# Confused about protein
**URL:** https://boards.straightdope.com/t/confused-about-protein/1022151
**Category:** In My Humble Opinion
**Created:** [August 17, 2025, 1:23am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151 "2025-08-17T01:23:51Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@DSeid](https://boards.straightdope.com/u/DSeid)
#### Post date: [August 17, 2025, 1:23am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/1 "2025-08-17T01:23:51Z")
Just sharing here but given that high protein intake is all the rage I’ve been digging and I am getting more and more confused.
From a practical POV I’m fine - my sense is that most of us would do better working on increasing our vegetable and fruit intake than worrying about our protein, but the more I read the more I wonder if some of the protein hype is causing harms greater than goods?
A review. Five years old but pretty good.
> **[The impact of dietary protein intake on longevity and metabolic health](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/)**
>
> Lifespan and metabolic health are influenced by dietary nutrients. Recent studies show that a reduced protein intake or low-protein/high-carbohydrate diet plays a critical role in longevity/metabolic health. Additionally, specific amino acids (AAs),...
I’m skipping to the human studies bits -
> Levine et al. investigated the relationship between the level of protein intake and all-cause, cancer- and diabetes-related mortality in a major nationally representative study of nutrition involving a United States population (6381 individuals aged 50 years and over) [[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#bb0030)]. The results were analysed using Cox proportional hazard models and revealed that both the moderate protein (MP;10–19% of calories from protein) and high protein (HP; ≥20% of calories from protein) intake groups had higher risks of diabetes-related mortality than the participants in the low protein(LP; \<10% of calories from protein) group ([Table 1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#t0005)). Among those aged 50–65 years, higher protein levels were linked to significantly increased risks of all-cause and cancer-related mortality ([Table 1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#t0005)). In this age range, the HP intake group exhibited a 74% increase in their relative risk of all-cause mortality and were \>4-fold likely to die of cancer than those in the LP group. Additionally, the higher risks of all-cause and cancer-related mortality in the HP intake group compared to those in the LP intake group were further increased among those who also had high levels of IGF-1 [[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#bb0030)] ([Table 1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#t0005)). However, among those aged 66 years and older, the HP diet was associated with the opposite effect on all-cause and cancer-related mortality ([Table 1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#t0005)). Compared to those in the LP group, the participants in the HP and MP groups exhibited a 28% and 21% reduction in all-cause mortality, respectively. Additionally, compared to those in the LP group, HP consumption resulted in a 60% reduction in cancer mortality. Thus, LP intake during middle age may be beneficial for the prevention of cancer and improvement of overall mortality. However, among elderly people, avoiding LP intake or consuming adequate dietary protein may be important to prevent sarcopenia and frailty, thus potentially preventing an increase in all-cause mortality. … after controlling for the percent of calories from animal protein, the association between the level of protein intake and all-cause and cancer-related mortality was eliminated or significantly reduced, suggesting that animal protein mediates a significant portion of those relationships. In contrast, after controlling for the effect of plant protein, there was no change in the association between protein intake and mortality, indicating not only that high levels of animal proteins promote mortality but also that plant proteins have a protective effect …
Methionine (high in animal protein) is suggested as the culprit and relative methionine restriction (MetR), by way of limited but nonzero animal protein, possibly the key.
> Met is directly involved in promoting the ageing process through multiple mechanisms. Metabolically, MetR also decreases adiposity … Among dietary interventions, MetR may be a candidate intervention for longevity and metabolic health ([Fig. 4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#f0020)). Food sources of animal protein, such as beef, lamb, fish, pork and eggs, contain higher levels of methionine than plant food sources, including nuts, seeds, legumes, cereals, vegetables and fruits [[96](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#bb0480)]. Therefore, an individual may need to eat less animal-based food to achieve MetR. For example, the Mediterranean diet [[97](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#bb0485)] or the Dietary Approaches to Stop Hypertension (DASH) diet [[98](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#bb0490)] may be useful for decreasing the consumption of animal protein, particularly red meat ([Fig. 4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6562018/#f0020)).
Again I have no clarity here, which is why I am throwing it out as an IMHO thread, but it seems to me that the messaging that we old farts “need protein” is often heard as a call to eat more meat as the easiest way to get to “high protein” levels, but that such may end up resulting in more harms than benefits?
