Upper limit on protein intake for health - Does it exist?

ForecasterJason

At the moment, there's an ongoing thread in the nutrition section ( http://community.myfitnesspal.com/en/discussion/10336658/too-much-protein-dangerous/p1) regarding an excessively high protein intake (2.5g per lb of bodyweight). I decided to create this thread where we can concentrate on debating extremely high protein intakes without derailing an important thread posted by a member.

My question is, do you believe there is a protein intake at which it becomes dangerous/detrimental to health (assuming fat and carb intakes are not inadequate)?
Based on some of the responses in the other thread, I'm going to guess there are mixed views on this. If 2.5g/lb is not too much, then what would be? Or is the sky truly the limit here? Take for example a professional football player who is 300 lbs and consuming 7000 calories a day. For those that would say 2.5g/lb is not harmful, do you think up to 750g of protein a day is still not dangerous in that case?

Personally, I tend to think that such intakes could very well be harmful, particularly if done on a regular/long term basis. There may not be any studies that indicate it, but most studies on protein intakes aren't using intakes that high (or for very long). In the thread I linked to, there has been one anecdotal account given (page 3) of an excessively high protein intake blamed for causing health issues.

californiagirl2012

Why would one even worry, too much food or any macro is detrimental. Eat the right amount of food for your size to not gain weight, balanced. Why make it so complicated?

auntiebabs

My understanding is that too much protein is hard on the kidney. But I have no recollection of where I heard that or how much is too much. .... okay editing... I found this from harvard http://news.harvard.edu/gazette/2003/03.13/09-kidney.html ... A study done on the effect of high loads of protein on people with already impaired renal function.. Also found this NYTimes article say if you have healthy kidneys, it's unlikely to be a problem ... http://www.nytimes.com/2011/05/31/health/31really.html?_r=0

zcb94

As @auntiebabs mentioned, too much protein is hard on the kidneys, but experts tell me that threshold is almost impossible to cross without going WAAAY over your calorie intake needs.

EvgeniZyntx

and in - for a person restricting calories and meeting fat needs, there is no upper limit to protein intake.

stevencloser

What's safe isn't necessarily linear.

yarwell

You might have to start looking at individual amino acids rather than just "protein".

The references in http://www.ncbi.nlm.nih.gov/pubmed/21535903 "A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats" might have some useful leads in humans but I don't have full access.

The 10-35% acceptable macro range in https://iom.nationalacademies.org/~/media/Files/Activity Files/Nutrition/DRIs/DRI_Macronutrients.pdf has its upper limit set to allow room for fats and carbs not due to identified detriment.

stevencloser

Aren't Sprague-Dawley rats the kind of rat that gets health problems when you so much as look at them funny?

richln

There is no known upper limit for healthy individuals:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262767/

One concern is that people with previously undetected renal disease can experience kidney problems instigated by high protein diet. Same concern for people with existing metabolic abnormalities that leave them predisposed to kidney stones, specifically uric acid stones:
http://www.niddk.nih.gov/health-information/health-topics/urologic-disease/diet-for-kidney-stone-prevention/Pages/facts.aspx

The paper linked above claims that although long-term effects of high protein diet are understudied, there is no significant evidence for detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.

senecarr

stevencloser wrote: »

Aren't Sprague-Dawley rats the kind of rat that gets health problems when you so much as look at them funny?

They're highly prone to developing cancer. That's a good thing because it means any results that happen to them tend to fall on the precautious side of things. Generally, if I had to set the bar for something causing cancer or health problems and had to pick between over or understimating the effective dose that does it, I'd rather underestimate it. Particularly for protein, no one's harmed by thinking having more than 400 grams a day is too much.

I do have to say that I do have a certain fear high protein and even lifting is essentially a form of the flame the burns brightest burns fastest. Protein synthesis, muscle protein included, does rely on activating the mTOR pathways that are involved in cells eventually facing ultimate breakdown. It might be that building muscle is protective against many common diseases and thus is associated with long life, but that doing so will short maximum achievable life span.

lemurcat12

As I posted in the other thread (with links) there is no current upper limit (UL) set by those who set the dietary guidelines. There are concerns that it increases the risk of kidney stones at an overly high level (but that level wasn't specified), and because reducing protein helps those with kidney disease they've looked at whether increased protein hurts the kidneys of those without, and not found that it does. They also looked at and have not yet identified any casual relationship with cancer and CVD (and in the Nurse's Study there's actually an inverse relationship between protein intake and CVD).

Despite these, the recommendation is 10-35% of total calories from protein, with the explanation that this is based on the amount left if you comply with the recommendations for fat and carbs (and that for carbs has the lower level at 45%, which is higher than many of us think is necessary or even ideal, of course -- I aim for 50%, but see no reason why 40% would be less healthful, or even lower carb diets). The biggest reason for the 10-35% recommendation -- and one I do agree with -- is that there's no benefit to going higher and a risk of pushing out other foods that you should be eating.

auddii

yarwell wrote: »

You might have to start looking at individual amino acids rather than just "protein".

