Folic acid is important for pregnant women.

­Paul Avis/Getty Images

Multivitamin Medical Research

Some studies in recent years have revealed a couple of negatives concerning multivitamins. One is that some of them may give you too much of a good thing, which can lead to health problems. The other is that some multivitamins don't contain exactly what the label says, and some even contain a little something extra. 

The Harvard Men's Health Watch published a study in March 2008 that indicated that large amounts of folic acid could be linked to prostate and colorectal cancers. Folic acid itself isn't so bad, but food companies started adding it to grain products in the mid-1990s, so if you're eating a healthy diet, you may be getting plenty of it from your food. The multivitamin then pushes you over the folic-acid edge and a step closer to cancer.

Another study performed by pharmaceutical watchdog ConsumerLab.com found that less than half of the multivitamins sold in the United States and Canada actually contained what the labels said they did. One of the vitamins even contained a little something extra -- lead. If you're thinking that you shouldn't have lead in your vitamin, then you're right. The product was The Vitamin Shoppe's Especially for Women multivitamin. It contained 15.3 micrograms of lead per daily dose. Among other things, lead in the body can lead to high blood pressure. Since the report was released in 2007, the product was removed from the shelves and a class action settlement was reached with consumers.

Another multivitamin for children, Hero Nationals Yummi Bears, contained 216 percent of the amount of vitamin A that was indicated on the label. That's more than double the amount of vitamin A that kids through the age of eight should be getting on a daily basis. What can too much vitamin A do to a growing child? Weaken their bones and potentially cause abnormalities in the liver. Not really very "Yummi" when you think about it.

So do you need to be worried and ditch your multivitamin? Not necessarily. Your best bet is to visit ConsumerLab.com and do a little research on the vitamins it recommends. Eat a balanced, nutritional diet and you may only have to supplement your food intake with vitamins specific to your needs. Mainstream multivitamins that have been around for many years are to be trusted and you can always check for a seal of approval from the United States Pharmacopoeia, the NSF International or ConsumerLab.com. If your brand of multivitamin fails to have one of these seals, that means the manufacturer didn't submit its product for voluntary testing. Vitamins aren't regulated like prescription and over-the-counter medications, so be wary of any that don't volunteer for testing.

Be your own advocate, do the research and talk to your doctor before you begin taking a multivitamin. If you already take one, compare its ingredients to your diet to make sure you aren't getting too much of any one vitamin or mineral.