ONLINE DRIVERS MEDIA

"No sun, no diabesity protection." The evidence is equivocal and the number of studies low, but there is evidence that this statement could be true.

Ok, its November and not exactly sunny in the Northern hemisphere, but if you look back at the months June-August, how much sun exposure did you actually get, this year? Hardly any? Well, thats bad news, because a recent review of the scant scientific evidence suggests that there is "a role of recreational sun exposure in reducing odds of T2DM incidence" (Shore-Lorenti. 2014).

In view of the fact that the contemporarily available evidence is not exactly comprehensive, you should yet consider the following overview of the potential effects and mechanism as a "work in progress".
As Shore-Lorenti et al. point out, the recent International Diabetes Federation (IDF) Diabetes Atlas (6th edition) describes a snapshot of the global diabetes burden in 2013 and projects this forward to the year 2035.1 Cur rently, an estimated 382 million global citizens have diabetes, costing around $1437 USD in 2013 for each person affected by the condition. Projections based on current trends predict that 592 million people will be living with diabetes by 2035; one in ten people will be affected, with an inordinate amount of fund ing required globally to treat diabetes and manage diabetic com plications ($627 billion USD in 2035).

And while scientists are feverishly searching for a solution for the diabesity epidemic, the ongoing research into the effectiveness of vitamin D supplementation in diabetes have yielded inconsistent results (Mitri. 2011). Against that background it appears almost negligent that only few scientists have yet taken a closer look at the factors that trigger vitamin D sufficiency or rather the global low vitamin D epidemia.

Lack of sun"low vitamin D" - thats not all!

Figure 1: Australians who use sunscreen chronically have 50% reduced vitamin D levels (Matsuoka. 1988)

A lack of sufficient (unprotected) sun exposure - previous studies have shown that chronic sunscreen use decreases circulating concentrations of 25-hydroxyvitamin (Figure 1 | Matsuoka. 1988) - is one of the factors of which researchers speculate that it contributes to the development of vitamin D deficiency even in those of us who live in areas with a high annual sun-exposure.

Now, if restoring the 25-OHD (vitamin D) levels to normal does not work the anti-diabetic magic it is supposed to do and our D-levels are low due to insufficient sun-exposure, it appears only logical to assume that a lack sun-exposure and not a lack of vitamin D is one of the factors that contributes to the ever-increasing rates of diabesity - in conjunction with the usual subjects, obviously: The consumption of a junk-food diet and a lack of exercise, which is without doubt the #1 reason people in the Western Obesity Belt develop obesity, diabetes and the other characteristics of the metabolic syndrome.

Against that background its all the more surprising that evidence for an association between sun exposure and fasting serum glucose level is scarce.

"Typically, the lowest glucose levels occur during summer and levels peak in winter or early spring. One of these analyses [Shore-Lorenti et al. reviewed] went beyond simply observing trends in fasting glucose throughout the year: fasting plasma glucose was positively correlated with a measure of available sun and inversely correlated with temperature." (Shore-Lorenti. 2014)

The study, the researchers from the University of Melbourne have in mind was conducted by Suarez, L. & Barrett-Connor, E. in 1988, already.
If you look at the data Suaraez & Barret-Connor generated, you can see - even without their statistical sophisticated analysis - that there is a significant correlation between possible sun exposure (Figure 1, left) and the fasting plasma glucose levels (Figure 1, right).
Since physical activity may follow a similar circannual rhythm, its yet difficult to exclude that the effects Suarez & Barret-Connor observed were not corroborated (or corrupted?) by an increase in physical activity. However, Shore-Lorenti et al. believe that ...

"[...c]onsidering that the unadjusted analyses and three of four of the studies included in the best evidence synthesis (including the study adjusting for physical activity) are in agreement, it is possible that future research may confirm that sun exposure reduces fasting glucose" (Shore-Lorenti. 2014).

Shore-Lorenti et al. also point out that the highest level of evidence (moderate) for an association between sun exposure and T2DM outcomes in adults originates from the study by Lindqvist et al. (2010). In their paper, the researchers from the Karolinska University Hospital report a reduction in odds of developing T2DM given increased recreational (rather than occupational) sun exposure. 

Figure 2: Leisure time sun exposure is associated with a significantly reduced risk (up to 50%!) of developing T2DM in Swedish adults (Lindqvist. 2010)

In subjects with a low BMI the beneficial effect of using the tanning bed and sunbathing is even more pronounced (-60% risk). In the obese, however, it is significantly reduced (-10%) compared to the average reductions you see in Figure 2.

The fact that only leisure time, but not occupational sun exposure was linked to a significant reduced risk of developing type II diabetes may, as Shore-Lorenti et al. point out be due ...

