As you know there is a daily rhythm to the magnetosphere. It can be seen in this plot;
As you can see there is diurnal daily variation that matches the day/night (light dark) cycle beat for beat.
The magnetic intensity peaks at noon and bottoms out at midnight.
Here is an example of magnetic entrainment you have seen before using the hormone melatonin;
Geomagnetic activity influences the melatonin secretion at latitude 70° N
by A Weydahl - 2000Now to pick up on the light/dark aspect of circadian entrainment I would like to point to the equator where day length is relatively standard most of the year, and to the far north where there can be months of darkness and months of light.
Factors other than light may affect variations in melatonin, including disturbances in the geomagnetic field. Such a possibility was tested in Alta, Norway, ...
Int J Circumpolar Health. 2003 Sep;62(3):242-54.I would infer from this that circadian entrainment metabolic variations due to day length would be mimicked by geomagnetic field intensity variation by latitude.
Alterations in serum melatonin and sleep in individuals in a sub-arctic region from winter to spring.
Bratlid T, Wahlund B.
Psychiatric Department, University of Tromsø, Norway. trond.bratlid@rito.no
Abstract
METHODS: In a sub-arctic region at 69 degrees N, seven individuals with self-reported insomnia during the 'dark period' and seven without, were followed with repeated measures of melatonin and questioned on ten different sleep variables, from the beginning of January to the vernal equinox in March.
RESULTS: The distribution of melatonin over a 24-hour period (five time points) indicated an increase in melatonin levels in both groups in the middle of January and a decrease at the time of year when the sun first rises over the horizon (23rd-24th of January). Moreover, an indication of a delayed phase shift of melatonin secretion was found during the dark period, which returned to "normal" secretion during the night at the equinox in March. Individuals with sleep problems had a slower return to "normal" melatonin secretion than those without sleep problems. A positive correlation between morning tiredness and morning levels of melatonin was found among individuals with sleep disturbances, but not in controls.
CONCLUSION: This study indicates changes in the internal circadian rhythm in humans at the end of the annual dark period of winter when there is a rapid increase in the number of hours of sunlight. For vulnerable individuals, the disturbance in sleep, and in particular morning tiredness, lasts at least until the vernal equinox in March
To document the annual geomagnetic intensity variations by latitude I offer this old U index plot. The U index has been replaced by the K index.
As you can see there is stronger seasonal variation as you move from the lower latitudes to the higher latitudes.
Again it appears the day/night cycle mimics the magnetic intensity cycle on a seasonal basis.
Since both the day/night cycle and magnetic cycle are primitive inputs to human evolution and early humans migrated very slowly away from the equator, as man migrated his metabolism adapted to the daily and annual stimuli around him. This includes the day/night cycle length and magnetic field intensity cycle length seasonally.
You can point to skin pigmentation, or gut adaptations flushing fat soluble vitamins, or adaptations in amylase concentration for breaking down carbohydrates, or variations in sleep patterns between the sub arctic and lower latitudes due to environmental adaptations by latitude. So why not a variation in the seasonal need for the hormone vitamin D in Caucasians?
We know early whites would have had to tolerate very high serum vitamin D in summer, and reduced levels of vitamin D in winter. Winter vitamin D would be released as summer fat stores would burn due to the limited winter food supplies. Storing fat in summer rich with vitamin D and burning that fat in winter was critical.
So how could early man have metabolically optimized the hormone vitamin D in winter? Well we know that the circadian entrainment of light/dark is enhanced in winter. The days are shorter but the ground is covered with snow reflecting unusually high light levels at noon. Similarly the nights were longer counter punching the darkness side of the equation.
Now look at how the winter magnetic field intensity plotted above and it mimics the light/dark cycle with a higher intensity in winter. I would infer the daily diurnal variation of the field also shows a similar larger diurnal amplitude.
This would indicate that the circadian rhythms taking entrainment from both elevated light and magnetic levels would be punched extra hard in winter. The melatonin cycle would have a higher nighttime amplitude in winter and run longer. So could there be a higher vitamin D amplitude with a longer cycle apex, even with limited availability of vitamin D in winter in the primitive inputs? Do Caucasians have vitamin D carburetors that punch up the winter effects with turbo chargers?
We know that Seasonal Affective Disorder is based in excess melatonin in winter and is treated with light boxes which helps alleviate the high melatonin. More recently they found vitamin D helps too in the prevention and treatment of SAD.
So what happens to Caucasians in winter who supplement vitamin D to summer levels, and the body is making better use of the hormone in some way? Could this lead to long term problems? This would indicate we should see little 1,25-Dihydroxy (activated hormone form) vitamin D variation seasonally;
The Journal of Clinical Endocrinology & Metabolism Vol. 53, No. 1 139-142
Absence of Seasonal Variation in Serum Concentrations of 1,25-Dihydroxyvitamin D Despite a Rise in 25-Hydroxyvitamin D in Summer*
RUSSELL W. CHESNEY, JOHN F. ROSEN, ALAN J. HAMSTRA, CONNIE SMITH, KATHRYN MAHAFFEY and HECTOR F. DELUCA
Departments of Biochemistry and Pediatrics, University of Wisconsin Madison, Wisconsin 53706. The Department of Pediatrics, Montefiore Hospital and Medical Center, The Albert Einstein College of Medicine Cincinnati, Ohio 45226 The Food and Drug Research Laboratories, Food and Drug Administration Cincinnati, Ohio 45226
The serum concentrations of the vitamin D metabolites 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3), and 1,25-dihydroxyvitamin D (calcitriol) have been measured in normal subjects whose ages varied from 18 months to 35 yr. Samples were obtained in all months of the year in order to assess the effects of season on serum concentration. During the months of April to September, 25OHD3 levels are higher than in the winter months. No seasonal variation in the 25OHD2 or calcitriol serum concentration was observed. Age-related differences in 25OHD2 and D3 concentrations did not exist. The levels of calcitriol are higher in adolescence and increase from 35 ± 19 pg/ml (SD) at 1.5–10 yr of age to 54 ± 21 pg/ml at 10–20 yr of age. In young adults, the levels fall again to 28 ± 16 pg/ml. Accordingly, despite a seasonal variation in the precursor of calcitriol, the levels of this most active metabolite of vitamin D do not change in relation to sunlight exposure. This lack of seasonal variation is further evidence of the tight feedback regulation of calcitriol.
With all this in mind does winter supplementation at summer levels make any sense in whites, or are the supplements simply being flushed down the toilet, or even stressing the metabolic changes that adaptation has put in place for Caucasians in winter? Winter metabolic adaptations would be in place, but the primitive input those adaptations are keyed to would be exceeded.
Should we only be supplementing in winter to the natural primitive input levels of summer fat being burned in winter releasing their vitamin D stores? Since we no longer burn summer fat in winter what is the proper target range? How much winter fat being burned daily does the system look for? What is the primitive input of vitamin D stored in summer fat? Can it be reached mathematically using melatonin seasonal ratios as a base calculation?
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