Below is the second part of the interview with Dr Tim Snijders. Part 1 can be found here.

Asker: The supplement you gave to your subjects was 300ml of a drink that contained 27.5g protein and 15g of carbohydrate. Why did you give carbohydrate and what was the effect of the carbohydrate? Would the results have been different if the drink would not have contained carbohydrate?

Tim: When carbohydrate is ingested insulin is being released to clear the glucose from the circulation into mainly skeletal muscle and the liver. However, previous studies have also demonstrated that insulin can further stimulate the muscle anabolic response by reducing muscle protein breakdown. As such, a supplement combining protein and carbohydrates is considered to be most beneficial.

Asker: What type of protein was used in these studies, why was this protein source chosen and what in your view would the optimal protein look like?

Tim: In the current study participants consumed either a protein based supplement or a non-caloric placebo on both training and non-training days for the 12 week intervention period. The protein based supplement contained 27.5 grams of protein (1:1 casein isolate and casein hydrolysate (Peptopro; DSM)). Casein is absorbed and digested more slowly compared to for example whey protein. As such, when casein is being ingested it would become available over a more prolonged period of time during post-exercise, and in this case, overnight recovery. A combination of both fast and more slowly digested proteins would most likely be most optimal to aid the skeletal muscle adaptive response during prolonged exercise training.

Asker: ~28 grams is quite a large amount of protein. What was the feedback from the participants in the study? Did it affect their sleep quality in any way?

Tim: During the study all participants were asked to complete a questionnaire on a regular basis to keep record of how the supplement was perceived during the 12 week intervention program. Overall the supplement was very well perceived and no sleeping problems were reported by any of the participants after supplement consumption during the study. This provides further support for our conclusion that protein ingestion prior to sleep may represent an effective dietary strategy to augment the increase in muscle mass and strength during prolonged exercise training.

Asker: If you would have given even larger amounts of protein would you have seen greater effects?

Tim: Previous studies have shown the post-exercise muscle protein rates increase more with the ingestion of greater amounts of protein, with a maximal stimulation after ingestion of 20-25 grams of high quality protein. Therefore, I would not expect that ingesting more protein would result in a significant greater increase in muscle mass and/or strength in this study.

Asker: In my blog I called these studies heroic because they are so difficult to perform. Can you tell us a bit about how difficult these studies are or do you have an anecdote of something funny or memorable that happened during the trials?

Tim: Performing large exercise intervention studies is quite challenging. It is hard to imagine the logistics that are involved in running these kind of studies. I found that it is virtually impossible to run long-term exercise training studies by yourself, it is a real team effort. Furthermore, when you are supervising training session 3 times a week during the evening, over the course of nearly 2 years, it takes a big bite out of your personal life as well. But in the end it is all worth it, as we can truly assess the effects of nutritional supplementation and exercise training in humans.

As an example of one of the great number of challenges that you need to overcome when performing long-term exercise training/ nutritional supplementation studies is the logistics. Besides performing all the exercise sessions, it is critical that all the measurements are performed at all the right times during the intervention program. For example, in this study, CT-scan were performed before and after the intervention program to determine the change in thigh muscle cross-sectional. Fortunately, we were able to perform CT-scan in the Maastricht University Medical Centre. As these CT-scanners are normally heavily booked for patient care we only had a short time window to perform scans for our research project, typically very early in the morning. Getting out of bed early in the morning is not always the easiest task for the young men (mostly university students) participating in our research study. To meet the time schedule for these scans I remember we had to, in some cases, personally pick up the participants from home just to make sure that they would make it on time to perform the scan that day and collect the required data.

Asker: Finally, what are the next steps, which studies need to be done, or which studies will you be doing next?

Tim: Although this study shows that protein ingestion prior to sleep has a positive impact on the increase in muscle mass and strength when performing resistance exercise training, it remains unknown whether this time point of supplementation is better compared to other time points. Future research will be required to determine whether other time points may be even more effective to provide great gains in muscle mass and strength. Furthermore, it would be interesting to observe whether similar results can be found with other sources protein, like plant-based proteins.

Read blog about protein and sleep