ONLINE DRIVERS MEDIA

Yes, coconut oil does contain MCTs, but it is not as some people believe pure MCT. Only ~50% of the fat in coconut oil is actually in MCT form. If you want pure MCTs you have to resort to specific MCT supplements / oils.

The mechanisms by which medium-chain triglycerides (MCTs) may help you to lose fat are manifold. They are not only hard to store for your body. They also counteract fat deposition in adipocytes by increasing thermogenesis and satiety.

MCTs contain 8 to 12 carbon atoms and include caprylic acid (C8:0, octanoic acid), capric acid (C10:0, decanoic acid), and lauric acid (C12:0, dodecanoic acid). Foods high in MCTs include coconut oil (58%), palm kernel oil (54%), desiccated coconut (37%), and raw coconut meat (19% of total energy) (USDA). Average intakes of 1.35 g/day (0.7% of total energy intake | USDA. 2008) MCTs have been reported in the United States and 0.2 g/day in Japan | Kasai. 2003).
MCT is cleaved into glycerol and medium-chain fatty acids in the gut lumen.5 The medium chain length makes a smaller, more soluble molecule compared with a longchain fatty acid, giving it a preferential absorption and metabolic route in the body. As the authors of the latest meta-analysis of the effects of MCTs on body weight say:

"[t]his physicochemical nature of medium-chain fatty acids allows them to pass into the portal vein on route to the liver to be rapidly metabolized via b oxidation with no requirement of reesterification in intestinal cells, incorporation into chylomicrons, or the rate limiting enzyme carnitine acyltransferase for intramitochondrial transport. In comparison, long-chain fatty acids have a slower route, being re-esterified in the small intestine and transported by chylomicrons via the lymphatic and vascular system before being oxidized for energy or stored. Thus, rapid metabolism of MCTs reduces their opportunity of adipose tissue uptake." (Mumme. 2015)

Several human intervention studies have been conducted investigating the weight-reducing potential of MCT, with mixed results. In their latest meta-analysis, Mumme et al. set out to separate the wheat from the chaff in order to answer the question whether MCTs, specifically C8:0 and C10:0, provide significant weight loss benefits and/or trigger changes in body composition compared to "regular" long-chain fatty acids (LCT).

Figure 1: Meta-analysis for changes in body weight (in kilograms) in randomized control trials that compared dietary medium-chain triglycerides (MCTs) with a longer-chain triglyceride (control) shows a favorable effect of MCT intervention on body weight. *Oleic acid as control. **Myristic acid as control. #Body mass index < 23. ##Body mass index > 23. IV inverse variance. SD standard deviation (Mumme. 2015).

The researchers primary outcome measures were body mass, waist and hip circumference, total body fat, and subcutaneous and visceral fat. Secondary outcomes were blood lipids, including triglycerides (TG), total cholesterol, high-density lipoprotein (HDL) cholesterol, and LDL cholesterol. Of the latter the foremost values are those that are of greatest interest and among them the body mass shows a measurable, albeit not earth-shattering reduction in almost all trials. Only the in the 2001 study by Matsuo et al. there was an increase in body weight in response to an MCT supplement that contained almost no medium chain triglycerides.

Figure 2: Meta-analysis for changes in total body fat, total subcutaneous fat, and visceral fat (Mumme. 2015).

In view of the fact that the most relevant obesity parameters, i.e. the waist and hip circumferences and body fat percentages (Figure 2) dropped in all studies that investigated this parameter and considering the fact that there were no significant deterioration - rather improvements - in blood lipids, it appears warranted to assume that the replacement (!), but not the addition, of 2g/day MCTs (1% of the energy) to 54 g/day MCTs (20% of the total energy intake)  over a duration of 4 to 16 weeks leads to measurable and potentially health relevant weight loss, compared to bacon, butter & co, i.e. regular long chain fatty acids.
References:

• DeLany, James P., et al. "Differential oxidation of individual dietary fatty acids in humans." The American journal of clinical nutrition 72.4 (2000): 905-911.
• Hamman, Richard F., et al. "Effect of weight loss with lifestyle intervention on risk of diabetes." Diabetes care 29.9 (2006): 2102-2107.
• Kasai, Michio, et al. "Effect of dietary medium-and long-chain triacylglycerols (MLCT) on accumulation of body fat in healthy humans." Asia Pacific journal of clinical nutrition 12.2 (2003): 151-160.
• Mumme et al. "Effects of Medium-Chain Triglycerides on Weight Loss and Body Composition: A Meta-Analysis of Randomized Controlled Trials." EAT RIGHT - Research Review (2015).
• US Department of Agriculture. Nutrient Intakes From Food: Mean Amounts Counsumed per Individual, One Day, 2005-2006. Washington, DC: US Department of Agriculture, Agricultural Research Service; 2008.

