Scientists estimate that they occur in 25-50% of the population (depending on the geographical region, season, climate, diet, and genetic background of the inhabitants of a given region). British research conducted in a group of 7,000 patients (average age 10 years) showed that about 30% of teenagers have vitamin D deficiencies. In 18-year-olds, deficiencies were diagnosed in even 75% of those examined. In Poland, vitamin D deficiencies occur in up to 90% of the population...
Where do these deficiencies come from?
After all, we are aware of the importance of vitamin D for our health. A year ago, marked 100 years since the first publication on its role in the body's calcium metabolism and in the etiology of rickets. Vitamin D is present in food and is also produced in the skin under the influence of sunlight. However, food provides only 20% of the daily requirement for this vitamin. The remaining 80% should be produced in our skin under the influence of UV radiation.
However, societies in industrialized countries spend most of their time indoors (type of work, fear of skin cancer, doctors' warnings). Therefore, the amount of vitamin D synthesized in the skin is also insufficient. Sensible solutions seem to be vitamin D supplements. It is necessary, preferably under the supervision of a doctor, to decide what dose will be best for us: 1000, 2000, or even 4000 units?
Doctors, however, urge people not to take vitamin D in excessive doses, as according to the latest research it is a hormone. It acts not only as a regulator of calcium homeostasis, but also as a regulator of the immune system. Overdose can therefore be dangerous for our health.
Supplementation - yes! But what kind?
So far, there are no clear recommendations on what vitamin D supplementation should be, as its role is different in the case of children, adults, and seniors. Besides, its level in the body largely depends on the geographical zone and the number of sunny days in a given climatic zone, as well as our lifestyle and type of work.
The latest scientific research indicates that there is another important factor, the existence of which we were not aware of until recently, namely genes. This is not about the genetic background inherited from parents or grandparents, but from ancestors living tens of thousands of years ago. It is worth knowing that contemporary Europeans are descendants of three great waves of migration. The first to appear in Europe after the Neanderthals were hunter-gatherers 40-45,000 years ago. Later, about 8-10 thousand years ago, Neolithic farmers from Anatolia (today's Turkey) came to Europe.
This wave of migration is now associated with the oldest known civilization, which earlier, around 12,000 years ago in the region of Gebekli Tepe and Karahan Tepe (Turkey), laid the foundations for a sedentary lifestyle based on agriculture and animal husbandry. The youngest wave of migrants were nomads from the steppes of Eurasia, who came to Europe 5,000 years ago. They had light skin, brought the wheel and Indo-European languages to Europe. Due to the type of burials dominant among the nomads, archaeologists refer to them as the "pit grave culture".
Genetic research indicates that compared to earlier waves of migration, the nomads were best prepared for vitamin D deficiencies. Tens of thousands of years ago, the "natural selection" factor for
them were very difficult conditions on the steppe, long dark winters, and lack of sun. As a result, they brought to Europe a set of genes that provide their descendants with the most efficient metabolism, transport, and use of vitamin D, including for better immunity. Part of the contemporary European population has the genes of the ancient nomads from the steppes of Eurasia and copes better with vitamin D deficiencies. But 25-30% of Europeans (including residents of Sardinia and Tuscany) have a different genotype, inherited from the farmers of Anatolia, and not so efficient in synthesizing vitamin D and managing its resources. These people should take larger doses of vitamin D or expose themselves to the action of sunlight.
Comparing this distant past of the European population and how much life has changed in the last decades for two generations, we come to disturbing conclusions. For a long period of time, representatives of Homo sapiens had dark skin and a traditional lifestyle, which provided them with a sufficient level of vitamin D synthesis in the skin. Mass migrations did not happen too often, and the time intervals between them were long enough for migrants to adapt to new climatic and geographical conditions. This adaptation involved the formation of appropriate changes in DNA (i.e., different gene variants, or alleles).
However, the transport of slaves from Africa to Central and North America (16th - 19th century) and economic migrations from Europe to the USA (19th century) caused millions of people to find themselves in conditions of reduced sunlight and "genetically" did not have time to prepare for this change. Hence the serious deficiencies of vitamin D and related diseases.
The latest "inventions" of humanity, namely the industrial revolution 200 years ago (at least in Europe) and, recently, climate change and globalization, have caused hundreds of millions of people to drastically change their lifestyle, and often also their place on Earth. Therefore, currently for several billion people, and especially dark-skinned inhabitants of our planet, the level of vitamin D is a serious risk factor and increased probability of many diseases.
Approximately 25% of the population are so-called "poor absorbers of vitamin D", who are very sensitive to its deficiencies. These people should take more vitamin D (about 50-100 µg per day, i.e., 2000 - 4000 IU). They are referred to as "low responders".
The second group is the so-called "high responders": they absorb vitamin D very well; they need 10–20 µg per day, i.e., 400 – 800 IU.