ETA this interesting recent study. Mouse study but interesting
[https://www.science.org/doi/10.1126/sciadv.ads1532](https://www.science.org/doi/10.1126/sciadv.ads1532)
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### Author:  [@Velocity](https://boards.straightdope.com/u/Velocity)
#### Post date: [August 17, 2025, 1:32am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/2 "2025-08-17T01:32:16Z")
Unless you are doing intensive exercise, there is no need to consume more than just a little bit over the recommended daily intake for protein. Excessive protein does no good and will just harm the kidneys and maybe raise your body inflammation.
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### Author:  [@Llama\_Llogophile](https://boards.straightdope.com/u/Llama_Llogophile)
#### Post date: [August 17, 2025, 1:34am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/3 "2025-08-17T01:34:00Z")
It’s been a couple of decades since I was in grad school, but when I studied physiology we were told a typical person needs about a half can’s worth of tuna per day for protein. If you’re a bodybuilder, maybe a full can. Beyond that, it’s excreted out. The body can’t store protein the way it stores carbohydrates.
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### Author:  [@DSeid](https://boards.straightdope.com/u/DSeid)
#### Post date: [August 17, 2025, 2:06am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/4 "2025-08-17T02:06:18Z")
Another study to throw in there for those of us who like being in the weeds.
> **[Association between plant and animal protein and biological aging: findings...](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/)**
>
> This study aimed to evaluate the relationship between plant protein, animal protein and biological aging through different dimensions of biological aging indices. Then explore the effects of substitution of plant protein, animal protein, and their...
Specifically replacing some meat intake with whole grains and nuts as the protein source was of significant impact on markers of biological aging. Yogurt though was cool. “Negative” effect on aging markers is desirable:
> Whole grains and nuts rich in plant protein had a stronger inverse association with biological aging, while legumes had inconsistent relationships with the four indices. Previous studies have suggested that higher whole grains and nuts intake can increase life expectancy [[52](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/#CR52)], reduce the risk of frailty, and improve metabolic health by regulating blood glucose and lipids [[53](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/#CR53)]. … The intake of cheese and yogurt was also negatively associated with biological aging, and the association between yogurt and biological aging was stronger. Increasing dairy intake can improve cognitive function in older adults [[59](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/#CR59)]. Yogurt contains bacterial cultures with proteolytic activity, making it a great source of high-biological-value essential amino acids [[60](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/#CR60)], which has been shown to have a positive effect on improving both bone health in aging and immune aging [[61](https://pmc.ncbi.nlm.nih.gov/articles/PMC11519226/#CR61)]. This strong healthy effect partly explains our findings that replacing yogurt with plant-based protein sources may not have negative relationships with biological aging.
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### Author:  [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)
#### Post date: [August 17, 2025, 2:23am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/5 "2025-08-17T02:23:41Z")
Thin Type 1 diabetic here.
My doc and nutritionists tell me to stay within guidelines for the percentage I need. Nutritionists suggests lots of legumes.
Protein digests slower. That’s a plus. If you have kidney disease you have to be more careful. You don’t want those struggling.
Unless you’re body building or in training the recommendations you see or your nutritionists gives you will work, IMO.
No giant increase needed.
Beans: a diabetic girls best friend.
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### Author:  [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)
#### Post date: [August 17, 2025, 2:45am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/6 "2025-08-17T02:45:18Z")
There are a lot of conflicting studies, and people really get into the weeds discussing the benefits of amino acids like cysteine, the mixed messages of methionine, the good-for-muscle-building-bad-for-longevity branched chain amino acids (BCAA) and so forth.
The first study showing 74% mortality differences does not pass the sniff test. I think the benefits of being really picky about amino acids are very modest and our current knowledge does not justify such micromanagement. For most people the kidneys can handle protein but if you have certain chronic diseases you should get advice from a medical professional aware of your numbers.
Best advice is to get adequate fiber and eat five servings of whole fruit and vegetables every day. After that, eat enough protein to meet your needs and increase amounts if trying to gain muscle or if losing muscle. Eat healthier fats most of the time and when cooking at home. Enjoy a few whole nuts every day and eat more beans. Choose healthier carbs over sugar much of the time, but if you eat well for 90% of meals that is good enough. The best time to enjoy some sugar is before strength training when you can put it to good use - 30-60 grams of sugar may help you gain muscle and this can be tailored to your desire for leanness and current physique.
