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Most of us have coupled travelling with psychological uplift. It is a fact that a pleasure trip not only improves our spiritual clarity but also our health.

The euphoria we feel as we walk into new places and taste different cuisines is due to the secretion of certain substances in our brain and our body. Biochemical molecules such as dopamine (DA), serotonin (5-HTP) and endorphins make up a chemical chorus that travels our minds at moments of relaxation and enjoyment.

However, the body’s biochemical response is not limited to the brain. Traveling in sunny countries like Greece, during the spring and summer, it promotes the production of vitamin D (hereinafter vit. D), which plays an important role in bone health and beyond.


What is vit. D;

The vit. D is a group of fat-soluble vitamins (D3, D2), which can be taken up by food but are mainly produced during skin exposure to solar radiation UVB (280-315 nm). It is worth noting that the maximum composition of vit. D occurs between 295-297 nm only.

Below , Figure 1 schematically shows the biosynthetic pathway of vit. D. As depicted there are 2 forms of vit. D. The first and most important is D3, also known as cholecalciferol, which is the natural form of vit. D, readily bioavailable, when produced during the “photosynthesis” of the organism. The second is D2, alternatively ergokalciferol, which is taken from food.

Figure 1: (1)Reaction catalyzed by UVB (290-310 mm). (2) Isomerization reaction catalyzed by heat. (3) Reaction catalyzed by 25-hydroxylase. (4) Reaction catalyzed by renal 1-α-hydroxylase. (5). Reaction catalyzed by tissue 1-α-hydroxylase. Where: 25 (OH) D3: 25-Hydroxyvitamin D3, DBP: Vitamin D binding protein. 1,25 (OH) 2 D3: 1,25-Dihydroxyvitamin D3.   Reference:


The form of vit. D measured in the laboratory is 25-hydroxyvitamin D, briefly 25(OH)D, which has halflife of 2 weeks and is stored in the body. These stocks reach up to 2-3 months in a period of low UVB exposure, such as the Mediterranean countries in the winter, or those in the north and south that receive less sunlight during the year (Figure 2).


Figure 2: The above map illustrates the differentiation of UVB irradiation, which is  necessary for the synthesis of vit. D, in different regions of the planet. The lower the radiation rate, the more severe the deficiency of vit. D.


What is the normal limit of vit. D in blood and how can I cover my body’s needs?

According to the latest scientific advances, the limits of vit. D ranges as follows:

  • High Risk Deficiency: below 30 nmol / L (12 ng / ml)
  • Deficiency: 30-50 nmol / L (12-20 ng / ml)
  • Sufficient: 50 – 80 nmol / L (20 – 32 ng / ml)
  • Optimal:> 80 nmol / L (32 ng / ml)
  • Toxicity risk:> 125 nmol / L (50 ng / ml)
  • High Risk Toxicity:> 220 nmol / L (88 ng / ml)


To optimize the amount of vit. D in the blood requires the body’s greatest exposure to solar radiation. Although there are no clear lines about the duration of exposure and the percentage of body to be exposed-because  factors such as latitude and skin color play an important role- most scientists respond with an average exposure of 15 minutes per day .

If this is impossible, then it is necessary to enrich our diet with fatty fish, eggs along with yolk and beef liver. In this situation, these foods should be accompanied by dark green leafy vegetables and long-maturing yellow cheeses rich in vitamin K2, a necessary enhancer of D3’s calcium absorption.

In addition with, there are nutritional supplements suitable to cover body’s needs in D3. It is good to choose those that have both K2 and a sufficient quantity of D3, at least 2000U, so that we have the maximum and quickest result.

Why vit. D is so important for our  organization?

The discovery of vit. D receptors (VDR) across bones and  in tissues such as pancreas, kidneys, skin and specific immune cells, indicates the multiple importance of this vitamin in maintaining health.

In particular, it appears that sufficient amount of vit. D in the organization contributes to:

  • Maintain the health of bones and teeth
  • Reduce the feeling of fatigue
  • Improve muscle strength
  • Promote the treatment of asthma
  • Increase the chances of a successful reproductive process
  • Treat rachitis
  • Improve the immune system by treating autoimmune and infectious diseases
  • Offer psychological improvement
  • Regulate sleep process and
  • Blood pressure.

It has also been found that vit. D regulates 3% of the total human genome. This means that this vitamin regulates a significant percentage of our genes, which are involved in a variety of processes regulating body’s healthy status. Therefore, our exposure to sun for producing  vit. D is more than necessary.


Is the importance of Vit. D changing  in people with darker skin?

It is important to note that the “photosynthesis” of vit. D occurs in all skin types of human skin. What changes is the percentage of the produced vitamin, which is reduced in  darker skins. The reason is that eumelanin, a pigment of the human skin with a protective role, competes with the precursor molecule of vit. D about the exploitation of UVB photons.

Therefore, people with darker skins need to stay longer in the sun, not only to produce enough vitamin, but also to store enough of it.


5 Tips to organize your holidays in Greece and get multiple benefits to your organization.


  1. Relax and enjoy your trip. Increased stress levels block many of body’s biosynthetic pathways, leading to biochemical imbalances that are opposed to health.
  2. Expose yourself daily and for reasonable periods of time in the sun. During summer in Greece, prefer the hours between 9: 00-11: 00 and/or after 18:00, where solar radiation is more harmless and more beneficial to our body.
  3. iii. Avoid sunscreens with a very high protection factor (SPF), as the higher it is the lower amount of vitamin D is synthesized by the body.
  4. Protect your skin from sunburns. An “injured skin” has a low vitamin D synthetic capacity. In conclusion, sunbathing is desirable and necessary under specific conditions, such as sun exposure time, exposure duration and protection media (sunscreen, shade, hydration).
  5. Try Greek recipes that contain foods rich in vitamins D and K such as mackerel, trout, sardine, eggs, beef, yellow cheese, spinach and sesquillage. Meals like these not only provide your body with all necessary vitamins and minerals but also travel you to Mediterranean cuisine, which is famous for its multiple health benefits.



  • Jablonski, N.G., International Journal of Paleopathology ,2018, The roles of vitamin D and cutaneous vitamin D production in human evolution and health,
  • Bouillon, R., Carmeliet, G., Verlinden, L., van Etten, E., Verstuyf, A., Luderer, H.F.,
  • Lieben, L., Mathieu, C., Demay, M., 2008. Vitamin D and human health: lessons from vitamin D receptor null mice. Endocr. Rev. 29, 726–776. er.2008-0004   .
  • Jing Guo, Julie A. Lovegrove, D. Ian Givens, 2017, 25(OH)D3-enriched or fortified foods are more efficient at tackling inadequate vitamin D status than vitamin D3, Proceedings of the Nutrition Society, Page 1 of 10,
  • Julia Khéde Dourado Villa, Marisa Alves Nogueira Diaz, Virgínia Ramos Pizziolo & Hércia Stampini Duarte Martino (2016): Effect of vitamin K in bone metabolism and vascular calcification: a review of mechanisms of action and evidences, Critical Reviews in Food Science and Nutrition, DOI: 10.1080/10408398.2016.1211616



Konstantara Lamprini

Biologist – MSc Neuroscientist

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