Amino acid intake and plasma concentrations and their interplay with gut microbiota in vegans and omnivores in Germany

PURPOSE: It has been estimated that most vegans meet the total protein requirements, but whether this is also true for individual essential amino acids (AAs) is unclear. Furthermore, a shift in protein intake is suggested to alter microbiota composition, but this association is unknown in terms of veganism or individual AAs. This cross-sectional study compared vegans and omnivores regarding dietary intake and plasma concentration of AAs. The prevalence of insufficient intake of essential AAs among vegans was determined using estimated average requirements (EAR) of WHO. Moreover, correlations between AAs intake and gut microbiota were investigated. METHODS: Data of 36 vegans and 36 omnivores (30–60 years) were analysed. AA intake, AA plasma concentrations and gut microbiota were ascertained by three-day weighed food protocols, gas/liquid chromatography-tandem mass spectrometry and 16S rRNA sequencing, respectively. RESULTS: At almost the same energy intake, the intake of 9 AAs in vegans was significantly lower than in omnivores, with median differences of − 27.0% to − 51.9%. However, only one female vegan showed total protein and lysine intake below the EAR. Vegans showed lower lysine (− 25.0%), but higher glycine (+ 25.4%) and glutamate (+ 13.1%) plasma concentrations than omnivores. Correlation patterns between AA intake and bacterial microbiota differed between vegans and omnivores. In vegans 19 species and in omnivores 5 species showed correlations with AA intake. CONCLUSION: Vegans consumed apparently sufficient but lower AAs than omnivores. In addition, the different AAs intake seems to influence the microbiota composition. The use of short-term dietary data without considering usual intake limits these findings. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00394-021-02790-y.