Study shows that Protein Requirements increase with age:
When you see advise for protein intake in the popular press, numbers are all over the place, and there seems to be wide disagreement on amounts and sources. The popular position for aging seniors has long been that we need progressively less protein because all our metabolic and anabolic functions are slowing, along with an over-cautious belief that excess protein is a stress on the kidneys, which are also declining in function.
Body builders have their requirement very well calibrated; principally, about 1.5 grams per pound of lean body weight to pack on muscle. They also agree on the best source as animal protein, most conveniently from the milk cows make for nurturing their young, in the form of powdered whey, a byproduct of making cheese, which makes it widely available. Other protein sources are used as well, but the basic foundation is whey, and whey-derived complexes or isolates. But these are generally men and women between the age of 18 and 45; there’s not been much consideration (or study) has been given to protein intake for holding off the ravages of aging.
But now comes a study from 2016 that finally documents some definitive testing and data-mining to conclude that requirement for protein intake actually increases with aging.
The Abstract of the study lays out the primary problem for the aging as ‘Sarcopenia’ or loss of muscle with age, leading to that well known ad line; “I’ve fallen and can’t get up!”.
My 95 year-old father had a dream one night that he had a snake in his bed and leapt out of bed to escape it. He had indeed rolled out of bed for real and couldn’t get up. Although he lived in a very nice assisted living facility, no one came to his assistance because he had left his call pendant hanging on the bed post and couldn’t reach it. Lying on the floor overnight triggered the process of systemic shut-down. Rushed to the hospital in the morning when discovered, he became more incapacitated and rigid as the day wore on and died before morning the next day.
The threshold for dependent living is commonly thought of as being unable to rise from a chair; my dad had already reached that point a year before, but he was still enjoying life; not at all ready to give it up. But he didn’t believe that exercise or diet could do anything about the decline in strength he was experiencing. We know today that we can push that threshold out many years by persisting with strength training and proper nutrition, including supplying the raw materials for muscle repair and growth by greater protein intake.
Protein intake is unique in that it stimulates an anabolic or building/repair mechanism – protein ingestion causes muscle growth if enough is eaten in one sitting to trigger the anabolic response. This 2016 study measured the anabolic response threshold of aging adults to increasing amounts of protein, and discovered that although the threshold increases with age (takes more protein per meal) the anabolic response can be achieved with higher protein intake per meal.
Optimal protein intake per meal can be defined as the minimal dose of protein intake that results in the maximal anabolic response and thus can help maintain or improve muscle mass (reflected as lean body mass) and function over time. It has been reported that the optimal dose of dietary protein consumption in a meal that results in a near maximal anabolic response is ~35 g/meal  or 0.40 g/kg/meal of high-quality protein in elderly adults , translatable to 1.2 g/kg/day or 96 g/day for an 80 kg elderly adults. But this is based on the notion that protein is best used if intake is uniform over the three meals of the day, a notion that is not normal, in that protein intake in the western world is skewed toward the evening meal.
My practice over the years has been to include some level of protein in every meal, but to focus on breakfast and dinner as my primary meals for protein. This gets changed around some depending on what time I hit the gym. Most of the years that I worked in industry, I worked out during lunch, and would use a post-workout protein drink as the way to get 50 grams or so of protein intake during the first hour after the workout during the so-called anabolic window when worked muscles are eager to sop up nutrients to kick off the repair and rebuilding process. At any rate, this study implies that higher amounts in two meals is more anabolic than evenly dividing a protein quota evenly between three meals.
This study considered both muscle protein synthesis and whole body protein breakdown, and showed that whereas muscle protein synthesis tops out at about the 1.2 g/kg/day, the breakdown of protein throughout the body continues to decline favorably in a linear manner. A large part of this is involved in the replacement and repair of gut-lining cells, vast numbers of which are shed on a daily basis. On this basis, protein requirements show a linear increase for optimal health/fitness with aging, by progressively improving a wide range of repair and maintenance functions, from bones to brains, gut health structures, immune function, enzyme production and most of what keeps us living and functional.
