Exposure To Blue Light Before And During Your Evening Meal Linked To Increased Hunger

Alan McStravick for redOrbit.com – Your Universe Online

It cannot be argued that in the last decade we have been spending more time looking at our phones, tablets and computers than ever before. Back in 2010, the Harvard Medical School began sounding the alarm about the potential hazards of blue light, the hue of light emitted by our electronic devices and energy-efficient light bulbs, and how it may be detrimental to our health, especially as the sun sets and we move from day into night.

Blue light, the publication contends, has the ability to affect our circadian rhythm causing poor and diminished sleep. Even worse, they say, blue light could be a significant contributor to ill health in the forms of heart disease, diabetes, cancer and obesity.

Cutting out all blue light is not necessarily recommended, however, as during daylight hours, it aids in boosting our attention, reaction times and mood. At night, however, increased attention brought on by blue wavelengths can suppress the secretion of melatonin, a hormone that influences our circadian rhythm. As of 2010, there was at least some evidence that diminished levels of melatonin could explain the association with diagnoses of cancer.

A separate Harvard study also examined the links between blue wavelengths of light and the onset of diabetes and obesity. A cohort of 10 participants was placed on a gradually changing schedule which shifted the timing of their circadian rhythms. The researchers noted an increase in blood sugar levels to such a degree that it placed the participants into a pre-diabetic state. Additionally, the participants leptin levels, a hormone associated with the feeling of fullness, decreased as well.

All of the Harvard research preceded a new study that builds on the idea of hunger and metabolism manipulation as a result of exposure to blue-enriched light. Researchers at Northwestern University in Chicago, Illinois have determined that with just 15 minutes of exposure to blue light prior to mealtime there is an increase in the sensation of hunger that remains for a full two hours after the completion of the meal. They also detected the same lack of sleeplessness and increased insulin resistance noted in previous studies.

“It was very interesting to observe that a single three-hour exposure to blue-enriched light in the evening acutely impacted hunger and glucose metabolism,” said study co-author Ivy Cheung, a doctoral candidate in the Interdepartmental Neuroscience program at the university. “These results are important because they suggest that manipulating environmental light exposure for humans may represent a novel approach of influencing food intake patterns and metabolism.”

Like the Harvard study noted above, the Northwestern University study consisted of a cohort of 10 healthy adult participants who presented regular sleep and eating schedules. During the course of the study they received identical carbohydrate-rich isocaloric meals. Over four days of the study, they were subjected to dim-light conditions on days one and two. Dim-light conditions refers to having been exposed to less than 20 lux during 16 hours awake and less than 3 lux during eight hours of sleep. Beginning on day three, the light exposure was increased to 260 lux, blue-enriched light for three hours. The effects of the increased lux exposure was compared to the conditions experienced on day two.

According to Cheung, further research is needed to determine the mechanisms of action involved in the relationship between light exposure, hunger and metabolism.

With the growing prevalence of energy-efficient lighting, including compact fluorescent light bulbs, it may seem that we are technologically advancing ourselves to ill health. Experts recommend a few keys to combating prolonged exposure to blue wavelengths such as:

– Use dim red lights in the evening. Red light has the least power to shift circadian rhythm and suppress melatonin.

– Avoid looking at bright screens beginning two to three hours before bed.

– Graveyard shifters are urged to invest in blue-blocking glasses (approx. $80)

– Seek prolonged exposure to bright light during the day to help facilitate sleep in the evening.

– Seek out software products for your devices that automatically shift your screens light to a diminished amount of blue light as the evening progresses. F.lux is one provider of blue-blocking software available.

Results of the study, having already been published online in the journal SLEEP, will be formally presented at this year’s SLEEP 2014 in Minneapolis, Minnesota. This year’s conference marks the 28th annual meeting of the Associated Professional Sleep Societies, LLC.

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