This week in my ongoing quest to learn how to best maximize protein synthesis I will be shifting my focus from nutrient timing surrounding workouts to overall meal frequency. What I want to do is find out if there really is an ideal timing between meals that best enhances protein synthesis. Meal frequency is a topic we recently discussed in round table 4. In that discussion I mentioned that meal frequency does not matter much and as long as you are getting in all your nutrients at some point during the day you are good to go. I still believe that for the most part, but if there really is an ideal way to eat, I think it’s worth taking a look at and giving it some real food for thought, pun intended.
The first thing we need to determine is if there is a certain amount of protein in a meal that works best for protein synthesis. You may have heard in the past your body can only use so much protein at once for anabolism. Research has shown that the optimal amount of protein that can be used for anabolism per meal is somewhere around 20-30 grams of protein or roughly 10-15 grams of essential amino-acids. Of course it can vary greatly between each person. It’s also not necessarily just about the amount of protein either, as not all proteins are created equal. We know leucine is the best amino-acid for building muscle out there, so the amount of leucine in the food you are eating plays a role too. For instance, since we know 10-15 grams of essential amino-acids is roughly the highest amount we can take in at once for building muscle, that would mean roughly 3 grams of leucine would be optimal. To get 3 grams of leucine from eggs you would need 35 grams of protein but to get the same amount of leucine from chicken you would need 40 grams of protein. So the source of the protein could play a role in how much we can utilize at once as well.
Now that we know roughly how much protein in a meal can be used for muscle growth, the question becomes how often we should eat to maximize protein synthesis. You have probably heard at some point that eating frequently, like every 2-3 hours throughout the day is the best way to go. If you can only use so much protein, wouldn’t it make sense to eat less more often and in turn have a greater anabolic response? That is certainly what I believed for a long time. Say I’m going to eat 180 grams of protein in a day. If I can utilize 30 grams of protein in each sitting, and I eat 6 meals in a day, that would get me to my 180 for the day. That would be 6 meals each utilizing all the protein my body can use for protein synthesis making sure each and every gram of protein I eat gets used instead of wasted, right? It sure seems to make sense, but does science back it up?
Norton et al (2009) showed that when a meal containing carbohydrates, protein and fat is consumed the increase in protein synthesis lasted for 3 hours. Although this study was done on rats and not humans. Still upon first reading this, it once again seems to make sense that eating every 3 hours would be ideal, but not so fast. They also found while protein synthesis returned to normal levels after 3 hours, plasma amino-acid levels stayed elevated by almost 3 times their normal levels at that same point. Bohe et all (2001) showed in a human study when they infused essential amino-acids for 6 hours, muscle-protein synthesis rose significantly between 30-60 minutes and continued to rise between 1 and 2 hours. From 2 hours to 6 hours the rate of mixed-muscle synthesis fell markedly from its peak value, becoming similar to the basal value. So even though they continued to infuse with essential amino-acids for 6 hours, only the first two hours had an increase in protein synthesis.
When you put all of this together it tells me even though protein synthesis goes back to normal levels after 2-3 hours, the signal to increase protein synthesis doesn’t necessarily get triggered again for 2-3 hours after it returns to normal. This really raises the question if eating every 2-3 hours does anything for protein synthesis. If anything it makes me wonder if continually eating throughout the day would actually cause your body to stay around the basal level instead of keeping protein synthesis high. It seems to me that waiting longer between meals with higher amounts of protein would give you the best response for protein synthesis, or at least make sure that you are getting an increase each time you eat.
My recommendation if you want to try to maximize protein synthesis with your meals throughout the day: Eat every 4-6 hours and make sure to include a good source of protein with each meal. Make sure you are getting enough protein to get around 3-4 grams of leucine from whatever protein source you are eating to make sure you are maximizing your chances to take in as much protein as possible. All of that said, I still stand by my opinion that no matter how often you eat it still matters more that you get the proper amount of calories and macros in than it does when you eat them. I’m not sure either way makes that big of a difference, and most of this is speculation based on research. However, if you want to do everything possible to increase protein synthesis, my mentioned strategy would be a good place to start.