It is not usually necessary for most people to take vitamins if they have a well-balanced diet. However, if you do not eat enough throughout the day or avoid certain foods, a multivitamin may help fill in some nutritional gaps. Some vitamins may be necessary for specific health issues, such as calcium and vitamin D for osteoporosis or iron for anemia. If you do not have any specific health concerns, taking a vitamin may not be necessary. Taking vitamin D during the winter can be beneficial, as our bodies produce less of it due to limited exposure to sunlight. Many professionals may have different opinions on whether taking vitamin D supplements during the winter is necessary, but it is generally safe for most people.