“Importantly, the linear relationship between the amount of protein intake and anabolic response has been recognized for more than half a century, as determined by a nitrogen balance technique, although the anabolic response beyond RDA for protein (i.e., 0.8 g protein/kg/day) has been ignored . Therefore, data indicate that there is no practical limit to the anabolic response in increasing amount of dietary protein intake.” (Accent mine)
Another point of interest in the study regarding anabolic threshold and age is this: “The optimum amount for elderly adults (0.24 g/kg/meal) is approximately 70% greater than that for young adults (0.8 g/kg/day) , indicating an age-associated anabolic resistance to dietary protein. It is likely that elderly individuals need more protein intake to achieve a maximal anabolic response per meal considering the varying degrees of quality of protein eaten in the real world.” The statement proposes 70% more protein intake for the aged, but the numbers in brackets don’t make sense to me for 3 meals/day. But using 1.2g/kg/day as the anabolic threshold for the young, and 70% increase for the aged, you get 2.04g/kg/day. Pack that into 2 meals and we arrive at about 0.4 g/lb/meal for us old folks. For me, at 160 lb, that would be about 64 grams with a meal. Why two meals? Because if you are doing intermittent fasting by delaying or skipping breakfast or making one meal strictly fibrous vegetables in a salad, that leaves two.
Meats and fish of all kinds are about 7 grams per oz. So a 9 oz steak or a couple of chicken breasts get us there. Personally I have trouble eating one chicken breast because it has hardly any fat and just sticks in my throat; I much prefer dark meat from fowl. On the other hand, I can down a grilled 10 oz ribeye no problem. Mornings are a little harder to get a serious load of protein, but I do my best with 4 oz of pork sausage, three eggs, a variety of diced veggies and a couple oz of different shredded cheeses scrambled in a mix of olive and coconut oils. If that seems like a lot of food, remember that the aging body needs higher input of protein to hang onto or build muscle, and simply eating more protein can keep you strong and independent much longer, according to recent science.
Here are the study conclusions:
“Elderly adults are less responsive to the anabolic stimulus of low doses of amino acid intake compared to younger adults . However, this lack of responsiveness in elderly adults can be overcome with higher levels of protein consumption . This is also reflected in studies comparing varying levels of protein intake . This suggests that the lack of muscle responsiveness to lower doses of protein in older adults can be overcome with a higher level of protein intake. The requirement for a larger dose of protein to generate responses in elderly adults similar to the responses in younger adults provides the support for a beneficial effect of increased protein in elderly populations . The consumption of dietary protein consistent with the upper end of the AMDRs (as much as 30%–35% of total caloric intake) may prove to be beneficial, although practical limitations may make this level of dietary protein intake difficult. The consumption of high-quality proteins that are easily digestible and contain a high proportion of EAAs [essential amino acids] lessens the urgency of consuming diets with an extremely high protein content.” See the study here to follow the references shown”.
Intermittent Fasting and Protein intake
Much of today’s longevity science leads to the understanding that optimal aging can be achieved by alternating between periods of FEASTING of foods that promote repair and building the body (anabolic state) versus periods of FASTING to put the body in a state of autophagy (catabolic state). Autophagy is a process of ‘self eating’ wherein cells break down and recycle materials, including metabolic ‘junk’ and damaged elements, making these materials available for other metabolic purposes. This state also turns on a basket of survival and longevity genes and processes that lead to longer life. The general idea of intermittent fasting is that most of the benefits of severe caloric restriction upon longevity and health can be achieved by cycling between anabolic and catabolic states for mere days or even hours at a time.
The switch to autophagy can be triggered either by reducing protein intake OR carbohydrate intake, independent of fat intake! This makes switching between fasted/catabolic/autophagy and anabolic/muscle-building fairly painless. I’m already urging my readers to be on a Paleo, low carb lifestyle (carbs from seasonal vegetable and fruit sources only). So all we have to do is alternate between low protein meals and high protein meals on a time scale that allows sufficient time in both states. I’m now weight training two days/week, usually Tuesday and Saturday. That lets me cycle protein intake on a two-low, one-high in the first three days and two-low, two-high for the last four days. So far this is allowing me to stay lean and hang onto muscle easily. I’m not rigorous about it, but I generally get close to this ratio.
- Cycle protein intake to initiate intermittent fasting on low protein days; increase fat intake to produce ketones (about 70% of calories)
- In terms of body weight, on high protein days get about 0.4-0.5 grams per pound of body weight for two meals; on low protein days eat a quarter of that or less
- Use Digestive Enzymes and Betaine HCl to insure breakdown of your protein intake into amino acids for best absorption and uptake; you make less of enzymes and stomach acid with aging
To your greater health and fitness!
Your Senior Fitness Coach,