"[...] to the frequency of sun exposure (perhaps leading to tolerance), duration, intensity and site of exposure (sun protective clothing and behaviour differences between the two settings), or perhaps selection biases for such work (for example, fair-skinned people may avoid occupational sun exposure or a less healthy lifestyle may be associated with manual labour)."

Incidentally, a similar disparity between recreational and occupational sun exposure is well described for risk of developing melanoma (Chang. 2009).

A review by Chen et al. (2008) provides low-level evidence for an association between sun exposure and fasting insulin levels; fasting serum insulin was higher in summer than in winter. Overall, the results are yet inconclusive. A fact, Shore-Lorenti et al. ascribe to "the lack of adjustments made by the included study – particularly for BMI" (Shore-Lorenti. 2014)
Overall, we are thus left with the above overview (Table 1) as a conclusion of which the mere number of "unkown"s and "inconsistent"s tell you that we are not yet at the point to draw a water-proof conclusion.
References:

• Chang, Yu-mei, et al. "Sun exposure and melanoma risk at different latitudes: a pooled analysis of 5700 cases and 7216 controls." International journal of epidemiology (2009): dyp166. 
• Chen, Shui-Hu, et al. "Community-based study on summer-winter difference in insulin resistance in Kin-Chen, Kinmen, Taiwan." Journal of the Chinese Medical Association 71.12 (2008): 619-627.
• Lindqvist, Pelle G., Håkan Olsson, and Mona Landin-Olsson. "Are active sun exposure habits related to lowering risk of type 2 diabetes mellitus in women, a prospective cohort study?." Diabetes research and clinical practice 90.1 (2010): 109-114.
• Mitri, J., M. D. Muraru, and A. G. Pittas. "Vitamin D and type 2 diabetes: a systematic review." European Journal of Clinical Nutrition 65.9 (2011): 1005-1015.
• Nelemans, P. J., et al. "An addition to the controversy on sunlight exposure and melanoma risk: a meta-analytical approach." Journal of clinical epidemiology 48.11 (1995): 1331-1342.
• Shore?Lorenti, Catherine, et al. "Shining the Light on Sunshine: a systematic review of the influence of sun exposure on type 2 diabetes mellitus?related outcomes." Clinical endocrinology (2014).
• Suarez, L., and E. Barrett-Connor. "Seasonal variation in fasting plasma glucose levels in man." Diabetologia 22.4 (1982): 250-253. 

No, the sun does not kill you. If you control your exposure it may extend your life and improve your life-quality significantly.

Its about time to "let there be light" to illuminate the benefits of regular well-timed exposure to sunlight and its short frequency component. Only recently, researchers from the Japanese National Institute of Advanced Industrial Science and Technology (AIST) were able to show that daytime light exposure has significant beneficial effects on cognitive brain activity. Significant enough to have the subjects perform better on an oddball task and to significantly increase cortical activity related to cognitive processes (Okamoto. 2014).

But is that really all, bright light, or more specifically, the regular and well-timed exposure to bright light can do for you?
Certainly not. I mean if its ill-timed, like the evening use of light-emitting eReaders it will negatively affect your sleep, mess up your circadian rhythm and decrease your alertness on the next morning. Similar results, i.e. drowsiness and suppression of energy metabolism the following morning, have been reported by other studies, as well (Kayaba. 2014).

As a SuppVersity reader you do yet know all about those negative effects from the circadian rhythm series, anyway. Reason enough for me, to focus primarily on all the good stuff, the well-timed exposure to bright light can do for you in todays Special of the SuppVersity Short News.

• If you cant let go off your mobile at night, use blue blocker glasses as a countermeasure for alerting effects of evening light-emitting diode screen exposure - According to researchers from the Psychiatric Hospital of the University of Basel, blue blocker glasses (BB) significantly attenuate LED-induced melatonin suppression in the evening and decrease vigilant attention and subjective alertness before bedtime.
  
  Strangely, though, visually scored sleep stages and behavioral measures collected the morning after were not modified. Still, van der Lely et al. conclude: "BB glasses may be useful in adolescents as a countermeasure for alerting effects induced by light exposure through LED screens and therefore potentially impede the negative effects modern lighting imposes on circadian physiology in the evening "(van der Lely. 2014).
• UV-light protects against "brainflammation" in MS model - Scientists from the University of Wisconsin-Madison report in their latest paper that UV light selectively inhibits spinal cord inflammation and demyelination in experimental autoimmune encephalomyelitis.
  
