Note to readers: the author of this article is a nutrition expert whose opinion we respect, otherwise we would not publish her work on our blog. However, we rate this post with a science score of 2 as we believe the opinions expressed here run contrary to the best science at present, specifically research by longevity expert Dr. Valter Longo, who advocates for fish and small amounts of animal protein for older adults so as not to become malnourished. Please consider this post as the “Vegan perspective” on how seniors may want to get their protein for optimal health.
For many years, it was generally accepted that the standard recommendation for protein intake was a one-size-fits-all sort of deal for healthy adults who aren’t pregnant or nursing an infant. Eat whatever you need to get your 0.8 g of protein per kilogram of healthy body weight and you’re set, right? Well, not quite.
More recently, a handful of researchers have begun to point out that there’s a stark difference between ‘adequate’ and ‘optimal’ when it comes to protein, especially for older adults. What’s more, it seems that the type of protein you eat (animal or plant) is also key to healthy ageing.
A low-protein diet for longevity… until you’re 65
In a much-discussed study published in 2014, researchers looking at data from over 6,000 adults in the U.S. revealed that people under 65 who ate a lot of protein had a 73-fold increased risk of dying from diabetes (R). Even those eating a ‘moderate’ amount of protein had a 23-fold increase in the risk of diabetes-related death compared to the so-called low protein group.
Demonstrating that many of us eat far more protein than we need to, this study classified people as eating a ‘low’ protein diet if they consumed around 50 g of protein a day, providing less than 10% of daily calorie intake. This is, in fact, fairly close to the recommended daily intake of protein for most adults. Those in the high protein group got 20% or more of their calories from protein, and the moderate protein group got 10-19% of their calories from protein.
The benefits associated in this study with the low protein intake decreased over time. In people aged 50-65, a high protein intake was associated with around a 1.74-fold increased risk of all-cause and cancer mortality. This group was also four times more likely to die of cancer compared to the low protein group. Not quite the 73-fold risk, but still a concern.
Seniors need more protein
But what about adults over 65? Well, the same researchers noted that the effect of a ‘low’ protein diet flipped after this age. Instead of being protected by a low protein intake, older adults were more likely to live longer if they had a moderate to high protein intake at this point in their lifespan.
So, your 65th birthday party should feature a cake made of steak, yes? Not quite.
That’s because something else was revealed in this study. Something that many people seem to have ignored. When the researchers controlled for calories from animal protein, the association between total protein and all-cause and cancer mortality disappeared or was at least significantly reduced. Basically, this strongly suggests that it is animal protein, not simply protein itself, that is to blame for a good chunk of that increased risk of death seen in the earlier calculations.
Why would this be the case? Well, for a start, the modern Western diet based on animal products tends to be higher in saturated fat, cholesterol, and pro-inflammatory substances, and low in fiber, healthy fats, and important vitamins, minerals, and polyphenols. What’s more, a diet that includes a lot of animal products increases acidity in the body, which isn’t good for health.
Animal protein and metabolic acidosis
Animal proteins contain higher levels of acidifying sulfur amino acids, so if you eat a lot of animal protein and skimp on the fruit and vegetables you could be living for years, if not decades, in an increasing state of metabolic acidosis. You may have already experienced some of the symptoms of metabolic acidosis if you’ve tried to stick to a ketogenic diet as this is almost guaranteed to raise your blood acidity in an unhealthy way. Such symptoms include fatigue, confusion, lack of appetite, bad breath, headache, sleepiness, and rapid shallow breathing.
Your body functions optimally when blood is stable within a very tight pH band. Ideally, blood pH should be 7.4, with acidosis characterized by a pH of 7.35 or lower and alkalosis characterized by a pH level of 7.45 or higher. If your blood becomes too acidic (or alkali), your body works very hard to restore optimal pH. This hard work falls, in large part, to the kidneys, which try to restore acid-base (alkaline) balance in a variety of ways.
