(P11-017-23) Re-Evaluation of the Tolerable Upper Intake Level for Magnesium Supplements

Objectives: Over 15 years ago, the 2005 Dietary Guidelines for Americans identified magnesium (Mg) as an under consumed nutrient; this is still true today. In 1997, the US Institute of Medicine (IOM) established a tolerable upper intake level (UL) for adults of 350 mg Mg/day from supplemental intake alone, setting diarrhea as the limiting factor. The safety of oral Mg dietary supplements exceeding the UL is currently in debate. This review aims to re-evaluate the UL set by the IOM, based on the occurrence of diarrhea from Mg supplements, utilizing more recent and comprehensive evidence-based data.

Methods: To update the literature base used by the IOM to establish the Mg UL, a PubMed literature search was conducted to identify intervention studies published between 1997 and 2022, using single-ingredient Mg products reporting a priori diarrhea adverse events among adults. Studies that involved patients with acute illness or used intravenous Mg sulfate were excluded. In addition, the FDA CFSAN Adverse Event Reporting System (CAERS) was searched for adverse events due to Mg supplementation reported between database inception (2004) and 2022.

Results: Ten studies (five meta-analyses, and five randomized clinical trials) met the search criteria. Ten different Mg supplements were tested in studies lasting 2 to 24 weeks. Seven studies examined intakes of 300–1200 mg Mg/day and found no significant difference in the occurrence of diarrhea or toxicity in the intervention vs control groups. Two studies assessed intakes of 300–520 mg Mg/day and noted a significant difference between groups. Finally, one study examined intakes of 120–973 mg Mg/day, but a difference between groups could not be determined. Since its inception, there have been over 79,000 adverse event cases reported in the FDA CAERS Vit/Min/Prot/Unconv Diet (Human/Animal category). After the search was limited to Suspect Mg single-ingredient products, only 40 (0.0005%) adverse event cases were identified and only one-third of these noted a gastrointestinal complaint.

Conclusions: This review provides updated safety data on the consumption of supplemental Mg at doses currently exceeding the UL and recommends re-evaluation of the UL for Mg supplements, given the nutrient’s long-standing low intakes in the US.

Funding Sources: No funds were provided for this work.