  Previous studies have already shown that UV radiation (UVR) can suppress experimental autoimmune encephalomyelitis (EAE), an animal model of multiple-sclerosis (MS), independent of vitamin D production. The mechanism of this suppression did yet remain to be elucidated, until Wang et al. (2014) observed that UVR (10kJ/m²) does not just inhibit the inflammation and demyelination of the spinal cord, but will also dramatically and significantly reduce spinal cord chemokine CCL5 mRNA and protein levels.
  
  In conjunction with an increased production of intereron-gamma (IFN-?) and IL-10, which are actually used to treat all sorts of autoimmune diseases, artificial and natural UV light can thus actually "prevent the migration of inflammatory cells into the CNS" (Wang. 2014).

• Melatonin conc. after 4 days w/ dim vs. bright light and tryptophan rich vs. poor breakfast (Fukushige. 2014).

  Bright light in the AM and the consumption of a breakfast thats high in tryptophan can help you maintain a healthy circadian rhythm - In case you are asking yourself how you can grasp all the benefits that are associated with having an intact circadian rhythm, you may be intrigued to hear that researchers from the Fukuoka Womens University have been able to show that an increase in tryptophan intake at breakfast combined with daytime light exposure has beneficial effects on melatonin secretion and sleep quality. As you can see in the figure to the left it will significantly elevate the evening melatonin peak, which is critical for an optimal circadian rhythm.
  
  If you are looking to optimize your internal clock bright light (either sunlight or a 10,000 Lux daylight lamp) + tryptophan (seeds, nuts, soy, cheese, chicken, turkey, fish, oats, beans and eggs are the TOP10 sources) are the way to go. If you want an extra "kick" add some coffee to the equation. This will increase the light responsiveness of the circadian pacemaker - well, at least in mice it does (Diepen. 2014).

• Bright lights at work will keep you sane, happy and alert - If you are working in an insufficiently lit office without natural sunlight, you should be prepared to develop physiological, sleep and depressive symptoms.
  
  Assuming you have a window in your office, you will get a significantly more pronounced total and peak exposure to bright light thats going to correlate with 33% reduced levels of the stress hormone cortisol, a more natural rhythm of melatonin and a reduced risk of minor psychiatric disorders and depressive symptoms (MA) in the evening.
  
  Thats at least what the results of a recent study from the UFRGS in Porto Alegre indicates (Harb. 2014). A study the authors of which proudly say that their "study demonstrated that not only may light pollution affect human physiology but also lack of exposure to natural light is related to high levels of cortisol and lower levels of melatonin at night, and these, in turn, are related to depressive symptoms and poor quality of sleep" (Harb. 2014).

• If you want to light up the darkness, when its actually time to sleep do it with green (555nm) or red, not blue light, which suppresses melatonin (Bonmati-Carrion. 2014).

  Staying away from nightly night exposure may also help to keep your arteries clean even in the old age - Studies indicate that even after  adjustment for confounding factors, including age, gender, body mass index, current smoking status, hypertension, diabetes, dyslipidemia, sleep medication, estimated glomerular filtration rate, nocturia, bedtime, duration in bed (scotoperiod), day length (photoperiod), urinary 6-sulfatoxymelatonin excretion and daytime and nighttime physical activity, exposure to light at night is associated with carotid intima-media thickness (Obayashi. 2014).
  
  If you dont want to develop subclinical carotid atherosclerosis, when you are old, it would thus be a good idea to adhere to the basic rules of sleep hygiene: a dark room and/or blindfolds will keep your arteries clean and may thus save your life ;-)
• If you have kidney problems, get out in the sun if you want to survive - Scientists from the University of California Irvine Medical Center were able to show that dialysis patients residing in higher UV index regions have lower all-cause mortality compared to those living in moderate-high UV regions (Shapiro. 2014).
  
  More specifically, the ~60year-old subjects residing in moderate-high UV index regions had a 16% reduced risk of all-cause mortality. Those living in very-high UV index regions had a 1% higher risk reduction (17%). Interestingly, there was a similar inverse association between UV index and mortality was observed across all subgroups, but it was more pronounced among whites vs. non-whites.
• Wear those shades (or bluelight blocker glasses) before any important sport event - Why? Stupid question. If you dabble around with your smartphone "unprotected" the evening before an important sport event for only 30 minutes, this can influence exercise performance under hot conditions during the subsequent early morning (Thompson. 2014).

Sleep disturbance and adaptive immunity. Following a night of sleep loss, or during a period of sleep disturbance, nerve fibers from the sympathetic nervous system (SNS) release the neurotransmitter norepinephrine into primary and secondary lymphoid organs and stimulate the adrenal gland to release stored epinephrine into systemic circulation. Both neuromediators stimulate leukocyte adrenergic receptors (e.g., ADRB2) and activate nuclear factor (NF)-?B-mediated inflammatory programs (Irwin. 2015).

