* This post is a little long because I couldn’t think of what to leave out. Everything seemed important. Hopefully, when you’ve finished reading you’ll understand the critical importance of adequate protein consumption for good health and aging well.
As you get older, you begin to take more notice of your age and the age of those around you.
You start seeing more older men and women who are unable to navigate the simple physical tasks of life without the help of an aid.
Maybe you’ve seen it amongst your loved ones. Your aging dad’s once powerful arms and legs now have shrunk to what appears to be mere skin and bones.
Your mom, now definitely well into her senior years, seems to be permanently attached to her walker.
Maybe we notice it more because there’s a fear in us that we may end up like that as well. After all, isn’t frailty and weakness just an inevitable part of growing old?
Well, we may believe that’s what aging is supposed to be like because that’s what we generally see. But does it have to be that way?
Often, what we interpret as “normal aging” is a result of the considerable loss of muscle mass experienced by older people.
Health professionals know that good muscle mass is necessary for maintaining good health and mobility.
Unfortunately, most older people simply do not have enough muscle mass to maintain a good quality of life.
But here’s the good news. The loss of muscle mass loss resulting in poor health and disability isn’t necessarily an inevitability of aging.
Today, there are scientifically proven ways to mitigate the loss of muscle as we age.
Studies have shown that the best way to maintain good muscle mass throughout our lives is through the use of resistance training (RT). RT has even proven to maintain and increase muscle mass in individuals in their eighties.
But there’s another way to attenuate the loss of muscle due to aging. That’s through the proper dietary intake of protein.
Since good muscle health is dependent on proper protein consumption, it’s vitally important you know how much protein you need to consume daily.
Are you consuming enough protein to maintain healthy muscle?
Unfortunately, many of us today, especially those who are over the age of 65, are simply not consuming enough protein to optimally maintain muscle mass and strength.
What’s especially concerning is that while most young adults are consuming more than the recommended daily allowance (RDA) of protein intake, about ⅓ of older people are not meeting that requirement.
Now as if that wasn’t bad enough, the current RDA for protein might actually be underestimating your daily need of protein.
Many of today’s leading protein researchers have even become openly critical of the current RDA for protein. They suggest that the current RDA for protein is out of touch with the current scientific research and is woefully inadequate as a reference for older adult populations.
But before examining the current RDA for protein intake and exploring what is currently recommended by top protein researchers, I’d like to take a short detour.
The importance of muscle
You know your skeletal muscles are important for enabling you to move from here to there and for helping you lift things. When you suddenly can’t do some of those things, you become acutely aware of how important your muscles really are.
But your muscles are much more important than simply being parts of your body that when contracting and relaxing allow you to be mobile.
Skeletal muscle is an organ that constitutes about 30% – 40% of your body mass.
It can act like an endocrine organ by secreting anti-inflammatory myokines. There is research to suggest that myokines released from muscle may play a role in tumor suppression.
Muscle is also the largest contributor to resting energy expenditure. More muscle means you’ll burn more calories at rest. That’s good for trying to maintain an optimal body weight.
There is also evidence that poor muscle strength is linked to dementia and cognitive decline. Researchers are, however, unsure of the exact link.
Studies have now shown that there is an inverse association between low muscle strength and increased mortality.
As I mentioned before, maintaining healthy muscle, therefore, is a key to healthy aging.
Unfortunately, aging is working against you in this respect. Everyone over the age of 35 is probably losing muscle mass every year.
Muscle loss is a normal part of aging. Sedentary individuals can expect to lose as much as 3% – 5% of their muscle mass per decade after the age of 30.
However, after the age of 50, muscle mass loss can be as great as ∼0.8% annually. By the time you’re 75, that can add up to a lot of muscle loss.
Associated with this is dynapena. This is the loss of muscle strength. It can take place at a much more dramatic rate than sarcopenia. Some researchers estimate that strength loss could be as much as about 2–3% annually.
The only known pharmacological treatment for age related sarcopenia is testosterone therapy.
While RT is acknowledged to be the most potent treatment for age related sarcopenia, researchers now suggest that proper protein intake can work synergistically with RT to attenuate the effects of sarcopenia.
And in some cases even induce muscle hypertrophy in older individuals.
In order to understand why proper protein intake is important for maintaining healthy muscle, it’s important to understand how muscle is synthesized and maintained.
A muscle metabolism primer
Muscle protein synthesis
Protein is the major building block of muscle. To get a picture of how muscle is synthesized consider the analogy of building a brick wall.
As you add bricks to the end of a wall, it gets bigger. As protein (actually amino acids) is added to muscle, it’s like adding bricks to a wall. It gets larger.
