Vitamin D is a fat-soluble vitamin that is produced endogenously when ultraviolet rays from sunlight strike the skin. Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate. Vitamin D has other roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation. So we know that Vitamin D is very crucial for our health.
The natural and most effective way of producing Vitamin D is by exposing our skin to UVB radiation. The body will produce just the amount it needs. Vitamin D produced by UVB radiation lasts longer. The average half life of Vitamin D is around 10 weeks. But people who live farther away from the equator are exposed to less amount of UVB radiation. The obvious solution provided by industry are Vitamin D supplements.
The supplement industry will spread misleading information. But the reality is that Vitamin D supplements may cause more harm than benefit.
There is research that says that says that Vitamin D supplements actually increase the risk of fractures. You can also build up toxic amounts of Vitamin D in your body. This will lead to high calcium levels in the blood which damages your arteries and kidneys. If a pregnant woman takes up too much synthetic Vitamin D, it can cause placental calcification which limits blood and oxygen supply to the baby. This does not happen in the case of excessive sun exposure.
Scientists have known that there is a link between sunshine and blood pressure. More sunshine can lower blood pressure. A study even showed that exposure to indoor UV radiation lamps lowers blood pressure. In 2015 a review was published which showed that Vitamin supplements do not lower blood pressure.
There is a false public perception that Vitamin D supplements prevent diseases without any evidence.