The Science of Getting Adequate Protein to Build Muscle in Midlife and Beyond

The Recommended Dietary Allowance (RDA) is near-identical in the US, UK, Canada and Europe at 0.8 g/kg/day (to one decimal place!) for all adults over 18 years old. But, experts have been calling for a higher dosage recommendation in older adults for some time.

Getting older triggers two negative impacts, that may justify higher protein intake. Firstly, the muscle loss caused by Sarcopenia starting in your thirties. And, secondly, it has been found that older adults synthesize protein into muscle less effectively.

How big a deal is it? Well, one study[2] in 2015 found muscle protein synthesis rates >3 fold more responsive to dietary protein ingestion in 21-23 year olds versus 73-75 year olds. But, the same study also found that muscle protein synthesis (MPS) rates did not differ significantly between the young and older groups when in a fasting (post-absorptive) state.

This means that, when it’s been sometime since you last ate, so your insulin levels are very low to zero, an older body synthesizes protein as effectively as a younger one. A good example, is when you are asleep at night.

But, the same study[3] also noted that ingestion of 35g of whey protein increases resting muscle protein synthesis rates to a greater extent than 20g (in older subjects). And, later concludes the available evidence suggests 30 – 40g is adequate.

Another study[4] concluded that due to anabolic resistance, “older adults appear to need 30–35g or more of whey [protein] to achieve similar anabolic effects” – ie comparable to young or middle-aged adults taking 20g of whey.

Overall, it seems logical to set 30g as a target minimum dosage per meal and to assume that going beyond 40g per meal is probably unnecessary.

A typically low protein meal in Western diets is breakfast, especially if you eat cereal with milk or toast and a conserve or Marmite. Given the research, recording protein in meals like this as part of your RDA, could give the false impression you are eating sufficient protein.

The answer seems to be to ensure an adequate amount of protein is included in every meal. Or, at the very least, ensuring your protein intake is not too thinly spread. If you are a “snacker” or “grazer” like me, these findings are not good news.

But, there’s an additional complication for older adults. Yes, again!

This is a confounding outcome, because insulin is an accepted potent anabolic stimulus for muscle proteins. Several studies have reported higher than healthy levels of insulin in the blood (associated with type II diabetes) can increase muscle protein synthesis when muscle amino acid availability is increased[6].

Another study[7] found dramatically delayed absorption of amino acids was the outcome of mixed meal consumption by older adults. Essential amino acid (EAA) and branched-chain amino acid (BCAA) concentrations in younger adults peaked at 1 hour post meal. Whereas peak EAA and BCAA concentration in older adults occurred after 3 hours. Likewise, peak total amino acid concentrations in older adults were not reached until 3 hours after eating.

A modest bout of physical activity has been shown to neutralise the negative impact of eating carbs with your protein[8]! Just 45 minutes of treadmill walking the evening before, restores the ability of insulin to stimulate muscle protein synthesis. This suggests that post-exercise MPS may not be impacted by the carbohydrate choke-hold.

The same researchers[8] showed ingestion of leucine-enriched essential amino acids stimulates muscle protein synthesis to a similar extent in young and elderly, during the first 6 hours following exercise.

The magic amino acid

Leucine is an essential (we must get it in our diet) amino acid that is used in the biosynthesis of proteins. This role means its concentration in the amino acid mix can have an overall effect on MPS, especially in (yes, you guessed it) older adults!

Research in 2006 [9] found that the leucine proportion of an essential amino acid mixture affected changes in muscle protein metabolism in older subjects. A whey protein with either 26% or 41% leucine was given to 2 elderly and 2 young groups of subjects. Both doses increased the fractional synthesis rate in young subjects, but only the higher leucine formula older group experienced the same effect. This means we could benefit from eating proteins with a higher leucine content or supplementing in leucine as we age.

Meat, fish, poultry and dairy are all good sources of leucine: salmon, tuna, chicken, turkey, cottage cheese, whey proteins, eggs and cheeses. Good plant-based sources include: pea protein, peas, lentils, peanuts, sunflower and sesame seeds and oats. And, one of the highest leucine foods per gram is Spirulina; 100g of this provides 181% of your RDA, whereas 100g of chicken contains 75%.

Researchers[10] have concluded that the dose of leucine necessary to achieve the maximal stimulation of muscle protein synthesis in older persons is ∼3–4 g/meal. This would typically require eating ∼25 – 30g protein per meal, which brings us nicely back to our magic number. (That wasn’t a fix, I promise!)

Science says no! Research has found no “golden window” for getting your protein shortly after a workout. A meta-analysis (a study of studies) in 2013 [11], considered hypertrophy (muscle growth) and strength. It covered 43 studies with 1003 participants in total. Its conclusion was clear: “These results refute the commonly held belief that the timing of protein intake in and around a training session is critical to muscular adaptations”[11]

Specifically relating to building bigger muscles, their analysis showed total protein intake was the strongest predictor of growth. And, that confirms the importance of ensuring you are getting adequate protein and in adequate doses.

Well, no (and I’ll quote the research) “evidence does not support a relationship between increased dietary protein content and a decline in renal function”[4] .

And, no again in this systematic review and meta-analysis from 2018: “Our analysis indicates that HP [High Protein] intakes do not adversely influence kidney function on GFR in healthy adults.”[12]

And, I found a consensus of other “no” conclusions, unless you have pre-existing renal disease, even if you’re an older adult: “Advanced age alone does not, therefore, appear to be a reason to avoid increased dietary protein intake”[4]

What happened to eating a balanced diet? Well, up to 35% of your daily energy intake can be from protein, as part of the Acceptable Macronutrient Distribution Range (AMDR).

For a man eating the recommended 2500kcal a day, that equates to 219g of protein (at 4kcal/g). Allowing 1.2g/ kg body weight (+50% over the standard RDA), you could weigh 182.5kg or 402lbs.

A woman eating the RDA of 2000kcal is allowed up to 175g of protein, so could weigh up to 146kg/ 321lbs and still be getting 1.2g/ kg body weight.

On a typical recovery day, I definitely achieve the 1.2g per kg in body weight. But, my diet differs between training days and recovery (non-workout) days. I prioritise protein after my workout for at least the next 24 hours.

But, I also make sure I get enough carbohydrate and water. Your muscles are actually 76% water and carbohydrate is required to replace glycogen after intense exercise.

Immediately after my workout, I drink lots of water and some pure sugar carbohydrate to help replace the glycogen in my muscles. I will then wait for 45 mins or more before eating a high protein meal that includes carbohydrate. This regimen has definitely worked better for me, than the post workout protein shakes of old!

Steve — MiniWorkoutDad