The usual answer to the question of how much protein we need is "More, more, more." The truth is, there are both maximum and minimum daily requirements for protein, and getting either too much or too little is problematic for general health. I think it's helpful to consider the question of how much protein in context.
Many sincere seekers of the ideal diet, especially Paleo dieters, tend on getting enough of the micronutrients. They try to build a diet around vitamins, minerals, and antioxidants.
Or people focus on the anti-nutrients. These are gluten (the potentially toxic protein in wheat, rye, barley, and oats), lactose (the milk sugar that requires the production of the enzyme lactase for its digestion), phytate (a component of plant foods that is particularly abundant in whole grains), or lectins (the toxic compounds in plant foods such as beans).
The problem with this approach is that it “majors on the minors.” Where many Paleo fans and people of similar dedication go astray is in getting just enough, but not too much or too little, of the five macronutrients. The five micronutrients are:
• Fat, which can be subdivided into short-chain and medium chain fatty acids, long-chain saturated fatty acids and monunsaturated fatty acids, and omega-6 and omega-3 essential fatty acids,
• Fiber, and, yes,
Alcohol is not an essential macronutrient, but it is so commonly consumed that it is worthy of explanation in terms of healthy diet. It's almost a matter of religious devotion for many people.
The Bible, after all, doesn’t tell us that Jesus turned water into grape juice. The word in the Greek manuscript (οἶνον) really does mean “wine.”
Fiber is essential food for our probiotic bacteria rather than for ourselves. It is also an important consideration in healthy diets, just not as important, as some diet gurus make it out to be. And we all need protein, carbohydrate, and fat, but in the right amounts.
Despite what you may have heard about nutrient ratios of the Zone Diet (which was based on research of the most effective ratios of macronutrients for race horses, not people), the fact is we don't need any exact ratio of protein, carbohydrate, or fat in our daily diets. Our bodies do just fine as long as we get enough but not too much, a healthy range of protein, carbohydrate, and fat. It’s not about ratios. It’s about absolute minimums and maximums.
Regardless of the ratios of nutrients, an adult woman's body on average:
• Needs at least 46 grams (184 calories) of protein per day, but cannot process more than about 200 grams (800 calories) of protein per day.
• Doesn’t “need” any fructose at all, although it can benefit from small amounts, about the same amount of fructose as would come from an occasional piece of fruit or an occasional spoon of honey. A woman’s body can't process more than about 25 grams (100 calories) from fructose per day. It's OK not to consume any fructose at all.
• Needs at least 40 grams (160 calories) of carbohydrates per day. The rest of the body's glucose needs can come from protein the body does not use to repair itself. The body breaks down extra amino acids into glucose and urea. The kidneys “alkalize” urea with glutamate and/or calcium.
• Usually cannot process more than about 150 grams (600 calories) of carbohydrate per day.
• Treats unsaturated fat and monosaturated fat non-toxic in essentially any amount, although when women consume too many calories overall, they gain weight. We’ll take a closer look at what those fats are a little later.
• Treats polyunsaturated fat non-toxic in amount of up to 100 calories (10 grams) per day. Again, we’ll take a closer look at what polyunsaturated fat is a little later.
• Needs just 0.6 grams (6 calories) of omega-6 essential fatty acids per day if the diet includes 2.0 grams (20 calories) of omega-3 essential fatty acids. Women who consume more than the minimum of omega-6's (and most women do) need far more omega-3's, although both kinds of essential fatty acids can become toxic. It’s actually possible to consume a toxic amount of fish oil, microalgae oil, or healthy plant oils.
• Needs fiber to keep probiotic bacteria happy, but gets enough from 5 servings of plant foods daily.
• Actually benefits from moderate consumption of alcohol, as long as the alcohol is not consumed with polyunsaturated fats. The combination of alcohol and fat, even “healthy” fat, can turn non-toxic fat into toxic fat. It’s OK, however, to consume moderate amounts of alcohol, if you can otherwise handle it, when you aren’t eating lots of fatty foods. Jesus probably never had the disciples over for wine and cheese.
Regardless of the ratio of nutrients, an adult man's body on average:
• Needs at least 56 grams (224 calories) of protein per day, but cannot process more than about 230 grams (920 calories) or protein per day.
