Protein poisoning is a condition that happens when one consumes too much protein and not enough fat to balance it. A pure-protein diet will produce it, but a mixed diet will not. Even in a mixed diet, however, there appears to be an upper limit to the amount of protein that a human can eat before their body gives up.

I googled “protein poisoning” and the first thing that pops up is an ezinearticle post that’s filled with such rabid tripe that I felt the need to respond. I was really thinking I’d be posting here once a day, saving my ideas to make sure each post had the biggest impact (ie no thin, content-free posts), but google flat-out failed in this case. That ezine article is lies, half-truths, and misinformation.

There are hundreds of thousands of identified proteins in the body, so any and all forms of disease will be associated with some over-abundance of one of those proteins. Does that mean that they are “protein poisoning?” No — the phrase is a tactic to scare people away from eating meat. “Protein poisoning” is a real thing, and it isn’t the cause of cancer, or schizophrenia, or arthritis, or any of the other things mentioned on that page.

Brain Food

My interest I’ve been wondering how humans can sleep (or fast longer than 7 hours, really) without breaking down muscle tissue. I’ve been poking around and what I came up with is this:

The human brain burns about 10g an hour doing its thing. At less than 6g an hour, you’ll go into a coma, and this is why diabetics are so worried about insulin shock: too much insulin means too little glucose which means brain pain. The brains of people that are adapted to low-carb diets need less glucose than those on high-carb diets, and from what I’ve read I’m guessing that ketogenics have lower limits here (maybe 6-7g an hour normally and a minimum requirement of 3-5g/hr). The brain of us low-carbers burn ketones for some of its energy, but not 100% — it still needs glucose.

That glucose can be provided by eating carbs (which produces blood sugar directly) or by the liver, which will cough up its glycogen stores to produce glucose. But the liver only stores 75-100g of glycogen; again, those adapted to a low-carb diet will have a smaller store of glycogen. And 100g is the maximal amount; high-carb dieters that carbo-load before a race have been estimated at storing more, but 75g is more common. That means you and I have about seven hours of glucose available when we go to bed.

What happens when the glycogen runs out? One option is to eat late at night, and let the slow uptake of nutrients during digestion provide some extra carbs, but this seems strange to me — and still leaves the issue of dealing with extended fasting periods. If my brain only needs 6g/hr, I’d need 90g to cover a 15-hour fast, and a 36-hour fast would need over 200g. My liver won’t be providing that.

Gluconeogenesis

When blood glucose and liver glycogen stores are both depleted, the liver resorts to gluconeogenesis. This is the de novo production of glucose from lactate, pyruvate, or glycerol. Glycerol is a byproduct of ketone production — glycerol is the backbone of triglycerides, and once the fatty acids are stripped off and turned into their own energy source, the remaining gylcerol can be converted to glucose. Lactate, likewise, is the byproduct of energy production, but this time of glucose metabolism. Except for sleepwalkers, who exercises in their sleep? That means overnight gluconeogenesis comes from pyruvate, from the breakdown of proteins. And that means breaking down muscles.

Combine this with intense workout sessions (as is common in the primal community) and the primal practitioner needs 200g or more of protein every day. I ran into some quotes that suggested that 300g is the upper limit that a person can eat each day lest they run into protein poisoning — specifically, the liver’s inability to remove excess ammonia (a byproduct of the breakdown of amino acids in gluconeogenesis).

Rabbit Starvation is a similar thing, but the two are hard to tease apart. It appears that consuming fat helps in overcoming this protein barrier, perhaps by preventing protein from being absorbed from the digestive tract, or by assisting in clearing excess nitrogen. Or, maybe, because those that eat fat find it much harder to eat 300g of protein a day.

The Debate

While putting this post together I’ve been comparing Don’s Primal Wisdom posts on potatoes to a post by the Rambling docs that disagrees with Don. The debate comes down to, how much glucose does the body need each day? What if you’re doing high-intensity activity?

The docs make a few points about how far a person can run on aerobic metabolism, but that’s really beside the point. Does high-intensity activity burn through glycogen stores rapidly or not?

