Sunlight, L-Tryptophan & Vitamin B6 With Breakfast Increase Serotonin and Wakefulness During the Day and Melatonin and Restful Sleep at Night

Image 1: For these kids the high tryptophan + B6 breakfast would be useless unless they already got their 10min+ of direct sun exposure this morning
A recently published study that was conducted by a team of international researchers led by Miyo Nakade from the Gakuen University in Nagoya, Japan (Nakade. 2012), concludes that sunlight exposure and vitamin B6 and l-tryptophan intake with breakfast could be profound modulators of circadian rhytmicity in young children (N=816, age = 2-6 years). The results the researchers published in the latest issue of the Journal of Physiological Anthropology clearly suggest that the increased production of serotonin from l-tryptophan and the vitamin B6 metabolite pyridoxal 5’-phosphate (also known as PLP or p5p) exerts beneficial effects on the morningness-eveningness (M-E) score - a measure for the natural and highly desirable difference in wakefulness in the morning and sleepiness in the evening, the disturbance of which is among the emerging correlates of metabolic diseases, such as diabetes, obesity and abnormal lipid metabolism.
[C]hildren showed a tendency to be more morning-typed if they ate breakfast with
a high estimated Trp content. This study also confirmed a similar trend with estimated Vi-B6
content. Among essential amino acids, the Trp content in food is quite small, and thus it is
necessary to make a special effort to consume a sufficient amount in one’s diet.
That those foods with specifically high tryptophan content are, as so often, eggs, meats, and fish is something I probably don't have to tell you - just as I don't have to tell you that soybeans, and other soy products, which also contain significant amounts of tryptophan should not constitute a major part of your diet; regardless of whether you are a man or a woman.

Sunlight must not be hidden behind curtains or seen just through the windows your car

Interestingly, all the vitamin B6 and tryptophan in the world appears to be of little use, if you get too little sun-exposure (Rosenthal. 1997). And, now listen up!, they can become disturbed when you sleep with black out curtains and use an alarm clock to wake you up (Harada. 2003) - in how far these effects are mitigated, or even reversed (i.e. using black-out curtains = beneficial) in people who would otherwise be constantly exposed to unnatural light-exposure (e.g. a street lantern right before your window) would require further investigation, though.
Figure 1: Distribution of early birds (low M-E score on the x-axes) and late risers (high M-E score) among the study population (data calculated based on Nakade. 2012).
Anyways, as you can see in figure 1 the effect of the curtains was statistically significant, but not as pronounced as the scientists' emphasis in their report would have it. There are tendencies for more morning types (lower M-E scores) in the children sleeping without blackout curtains, yes. And there are no real evening types in the children sleeping without blackout curtains, but the broad majority falls into the same 18-23 M-E score range on the 7-28 early bird to long sleeper scale Nakade et al. employed.
Vitamin B6 and inflammation: Although this is only indirectly related to the topic of circadian rythmicity and wake-sleep patterns, it is quite intriguing that vitamin B6 is still touted as an anti-inflammatory agent. And though even very recent population based studies confirm that there is in fact an inverse relation of low plasma vitamin B6 and its active metabolite pyridoxal-5-phosphate (PLP) are inversely associated with the "overall inflammation" score in the US population (Sakakeeny. 2012), another recent study by Ulvik et al. clearly suggests that these associations are corollary, at best (Ulvik. 2012). In their trial, the results of which have been published in the May issue of the American Journal of Clinical Nutrition, Ulvik et al. administered 40 mg pyridoxine hydrochloride per day to patients with stable angina pectoris. Contrary to their expectations, this practice did neither replete the low vitamin B6 levels, nor sooth the inflammation. On the contrary, the rapidly metabolized vitamin B6 appeared to preserve or even increased the expression of inflammatory markers.