The references in http://www.ncbi.nlm.nih.gov/pubmed/21535903 "A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats" might have some useful leads in humans but I don't have full access.

The 10-35% acceptable macro range in https://iom.nationalacademies.org/~/media/Files/Activity Files/Nutrition/DRIs/DRI_Macronutrients.pdf has its upper limit set to allow room for fats and carbs not due to identified detriment.

Interestingly, the rats on high protein in the first study lost body weight and ate less food. And the kidneys were larger and had a faster flow rate in the high protein group. And the discussion calls the effect on healthy kidneys moderate, and more use it as a reason for why people with mildly compromised kidney function should also avoid high protein.

koinflipper

Body Builders typically limit carbs to 10-30% so are taking in a lot more protein and their goal is to bulk up muscle mass. Those of us losing weight, we would like to replace the fat with healthy muscle mass (not extreme) so higher protein intake is usually fine.

CATS go into kidney failure and are prescribed low protein diets because their kidneys cannot handle the load of higher protein. However, most of the time, the kidney failure started with not enough daily intake of water when owner feeds dry food to cat. Cats have lower drive to seek water. Sometimes I had to put broth in my cat's water to encourage her to drink enough.

All dialysis patients have extremely restricted protein diets because kidneys already damaged and unable to handle the load of much protein.

People with healthy kidneys who are doing reasonable exercise should be just fine with more protein. Just drink more water to be sure help kidneys handle the protein breakdown products.

lemurcat12

Cats are carnivorous. They should naturally have a high protein diet.

DaddieCat

lemurcat12 wrote: »

Cats are carnivorous. They should naturally have a high protein diet.

I agree. I'm a cat person and I feed my cats grain free food because grain, and not protein has given two of them kidney stones (per vet diagnosis). Feeding them a meat based food per my vet's advice has completely eliminated the issue which cropped up several times over the past 5 years prior to my switching foods. The vet confirmed that some cats are unable to properly digest too much grain intake and kidney issues are the result.


But, cats are not humans either.

juggernaut1974

koinflipper wrote: »

Body Builders typically limit carbs to 10-30% so are taking in a lot more protein and their goal is to bulk up muscle mass.

Ummm....no. Body builders generally INCREASE carbs to give them the building blocks they need to build muscle mass. They may temporarily cut them right before a show or competition for aesthetic purposes

lemurcat12

BecomingBane wrote: »

lemurcat12 wrote: »

Cats are carnivorous. They should naturally have a high protein diet.

I agree. I'm a cat person and I feed my cats grain free food because grain, and not protein has given two of them kidney stones (per vet diagnosis). Feeding them a meat based food per my vet's advice has completely eliminated the issue which cropped up several times over the past 5 years prior to my switching foods. The vet confirmed that some cats are unable to properly digest too much grain intake and kidney issues are the result.


But, cats are not humans either.

Yep, there are big differences between the ideal cat diet and the ideal human diet (varied as the latter can be, of course).

ForecasterJason

juggernaut1974 wrote: »

koinflipper wrote: »

Body Builders typically limit carbs to 10-30% so are taking in a lot more protein and their goal is to bulk up muscle mass.

Ummm....no. Body builders generally INCREASE carbs to give them the building blocks they need to build muscle mass. They may temporarily cut them right before a show or competition for aesthetic purposes

Agreed. If in general they only consumed 10-30% carbs then they would have to be eating over 50% protein, since I think most of them keep fat to 20-30%. And a protein intake that high would easily translate to over 500g of protein considering the caloric intake most body builders are taking in.

Now I'm sure there may be some bodybuilders who do a LCHF diet, but even with that they wouldn't be eating ridiculous amounts of protein.

Carlos_421

ForecasterJason wrote: »

At the moment, there's an ongoing thread in the nutrition section ( http://community.myfitnesspal.com/en/discussion/10336658/too-much-protein-dangerous/p1) regarding an excessively high protein intake (2.5g per lb of bodyweight). I decided to create this thread where we can concentrate on debating extremely high protein intakes without derailing an important thread posted by a member.

Just want to point out that it wouldn't have been derailing since this is precisely the topic the OP in that thread brought up.

Carlos_421

And here ya go.

http://www.biolayne.com/uncategorized/myths-surrounding-high-protein-diet-safety/

ForecasterJason

Carlos_421 wrote: »

And here ya go.

http://www.biolayne.com/uncategorized/myths-surrounding-high-protein-diet-safety/

But this goes back to my point in the OP "most studies on protein intakes aren't using intakes that high (or for very long)". Even the study that investigated an intake of 2.8g/kg is only a little over half of what's being discussed here (5.5g/kg, which is the same as 2.5g/lb). And that study was only carried out over 7 days.