You have to get your vitamins from different sources - preferably from food, but especially in winter, you should have a multivitamin every day, as you don’t get the same variety of vitamins from fruits and vegetables, as you do in summer.
But you have to be careful not to get to much of certain vitamins!!
Actually the only vitamin you can eat in unlimited amounts is vitamin C. Any excess will be washed out. Other vitamins will build up in the body, causing more harm than good!!