Variable glycemic responses to intact and hydrolysed milk proteins in overweight and obese adults reveal the need for precision nutrition

Background: Dietary modifications can contribute to improved pancreatic beta cell function and enhance glycemic control.
Objective: The objectives of this study were to 1) investigate the potential of milk protein hydrolysates to modulate postprandial glucose response, 2) assess individual responses, 3) explore the inter and intra-individual reproducibility of the response.
Methods: A 14-day randomized crossover study investigated interstitial glucose levels of participants in response to 12% w/v milk protein drinks (intact caseinate and casein hydrolysate A and B (CH-A and CH-B) consumed in random order with a 2-day washout between treatments. Milk protein drinks were consumed immediately prior to study breakfast and evening meals. Twenty participants (11 male/ 9 female) aged 50 ± 8 y with a body mass index of 30.2 ± 3.1 kg/m2 were recruited. Primary outcome was glucose levels assessed at 15 min intervals using glucose monitors.
Results: Repeated measures-ANOVA revealed that for breakfast there was a significant difference across the three treatment groups (P = 0.037). The ability to reduce postprandial glucose was specific to CH-B in comparison to intact caseinate (P = 0.039). However, despite this significant difference further examination revealed that only three out of 18 individuals were classified as responders (P < 0.05). High intraclass correlation coefficients (ICCs) were obtained for glucose response to study meals (ICC: 0.892 for breakfast with intact caseinate). The inter-individual coefficient of variations (CVs) were higher than intra-individual CVs. Mean inter- and intra-individual CVs were 19.4% and 5.7%, respectively, for breakfast with intact caseinate.
Conclusion: Ingestion of a specific casein hydrolysate successfully reduced the postprandial glucose response, however at an individual level only three participants were classified as responders, highlighting the need for precision nutrition. Exploration of high inter-individual responses to nutrition interventions is needed, in combination with the development of precision nutrition, potentially through an n-of-1 approach.