Over time, this pressure on the kidneys can increase the risk of multiple diseases and health issues, including kidney stones and chronic kidney failure. What’s more, metabolic acidosis increases insulin resistance and the risk of diabetes and can lead to muscle wasting. In contrast, a diet rich in vegetables and fruits helps support acid-base balance, thereby supporting normal physiological processes (R). So, even if you’re just reading this because you want to preserve muscle mass as you age, you need to know about metabolic acidosis.
Older adults and muscle mass
Concern over optimal protein intake is especially important when talking about protein requirements for older adults (i.e. those over the age of 65). This is because older adults tend to eat less (meaning lower overall protein intake) and process protein less efficiently (R).
What happens if older adults don’t get enough protein? For one thing, they lose muscle mass and strength. This is known as sarcopenia and it can happen very quickly.
Most of us achieve peak muscle mass in our late 30s to early 40s. It’s pretty much downhill after that, with a gradual loss of muscle mass as we age. Sedentary people over 65 lose about 1.2% of muscle mass every year. Younger people who are sedentary also lose muscle mass, but at a much lower rate than older adults. In fact, older adults may lose muscle mass six times faster than young people, at a rate of -95 g/day vs -14 g/day when on bed rest for even a short period of time (R).
How quickly you lose muscle mass with age can influence the years in your life and the life in your years. Reduced skeletal muscle mass and strength increases your risk of osteoporosis, falls, injuries, and fractures. It also increases your risk of becoming sedentary and of developing diabetes, cardiovascular disease, and other health issues. As well as helping to build and maintain lean muscle mass, protein is also important for maintaining bone health, immune function, digestion, healing, and mood.
On a biochemical level, the result of too little protein is… metabolic acidosis. Yes, just as an excess of animal protein can cause metabolic acidosis, so can too little protein overall. Confused? That’s understandable, so let’s break it down.
Basically (!), if your body is more acidic than it should be, one of the steps it takes to redress the balance is to break down (catabolize) muscle tissue. This releases individual amino acids, which your liver uses to produce glutamine. Your kidneys then use this glutamine to neutralize and remove the acid from your body. The result? Nicely buffered blood, but a serious loss of muscle.
Thankfully, a diet higher in protein, combined with resistance exercise and a reduction in sedentary activity (sitting) has been shown in several studies to help slow age-related loss of muscle mass.
Where do you get your protein?
One recent analysis found that an intake of 1.0-1.3 g/kg/day of dietary protein combined with twice-weekly progressive resistance exercise was effective for reducing age-related muscle mass loss (R). Other analyses suggest that a dietary intake of 1.0-1.2 g/kg/day of dietary protein may be beneficial for older adults (R). This level of intake could help overcome age-related concerns such as reduced digestive function and absorption of amino acids, as well as reduced kidney function that hampers the body’s ability to correct acidosis.
So, to make sure you get enough protein and stave off age-related muscle loss, it makes sense to tuck into a steak or have a whey protein shake every day, yes? Well, no. If anything, it seems that increasing your intake of animal protein (from a diet high in fish, pork, poultry, cheese, beef, and eggs) could worsen metabolic acidosis and increase muscle loss further, in addition to potentially causing kidney damage.
And herein lies the problem. We appear to need more protein in older age, but we should seemingly avoid getting that protein from the very food most people think is synonymous with protein: meat.
What’s a senior to do when even the dairy and eggs lobbyists can’t spin the science to make their products look good in older age? Seriously, studies financially supported by these major industries were forced to conclude that increasing the intake of egg and dairy protein did not enhance muscle strength and size in older people in response to resistance training if protein intake was already adequate (R, R). What has been shown to help preserve muscle mass, though, is… vegetables.
Seriously. Consuming recommended levels of vegetables was associated with greater protection against age-related loss of muscle mass than aerobic exercise (48% vs. 38%) in women in one study (R). This is probably because vegetables not only help to neutralize the mild metabolic acidosis that occurs with age, they also contain protein. In fact, the only major sources of dietary protein that are alkaline- rather than acid-forming are beans and other legumes.
