Hydrogenated vegetable fats are not the main source of nickel in confectionery, finds Czech study

By Michelle Yeomans

- Last updated on GMT

Study sheds light on nickel contamination in confectionery. ©iStock/vchal
Study sheds light on nickel contamination in confectionery. ©iStock/vchal

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Hydrogenated vegetable fats are not the main source of nickel in finished confectionery products as previously assumed, a Czech study suggests.

In a paper published in the journal Food Chemistry​, researchers Lucie Dohnalovaet al.,​ found the content of nickel in confectionery products varying between 0.742 ± 0.066 and 3.141 ± 0.217 mg.kg1, to be significantly higher than those found in vegetable fats at 0.086 ± 0.014 mg.kg1 or lower.

In the case of confectionery, all of the analyzed products contained more nickel per gram than the analyzed fats (from 4 to 40 times). If vegetable fat products used in the production in confectionery are of similar nature, it can be concluded that the use of hydrogenated vegetable fats is not the main source of nickel in the final products,​” the study reads.

Health risk?

According to the researchers, while the daily intake of nickel from vegetable fats is half of that from confectionery products, levels found in either do not represent a significant health risk.

Furthermore, using a newly developed method - combining microwave digestion and graphite furnace AAS - they discovered that while levels may be higher in confectionery products, they are slightly lower values than observed in 2012.

This could be explained by changes in food processing where hydrogenation of vegetable oils have been replaced with the use of naturally hard palm oil, coconut fat or interesterified triacylglycerols​,”they further explained.

Nickel can be present in products containing hardened edible oils, possibly as leftover catalyst from the vegetable oil hardening process.

Hydrogenated fats have replaced high-cholesterol butters and are used for products with more viscous or solid textures, such as various toppings or fillings in sweets and confectionery.

Carcinogenicity is not yet fully understood

While Nickel has been reported to potentially cause toxic effects including the promotion of cancer and contact allergy, it is not carcinogenic and acts more as a promoter than an inducer.

Although the molecular mechanism of nickel carcinogenicity is not yet fully understood, interaction of Ni (II) ions with various cellular components, including proteins and DNA, is considered to be a key factor.

Absorption of nickel in gastrointestinal tract is lowest for free Ni (II) ions but increases with complexation and solubility (Lodyga-Chruscinska, Sykula-Zajac, & Olejnik, 2012).

According to the researchers, data dealing with Ni speciation in foodstuffs are scarce or non-existent and is therefore not possible to estimate the bioavailability of nickel from margarines and hardened fats. 


Food Chemistry - 217 (2017) 456–460
‘Determination of nickel in hydrogenated fats and selected chocolate bars in Czech Republic’
Authors: Lucie Dohnalova​, Pavel Bucek​ , Petr Vobornik​, Vlastimil Dohnal

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