 As you reach into the kitchen cabinet today, is a multivitamin every day really giving you a health boost? A new study from the National Institutes of Health suggests a daily multivitamin may not help you live a longer life. Researchers looked at data on more than 400,000 healthy U.S. adults over 20 years and found no differences in mortality or risk of death for those who took multivitamins versus those who did not.