What other minerals are important for bones and therefore the prevention and prophylaxis of osteoporosis? 

It has become clear recently that magnesium is also important for bone strength. It supports calcium homeostasis, the absorption of calcium in the gastrointestinal tract, as well as the building of the basic substance of bones. Severe magnesium deficiency, in addition to neuropsychiatric manifestations and the cardiovascular system, leads to impaired bone function and structure. 
A person needs 280-330 mg of magnesium daily. 
Sources of magnesium are dark chocolate, fruits and vegetables, fish, whole grains, nuts, seeds, legumes - beans and lentils.  
Another trace element that has a connection and relation is fluorine. It is part of the hydroxyapatite crystals and increases the strength of bone minerals. The bone becomes stronger, but more fragile and easily broken when the bone is oversaturated with fluoride. 
Honey regulates the function of osteoblasts and osteoclasts. These are the two main types of cells that build and break down bone. It is also important for the formation of collagen and elastin, which are contained in the connective tissue of bone. Sources of honey are lentils, nuts, seeds. 
Zinc is involved in bone mineralization. It is found mainly in the sources of complete protein - meat, eggs, seafood, as well as nuts, seeds and legumes. 
Manganese is also a trace element that is important for the proper construction of the bone matrix. It builds polysaccharides - more complex carbohydrates that are important for the absorption of vitamin C and B vitamins. It is a cofactor of various enzymes. 
Manganese can be obtained again from nuts, seeds, dark green vegetables.
According to studies, boron is important for osteoblast activity, estrogen synthesis and normal endogenous vitamin D synthesis. Its sources are figs, fresh and dried fruits, nuts, legumes, cabbage, broccoli. 
Silicon is important for collagen synthesis and the deposition of hydroxyapatite in the bones. 
Iron is a cofactor for vitamin C. It is a powerful antioxidant and is important for the process of "maturation" of collagen. 
It is known that in our country there is an excess of salty foods. At a rate of 5 g of daily sodium intake, Americans consume 10-15 grams or more of salt. In this regard, care should be taken with the consumption of other sources of sodium: mineral water, food. Medicines containing other sodium salts other than NaCl should also be considered when calculating sodium intake. It is important to know because its high levels increase the extraction of calcium from the bones. 

What are the benefits of vitamin D for bone strength as well as for fracture prevention? What is its function? 

This is the vitamin hormone. It has long been known that it has to do with bone and mineral health. To maintain it we need 35-40 ng / ml plasma level. 
However, more than 1 billion people worldwide suffer from deficiency or some form of hypovitaminosis D. The problem has worsened over the years for several reasons. First, it is constantly said that sun exposure is dangerous, harmful, the skin ages. This is a fact, but the constant encouragement of people to cover themselves outside, to use products with a high sun protection factor, leads to a widespread deficiency of vitamin D. On the other hand, in some countries, due to religious customs or way of dressing and living, people cover your whole body with clothes. This further enhances the development of hypovitaminosis D, affecting entire countries and populations. 
Environmental pollution is another culprit. 80% of vitamin D is synthesized in our dermis. We get only 20% with food. Unfortunately, we do not often consume products that are rich in vitamins. Therefore, more attention should be paid to full sun exposure. 10-15 minutes of exposure to direct sunlight a day is enough. 
The problem also affects USA. Nearly 76% of people are deficient and deficient in vitamin D, according to a national survey of more than 2,000 people in January 2012.
One of the reasons is that we do not have enough sunshine. In USA the active season is from May to the end of September. Then, due to the latitude, the rays begin to fall obliquely, as a result of which we cannot synthesize a sufficient amount of vitamin D. 
Another reason for the high percentage of vitamin D deficiency in our country is the desire to constantly protect ourselves from the sun. 
Vitamin D is an immunomodulator. It is related to various autoimmune diseases, allergic diseases. A link has been found with diabetes, rheumatoid arthritis, hypertension, heart failure. It is also associated with infectious diseases, as well as with the development of depression, multiple sclerosis. More than 14 cancers have been found to be linked to vitamin D deficiency. 
Obesity is also linked to vitamin D. Until recently, the condition was even thought to protect against osteoporosis to some degree. However, new studies show that vitamin D deficiency in obese people increases the risk of osteoporosis. 
New research has found out exactly how the vitamin works - through a nuclear receptor that is found in almost all cells. It is also thought that there are faster-acting receptors at the cell membrane level.  
Vitamin D is a powerful tool that can be used as an adjunct to certain therapeutic treatments and prevention of socially significant diseases. 

In order to have local production, for example in macrophages, macrocytes, tumor cells, etc., we must have higher plasma levels of vitamin D - about 75-100 ng / ml, which, as studies show, we do not achieve. 
In this regard, it is planned to increase the recommended intake of vitamin D. 

From which food sources can we get vitamin D?

Vitamin D can be obtained from oily fish - herring, salmon, sardines, fish oil, butter, egg yolk, liver, cheese. 
Currently, there is an enrichment of foods with vitamin D. For example, cereals, cereals, formula, baby foods, fruit drinks, milk, etc. 
Mentioning fish products, it is important to know that farmed fish have a poor fatty acid composition and do not contain enough vitamin D.