Reading the labels: mineral doses in food supplements

Abstract

Introduction: Food Supplements (FS), used regularly by many adults, can add significant amounts of nutrients and other ingredients, such as minerals, to the diet. Although the Recommended Daily Allowance (RDA) for most nutrients is mainly provided by diet, mineral supplements (MS) are one of the largest growing category of FS used. Given the high prevalence of MS use among consumers and their potential for drug interactions [1], as well as adverse effects of excess consumption, special attention should be given to the Label Recommended Daily Dose (LRDD). As intake increases above the Tolerable Upper Intake Level (UL), the potential risk of experiencing adverse effects may rise [2].The aim of this study was to evaluate if LRDD of MS are in conformity with the RDA defined by European Union Directive [3].

Materials and methods: A total of 210 FS sold in Portuguese pharmacies, supermarkets, health shops and on internet were examined for LRDD of 14 minerals (Ca, Cl, Cr, Cu, Fe, F, I, K, Mg, Mn, Mo, P, Se and Zn). Selection criteria: oral solid pharmaceutical forms for adults, containing any of the 14 minerals, as stated in the label, regardless of the purpose of its use.

Results: 56% of FS labels presented LRDD of at least one mineral > RDA and 6% of FS indicated LRDD > RDA, for 7 or more minerals. For most minerals (excluding Cl, F and K), Maximum Label Recommended Daily Dose (MLRDD) is much higher than RDA, with some FS mentioning doses of Se and Zn above UL defined by EFSA [2] (Table 1).

Discussion and conclusions: It is noteworthy that some minerals can be harmful in large doses with risk of oral and systemic manifestations: e.g. excess of Zn may promote hypocupremia, anemia, gait and balance disorders and paresthesias; excess of Se can cause alopecia, hair and nail brittleness and garlic odor to breath. This study revealed that, for most minerals, the majority of FS labels recommended daily doses above RDA and some even above UL. Therefore, it is crucial to review doses of minerals present in FS ensuring the safety of these products.

Table 1. Results of FS containing minerals.

Mineral	Ca	Cl	Cr	Cu	Fe	F	I	K	Mg	Mn	Mo	P	Se	Zn
Unit	mg	mg	μg	mg	Mg	mg	μg	mg	mg	mg	μg	mg	μg	mg
Number of FS	100	5	102	132	104	4	94	32	136	116	53	40	123	156
RDA	800	800	40	1	14	3.5	150	2000	375	2	50	700	55	10
LRDD > RDA(%)	5	0	49	31	21	0	16	0	7.4	34	34	2.5	49	50
UL	2500	ND	250	5	ND	7	600	ND	250*	ND	600	ND	300	25
LRDD > UL (%)	0	–	0	0	–	0	0	–	22	–	0	–	1	3
MLRDD*	2040	314	240	3	42	1.8	451	340	600	20	600	1215	400	31

*Does not include Mg present in diet; ND: Not defined