The lights we depend on after dark – to work, read, use the computer, and get around - the huge advantages of electric light - have a downside. They upset our natural sleep-wake cycle. The pineal gland, located midbrain, behind the eyes, secretes a hormone called melatonin, synthesized from the amino acid tryptophan. Melatonin comes out as the day gets dark, making us sleepy and lowering our body temperature. When we turn on the lights and stay up late working or playing, this reduces the time we are in darkness. Less melatonin is put out, and sleep can become elusive. We may fall asleep, but not stay asleep – a common complaint of older people, who secrete less melatonin with advancing age. Instead of deploring the genius of Thomas Edison, we can be grateful for current researchers who have found out how we can live with the advantages of light and still sleep. Studies have shown that it is the blue component in light that causes the most melatonin suppression; it is possible to block blue light by wearing goggles that filter out over 90% of the blue light. By putting on these yellow-orange goggles for 1-2 hours before bedtime, melatonin will flow out and sleep will improve. To apply this research to your own sleep patterns, go to LowBlueLights.com. Meet Richard Hansler, at the Lighting Innovations Institute at John Carroll University in Cleveland. Hansler, now 87, is a physicist who has pushed the development of lighting that does not disrupt melatonin outflow. At this website they sell blue blocking glasses, as well as special lights low on the blue part of the light spectrum, both incandescent and fluorescent. Their glasses, which can be worn over reading glasses if needed, cost from $68 to $80. I have used these glasses for over 2 years and find them very effective. Much less expensive blue blocking glasses can be found elsewhere on the internet – read customers’ comments carefully to find out if they are effective.
Eva Schernhammer at Harvard has studied the effects of night light on cancer risk through the melatonin pathway. She found that nurses who had worked for more than 15 years on rotating night shifts had a 35% higher risk of breast cancer than those who never worked rotating shifts. Shift workers have disrupted melatonin output. She also found that women with invasive breast cancer had less of a melatonin metabolite in their overnight urine. She found that women who were totally blind had a lower rate of breast cancer than blind women who still respond to light. Dr. Schernhammer concluded in a 2009 paper that melatonin is able to fight breast and other cancers by being a powerful antioxidant that can destroy damaged DNA before it can initiate cancer, by preventing cell mobility that causes metastasis, and preventing blood vessel growth that may nourish cancer cells.
A Japanese study in 2006 found that men who worked rotating shifts had a significant increased risk of prostate cancer over those who worked non-rotating shifts.
A 2005 Canadian paper showed a positive correlation between the duration of exercise and the amount of melatonin produced in overnight urine. This is suggested as a mechanism by which exercise reduces the risk of breast cancer.
Here’s my take-home lesson from the research on melatonin. Investigate blue-blocking glasses - and try using them 1-2 hours before your regular bedtime. Increase the duration of your daily exercise if you have trouble sleeping, or staying asleep. And – if you do wake at night and can’t fall back to sleep, get up and have a small snack of food, especially one containing milk. Milk contains enough tryptophan to promote sleep. Something sweet, like a piece of banana, will stimulate insulin which helps transport tryptophan across the blood-brain barrier.
In my next column I will write about new data on the potential dangers of prescription sleeping pills, and more natural alternatives. Also – there is new data on the importance of sleep in the prevention of diabetes and dementia. Stay tuned!
Sadja Greenwood, MD, MPH back issues on this blog
Sleep is the best meditation – the Dalai Lama