blocking are wanted. For now, this novel study by Liset et al. provided the first evidence that BB-glasses worn in the evening for three hours before bedtime can serve as a simple, low-cost and safe means of non-pharmacological strengthening of circadian health for mother and fetus.