Some butter on top of the broccoli would allow for the assimilation of the absorption of the 101.6?g vitamin K 623IU vitamin A (various).

There are a handful of very basic questions in nutrition science, no one appears to have an answer to. One of these questions, which is directly related to the  well-known fact that the vitamins A, D, E & K are "lipid soluble". This means that they are "solved" and thus made absorbable by fats and oils. The general assumption is thus that the vitamins A, i.e. the retinol and carotenoids, all forms of vitamin D, the tocopherols and -trienols (vitamins E) and the two major forms of vitamin K, i.e. phylloquinone (K1) and menaquinone (K2) will only be absorbed, if you consume them with a sufficient amount of dietary fat. Now, the questions obviously are (a) is this correct and (b) how much is sufficient.
In view of the fact that the answers to (a) and be are not necessarily identical for all four vitamins of interest, it appears sensible to tackle them one after the other.


Starting with vitamin A and the various forms of carotenoids, we can already confirm that (a), i.e. the assumption that we need dietary fats to optimally absorb vitamin A is correct. As Karin van het Hof and her colleagues point out, the "amount of dietary fat required to ensure carotenoid absorption [does yet] seem low (?3–5 g per meal), although it depends on the physicochemical characteristics of the carotenoids ingested." (van het Hof. 2000) In spite of the fact that 5g of fat are not exactly much, the classic uncooked vegetarian orthorexic salad often comes with a total of only 5g of fat of which 95% remain at the bottom of the salad bowl. If that sounds like your favorite dish, you should be aware that you are risking that all the good  beta- and other carotenoids in the salad will pass right through.

Figure 1: Changes in hepatic vitamin A (retinol) and carotenoid stores in gerbils after 14 days on high fat (30%) vs. low fat (10%) diet (Deming. 2000)

In that, the concomitant presence of both dietary fat and carotenoids in a meal is a necessary prerequisite for the absorption of vitamin A, also because the fatty acids will trigger the conversion of of beta-carotene into vitamin A and its subsequent absorption via the lymphatic system (Ribaya?Mercado. 2002). It is thus not surprising that animal studies by Lakshman et al. (1996) and Deming et al. (2000; see Figure 1) suggest that low fat diet can lead to a depletion of the vitamin A tissue stores even if the serum levels remain constant. The amount of fiber in the diet, on the other, has no influence the absorption of vitamin A (Mills. 2009).

Interestingly enough, the provision of the fat blocker Orlistat reduces the absorption of vitamin A only insignificantly, as a 1996 paper by Angela T. Melia, Susan G. Koss?Twardy, and Jianguo Zhi would suggest (Melia. 1996).

Which takes us right to vitamin E, the absoprtion which is - in spite of being "blocked" by the fat blocker orlistat (Melia. 1996) - less susceptible to the absence of dietary fat than you may think. Annet JC Roodenburg, Rianne Leenen, Karin H van het Hof,  Jan A Weststrate, and Lilian BM Tijburg do in fact argue that the optimal intake of vitamin E requires only "a limited amount" of dietary fat (Roodenburg. 2000).

Figure 2: Vitamin E serum levels after 7 days on control (low fat, 3g) or high(er) fat (36g) diet with and without supplemental vitamin E (Roodenburg. 2000)

As you can see in Figure 2. A minimum intake of only 3g per day was sufficient to keep the vitamin E levels stable. The short study period of 7-days (each) and the absence of measures of tissue concentration of vitamin E do yet reduce the practical relevance of the data, Roodenburg et al. present in their Y2k paper in the American Journal of Clinical Nutrition.
If you take a look at the high prevalence of vitamin E dieficiency among the fat (and PUFA) "loving", or at least eating, majority of Americans, it does yet become obvious that a lack of dietary fat is not just theoretically, but also practically not exactly the #1 reason you may become deficient in tocopherols and -trienols. That the latter is an increased demand due to chronic inflammation and the (over-)consumption of exactly those PUFAs that come with a shitload of vitamin E in nature, for a reason would yet be a topic for another SuppVersity article and thus something we will skip to fast forward to ...

...Vitamin K, obviously. Vitamin K is a relative newcomer to the publics understanding of the alphabet soup. Aside from being it a good tool to rip customers vitamin K, or rather K1 (plant sources) and K2 (animal sources) are thus also the only fat soluble vitamins not everyone knows. The fact that the amount of phylloquinone (K1) that makes it into your blood stream is ~70% reduced if you eat your spinach without fat (Gijsbers. 1996).

