Taking a multivitamin every day is fine, just don't overdo it.  Here are five vitamins that can actually be bad for you according to  Prevention.

Calcium supplements.  A few recent studies have found they can calcify your arteries and cause heart disease, and might not even make your bones any stronger.  So you're better off eating FOODS with calcium, like milk, salmon, and broccoli.

Vitamin E.  They used to think it lowered your risk for heart disease and cancer, but now they think it might do the OPPOSITE.  Multivitamins are fine though, because they don't have enough vitamin E to make much of a difference.

Iodine supplements.  A lot of food in the U.S. already has iodine in it.  And too much of it can mess with your thyroid.  So you shouldn't take a supplement unless your doctor tells you to.

Iron supplements.  Too much iron can damage your liver, your pancreas, your heart, and also cause cell damage.  So you shouldn't take a supplement unless a test shows that you have an iron deficiency.

Vitamin B-6.  High doses of it can mess with your nervous system.  And you can get plenty of it without taking a supplement by eating fruit, vegetables, chicken, and fish.