Risk Assessment of Magnesium in Food Supplements

ABSTRACT

The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) has, at the request of the Norwegian Food Safety Authority (Mattilsynet; NFSA), assessed the risk associated with magnesium in food supplements. VKM is requested to evaluate upper tolerable intake levels for magnesium and high and low intakes in the Norwegian population. Pending establishment of common maximum limits in the EU, the NFSA is evaluating the national maximum limits for vitamins and minerals in food supplements. This risk assessment is the scientific basis for NFSA's evaluation of national limits for magnesium. Directive 2002/46/EC on food supplements was implemented in Norwegian law in 2004 in Regulation 20 May 2004 No. 755 on food supplements. Common maximum and minimum levels of vitamins and minerals in food supplements shall be set in the EU. Until common limits are established in the EU, the national limits apply. The present report is a risk assessment of magnesium in food supplements. It is based on published articles retrieved from literature searches and previous risk assessments of magnesium. Magnesium is an essential alkaline mineral and occurs as free cation Mg2+ in aqueous solution, or as the mineral part of a large variety of compounds such as chlorides, carbonates and hydroxides. Dietary sources of magnesium include green leafy vegetables, legumes, whole grain cereals, dark chocolate, nuts, fish and seafood, banana and coffee. NFSA has especially requested VKM to consider water as a source of magnesium. A few waterworks reported magnesium concentrations at 10 mg/L. Consumption of water from these waterworks may contribute up to 10% of recommended magnesium intake. However, most waterworks reported negligible magnesium concentrations. Magnesium has multiple functions in the body; it is a required cofactor for more than 300 enzyme systems in the body; for energy-dependent membrane transport, for gene regulation, and for sustained electrical potential in excitable cells. Magnesium also plays a major role in bone and mineral homeostasis. No tolerable upper intake level (UL) has been established for magnesium intake from food sources for the reason that no adverse effects have been recognised in healthy populations. Magnesium salts in food supplements may cause osmotic diarrhoea which is the most frequently reported adverse effect. However, these effects are considered relatively mild. Previous reports have arrived on UL or guidance levels (GLs) for supplemental magnesium ranging from 250 mg/day in the EU (Scientific Committee for Food (SCF, 2001)) through 350 mg/day in the USA (Institute of Medicine (IOM, 1997)) and up to 400 mg per day in the UK (Expert group on Vitamins and Minerals (EVM, 2003)). The UL from SCF (2001) is below the recommended daily dietary intakes for adults. Since the critical endpoint (gastrointestinal symptoms) is mild, rapidly reversible and no NOAEL could be identified, VKM finds it appropriate to base the UL for magnesium salts in food supplements on the LOAEL from IOM (1997). For the same reason, an uncertainty factor of 1 may be applicable for establishing a UL for magnesium salts in food supplements. VKM therefore proposes an amendment of the ULs suggested by SCF (2001) for magnesium in supplements. The IOM (1997) suggestion of a UL at 350 mg supplementary magnesium per day for adults was based on a LOAEL for mild diarrhea. VKM found no results to support an alteration of this UL. VKM therefore suggests a UL of 350 mg magnesium in food supplements per day in adults which is in accordance with the UL suggested by (IOM, 1997). This UL will also cover the recommended intakes for the adult population. VKM suggests that the ULs for children equal the recommended intakes for each age group Age group ULs (mg/day) Children 1-3 years 85 Children 3-10 years 120-200 Children (10-<14 years) 280 Adolescents (14-<18 years) 280 Adults (≥18 years) 350 According to the habitual dietary intakes of magnesium estimated from nationwide dietary surveys in Norway, about 25% of adults have intakes of magnesium below the recommendations from food and supplements. Almost the same percentage was below the recommended intakes among 9-year-old children, while approximately 70% of 13-year-olds had an intake of magnesium below the recommendations. It should be noted that the intakes have been estimated with use of different dietary survey methods for the different age categories and a comparison of estimates across age groups can be misleading and has a high degree of uncertainty. Concentration of magnesium in water is low and about 60% of the waterworks reporting to the Norwegian Waterworks Registry had a magnesium concentration below 2 mg/L, indicating water as a negligible source of magnesium for the majority of the population.