Scientists have tested the effects of multivitamins again and again, but they just haven't found good evidence of any real benefits for our health.

"Show me a single study ever done saying people who took a multivitamin pill ... did better. There's no study," Ajay Goel, a biophysicist who researches cancer, recently told Business Insider.

The US Preventative Services Task Force does not recommend that people take vitamins or supplements as a preventive measure for heart disease or cancer, the leading causes of death in the US. In fact, there's evidence that supplements can do more harm than good.

"Extra vitamin A supplements can lead to dangerous, toxic levels if taken too frequently," Dr. Clifford Lo, associate professor of nutrition at the Harvard School of Public Health said in a blog post.

Try getting important vitamins and minerals from fresh fruits and vegetables.