And if we take the results researchers from the Gifu University School of Medicine present in a 1996 paper in the Journal of Pharmacological Sciences, as a reference, the amount of fat you need to optimally absorb your K2 (menaquinones), is not exactly low.

Figure 3: For optimal absorption of K2, there has got to be a huge amount of fat in the meal - but who wonders. K2 comes with a high amount of fat (Uematsu. 1996)

Uematsu et al. had to supply their subjects, who consumed otherwise identical test meals with 8.8, 20.0 and 34.9g of fat in them with the maximal (i.e. 35g) of fat before the K2 absorption maxed out. In that the total area under the curve did not really differ between those subjects who consumed the K2 before and those who took it immediately after the test meal.

Thats a pity, cause a high intake of vitamin K (menaquinone from animal sources) has been associated with a 27% reduced risk of developing heart disease (Geleijnse. 2004), an ailment of which many still believe that it was brought about by the fat they need to optimally absorb their vitamin K.

For vitamin D, our last "V" on the list, things look differently. For one, everybody knows about this miracle vitamin and for two, it may be "fat soluble", but the amount of fat thats required to optimally absorb it turned out to be much lower than previously thought (see "A Fat D-Ficiency! Do You Really Need More Vitamin D or Simply More Fatty Foods? Study Shows, Even 50.000 IU of Vitamin D3 Useless, When You Ingest It Without Fat. " | read more).
In fact, Niramitmahapanya et al. found in 2011 that its not necessarily a high amount, but rather the right type of fat that determines if and how much of the vitamin D you take in capsule form or find in comparably low amounts in your foods that determines how much of the vitamin D actually makes it into your bloodstream:

"The change in plasma 25OHD (nanograms per milliliter) during vitamin D supplementation was positively associated with MUFA, (? = 0.94; P = 0.016), negatively associated with PUFA, (? = ?0.93; P = 0.038), and positively associated with the MUFA/PUFA ratio (? = 6.46; P = 0.014)."

In plain English this means, that the "good" seed and vegetable oils with their high PUFA content will effectively inhibit the absorption of vitamin D - an observation that adds to the many reasons the modern sedentary, sun-avoiding, sun-screen using, soybean oil (MUFA:PUFA = 0.4) guzzling American is low in or  quasi devoid of vitamin D.

Figure 4: 25(OH)D levels of 30 healthy men and women after ingestion of 50.000IU vitamin D3 supplement in conjunction with a normal or low fat breakfast (Raimundo. 2011)

Against that background its not surprising that you will not find a conclusive answer to the question how much fat you actually need. In a study that used a fatty meal with soybean oil in it, the effect would be totally different from one in which the subjects consumed meals that were made with sunflower oil, an oil with a MUFA:PUFA ratio >1. In view of the results Gnadinger et al present in a recent appear it does still seem appropriate to consume at least some fat alongside your vitamin D supplements. As far as the food-borne vitamin D is concerned, you dont have to worry, anyways. Foods that are high in D3 usually come with all the fat you need to absorb it.

How much fat, exactly you would need to make the most of dietary and supplemental vitamin D, on the other hand, is still not known. The previously mentioned data from the study by Raimondo et al. (see Figure 4, to the right) I wrote about in "A Fat D-Ficiency" is obviously still valid. The extremely high amount of vitamin D (50,000IU!) could yet require a correspondingly high amount of fat to be optimally absorbed and the fact that the fat in the study came from a "vegetable margarine" with an undisclosed ratio of MUFA:PUFA does not make the real-world effects any more predictable.
References:

