D-AMINO ACIDS IN PROCESSED FOODS : WHAT HAPPENS INSIDE THE BODY?

Food processing makes two major changes in plant proteins -

• Racemization of all L-amino acids to D isomers
• Formation of cross linked amino acids (ex. lysinoalanine)

Racemization is depend on pH, time and temperature exposed. Conversion rates of isomers differ. However, D-amino acids present in food comes from both processed as well as from natural foods. Latter sources include plants, micro organisms and marine invertebrates. Whatever the source, racemization impairs nutrition quality and digestibility.

Some D-amino acids can be used in animal bodies.

• D-methionine: nutritional source of L-isomer
• D-phenylalanine: nutritional source of L-isomer

Others either useless or cause harmful effects.

• high concentrations of D-tyrosine fed to mice, inhibited their growth rates
• D-serine: cause histological changes in rat kidneys
• Lysinoalanine: cause histological changes in rat kidneys
• D-lysine: no nutrional value
• D-cysteine: no nutrional value

Humans expose to these D-amino acids, specially from diets high in processed foods. but their safety, physiological roles and potential harmful effects are grossly under studied.

Source:

Chemistry, Nutrition, and Microbiology of d-Amino Acids. Mendel Friedman. Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, California 94710. J. Agric. Food Chem., 1999, 47 (9), pp 3457–3479