This is known as muscle protein synthesis (MPS). However, this is not the whole story. There is also something important going on at the other end of the wall.
Muscle protein breakdown
Protein is constantly being turned over by your body. That means that protein is constantly being removed from muscle. This is known as muscle protein breakdown (MPB).
Getting back to the wall analogy: while bricks are being added to one end of the wall, bricks are constantly being removed from the other end.
Net protein balance
Now, in order for muscle hypertrophy (growth) to occur, MPS must be greater than MPB. When this is achieved, scientists say we have a positive net protein balance (NPB).
When MPS and MPB are equal, we have homeostasis, and muscle mass is maintained. However, if MPB > MPS, then there is a negative NPB. If this occurs you’ll lose muscle mass.
How do you achieve muscle protein synthesis?
The key to mitigating muscle loss is to achieve muscle protein synthesis (MPS). The greater amount of MPS going on in your muscle, the less muscle you’ll lose.
Outside of hormone therapy there are two ways to stimulate MPS. This can be done through RT or a sufficient intake of dietary protein. RT, though, appears to be a much more potent stimulus for triggering MPS than consuming protein.
However, when RT and optimization of protein consumption are combined, there is a synergistic effect of MPS.
Now, let me put this all together to see how it affects age-related muscle loss and the building of muscle mass.
Preventing muscle loss and increasing muscle mass
We know that if you engage in resistance training, you will significantly increase the MPS occurring in your body. RT during the post-absorptive state (when food has not been consumed prior to or after RT) stimulates MPS by more than 100% above basal levels.
However, and this is important. Even though RT may not stimulate MPS enough to create a positive NPB, it will aid in the sparing of muscle mass loss.
Protein consumption and MPS
Now, we also know that protein ingestion will increase MPS. Later, I’ll explain why the proper amount and type of protein, including when it’s consumed, is important for achieving optimal MPS.
However, even though protein ingestion will stimulate MPS (independent of RT) and thus limit muscle breakdown, it will not induce muscle hypertrophy. Again this is because NPB remains negative.
So, while RT and protein ingestion independently increase MPS, muscle mass may still be decreasing. But it won’t be decreasing as fast if neither was employed.
Now, here’s the really good news!
Repetitive bouts of RT in combination with protein intake after exercising can increase NPB to a positive state and promote muscle protein accretion over time.
Therefore, in terms of mitigating muscle loss due to age-related declines both RT and proper protein ingestion combined are excellent strategies.
Both strategies will attenuate the loss of muscle due to sarcopenia. However, when combined they can produce a maximal MPS that can cause a positive NPB and thus muscle hypertrophy.
Okay, this is the third time I’m going to mention this. But I really want to drive home this point. This strategy will even create muscle hypertrophy in eighty year olds.
Okay that’s great news. But there are several questions that have to be answered. You may be asking them already.
I’ve already hinted at the other question. If protein consumption is an important factor in achieving MPS and preserving muscle mass, then how much should we consume on a daily basis?
What’s the current recommended daily allowance of protein?
The current recommended daily allowance (RDA) of protein for adults is 0.8 grams of protein per kilogram of body weight per day (designated as 0.8 g/kg/d).
So, according to the RDA, if you weigh 150 lbs (68 kg), regardless of age or gender, you would need a minimum of (68 x 0.8) 54.4 grams of protein per day to stay healthy.
Hopefully, “healthy” would include maintaining good muscle and fulfilling other protein requirements of your body.
If you were to do a quick google search for the RDA for daily protein consumption, the results probably wouldn’t specify what kind of protein meets the 0.8 g/kg/d requirement.
In some places, the RDA specifies high quality-protein, but it doesn’t define what high-quality means. More on this later.
However, the important thing to understand is that the RDA for protein is not the amount you’re allowed to eat daily. It’s the minimum amount of protein needed to meet the basic nutritional requirements of a healthy person.
Recently, however, the RDA for protein has come under criticism by leading protein researchers.
One criticism is directed against the method used to determine the RDA.
Another is that the RDA may significantly underestimate protein requirements for older people because it neglects the fact that the ability of protein to stimulate MPS is blunted in older adults.
Let’s take a look at the first criticism.
Is the current RDA for protein determined by a flawed method?
The RDA for protein is established by using nitrogen balance technology. This method, which has been used for at least 50 years, basically measures the nitrogen going into your body (food) and the nitrogen coming out (excretion).
It theoretically assumes that nitrogen serves as a proxy for essential amino acid (EAA) utilization by your body. Therefore, the difference between the two measurements will tell whether EAAs are in a deficit or abundance.
