I wondered what could have been the cause of getting tired during the day even though I slept and ate well. Then I heard that the cause could be lack of vitamin D and decided to give this product a try. I live in Finland and we have long dark winter period which means people don't get much sun and thus not enough vitamin D. Moreover most of the additional vitamin D products that are available here have really low portion of the vitamin (around 400 IU). It was good thing to find out that there are products like this that have much higher amount of the vitamin. By starting to use these daily I have felt better and I don't get tired during the day anymore (if I sleep well :) ). + Cheap price (compared to local products) + Amount of vitamin D / softgel + Lasts for a year ------------------------- Overall this item is really good