• Can't process more than about 25 grams (100 calories) from fructose per day. As is the case for women, it's OK for a man not to consume any fructose at all.
• Needs at least 50 grams (200 calories) of carbohydrate per day. As with women, the rest of a man's glucose requirements can be satisfied by the conversion of excess amino acids into glucose and urea. The kidneys alkalize urea with, ironically, one of the amino acids, glutamate, or with calcium from bone, so it’s better for most men to get at least some carbohydrate at every meal, just not too much.
• Usually cannot process more than about 200 grams (800 calories) of carbohydrate per day.
• Treats polyunsaturated fat as non-toxic in amount of up to 100 calories (10 grams) per day.
• Treats unsaturated fat and monosaturated fat non-toxic in essentially any amount, although when men consume too many calories overall, they gain weight.
• Like women, needs just 0.6 grams (6 calories) of omega-6 essential fatty acids per day if the diet includes 2.0 grams (20 calories) of omega-3 essential fatty acids. Men who consume more than the minimum of omega-6's need more omega-3 to balance them out, but both kinds of essential fatty acids can become toxic, especially if they are consumed at the same meal as alcoholic beverages are drunk. No fish oil capsules with a whiskey chaser for healthy men.
• Needs fiber, but gets enough from 5 servings of plant foods daily.
• Actually benefits from moderate consumption of alcohol, as long as the alcohol is not consumed with polyunsaturated fats.
Protein, carbohydrate, different kinds of fat, fiber, and alcohol are all fine within limits, but it's important not to get too much. Protein, carbohydrate, different kinds of fat, and fiber are essential, and it's important to get enough. The question is, how do you know how much is enough without weighing out your food?
Our Bodies Tell Us How Much Protein We Need
Just about everybody who has access to protein automatically eats the right amount of protein. Just about the only way you can get the wrong amount of protein in the modern world is to pursue an intentionally extreme diet. There are some vegans who don’t enough protein. (Dehydrated spinach has as much protein as steak, but nobody is going to eat a big old plate of dried spinach without soaking it first.) Some bodybuilders and excessively enthusiastic paleo dieters get too much protein, more than their bodies can use, so the excess is turned into—horrors—sugar. Although it wasn't the case in much of the world even 50 years ago, and isn’t even now in a few places in Africa and Asia, just about everyone's diet today provides plenty of protein. Certainly in the United States and Canada, there is a real possibility of eating too much.
Our brains tell us we have eaten enough protein when we have eaten enough of both carbohydrate and protein. If we don't have carbohydrate-rich foods at our meals, our brains tell us to keep on eating protein until we eat enough for both our protein needs and our energy needs. That’s because the body can break down excess protein into sugar. If we have both carbohydrate and protein foods at our meals, our brains tell us we are satisfied when we have eaten a small amount of protein, since the body prefers to make glucose from carbohydrates.
High-protein diets cause high protein-hunger. But even on a high-protein diet, our brains tell us when we have eaten enough. Protein is the predominant determinant of appetite. If we ignore (or can't get) carbohydrate foods long enough, however, our brains eventually tell us that other nutrients are missing, and we typically become hungry for both protein and carbohydrate.
Whose diet in the twenty-first century is most likely to be protein deficient? It turns out that it is the modern hunter-gatherers, the very same people who eat a genuinely ‘Paleo diet’, who are most at risk of protein deficiency. These people, like the modern bush people of Botswana and Namibia, live an ancient lifestyle. They expend an enormous amount of energy tracking, killing and preparing food.
Animals don’t show up with signs saying “Please eat me,” so protein deficiency is a real problem. If you have to track an animal for several days, shoot it with a poisoned dart, run after it for miles as the poison takes effect, kill it, and then carry it back 10, 20, or 30 miles back to your camp, it is easy to become protein deficient.
Protein deficiency is rare in most of the modern world. It is common in the very same countries where the largest numbers of people actually follow hunter-gatherer lifestyles, in the Democratic Republic of the Congo, in Namibia, in Paraguay, and in the most isolated parts of Indonesia.