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### Author:  [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)
#### Post date: [August 17, 2025, 3:05am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/7 "2025-08-17T03:05:54Z")
There are several blood and urine tests to check your protein levels, your doctor can run.
Then you can tailor your menu to fit your exact needs.
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [August 17, 2025, 3:32am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/8 "2025-08-17T03:32:26Z")
ISTM one of the confounders is we have to eat something. If every constituent of every food is defined as either protein, carbohydrate, or fat, then low(er) protein implies high(er) fat and/or high(er) carbohydrate.
Carbs can be usefully categorized into simple or complex, while fats can be usefully categorized as mono-unsaturated, poly-unsaturated, trans-, and saturated. I’m not aware of any useful categorization of proteins.
But just sticking to the Big 3, if one is to reduce protein from the standard American, arguably excessive, level then what ought you eat instead? Raising carbs is tough for diabetics and is generally viewed as obesogenic. Raising fats is generally atherosclerosis-genic. Neither are great news for health on an individual or population basis.
I suppose a diet of limited protein, nil simple carbs, lots of complex carbs, lots of unsaturated fats, especially mono-unsaturated, and nil saturated fat might be pretty nice. Speaking from some experience it is hard to eat that way long term though.
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### Author:  [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)
#### Post date: [August 17, 2025, 5:14am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/9 "2025-08-17T05:14:22Z")
The thing is you can’t really eat your way to health. You have to achieve a balance. Exercise is important.
Balance is my daily routine.
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### Author:  [@DSeid](https://boards.straightdope.com/u/DSeid)
#### Post date: [August 17, 2025, 5:15am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/10 "2025-08-17T05:15:49Z")
> [@Dr\_Paprika](#):
>
> There are a lot of conflicting studies
Definitely true. Which is where meta analysis is of some use. Some.
> **[bmj.m2412.full.pdf](https://www.bmj.com/content/bmj/370/bmj.m2412.full.pdf)**
>
> 251.71 KB
- “High intake of total protein is associated with a lower risk of mortality from all causes
- Intake of plant protein is associated with a lower risk of mortality from all causes and from cardiovascular diseases, and an additional 3% of energy from plant proteins a day is associated with a 5% lower risk of death from all causes
- These findings support current dietary recommendations to increase consumption of plant proteins in the general population”
(Not showing up as quote box but is)
@LSLGuy proteins crudely can be plant or animal or by amino acid patterns. But of course we actually eat foods which contain more than the macronutrients, but have other stuff and how it is packaged with it. Is it the increased plant protein in that meta analysis or the stuff that both does and does not travel with it as it increases and something else decreases, as you point out?
I _suspect_ that the increase in plant protein impact listed above is impactful more from the fiber, the phytochemicals, the healthy fats, and the matrix of the real foods, than the protein itself. And that the association also travels with more intake of vegetables and fruits in general.
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### Author:  [@Alessan](https://boards.straightdope.com/u/Alessan)
#### Post date: [August 17, 2025, 8:20am UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/11 "2025-08-17T08:20:23Z")
> [@Velocity](#):
>
> Excessive protein does no good and will just harm the kidneys and maybe raise your body inflammation.
Won’t your body just break excess protein down for calories?
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [August 17, 2025, 2:12pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/12 "2025-08-17T14:12:55Z")
> [@Beckdawrek](#):
>
> The thing is you can’t really eat your way to health. You have to achieve a balance. Exercise is important.
>
> Balance is my daily routine.
Agree. But …
My late wife had a part time gig as a personal trainer. One of her mottos was “You can’t out-train a bad diet”.
The two-fold point being that exercise is probably the largest positive influencer you have conscious control over. And diet is probably the largest negative influencer you have conscious control over.
Bad diet (quality, quantity, or both) can actively make you unhealthy. Good diet doesn’t so much make you healthy, as it does avoid making you unhealthy. Exercise, at least at levels below serious athletes risking injury, is kinda the opposite. Doing none is actively unhealthy. Doing some is actively healthy. Doing more is actively healthier.
For most of us paying any attention to health at all, there is more room to improve our exercise vs our diet. There are exceptions of course, but for sure that’s true of me.