The pee test for protein
Scientists use something called the potential renal acid load (PRAL) list of foods to estimate the likely acid load of any given diet. There is now also an extended list of foods. Researchers conducting acid-base testing of 60 adults aged 18-30, half of whom were omnivores and half vegetarian, found that the PRAL value (using the standard list) was alkaline for vegetarians (-5.4 +/- 14.4 mEq/d) compared to an acid load of 10.3 +/- 14.4 mEq/d in the nonvegetarians. Using the extended list, the vegetarians had mean PRAL values of -10.9 +/-19.7 mEq/d compared to an acid load of 13.8 +/- 17.1 mEq/d for the non-vegetarians (R).
Another study compared the urinary acidity and net acid excretion (NAE) of vegans, lacto-ovo vegetarians, and omnivores (all women) living in Boston (R). Neutral pH is 7, with lower numbers indicating acidity. The more acid your body excretes in your urine, the lower the number. In general, a urine pH of 6.5-7.5 is considered ideal. NAE is the net amount of acid excreted in a given amount of urine and is a good indication of a person’s acid-base status.
Unsurprisingly, the mean urine pH for vegans (6.15) was approaching neutral, was lower (at 5.90) for lacto-ovo vegetarians, and was even more acidic (at 5.74) for omnivores. While these numbers aren’t too different, NAE results did show some significant differences: 17.3 mEq/day for vegans, 31.3 mEq/day for lacto-ovo vegetarians, and 42.6 mEq/day for omnivores. It’s important to note that some meat analogs (i.e. fake steaks and such) are acid-forming, but even these are not as bad as animal products generally and are typically eaten as part of a plant-rich diet.
Plant proteins preserve muscle mass
Older adults who eat a plant-based diet with plenty of variety, including fruits, vegetables, whole grains, nuts, seeds, legumes and beans will have a higher intake of non-acid-forming protein as well as potassium. This helps to relieve mild acidosis, which means the body doesn’t need to cannibalize its own muscles to buffer pH. And, such a diet also provides plenty of protein to help preserve and even build muscles and strength.
In one 2013 study, a largely plant-based diet was positively associated with muscle mass and grip strength in women aged 18-79 years (R). A handful of other studies, however, suggest that animal protein has some benefits for building muscle quickly. This may be, at least in part, because of one particular amino acid, leucine, that is often low in plant foods, but which is found in abundance in our muscle tissue. Leucine seems to increase muscle growth and is present in high amounts in meat, which isn’t surprising given that non-human animals’ muscles and flesh are fairly similar to our own.
So, is animal protein better for older adults? Is veganism dangerous after 65? In short, no. While legitimate concerns have been raised over plant-based diets for seniors, these are fairly easily addressed and are definitely not deal-breakers.
For instance, folks might well worry that older adults, who tend to eat less, might not get enough calories and nutrients on a diet that has its own built-in methods for making you feel full and limiting food intake (i.e. fiber). There are, however, plenty of nutrient- and calorie-dense plant-based foods, including nuts, seeds, and a variety of fruits, legumes, grains, and vegetables. And, the reality is that many older adults are already carrying excess body weight that puts them at greater risk of diabetes, cardiovascular disease, and a range of other illnesses.
And, as we have already learned, one of the key advantages to a plant-based diet is its potential for preserving muscle mass. In many ways, it’s preferable to try to hold onto muscle mass for longer rather than try to claw back lost muscle later in life.
What’s more, after many years of physicians worrying that a plant-based diet was dangerous for people with chronic kidney disease (because of worries over too little protein and too high a phosphorus intake), research now suggests that plant-protein could help lower the risk of death in people with this condition. In one study, for every 33% increase in the ratio of plant protein to total dietary protein, the risk of death was reduced by 23% in people with chronic kidney disease (R). And, in an analysis of current research, the authors noted several studies that found either no evidence of dangers associated with plant proteins and, in many cases, some clear advantages for people with chronic kidney disease (as well as people with diabetes) (R).
In conclusion, then, if you want to exercise caution and follow the science by increasing your protein intake after the age of 65, consider doing that with more plant protein. Indeed, whatever your age, a diet rich in fruits, vegetables, and good sources of plant protein appears to have some serious advantages for health and longevity.