The number they arrived at to achieve a nitrogen balance is 0.8 grams/kg/d.
It’s stated this way: 0.8 g/kg/d is,
Now, here is another important question to consider. While 0.8 g/kg/d is the absolute minimum protein intake people should be striving for, are there benefits to consuming amounts of protein above the RDA?
The Food and Nutrition Board’s recommendation for protein consumption
Nutrition guidelines from the Food and Nutrition Board (FNB) of the Institute of Medicine (IOM) make up the cornerstone of macronutrient recommendations in the United States. See also here.
Their Dietary Reference Intake (DRI) guidelines specify for males >19 years old a minimum of 56g of protein/day and females >19 years old a minimum of 46g of protein/day.
However, the DRI also recognizes biological differences in individuals and also uses the RDA of 0.8 g/kg of body weight/day as acceptable.
Interestingly, it goes one step further and proposes an Acceptable Macronutrient Distribution Range (AMDR) for protein.
The AMDR for protein as suggested by the FNB lies between 10% – 35% of the total calories you consume in a day.
This recommendation seems to allow individuals to target specific macronutrients in a complete diet. In other words, you can set protein intake along with fat and carbohydrate intakes.
It also allows you to set protein consumption in accordance with specific dietary goals. For example, an elite athlete might want to maximize their protein consumption.
However, what the FNB has done by proposing a AMDR is suggest that there is an amount of protein above 0.8 g/kg/d that might lead to better health outcomes.
AMDR versus the RDA: are they compatible?
By allowing 10% – 35% range of protein intake, the AMDR has set up guidelines that are not consistent with the RDA.
Let’s say you’re a female weighing 57 kg (125 lbs) and consume 2000 (k)cal a day and 10% of that was protein. Then you’d be consuming about 50g of protein a day. However, using the RDA metric you would need to consume (57 x 0.8) 46 g/day.
That means the AMDR recommends about 8% more protein than the RDA .
However, if you consume 30% of your daily calories as protein, which the AMDR states is acceptable, it would amount to 150 grams. Now that’s 30% higher than the RDA.
Why such a wide range of protein intake?
While the FNB allows for individual differences in its protein recommendation, it also suggests that higher intakes of protein might account for better health outcomes.
The FNB states that the AMDR,
…is provided to give guidance in dietary planning by taking into account the trends related to decreased risk of disease identified in epidemiological and clinical studies.
Thus, FNB acknowledges that there are protein intakes that are well above the RDA that are associated with good health.
Researcher Dr. Robert Wolfe observes, “In discussing the RDA for protein, the FNB points out that there may be benefits to eating amounts of dietary protein greater than that in the RDA, and it is extensively documented in the same chapter that no UL for protein intake beyond which adverse effects may result could be identified.”
So what’s the right amount of protein you should be consuming during the day?
Seeing that the amount of protein you ingest is crucial for good muscle and also good health in general, it’s important that we have a clearer answer.
The Indicator Amino Acid Oxidation (IAAO) Method for determining protein requirements
An alternate method now being used to determine minimum protein requirements is the Indicator Amino Acid Oxidation (IAAO) Method.
While there are some shortcomings associated with this method, protein researcher Dr. Donald Layman states that the IAAO does address many of the limitations of the Nitrogen Balance method.
When the IAAO method is used for determining protein intake, it has consistently yielded higher estimates than the nitrogen balance method.
Researchers using the IAAO have found that for normal healthy younger persons a safe minimal protein intake was 1.0–1.2 g/kg/day.
Notice that these minimum intakes are 40% – 50% greater than the current RDA.
Also, remember, these values are minimum values and not necessarily optimum values.
But, again, what is the proper amount of protein we should be consuming? Is the IAAO’s recommendation the final answer?
Advice from expert groups
Two independently formed groups of protein experts have recently come out with a call for higher protein intakes, especially for older persons. [Most studies consider older persons to be >65 years old.]
The European Society for Clinical Nutrition and Metabolism (ESPEN) suggests a protein intake of at least 1.0-1.2 g protein/kg body weight/day. For older people who are malnourished or at risk of malnutrition because they have acute or chronic illness, they recommend 1.2-1.5 g protein/kg/d, with an even higher intake for individuals with severe illness or injury.
The PROT-AGE study group, comprised of world recognized experts on protein nutrition, suggests that to help older people (>65 years) maintain and regain lean body mass and function, they have an average daily intake at least in the range of 1.0 to 1.2 g/kg/d.
The study group further recommends,
“Both endurance- and resistance-type exercises are recommended at individualized levels that are safe and tolerated, and higher protein intake (i.e., ≥ 1.2 g/kg body weight/d) is advised for those who are exercising and otherwise active. Most older adults who have acute or chronic diseases need even more dietary protein (i.e., 1.2-1.5 g/kg body weight/d).”