• If your grandparents have Alzheimers install a timer-based light system - This may not just increase their sleep quality, but it will also improve their behavior and mood as indicated by reduced depression scores on the Cornell Scale for Depression in Dementia and agitation scores from the Cohen-Mansfield Agitation Inventory (Figueiro. 2014).
  
  I must warn you, though: The recent field study from the Rensselaer Polytechnic Institute is promising, but the results should be replicated using a larger sample size and perhaps using longer treatment duration.
• If you have to work night shifts consider using 1-5mg melatonin 1h before you go to bed - Why? You have to counter the natural decline in melatonin production that occurs over consecutive days of night work (Dumont. 2014).
  
  In a recent study from the Sacre-Coeur Hospital of Montreal the melatonin production of the healthy volunteers decreased progressively decreased over consecutive days of simulated night work, both during nighttime and over the 24?h. Interestingly, this decrease was larger in women using oral contraceptives and independent of bright light exposure.
• Get out into the sun and cure your back pain - If your back hurts and neither you or your doctor have a clue why, try getting into the sun. A study from the UMIT in Austria shows that only three sessions in front of 5.000?lx lamp improved the depressive symptoms and reduced the pain intensity in CNBP adults with chronic nonspecific back pain (Leichtfried. 2014).

References:

• Bonmati-Carrion, Maria Angeles, et al. "Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure." International Journal of Molecular Sciences 15.12 (2014): 23448-23500.
• Diepen, Hester C., et al. "Caffeine increases light responsiveness of the mouse circadian pacemaker." European Journal of Neuroscience 40.10 (2014): 3504-3511.
• Dumont, Marie, and Jean Paquet. "Progressive decrease of melatonin production over consecutive days of simulated night work." Chronobiology international 0 (2014): 1-8.
• Figueiro, Mariana G., et al. "Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer’s disease and related dementia living in long-term care facilities." Clinical interventions in aging 9 (2014): 1527.
• Fukushige, Haruna, et al. "Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night." breast cancer 4 (2014): 9.
• Harb, Francine, Maria Paz Hidalgo, and Betina Martau. "Lack of exposure to natural light in the workspace is associated with physiological, sleep and depressive symptoms." Chronobiology international 0 (2014): 1-8. 
• Irwin Michael, R. "Why Sleep Is Important for Health: A Psychoneuroimmunology Perspective." Annual Review of Psychology 66 (2015): 143-172.
• Kayaba, Momoko, et al. "The effect of nocturnal blue light exposure from light-emitting diodes on wakefulness and energy metabolism the following morning." Environmental health and preventive medicine 19.5 (2014): 354-361. 
• Leichtfried, Veronika, et al. "Short?Term Effects of Bright Light Therapy in Adults with Chronic Nonspecific Back Pain: A Randomized Controlled Trial." Pain Medicine 15.12 (2014): 2003-2012.
• Obayashi, Kenji, Keigo Saeki, and Norio Kurumatani. "Light exposure at night is associated with subclinical carotid atherosclerosis in the general elderly population: The HEIJO-KYO cohort." Chronobiology international 0 (2014): 1-8.
• Okamoto, Yosuke, and Seiji Nakagawa. "Effects of daytime light exposure on cognitive brain activity as measured by the ERP P300." Physiology & behavior 138 (2015): 313-318.
• Partonen, Timo. "Obesity= physical activity+ dietary intake+ sleep stages+ light exposure." Annals of medicine 46.5 (2014): 245-246.
• Shapiro, Bryan B., et al. "The Relationship Between Ultraviolet Light Exposure and Mortality in Dialysis Patients." American journal of nephrology 40.3 (2014): 224-232. 
• Thompson, A., et al. "The Effects of Evening Bright Light Exposure on Subsequent Morning Exercise Performance." International journal of sports medicine EFirst (2014).
• van der Lely, Stéphanie, et al. "Blue blocker glasses as a countermeasure for alerting effects of evening light-emitting diode screen exposure in male teenagers." Journal of Adolescent Health (2014).
• Virginie, Gabel, et al. "Dawn simulation light impacts on different cognitive domains under sleep restriction." Behavioural Brain Research (2014).
• Wang, et al. "UV light selectively inhibits spinal cord inflammation and demyelination in experimental autoimmune encephalomyelitis." Arch Biochem Biophys. (2014). [Epub ahead of print]
• Zeitzer, Jamie M., et al. "Millisecond Flashes of Light Phase Delay the Human Circadian Clock during Sleep." Journal of biological rhythms (2014): 0748730414546532.