Our new study: can the production of milk protein lower its quality?

Milk is often heated to increase its microbiological safety and shelf life, or to make specific milk-based products (such as infant formulas and protein supplements).

Heating of milk can cause its sugar molecules (lactose) to stick to the amino acids of the milk protein, a process known as glycation. Especially the essential amino acid lysine is susceptible to this.

Therefore, it can be speculated that glycation influence the absorption of protein.

Our study investigated the effect of glycation of milk protein on plasma amino acid responses during the 6 hours after ingestion. Participants ingested three different protein drinks on three different days: 40 g of 3%, 20%, or 50% glycated milk protein.

The highly glycated milk protein appeared to severely impair lysine bioavailability: the incremental area under the curve was 92% lower.

This suggests that glycation can negatively influence the digestion and absorption of amino acids (especially lysine). Whether this also results in a lower muscle-building response remains to be determined.

In conclusion, glycation of milk protein can decrease lysine absorption.

Our study:

Nyakayiru et al. The glycation level of milk protein strongly modulates post-prandial lysine availability in humans. Br. J. Nutri, 2019.

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