The synergistic effects of good diet _and_ good exercise on good health is definitely a matter of the sum exceeding the parts.
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### Author:  [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)
#### Post date: [August 17, 2025, 2:28pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/13 "2025-08-17T14:28:32Z")
> [@Alessan](#):
>
> Won’t your body just break excess protein down for calories?
Too much of _anything_ will stress the body, including the disposal mechanisms specialized to deal with that specfic issue.
I recall reading an interview with a dietician once where they mentioned that was a major problem with fad diets; they tend to encourage people to eat lots of _one_ thing (protein, fruit, whatever), and that actually puts more stress on the body than just overeating in general since it concentrates the overload on a smaller subsystem of the body. Overloading everything by 10% is better than overloading one thing by 200%, essentially.
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### Author:  [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)
#### Post date: [August 17, 2025, 2:32pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/14 "2025-08-17T14:32:31Z")
> [@Beckdawrek](#):
>
> The thing is you can’t really eat your way to health. You have to achieve a balance. Exercise is important.
>
> Balance is my daily routine.
I believe, however, that the older you get, the more protein you need, and it has to do with muscle mass. Studies show that maintaining muscle mass leads to longer longevity. Eating enough protein and exercising regularly helps maintain your muscle mass. Exactly how much protein and exercise you need depends on your body mass and musculature.
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### Author:  [@Moriarty](https://boards.straightdope.com/u/Moriarty)
#### Post date: [August 17, 2025, 3:28pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/15 "2025-08-17T15:28:28Z")
> [@DSeid](#):
>
> Methionine (high in animal protein) is suggested as the culprit and relative methionine restriction (MetR), by way of limited but nonzero animal protein, possibly the key.
Methionine is an essential amino acid which our body needs to survive. You can obtain it from animal sources, but if you are vegan you can get it from many nuts and seeds, grains, and legumes.
You are correct that an excessive amount of Methionine is apparently harmful, and that not having any methionine is also harmful.
> [@](#):
>
> **Methionine is an essential sulfur-containing amino acid and plays a vital role in the production of important molecules such as antioxidants (e.g., glutathione, cystathionine), other non-essential amino acids (e.g., carnitine, cysteine, taurine, and creatine), methyl donors (e.g., S-adenosyl methionine), phospholipids (e.g., phosphatidylcholine) and vasodialatory intermediate (e.g., hydrogen sulfide) (Sbodio et al., 2019)**. Major dietary sources of methionine are eggs, sesame seeds, brazilian nuts, fish, meat, and cereal grains. Normal plasma concentration of methionine ranges from 13 to 45 µM and its average daily requirement is 10.4 mg/kg body weight/day (Ables and Johnson, 2017, Nimni et al., 2007, WHO/FAO/UNU, 2007). Methionine is converted to S-adenosyl methionine (SAM), a universal methyl donor required for methylation via methionine adenosyltransferase 2A. Similarly, other micronutrients such as folate, choline, betaine, vitamin B12, and other B vitamins also act as methyl donors. Altered DNA methylation status may lead to metabolic diseases, cancer, and aging (Navik et al., 2019, Salameh et al., 2020). Therefore, **the availability of dietary precursors such as methionine is critical for maintaining methylation status. This suggests that dietary methionine level plays a crucial role in maintaining homeostasis, and either supplementation or restriction of methionine can significantly affect health** (Guedes et al., 2011, Navik et al., 2019, Salameh et al., 2020).
> **[Methionine as a double-edged sword in health and disease: Current perspective...](https://www.sciencedirect.com/science/article/abs/pii/S1568163721002476#)**
>
> Methionine is one of the essential amino acids and plays a vital role in various cellular processes. Reports advocate that methionine restriction and …
(My emphasis)
I’m sure there’s some lesson there about moderation, or something.
What I find intriguing is that the same things which your body uses to build the body can also become a source of destruction. To my untrained mind, there seems to be a pretty fine line between the mechanisms your body uses to grow muscle and grow tumors. It can easily get out of control.
My speculative theory is that this is one of the reasons that weight lifting is so vital for longevity. By forcing the body through the cycle of physical stress followed by regular repair, you keep the body’s repair system functioning properly. Otherwise, the regular repair that your body already does becomes less effective over time, leading to more errors, which manifest as cancers and diseases.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 17, 2025, 3:51pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/16 "2025-08-17T15:51:58Z")
Pretty much anyone in the developed world already eats more protein than it’s been possible for us to eat for most of the span of our evolution. Whether it’s harmful is maybe debatable, but more protein certainly isn’t necessary.