Protein Poisoning

The brain alone will burn 240g of glucose a day. The glycerol in triglycerides will provide some of that glucose demand, but I’m not sure how much. If you’re eating zero carbs, that means 240g of protein a day — assuming you’re ok with wasting your muscles away to nothing. Assuming 1g/kg/day of protein to maintain nitrogen balance, and that’s over 300g of protein daily just to avoid coma and wasting. If the protein-to-glucose conversion ratio is 1:0.7, this pushes the daily need over 400g.

To quote Cordain, “The mean maximal protein intake for the average weight U.S. male (189.4 lbs ) is then 270 g/day (range 233-322 g/day), and for an average weight female (162.8 lbs ), 246 g/day (range 208-288 g/day).”

What happens if you consume that much protein? We’re talking over two pounds of lean meat, which will be nearly three pounds if you eat fatty cuts. I find it hard to consume more than about a pound and a half of meat each day, and even that is pretty rare; I’d guess my average daily consumption is about 120g of protein.

Near as I can tell, too much protein means you get sick: diarrhea, vomiting, nausea, weakness, dizziness, encephalopathy, and death. Absent disease (like kidney damage) that interferes with normal ammonia clearing, it would take 7-10 days for serious complications to set in, although the milder effects would occur within a day of starting a 300g+ protein diet. This is primarily the result of the buildup of ammonia in the body, which taxes the kidneys, possibly even with heightened water consumption.

Glycogen demands?

so… what? I’m at a loss here. I need more info. It seems to me that the only way to maintain lean mass (or grow it) while keeping my brain fed is to consume some carbs. Otherwise, I’m going to be breaking down lean mass in order to produce the glucose that my brain demands.

I did see someone postulate that someone adapted to ketosis only needs 4g/hr to feed their brain; this means about 200g per day to feed my brain and keep body mass intact, and it also means that 75g of liver glycogen will last nearly 20 hours.

There’s unanswered questions here. However they come out, it seems that intense exercise demands carbs; intensity without carbs means the loss of lean tissue, which might be built up on off days — but that means one can’t do intense exercise daily. Hence carbs enable daily intense exercise.

And more on that later!

If you can shed some insight to any of my questions, I’d appreciate it.

The conventional view of dieting and weightloss is calories in = calories out. People (especially geeks like me) love to cite the first law of thermodynamics: energy can neither be created or destroyed. Hey, that’s great — but humans aren’t closed systems or bomb calorimeters. The digestive system is complex, and the thousands of compounds that reach our bloodstream are then managed by an equally complex array of hormones, vitamins, anti-oxidants, immune cells, carriers, receptors, and more. The idea that the complexity of the human body can be neatly summed up into the simple phrase “calories in = calories out” is silly. As appealing as it is to dress up the phrase with an appeal to scientificalityness, it misses the important role that hormones (et al) have.

But I won’t talk about them per se. Instead, my point today is to say that when you eat carbs matters more than how much you eat. Carbs (whether sugars or starches) quickly convert to blood sugar. Excess blood sugar causes your pancreas to produce insulin, which then shuttles that sugar off into adipocytes (fat cells). But there’s a trick here between the conversion and insulin production; I said excess blood sugar.

When you’re fasting, you burn off the glycogen stored in muscles and your liver. The brain has a constant demand for glucose and if you’re not eating, it has to get it from somewhere. The major source is liver glycogen (muscle glycogen can not move out of muscle cells; it can only be used locally), and if your glycogen stores are depleted, your body wants to restore them. Consuming carbs when fasted, therefore, won’t increase body fat as much as it would right after a meal.

So here’s my point: The same calories consumed at different times can have different effects. Don’t eat dessert right after dinner. If you’ve got bad cravings for sweet things, consume them after fasting (whether that means at breakfast or after an all-day fast).

Of course, avoiding trouble carbs like fructose, alcohol, and grains is better than consuming them — but if you’re working on improving your diet, and need to take steps, the first thing I recommend is changing when you eat those carbs. You’ll start getting your insulin under control, and that makes it easier and easier to remove carbs altogether.