Magnesium supplements: 'Disturbing' discrepancies in actual and declared content

By Nikki Hancocks

- Last updated on GMT

Getty | FTiare
Getty | FTiare

Related tags Magnesium Quality control investigation

A new investigation into 116 Magnesium (Mg) food supplements on the Polish market reveals that huge differences between the declared and the actual content mean users may consume up to 304% more or 98% less Mg per day than they realise.

Mg is an essential mineral which participates in neuromuscular conduction, regulation of the body’s mineral homeostasis, regulation of blood pressure, insulin metabolism, and muscle contractility. 

A survey conducted by the SW RESEARCH agency (2017) involving 807 adults estimated that 72.4% of Poles use FS yet only 17% consult a doctor or pharmacist before starting supplementation. Other data from Poland indicate that FS with Mg account for a significant 7.56% of the market. 

Despite some legal acts being in force, the authors of the current study say the registration procedures and the placing of FS on the market are very simple and only require the presentation of documentation and packaging design to the chief sanitary inspector. No quality or safety tests are required. They say this makes it very easy for low quality products to enter the market.

The current investigation aimed to evaluate the Mg content in FS available on the Polish market, coming from local producers as well as producers known in various European countries. This is the first study that covers such data as a variety of chemical forms, pharmaceutical forms or preparations at different prices.

Samples of dietary supplements were selected on the basis of previously conducted surveys​ and popularity in the largest chain pharmacies in the country.

The study included 116 FS purchased in pharmacies and online. Samples were taken from three different blisters, analysed in triplicate (statistically insignificant differences between the determinations) and were harvested and tested in 2020–2021.


The resulting data revealed that the actual content of Mg was identical to that declared on the label in only two samples tested. Only 41.3% of the tested samples were within the acceptable range of deviations. A sizeable 58.7% of the tested FS were outside the acceptable range (chief sanitary inspectorate allows the deviation of minerals from −20% to +45% of the declared amount). 

The researchers assessed by what percent the value consumed would differ from that declared on the label if consuming these FS. They found that for 54.1% of the FS tested, consumers would consume a lower amount of Mg. In fact, for 3.4% of the supplements they would consume 90–100% less than the expected value. On the other end of the scale, in the case of one of the studied FS, consumers would consume as much as 300% more Mg than indicated on the packaging.

Overall, as a result of differences between the declared value and the measured value, the amount of the consumed element may deviate by a range of 98% less to 304% more than the declared value.

The authors conclude that food supplements should be routinely monitored to improve their quality.

The report states: "It is disturbing that if one of the tested FS is consumed, the patient will be take in 300% more Mg every day than it is stated in the declaration on the packaging...

"Such a large discrepancy between the declared values and those actually marked is very surprising. It may result from the improper production process of FS, lack of final product control, and inadequate labelling of the supplement.

"It seems necessary that FS sold in pharmacies should be subject to greater control, which will improve their quality and increase consumer confidence in this category of food products, sold in a form analogous to drugs."

The authors note a that further research should be based on the assessment of the bioavailability of various Mg compounds and the actual concentration obtained in the blood of patients after FS ingestion.

Current regulations

The legal regulations governing the FS market in Poland are both national and European requirements. An important legal act is the Food and Nutrition Safety Act of 25 August 2006, Regulation of the Minister of Health of 18 May 2010 amending the regulation on the composition and labeling of FS and the Regulation of the Minister of Health of 17 September 2018, on the composition and labelling of FS. The Regulation of the Minister of Health of 17 September 2018 lists vitamins and minerals and their chemical forms that may be present in supplements. 

Data from Poland show that from 2007 to 2017, over 29,000 FS were entered into the register of products. In 2016​, the chief sanitary inspector received about 600 notifications about the introduction of a new preparation on the market every month. The report states: "This indicates the need to introduce greater restrictions, preventing the placing on the market of preparation of inappropriate quality."

Source: Nutrients

Puścion-Jakubik, A.; Bartosiewicz, N.; Socha, K. 

"Is the Magnesium Content in Food Supplements Consistent with the Manufacturers’ Declarations?"

Related topics Research Supplements Minerals

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