Recent studies suggest nutritional supplements have no added health benefits for people who are already in good health.
A January study found high levels of vitamin B12 in a person's blood are associated with an increased risk of early death.
A May 2019 study also found that taking vitamin D without a deficiency is associated with greater risk of cancer and death.
Education and lifestyle factors play more of a role in health than supplements, according to study co-author Fang Fang Zhang, MD.
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