Quality of Dietary Supplements in Ophthalmology

Abstract

Purpose: : A rising number of dietary supplements are available to prevent age–related ocular pathologies such as AMD or dry eye syndrome. The purpose of this work was to evaluate the quality of dietary supplements containing omega–3 polyunsaturated fatty acids in terms of lipid, vitamin E and heavy metals composition. Dietary supplements designed for improving mental well–being were included in this study since they should share some similarities.

Methods: : Twenty dietary complements were analyzed (6 for dry eye prevention, 4 for AMD prevention and 10 for improving mental well–being). Lipids and lipophilic vitamins were extracted. The distribution of the lipid classes was evaluated by chromatographic techniques. The fatty acid profile was determined by gas chromatography. The vitamin E content was determined by high performance liquid chromatography. The index of lipid peroxidation was measured following the ISO 3960:2001(F) method. Heavy metals were quantified by atomic absorption spectrometry.

Results: : Huge differences were found in the lipid content when compared to the values claimed by the manufacturer (from –87.6% to +26.3%). Two products contained only ethyl–esters, while the others showed various mixes of free fatty acids, mono–, di– and tri–acylglycerols. The fatty acid composition of the supplements designed for dry eye prevention was very heterogeneous: linoleic acid, gamma–linolenic acid, EPA or DHA were found from less than 1% to 55%. The supplements designed for AMD prevention and for improving mental well–being were similar with large amounts of EPA and DHA. Vitamin E amounts were sufficient to prevent lipid oxidation in all but 4 products. Heavy metal levels were below the safety limits raised by French (AFSSA, CSAH) and international agencies (WHO, JEFCA).

Conclusions: : The huge variations in the lipid composition of dietary supplements designed for the prevention of age–related ocular pathologies may surmise big differences in terms of efficiency.

Keywords: pharmacology • nutritional factors • lipids