1. Most multivitamins have no effect
A recent systematic review of 179 research papers on the impact of multivitamins found that regularly consuming multivitamins, vitamin D, calcium and vitamin C, had no impact on reducing heart disease, stroke or premature death rates. The only supplement found to have a positive impact was folic acid, which can reduce heart disease and stroke occurrences.
However, even here, the impact was very low — it would take 111 people taking folic acid supplements for one case of heart attack or stroke to be prevented. That is, each person taking the supplement only has a 0.9 percent of a chance of benefiting from it. For stroke, people would have a 0.5 percent chance of benefiting. Meanwhile, high levels of folic acid may actually increase the risk of prostate cancer.