A woman absorbs sunlight while standing on a balconyShare on Pinterest
Researchers say sunlight can help regulate blood sugar levels. Tempura/Getty Images
  • Disruptions in circadian rhythm can raise type 2 diabetes risk.
  • Researchers say spending more time outdoors may help prevent type 2 diabetes alongside a healthy diet and exercise.
  • They say that’s because exposure to natural light improves metabolism and blood sugar control

Want to double up on type 2 diabetes prevention?

Try eating a salad on a sunny patio. Or go for an afternoon run. Or take a nap in your backyard.

According to researchers, these are all good ways to help manage blood sugar levels.

Exposure to sunlight along with a healthy diet, regular exercise, and adequate sleep are effective ways to help prevent the development of type 2 diabetes (T2D), researchers say.

Additionally, they say that exposure to natural light can help treat and prevent type 2 diabetes.

The findings were presented this week at the annual meeting of the European Association for the Study of Diabetes. The research has not yet been published in a peer-reviewed journal.

Researchers say that metabolism and insulin resistance are directly tied to the body’s natural clock and that increasing exposure to natural light can help both.

Ivo Habets, a study co-leader and a PhD researcher at Maastricht University in the Netherlands, said in a press statement:

“The misalignment of our internal circadian clock with the demands of a 24/7 society is associated with an increased incidence of metabolic diseases, including type 2 diabetes. Natural daylight is the strongest [environmental cue] of the circadian clock, but most people are indoors during the day and so under constant artificial lighting.”

To test the theory, researchers conducted metabolic tests on a group of 13 people with type 2 diabetes as they were exposed to natural or artificial light. The study subjects were confined to a research facility to control their light exposure and to monitor and standardize diet and activity patterns.

Controlled light exposure took place over more than 4 days from 8 a.m. to 5 p.m. A month-long gap was established between each period of light testing.

Natural lighting intensity varied over the course of the day, whereas artificial lighting remained at a constant intensity of 300 lux — in the range of the amount of light normally recommended for a dining or work area.

At night, lighting was dimmed to 5 lux, and sleeping (11 p.m. to 7 a.m.) was in darkness.

The researchers reported that normal blood glucose levels persisted longer during the periods where study subjects were exposed to natural light (59% of the 4.5 days) than artificial light (51%).

The participants’ bodies also were able, as measured via respiratory exchange ratio, to switch more easily from carbohydrate to fat as an energy source when exposed to natural light.

“This usually follows a 24-hour rhythm, with the body switching from using carbohydrates as its source of energy during the day, to fat at night,” explained Habets.

“We’d previously shown that people at higher risk of type 2 diabetes are less able to make this switch, and we wanted to find out if exposure to natural light would make the switch over easier in people who already have diabetes.”

Per1 and Cry1, genes that help control circadian rhythms, were more active in natural light than in artificial light as well, the study found.

Researchers said that the findings, particularly around glucose tolerance, suggest that exposure to natural daylight is beneficial to metabolism and could help treat and prevent type 2 diabetes and other metabolic conditions.

“Our research shows that the type of light you are exposed to matters for your metabolism,” said Habets.

“If you work in an office with almost no exposure to natural light, it will have an impact on your metabolism and your risk or control of type 2 diabetes, so try to get as much daylight as possible, and ideally, get outdoors when you can.”

Future studies should look at the extent to which artificial light affects metabolism and how long people need to spend in natural lighting to compensate for artificial light exposure, he said.

“Sleep and circadian rhythm are definitely linked with diabetes risk,” Erin Davis, a registered dietitian and diabetes educator who was not involved in the study, told Medical News Today.

“Since our circadian rhythm is regulated by light, it makes sense that daylight exposure would be beneficial. Exposure to natural light, rather than artificial light, helps your body’s clock reset—resulting in better sleep and improved health.”

Sleep is essential for metabolic health, added Davis.

“When you are lacking in sleep, your cortisol levels go up. Cortisol can elevate glucose levels, worsen insulin resistance, and increase the hunger hormone ghrelin — making it difficult to stay within your glucose targets. Optimizing your sleep plays a crucial role in effectively managing your glucose levels. Instead of staying up late, fueled by the light of your device’s screen, aim for a bedtime that mimics the available daylight. Not only will you feel energized, you’ll lower your risk of diabetes.”
— Erin Davis, registered dietitian and diabetes educator

Dr. Bree Willis, medical director at Twin Health, not involved in the study, also noted the importance of natural light to sleep.

“We know that natural light exposure is linked closely to the sleep-wake cycles and these cycles have profound effects on eating patterns, activity levels, sleep quality and quantity, and overall health,” she told MNT.

“People who have regular disturbances in their sleep-wake cycles or circadian rhythms are at higher risk of obesity and other metabolic conditions such as diabetes.”

Dr. Willis said her practice strongly emphasizes the importance of regular sleep, healthy nutrition, and daily physical activity to support a healthy sleep-wake cycle in her patients.

“By doing so, our members have improved metabolic health overall,” she said.

Vitamin D from exposure to natural light also may help with diabetes prevention, said Melanie Murphy Richter, a registered dietitian, nutritionist, and instructor of nutrition physiology at the University of California Irvine, who was not involved in the study.

“A person’s vitamin D status can significantly impact how well their body utilizes insulin, the hormone necessary for pulling glucose into our cells for use as energy,” Richter told MNT.

“Without adequate vitamin D, research has shown that the body will be less sensitive to insulin, a hallmark characteristic of those with type 2 diabetes.”

In addition, vitamin D can stimulate insular receptor expression in the pancreas and enhance insulin responsiveness for glucose transport, resulting in decreased blood glucose.

“This makes vitamin D significant in the management and regulation of glucose in the body. Vitamin D is also highly important for proper immune function. Since people with diabetes are more prone to infections and slower wound healing, vitamin D can play a helpful role in optimizing the immune system and improve the health of those with this condition.”
— Melanie Murphy Richter, registered dietitian and nutritionist