The scientific answer is no, as long as you eat a well balanced diet rich in fruits and vegetables.
Until recently, I did suggest a standard multivitamin with minerals each day. They don't cost much, and earlier studies had shown some benefits. For example, it appeared that folic acid and other B vitamins might lower the risk of heart disease, stroke and possibly cancer. But more recent studies have shown no added benefit of multivitamins for healthy people that eat a balanced diet.
Still, there are some reasons for certain people to take vitamins.
Women should take 400 micrograms of folic acid a day during their childbearing years. This is the amount in a standard multiple vitamins. Taking in enough folic acid helps prevent pregnant women from having a baby born with spina bifida.
Also, people that arent exposed to sunlight too often which can cause a lack of vitamin D may benefit from a multivitamin. We need sunlight to change the inactive form of vitamin D in our skin to the active form. Most people in the upper half of the northern hemisphere don't get enough sunlight during winter and most of spring and fall as well. Also, we have been told to avoid sunlight because it ages our skin and causes some types of skin cancers.
Each multivitamin has 400 units of vitamin D. I don't think this is enough. Personally, I take a supplement with 1,000 units of vitamin D daily.
Heres another reason to take multivitamins: it may help slow down macular degeneration. This eye disease is seen mainly in older people. But it's not clear whether vitamins actually prevent the disease.
Strict vegetarians should take vitamin B12. They may also need an iron supplement.
The doses in standard multivitamins are safe. If your diet has too little of any vitamin or mineral, multivitamins are still a very low-cost way to protect yourself against vitamin deficiencies.