What's good in the morning won't hurt at night

With tryptophan being a serotonine precursor and vitamin B6 a necessary co-factor in its synthesis, it may come as a surprise that both, and the sunlight induced serotonin synthesis boost can boost "morningness" and make you more alert. After all, you will probably have read on the label of various dietary supplements that tryptophan is supposed to make you sleepy, right? What those labels don't tell you is that the exposure to sunlight and not the shear availability of precursors and co-factors, let alone the position of the hands on your clock modulate its destiny. And determine whether the tryptophan will get you going, as it obviously does in the children with the highest breakfast intake of tryptophan and vitamin B6 (cf. figure 2), or helps you fall and stay asleep at night.
Figure 2: M-E index relative to group mean in high / low tryptophan & vitamin B6 breakfast intake groups (data calculated based on Nakade. 2012)
That both is possible and obviously works quite fine, is thus the main message of this study, the results of which Nakade et al. interpret as direct evidence for the potential usefulness of
[...] a higher Trp and Vi-B6 intake [to] promote the synthesis of serotonin via light stimulation in the morning and have a natural sleep-inducing effect when converted to melatonin at night [and thus] help prevent a phase delay in young children’s circadian clocks and promote their morningness against the effects of the 24-h commercialization of society.
Against the background, that similar improvements have been observed in 35 middle-aged/elderly (aged 55-75 year) volunteers who consumed a tryptophan enriched  (+30mg per serving) cereal at breakfast and dinner for three weeks by Bravo et al. (Bravo. 2012). And since there is no effect without "side effects", I guess I better mention that the Spanish researchers also observed significant increases in
Table 1: Tryptophan content of various foods (in g per 100g, 2nd column), ordered by tryptophan per protein content (3rd column; data based on Wikipedia)
  • sleeping time,
  • sleep efficiency, and
  • immobile time
as well as concomitant decreases in
  • sleep latency (almost 25%!),
  • wake bouts,
  • total activity, and
  • sleep fragmentation index
If you take into consideration that their subjects' total antioxidant capacity levels and mood improved, as well and that the treatment elicited a -50% decrease in state anxiety and a significant drop on Beck's Depression Inventory Index, both of which returned to their initial value, when the treatment was seized, it should be obvious that you better make get out in the sun, immediately after you made the right food choices (and no, I am not talking about tryptophan-enriched breakfast cerals, here) at breakfast and watch the sunset after dinner ;-)

  1. Bravo R, Matito S, Cubero J, Paredes SD, Franco L, Rivero M, Rodríguez AB, Barriga C. Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans. Age (Dordr). 2012 May 24.
  2. Harada T, Matsumura A, Takeuchi H: Effects of the usage of a blacked-out curtain on the sleep-wake rhythm of Japanese University students. Sleep Biol Rhythms 2003, 1:179–181
  3. Nakade M, Takeuchi H, Taniwaki N, Noji T, Harada T. An integrated effect of protein intake at breakfast and morning exposure to sunlight on the circadian typology in Japanese infants aged 2-6 years. J Physiol Anthropol. 2009 Sep;28(5):239-45. 
  4. Nakade M, et al. Can breakfast Tryptophan and Vitamin B6 intake and morning exposure to
    sunlight promote morning-typology in young children aged 2-6 years? Journal of Physiological Anthropology 2012, 31:11
  5. Sakakeeny L, Roubenoff R, Obin M, Fontes JD, Benjamin EJ, Bujanover Y, Jacques  PF, Selhub J. Plasma Pyridoxal-5-Phosphate Is Inversely Associated with Systemic Markers of Inflammation in a Population of U.S. Adults. J Nutr. 2012 May 23.
  6. Rosenthal N, Schwartz P, Tumer E, Nalm S, Matthews J, Hardin T, Barnett R, Wehr T:
    The psychobiology of SAD and the mechanism of action of light therapy. Biol Psychiatry
    1997, 42:57S.
  7. Ulvik A, Midttun O, Ringdal Pedersen E, Nygård O, Ueland PM. Association of plasma B-6 vitamers with systemic markers of inflammation before and after pyridoxine treatment in patients with stable angina pectoris. Am J Clin Nutr. 2012 May;95(5):1072-8. 
  8. Wikipedia contributors. Tryptophan. Wikipedia, The Free Encyclopedia; 2012 May 26, 00:42 UTC [cited 2012 May 27]
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