α-Lipoic acid as an ingredient of specialized food product and dietary supplement

Abstract

A review of the literature in recent years was carried out using the RSCI, Google Scholar, Pubmed, and ResearchGate databases.The purpose of the review was to assess the content of α-lipoic acid (ALA) in foods and compare the doses allowed for use in dietary supplements and specialized food products with doses that provide a clinical effect. ALA or thioctic acid is synthesized in the organism and is also found in foods in free oxidized and reduced form, bound to proteins by hydrogen bonds, as well as covalently bound to lysine residues (lipoyl-lysine) in proteins, which complicates the analytical determination and reduces the bioavailability of this vitamin-like substances. Various methods for determining the natural content of individual forms (ALA and lipoyl-lysine) and their total content in food products have been described. The content of free ALA in 100 g of raw products of animal origin varies from 0.22 to 1.35 mg, of plant origin – from 0.22 to 2.04 mg. Losses during heat treatment reach 77–92%. Lipoyl–lysine content ranged from 2.11–3.99 µg/g heart, 0.56–1.17 µg/g liver, 0.71–1.40 µg/g kidney, while ALA amounts ranged from 0.22 up to 0.55 µg/g heart, from 0.38 to 0.51 µg/g liver. It is difficult to estimate the dietary intake of the total amount of all forms of ALA due to differences in extraction and detection methods. According to the domestic regulatory framework, the adequate level of ALA consumption for adults is 30 mg/day, the upper permissible level of daily consumption for adults as part of specialized food products (SFP), preventive and therapeutic nutrition and dietary supplements is 100 mg/day. ALA is often included in multicomponent dietary supplements and SPP in doses from 15 mg to 100 mg. A positive effect when taken for 10 or more weeks on lipid and carbohydrate metabolism, as well as other clinical effects in patients, is observed when taking ≥ 600 mg of ALA per day, which is significantly higher than the doses allowed for inclusion in the SFP.