Vitamin D is well-known for the health benefits it can bring to our bones. However, research has shown that this is just one of the many effects that this vitamin has in our body and how deficiency of this vitamin is so widespread and related to a variety of health problems. Vitamin D is a fat-soluble vitamin, known as "calciferol", and is present in the human body in two forms: as ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is present in foods of plant origin and is taken in through our diet; vitamin D3, on the other hand, is synthesised through our skin upon exposure to sunlight, and is present in food products of animal origin. It has many properties, as although the name defines it as a vitamin, it is actually a "para-hormone" in that it exerts its activity on organs and systems, just like a hormone. There is a great deal of scientific evidence to suggest that vitamin D plays a fundamental role in disease prevention. Just think how there are about 30,000 genes in the human body and vitamin D is found in nearly 3,000 of them, along with vitamin D receptors found throughout the body. Above all, it is essential for our skeletal system, it stimulates the absorption of calcium and phosphorus, as well as promoting their deposit; this role is essential for both children throughout their growth phase, as well as throughout the course of an adult's life, where it is essential to keep the bones strong and physiologically healthy, acting as a contrast to osteoporosis. What is most surprising is the disconcerting scientific evidence that suggests 50% of the population are deficient in vitamin D, i.e. they present a serum value of 25(OH)D lower than 30 ng/ml. It emerges that nearly 100% of people suffering from diseases have severe deficiencies even lower than 20 ng/ml. Getting even more specific, almost 60% of adults (and even 80% of the elderly) have a vitamin D deficiency, as the alarming data of the International Osteoporosis Foundation and the Italian Osteoporosis Society show. Those most at risk are: the elderly, whose skin is less efficient in converting the sun's rays into vitamin D; those who are overweight (since vitamin D is fat-soluble); and obviously those who have a sedentary lifestyle and use sunscreen in the summer (preventing the skin from producing vitamin D). From the latest research emerged another alarming fact: six out of ten children are Vitamin D deficient, some only mildly and some much more seriously. This deficiency is a clear consequence of our children's lifestyles, spending most of their time indoors. Instead of being outside, children spend much of their time in front of their computer screens or playing video games, all of which does nothing to stimulate the production of vitamin D.We mentioned sunlight in correlation with the production of vitamin D as it is synthesised by our body when our skin is exposed to sunlight. In fact, about 80% of our body's needs could be synthesised through our skin: that is why being outside is so important, even if nowadays we spend most of our time at school, in the office, at home or indoors. To produce the amount of vitamin D our bodies need, just 15 minutes of daily exposure is enough (darker skin phototypes need a few more minutes as dark skin synthesises less). In fact, the reason why we tend to get sick with more infectious illnesses in winter has a close correlation with the lower levels of vitamin D that we have in winter, precisely because it produced more throughthe exposure of our skin to sunlight and what we take in through food is almost insignificant or in any case it is not enough to fulfil our body's needs. Moreover, it is not a coincidence that the concept of health and good mood is associated with exposure, as vitamin D is essential in stimulating the production of endorphins, serotonin and dopamine, the neurotransmitters that modulate our mood, thereby counteracting depression-related phenomena. As further demonstration of the vast versatility of this vitamin, recent studies show that a vitamin D deficiency is also linked to a greater risk of heart attack and heart failure, and not only that. Low levels of vitamin D would also be associated with a more unfavourable evolution of a disease in those affected by heart attack. In general, vitamin D deficiency is associated with an increased risk of developing diabetes; in fact, vitamin D is one of the factors that can control insulin secretion, hypertension, and hypercholesterolemia (high-cholesterol), all factors of potential cardiovascular risk. Another important aspect is that linked to its action which modulates activity of the immune system. In fact, a deficiency of vitamin D is associated with a greater predisposition to infections, such as tuberculosis - which in the first decade of the last century, before the era of antibiotics, was treated "in the sun" at so-called "heliotherapy" hospitals - some autoimmune diseases, such as multiple sclerosis, inflammatory bowel disease and inflammatory arthritis. Taking vitamin D also has a certain influence on the synthesis of testosterone in men, supporting greater fertility. It is also good for the brain, preventing the risk of neurodegenerative diseases such as Alzheimer's or Parkinson's, as well as improving cognitive functions, especially memory and verbal fluency, and seems to reduce the risk of depression in the elderly. A real "all-rounder" of a vitamin.Unfortunately, however, in addition to not always having the opportunity to be constantly exposed to sunlight throughout the year in order to provide us with the body's important daily needs, "compensating" with food is often not enough, since there are not many foods naturally rich in vitamin D and these contribute to covering only 20% of our needs. Foods containing the most vitamin D are of animal origin such as cod liver oil (until recently, given to school-age children to prevent rickets), oily fish (salmon, tuna, cod, mackerel, sardines, herring etc.), but also swordfish, grouper, molluscs, bottarga and caviar, preferably free range; in meat (especially in offal), and although in smaller quantities, in egg yolk, butter and yogurt. With the exception of mushrooms, which contain a lot (2.6 micrograms equal to 104 IU in every hectogram), vitamin D is lacking in vegetables: negligible traces in the form of D2, however, can be found in green leafy vegetables, legumes, dried fruit and in sunflower seeds. Finally, do not forget that monounsaturated fatty acids, such as those in extra virgin olive oil, improve absorption (vitamin D, as mentioned at the beginning, is fat-soluble). For these reasons, it is now increasingly widespread to take vitamin D in the form of a dietary supplement, a practice relegated until not long ago to infants, children, pre- and post-menopausal women, or the elderly with osteoporosis problems.The Vitamin D3 food supplement produced by Yamamoto Research can be used in all cases of increased need or decreased intake, with the vitamin D diet that provides 50 mcg per capsule equal to 2000 IU of cholecalciferol (the D3 form of vitamin D).