The effect of casein, hydrolyzed casein, and whey proteins on urinary and postprandial plasma metabolites in overweight and moderately obese human subjects

BACKGROUND

Casein and whey proteins differ in amino acid composition and absorption rate; however, the absorption rate of casein can be increased to mimic that of whey proteins by exogenous hydrolysis. In view of these compositional differences, we studied the metabolic responses to intake of casein, hydrolyzed casein, and whey proteins in overweight and moderately obese men and women by investigating select urinary and blood plasma metabolites.

RESULTS

A total of 21 urinary and 23 plasma metabolites were identified by nuclear magnetic resonance spectroscopy. The postprandial plasma metabolites revealed a significant diet-time interaction for isoleucine (P = 0.001) and tyrosine (P = 0.001). The level of isoleucine and tyrosine peaked 90 min postprandially with a 1.4-fold difference following intake of whey proteins compared with either casein or hydrolyzed casein. A 1.2-fold higher urinary level of lactate was observed after intake of whey proteins compared with intake of intact casein (P < 0.01).

CONCLUSION

The plasma metabolites revealed different amino acid profiles reflecting the amino acid composition of casein and whey proteins. Furthermore, the results support that casein hydrolysates neither affect the postprandial amino acid absorption rate nor the amino acid level compared with that of intact casein. The urinary lactate increases following whey protein intake might indicate a higher metabolism of glucogenic amino acids. © 2018 Society of Chemical Industry.

The Effect of Lean-Seafood and Non-Seafood Diets on Fecal Metabolites and Gut Microbiome: Results from a Randomized Crossover Intervention Study

SCOPE

The impact of dietary protein types on the gut microbiome is scarcely studied. The aim of the present study is therefore to examine the effects of lean-seafood and non-seafood proteins on the gut microbiome composition and activity and elucidate potential associations to cardiovascular disease (CVD) risk factors.

METHODS

A crossover intervention study in which 20 healthy subjects consumed two diets that varied in protein source was conducted. ¹ H NMR spectroscopy and 16S rDNA sequencing analyses were applied to characterize fecal metabolites and gut microbiota composition, respectively.

RESULTS

A twofold increase in fecal trimethylamine excretion was observed after the lean-seafood diet period. Circulating TAG and the total to high-density lipoprotein (HDL) cholesterol ratio as well as circulating TMAO levels were each associated with specific gut bacteria. Following the non-seafood diet period, a decreased relative abundance of Clostridium cluster IV and a tendency toward an increased Firmicutes/Bacteroidetes ratio were found.

CONCLUSIONS

Lean-seafood and non-seafood diets differentially modulate the gut microbiome composition and activity. Furthermore, the gut microbiota composition seems to affect circulating TMAO levels and CVD risk factors.