Objective: The commercial availability of fish oil supplements rich in n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) has increased significantly in recent years. A recent study showed that n-3 LCPUFAs are more effectively absorbed in the form of triacylglycerol (TG) than ethyl ester (EE). However, there is a paucity of data on the specific forms of n-3 LCPUFAs in these supplements. Therefore, our aim was to investigate the main lipid classes (EE and/or TG) of fish oil supplements available in Hungary and Turkey.

Method: The lipid composition of randomly selected, commercially available fish oil-containing dietary supplement capsules from Hungary (n = 36) and Turkey (n = 30) was analysed by high-performance thin-layer chromatography. The supplements were divided into two subgroups: pure fish oil capsules (fish oil only), and mixed oil supplements (fish oil + other oils).

Results: In Hungarian capsules, 13 products contained predominantly TG, 15 EE, and 8 both TG and EE fractions. A number of samples were found to contain a variety of additional lipid fractions. Twelve pure fish oil capsules contained only TG, fourteen samples contained only EE, and one contained both TG and EE. In Turkish samples, some capsules contained plant-based oils, such as flaxseed, primrose, and corn oils. According to the label, these mixed-oil capsules had lower levels of EPA and DHA than pure fish oil capsules. Similarly, Hungarian capsules containing plant-based oils, including pumpkin, safflower, and linseed oils, had lower levels of EPA and DHA than those containing pure fish oil.

Conclusion: Hungarian fish oil supplements contain higher levels of EE than reported in previous studies. Therefore, the composition and concentration of these supplements should also be considered when selecting fish oil supplements to ensure their efficacy and associated health benefits. Preliminary studies may also be useful to select the fish oil capsule before starting supplementation trials or advising patients.