• Chitchumroonchokchai, Chureeporn, et al. "Dietary fats with increased ratio of unsaturated to saturated fatty acids enhance absorption of carotenoid and vitamin E by increasing both efficiency of micellarization and lipoprotein secretion." FASEB J 24 (2010): 539-3.
• Deming, Denise M., et al. "Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of ?-carotene to vitamin A in Mongolian gerbils." The Journal of nutrition 130.11 (2000): 2789-2796. 
• Geleijnse, Johanna M., et al. "Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study." The Journal of nutrition 134.11 (2004): 3100-3105.
• Gijsbers, Birgit LMG, Kon-Siong G. Jie, and Cees Vermeer. "Effect of food composition on vitamin K absorption in human volunteers." British Journal of Nutrition 76.02 (1996): 223-229.
• Goodman, Dew S., et al. "The intestinal absorption and metabolism of vitamin A and beta-carotene in man." Journal of Clinical Investigation 45.10 (1966): 1615.
• Jayarajan, P., Vinodini Reddy, and M. Mohanram. "Effect of dietary fat on absorption of ? carotene from green leafy vegetables in children." Indian journal of medical research 137.5 (2013).
• Kris-Etherton, P. M., et al. "Polyunsaturated fatty acids in the food chain in the United States." The American journal of clinical nutrition 71.1 (2000): 179S-188S.
• Lakshman, M. R., et al. "The effects of dietary taurocholate, fat, protein, and carbohydrate on the distribution and fate of dietary ??carotene in ferrets." (1996): 49-61.
• Melia, Angela T., Susan G. Koss?Twardy, and Jianguo Zhi. "The effect of orlistat, an inhibitor of dietary fat absorption, on the absorption of vitamins A and E in healthy volunteers." The Journal of Clinical Pharmacology 36.7 (1996): 647-653.
• van het Hof, Karin H., et al. "Dietary factors that affect the bioavailability of carotenoids." The Journal of nutrition 130.3 (2000): 503-506.
• Raimundo, Fabiana Viegas, et al. "Effect of high-versus low-fat meal on serum 25-hydroxyvitamin D levels after a single oral dose of vitamin D: a single-blind, parallel, randomized trial." International journal of endocrinology 2011 (2011).
• Ribaya?Mercado, Judy D. "Influence of Dietary Fat on ??Carotene Absorption and Bioconversion into Vitamin A." Nutrition reviews 60.4 (2002): 104-110.
• Roodenburg, Annet JC, et al. "Amount of fat in the diet affects bioavailability of lutein esters but not of ?-carotene, ?-carotene, and vitamin E in humans." The American journal of clinical nutrition 71.5 (2000): 1187-1193. 
• Uematsu, Toshihiko, et al. "Effect of dietary fat content on oral bioavailability of menatetrenone in humans." Journal of pharmaceutical sciences 85.9 (1996): 1012-1016.

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.

What now? Wait 3 minutes or off to the bench for an alternate set of bench presses or pulls ?

Traditional strength training with 80% of one-repetition maximum (1RM) utilizes 2- to 5-minute rest periods between sets. These long rest periods minimize decreases in volume and intensity, but result in long workouts. Performing upper-body exercises during lower-body rest intervals may decrease workout duration, but may affect workout performance.

The above is how Anthony B. Ciccone, Lee E. Brown, Jared W. Coburn, Andrew J. Galpin kick off their latest paper in the venerable Journal of Strength and Conditioning Research (Publish Ahead of Print).
The purpose of the corresponding study was to compare the effects of traditional to those of alternating whole body strength training on squat performance. To this ends, Ciccone et al. recruites 20 youn men, who had to perform two workouts:

• The traditional set workout (TS) consisted of four sets of squats at 80% of 1RM on a force plate with 3-minutes rest between sets. 
• The alternating set workout (AS) also consisted of four sets of squats at 80% of 1RM but with bench press, and bench pull exercises performed between squat sets 1, 2 & 3 with between-exercise rest of 50 seconds, resulting in approximately 3-minutes rest between squat sets. 

For both workouts, sets 1-3 were performed for four repetitions, while set four was performed to concentric failure. The total number of completed repetitions, the peak ground reaction force (GRF), peak power, (PP), and average power (AP) of every squat repetition were recorded and averaged for each set.

Figure 1: Maximal # of reps on last set and average power in the classic vs. alternating condition (Ciccone. 2014)

Interestingly, there was no significant interaction for GRF, PP, or AP. Only, the volume-equated AP was ca. 5% greater during the TS condition (989 ± 183) than the AS condition (937 ± 176). A more pronounced difference which was yet still within the margin of one standard deviation (in this case 2.2. reps) was observed for the fourth squat set to failure, where the TS condition resulted in 15% more reps to failure (7.5 ± 2.2) than the AS condition (6.5 ± 2.2). Reason enough for Ciccone et al. to suggest that:

1. Individuals who aim to optimize squat AP should refrain from performing more than three AS sets per exercise.
2. Those who aim to maximize squat repetitions to failure should refrain from performing upper body multi-joint exercises during squat rest intervals.

Certainly a sound advice, but in the end, we all live in a world where time is a precious gem and some people give a fuck about average power and the number of reps until they fail.
References:

• Ahtianen, Juha P., et al. "Short vs. long rest period between the sets in hypertrophic resistance training: influence on muscle strength, size, and hormonal adaptations in trained men." The Journal of Strength & Conditioning Research 19.3 (2005): 572-582.
• Ciccone AB, et al. "Effects of Traditional Versus Alternating Whole-body Strength Training on Squat Performance." J Strength Cond Res. (2014) Jun 17. Ahead of print.
• de Salles, Belmiro Freitas, et al. "Rest interval between sets in strength training." Sports Medicine 39.9 (2009): 765-777.