Nearly 20 percent of dietary supplement users are taking the substances in excess of the recommended doses and potentially putting their health at risk, according to a study.
The researchers said dietary supplement makers need to improve the clarity and accessibility of information on appropriate dosages.
The study was undertaken by a group led by Keiko Asakura, a professor of public health, and Minami Sugimoto, an assistant professor of public health, both with the Toho University Faculty of Medicine.
The team used purchase history data to find study participants who had bought at least one of the 25 dietary supplement products selected.
Those buyers were asked about how they used the supplements, including doses consumed at a single time and consumption frequency.
Valid responses were received from 2,002 participants.
Among all respondents, 371, or 18.5 percent, were taking dietary supplements beyond the recommended doses indicated on the product package.
Most of the excessive users were between 50 and 64, working either part time or full time, and using the supplements for six months or longer.
The researchers said some individuals may be relying on dietary supplements as a convenient means to gain nutrition during their busy schedules, leading to excessive intake.
They also said some participants may believe that consuming more doses will yield greater health benefits.
Among all respondents, 1,705 used products that contain folic acid, zinc or other nutrients for which authorities have set “tolerable upper intake levels” that involve no health risks.
Of them, 184, or 10.8 percent, exceeded the tolerable upper limit for at least one nutrient, putting them at a higher potential health risk.
“The public should know that excessive intake of dietary supplements could do harm,” Asakura said.