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### Author:  [@DSeid](https://boards.straightdope.com/u/DSeid)
#### Post date: [August 17, 2025, 4:04pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/17 "2025-08-17T16:04:44Z")
> [@dolphinboy](#):
>
> I believe, however, that the older you get, the more protein you need
That is part of what I was digging in on. The study reviewed in a cite in the OP specifically claims that over 65 “high protein”, defined as 20% of daily calories or more, and “moderate protein” ,10 to 20%, lowered all cause mortality compared to under 10%, but the 65 and under group had much worse outcomes in high protein compared to low protein conditions.
So those over 65 staying at least over 10% of calories as protein has a strong basis. 65 and under maybe not?
And there was further evidence that it was getting protein from plant sources in particular that mattered most.
> [@Der\_Trihs](#):
>
> a major problem with fad diets; they tend to encourage people to eat lots of _one_ thing (protein, fruit, whatever)
Another part of what motivated this dig: the protein craze. People who exercise moderately who are hearing that they should be eating a gram of protein per pound of body weight and feel the need to prioritize protein foods, often meats because plant protein sources are not as protein dense or they worry about them being incomplete, and supplement with powders to get there. Especially common among those who are trying to build muscle mass and definitely up to 0.7 g per pound helps build mass a bit better than significantly less.
Yes again from the practical perspective I remain convinced that the overall food pattern matters. Plant forward with a variety of vegetables, fruits, legumes, nuts, seeds, whole grains … fine on things like yogurt and kefir … some fatty fish … and some meat is okay but not required and not so much, especially processed meats. Avoid the highly processed stuff and added sweeteners in general. Of course exceptions can be had. Call that Mediterranean, Nordic, whatever. Exercise. Cardio. Moderate strength training. Balance work.
Boring.
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### Author:  [@Broomstick](https://boards.straightdope.com/u/Broomstick)
#### Post date: [August 17, 2025, 4:33pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/18 "2025-08-17T16:33:32Z")
> [@LSLGuy](#):
>
> But just sticking to the Big 3, if one is to reduce protein from the standard American, arguably excessive, level then what ought you eat instead?
Arguably, quite a few American should just _eat less_. In which case a mild reduction in all three categories might be beneficial.
> [@Alessan](#):
>
> Won’t your body just break excess protein down for calories?
Yes, but that produces nitrogen-containing waste products that your kidneys must then dispose of. Not usually a problem if you’re healthy but you can, if you try hard enough, overload your kidney capacity even when young and fit. For those with kidney disease getting into trouble with this is more likely. Basically, too much of anything is not a good thing
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### Author:  [@DSeid](https://boards.straightdope.com/u/DSeid)
#### Post date: [August 17, 2025, 4:33pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/19 "2025-08-17T16:33:33Z")
> [@Moriarty](#):
>
> By forcing the body through the cycle of physical stress followed by regular repair, you keep the body’s repair system functioning properly
I am very sure you are correct and not just for strength training but for a variety of stresses. (Which we have discussed elsewhere.) Stress - recovery.
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### Author:  [@Spice\_Weasel](https://boards.straightdope.com/u/Spice_Weasel)
#### Post date: [August 18, 2025, 9:15pm UTC](https://boards.straightdope.com/t/confused-about-protein/1022151/20 "2025-08-18T21:15:56Z")
My big question here is whether people who consume a high amount of animal protein are also consuming high amounts of, say, saturated fat or refined sugar.
I’ve always been interested in nutrition science, but it can be so hard to pin down.
On a personal level my diet is usually quite poor, alternating with periods of effort to make it better. Supposedly going into menopause I’m supposed to eat more protein, but I’ve also been trying to shift more plant-based, so my conundrum has been how to get adequate protein from plants when it would require consuming more calories than I burn. Also I just feel terrible when I don’t eat meat.
Reading through this, the obvious answer comes to me: eat some animal protein, but only what is needed to supplement plant protein. It seems plants have a protective factor against the harms associated with animal protein.
What’s the over/under on cheese?
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