As you can see, both the ESPEN group and PROT-AGE group are very similar in their recommendation of protein intake for older people.
Their recommendation is also similar to what the IAAO method suggested for minimal protein intake.
So it would seem that at least for older individuals, the RDA of 0.8g/kgBW/day for older individuals is woefully inadequate.
Researchers now though are shifting away from considering optimal protein in terms of daily intake.
Determining optimal protein intake based on a per meal basis
In order to discover an optimal protein intake for young and older adults, protein researchers are now turning their attention to a per-meal basis intake of protein rather than simply focusing on the total daily intake.
This brings us back full circle to the concept of muscle protein synthesis.
Remember that the primary process controlling muscle gain or loss is MPS. The greater your MPS, the better chance you’ll have of mitigating muscle loss or even producing muscle gain.
Researchers now know that there is a relationship between the amount of protein you eat at a meal and the amount of MPS created.
Studies have revealed that as the amount of protein you consume increases, there is a graded rise in the rate of MPS up to a point where consuming more protein has no appreciable effect on MPS.
Protein researchers Witard, Moore and Areta independently have all determined that consuming approximately 20 g of protein is enough to stimulate optimum MPS in young adults. Moore suggests this is about 0.24 g/kg/meal.
Note that these studies were done on individuals who engage in RT. RT does sensitize the body to MPS, so whether more protein would be needed to induce optimal MPS in untrained younger individuals is unclear.
Also, the type of protein used was high quality (whey, egg). Most of us do not consume this kind of protein throughout the day.
Interestingly, higher amounts of protein did not significantly raise MPS (20 g compared to 40 g) .
There’s about a 30 min delay in the stimulation of MPS. It then peaks at 2 hours and then reverts back to basal levels after about 2–3 hours regardless if more protein is consumed. This is what researchers call a muscle full effect.
The problem of unbalanced daily protein consumption
Most people eat an unbalanced amount of protein throughout the day, with most of their protein at dinner. This causes a problem for creating and sustaining MPS.
Let’s assume you eat 10 g of protein for breakfast, 15 g for lunch, and 70 g for dinner.
This means that because it takes 20 g of protein to stimulate MPS, you’ll only get the benefit of MPS for about 3 hours after dinner. For the remaining 21 hours, you’ll be experiencing MPB and losing muscle.
Now what if you have 3 meals at 15 g of protein/meal? Then you may not be in MPS at all, and you’d be in MPB throughout the day.
Because of these scenarios, researchers suggest the optimal strategy for building muscle is to spread protein consumption throughout the day.
Phillips et al, report that cumulatively the findings suggest “that ~20 g of high-quality protein (or ~0.3 g/kg/meal) is sufficient to maximally stimulate MPS after a single meal and, when repeatedly administered 3h apart, optimize MPS throughout the day.”
Therefore, the consensus among leading protein researchers is that young adults should consume at least 20 g/meal (0.24g – 0.3g/kg/) per meal and at least 3 – 4 meals per day.
Notice using 0.3 g/meal at 3 meals would bring you to 0.90 g/d/kg/BW. This is already greater than the RDA of 0.8.
Also note that the phrase “high quality protein” comes up again. If you’re not consuming this type of protein, you may need more than 20g at each meal to optimize MPS. More on this later.
Okay, but what about older people?
Protein recommendations for older people
Research has shown that the ability of protein to stimulate MPS is blunted in older people.
Theoretically, therefore, it should take a greater amount of protein to stimulate MPS in older adults than younger.
This is in fact what current research has shown.
Moore et al. compiled data from 6 studies and found that for older males it takes ~0.40 g/kg of protein to cause the same MPS observed in younger males.
This tells us that older people can have the same MPS response as young adults although they have to ingest more protein for it to happen.
However, two studies have shown that protein requirements for older people may have to be higher than even 1.2 g/kg/d.
Okay, so based on an increasing volume of epidemiological and experimental data, and several expert groups, it seems as though a higher protein intake of at least 1.0 g to 1.5 g/kg/d is necessary for attenuating skeletal muscle loss in older adults.
Remember, though, that this recommendation should be spread over at least 3 meals throughout the day with at least 0.4 g/kg/meal.
If we express this in terms of how many grams of protein older people should consume at each meal, recent recommendations state this should be at least 25-30 g/meal.
Interestingly, in a recent review, protein researcher Stuart Philipps suggests that older adults should consume 0.4–0.6 g of high quality protein/kg/meal for 3 meals per day to attenuate age-associated muscle mass loss.
