ARKHANGELSK, May 29. /TASS/. The annual minima and maxima of vitamin D differ in men and women. A minimum level in women is registered typically in December, while in men - in spring, scientists of the Federal Research Center for Integrated Arctic Studies (the Urals Branch of the Russian Academy of Sciences, Arkhangelsk), found in a research, Senior Researcher at the Professor Tkachev Laboratory of Endocrinology at the Center's Institute of Physiology of Natural Adaptations Victoria Alikina told TASS.

"We have determined accurately the difference between vitamin D levels in men and women," she said. "In men, vitamin D decrease and increase are delayed in season. In women, the level is decreasing earlier, it gets minimal in December already, while with men, on the contrary, everything is fine in December, and the decrease happens in spring."

Scientists have examined people who did not take vitamin D supplements, or took them from time to time. The control groups included 40 practically healthy people aged between 20 and 44 - 20 men and 20 women.

The study's objective was to identify vitamin D patterns in the blood of Northerners depending on the daylight length, including the white nights factor. Blood sampling was made when the daylight period was growing - March 20-21 (the vernal equinox day), when the daylight was maximum long - June 21 (the summer solstice day), and then on September 23 (the autumnal equinox day) and on the shortest day - December 22 (the winter solstice day).

Even in favorable light periods, average levels of vitamin D in the blood were close to the lower norm. In women, the peak values were in summer (June). And in men - in autumn (September). In absolute values - 39.39 nanograms per milliliter (ng/ml) and 47.02 ng/ml, respectively. Women's minimum of 25.71 ng/ml was in December, in men - a minimum of 33.53 ng/ml was in March. The Clinical Recommendations of the Russian Association of Endocrinologists (2016) say an optimal vitamin D concentration of 25 in the blood above 30 ng/ml is considered optimal. Insufficient concentration of 25 is recorded at a level of 20 to 30 ng/ml. "Thus, men consume slower than women," the researcher said. "In women, vitamin D is involved in a huge number of reactions, and in women, most likely, it is required...> as a catalyst for many other chemical reactions, and thus it is consumed in bigger amounts."

Therefore, women should rather test vitamin D levels in December, and men - in March. Results will be used by doctors to regulate necessary drug doses. In unfavorable December, 85% surveyed women had insufficient or deficient conditions. Whereas in March, that is unfavorable for men, only 45% of the surveyed had insufficient vitamin D levels, and none of them had deficient conditions.

Vitamin D and depression

The researchers also analyze how seasonal factors affect the content of vitamin D and neurotransmitters and hormones: dopamine, adrenaline, norepinephrine and serotonin - the production of which it may regulate.

As we all know, in the autumn-winter period when the seasonal insulation is falling, the level of depressive conditions is growing, which, in fact, points to a lack of important biogenic amines, which may be caused by a deficit of sunlight and vitamin D.

"I already can say that vitamin D and serotonin in men "go" the same way, they are similar in dynamics, and this is how it should be, because vitamin D regulates [the production of] serotonin with the help of an enzyme. Women don't have such dynamics whatsoever," the expert continued. "In women, and it's very strange, on the contrary, vitamin D levels are low in spring while serotonin levels are high."

The study is underway. The established simultaneous decrease in vitamin D, serotonin levels and an increase in adrenaline and norepinephrine in many surveyed highly likely may lead to a seasonal affective disorder and stress in the autumn-winter period.

The research's result would be to identify in the surveyed men and women types of reactions to fluctuations of vitamin D and neurotransmitters. The scientists also plan to determine regional norms for vitamin D, dopamine, serotonin, norepinephrine and adrenaline concentrations to recommend them to medical institutions in the region.