This would translate to about 30 – 40 grams of protein per meal.
Okay, let’s recap.
According to recent evidence, the recommendations for protein consumption are as follows:
Young Adults: Approximately 0.24 g – 0.3 g/kg/meal of high quality protein spread over 3 – 4 meals with at least 20g per meal.
Older people: Approximately, 0.4–0.6 g/kg/meal of high quality protein for 3 – 4 meals. At least 30 – 40 grams per meal.
Now, this seems to be straight forward but there’s one more variable to the equation.
According to current research, it appears that the essential amino acid leucine is the key to initiating MPS.
If you don’t have enough leucine in your protein, you won’t get any MPS.
The importance of leucine in protein consumption
Muscle growth is accomplished through a muscle building pathway called mTORC1 (mechanistic target of rapamycin). Researchers now know that the amino acid leucine is responsible for triggering this process.
While the actual amount of leucine necessary to trigger MPS is not known, researchers have a general idea of how much is needed per meal. They know that young adults are more sensitive to MPS activation by leucine (about 1 gram).
However, for older adults the amount of leucine necessary to stimulate MPS is considerably higher.
Researcher Donald Layman states,
Although dose-response trials are not available, there is a general pattern that appears from clinical trials that meals containing >2.2 g leucine in the form of EAA mixtures or whey protein stimulate muscle protein synthesis and meals containing <1.8 g leucine produce little to no response. It is important to note that these studies were performed in older, sedentary adults and represent the minimum response threshold.
So, older adults need >2.2 g of leucine per meal to stimulate MPS.
The PRO-TAGE group recommends older people get at least 2.5 – 2.8 grams of leucine per meal to optimize the anabolic response in skeletal muscle.
So, it’s not only the amount of protein you consume or when you consume it important, your protein must contain enough leucine to trigger MPS.
This is important because not all protein sources contain the same amount of leucine.
The importance of protein quality
Remember previously I mentioned the quality of protein? Here’s why it’s important.
Most of the protein studies are done using whey protein. Whey contains the highest amount of leucine.
So when protein researchers say that 20 g of protein in young adults and 30 g in older people is enough to stimulate MPS, they are basing this on an optimal protein source.
However, in the real world people are not usually consuming whey protein all day long.
Because different sources of protein have different contents of leucine, you may be consuming 20 g of protein, but it may not be have enough leucine content to trigger MPS.
For example, three large eggs will yield about 18 grams of protein. However, they will only contain about 1.0 gram of leucine. An older person would have to eat about 7-8 eggs to get enough leucine to stimulate MPS.
Also consider that you would have to eat a lot more plant protein to get the same amount of MPS than you would from red meat.
For example, 6 ounces of 90% lean ground beef contains about 3.5 grams of leucine. That’s more than enough to trigger MPS.
However, 7 ounces of quinoa contains about 28 grams of protein but only 0.5 grams of leucine. To get the required 2.5 grams of leucine to trigger MPS, you would need to eat about 35 ounces of quinoa.
Good luck with that!
You may have noticed previously that Phillips’ protein recommendation for older people was slightly higher than others (30 – 40 g as opposed to 25 – 30 g). I suspect the reason is that a higher protein amount would lead to a possibly better leucine content.
Okay, let’s recap again.
Young Adults: Approximately 0.24 g – 0.3 g/kg/meal of high quality protein spread over 3 – 4 meals with at least 20 g per meal. Leucine per meal unsure.
Older people: Approximately, 0.4–0.6 g/kg/meal of high quality protein for 3 – 4 meals. At least 30 – 40 grams per meal. At least 2.5 – 2.8 g of leucine per meal.
These recommendations are not for those who engage in RT. Phillips and others recommend higher protein intake in this case. See here.
I’m 62 years old and resistance train regularly. So, my protein intake is slightly higher than that recommended for older adults.
What about higher intakes of protein impairing renal function? Layman reports that there is no evidence that higher protein intakes impair renal function.
Layman also reports that,
The International Society of Renal Nutrition and Metabolism recommends, for patients with existing kidney disease, consume 0.6–0.8 g/kg body weight if not undergoing dialysis but to increase to 1.0 g/kg during any illness that is catabolic or limits physical activity. For those undergoing dialysis, International Society of Renal Nutrition and Metabolism recommends daily protein >1.2 g/kg, with at least 50% being of high biological value.
This recent study involving individuals who had type 2 diabetes and consumed a moderate 90–120 g/d found no negative effects on renal function during a 2-y period.
So there you have it.
Sufficient protein is a key ingredient for healthy aging. Make sure you’re getting enough.
God bless, and have a great week.
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