When protein intake is deficient, the body still has to use protein to make enzymes that enable life. It will harvest protein from:
• The lining of the gut, making it more permeable to allergens, infectious microorganisms, and undigested components of food,
• The immune system, reducing resistance to disease, and
• The kidneys and liver, reducing their ability to “detoxify” and to process nutrients when eating is resumed.
An infant can die of protein malnutrition in as little as five days. Adults can hang on for six or seven weeks, in some cases, even with no dietary protein at all, as the body consumes itself to stay alive.
So, How Much Protein Do We Really Need?
The level at which most adults are consuming neither so much protein that the liver has to transform it into urea and sugar nor so little protein that the body has to break down its own tissue is 0.8 grams of protein per kilogram of body weight per day. For an “average” woman weighing 57.5 kilos (127 pounds), the body stays in balance when, on average, the diet provides 46 grams (184 calories) of protein daily. The average 70-kilo (154-pound) man needs 56 grams (224 calories) of protein every day.
What’s this in common measurements? Men need about two ounces of pure protein (not counting the water and carbs in protein food) per day, and women need a little less.
Women are usually OK eating a little bit more protein than the guidelines. Men are usually OK getting a little bit less. But how could you get your 46 to 56 grams of protein?
There are 50 grams of protein in:
• About 100 grams (3-1/2 ounces) of fresh herring. OK, that’s not really a North American food, but here’s one that is.
• About 140 grams (5 ounces) of cheese, bacon, roast beef, jerky, or chicken.
• About 170 grams (approximately 6 ounces) of Marmite, Quark, or sesame seeds, if you could chew the latter or use them as flour.
• About 200 grams (approximately 7 ounces) of pepitas (shelled pumpkin seeds).
But we can get all the protein we need from veggies, right? Well, in theory, we can, but it would be quite a bellyful. There are 50 grams of protein in:
• About 2340 grams (4-1/2 pounds) of cooked spinach.
• About 1500 grams (3-1/3 pounds or 50 cups) of raw spinach.
• About 9900 grams (a little under 22 pounds) of steamed yellow crookneck squash.
• About 5650 grams (about 13 pounds) of raw squash.
Where advocates of vegan diets go wrong is they mess up the math. They tend to confuse the amount of protein in dried vegetables with the amount of protein in vegetables as we actually consume them. Sure, there’s protein in veggies, but there’s nearly 100 times as much water that also has to be consumed to get the protein.
Advocates of vegan diets would dispute the average of 46 to 56 grams per day recommended by the US Department of Agriculture as a recommended dietary intake. They would say we need only about half as much protein, or even less. But that still means we need huge amounts of vegetables if were are going to depend on them as our only source of protein. It's essentially impossible to go Paleo, and it’s challenging even if you eat grains and tubers, without planning to eat at least some meat. The real problem with meat for most of us, however, is eating too much.
And How Much Protein Is Enough?
Both men and women, sick people and healthy people, athletes and couch potatoes, can consume so much protein that they begin to get sick. When the diet provides about 150 grams (600 calories) of protein per day, the body begins to convert excess amino acids into glucose and urea. The kidneys, ironically, have to harvest glutamine from muscle or calcium from bone to keep the pH of the bloodstream constant, due to the acidity of the urea released in the degradation of protein. By the time an adult is eating 230 grams (920 calories) of protein per day, essentially all additional protein is turned into glucose and urea, and urea can build up to toxic levels.
Whether or not consuming a lot of protein is toxic depends on two factors:
• Whether the diet also provides fat and
• The presence of absence of certain toxic bacteria in the small intestine.
How do scientists know this?
Early in the twentieth century a Canadian ethnographer named Dr. Vilhjalmur Stefansson lived for over a decade with the Inuit people of Canada's arctic north. For nine of those years he ate nothing but meat and fish, a diet similar to that of his hosts. In his memoirs, Stefansson noted the skepticism of the nutritionists of his day that human beings could survive on protein food alone:
“A belief I was destined to find crucial in my Arctic work, making the difference between success and failure, life and death, was the view that man cannot live on meat alone. The few doctors and dietitians who thought you could were considered unorthodox if not charlatans. The arguments ranged from metaphysics to chemistry: Man was not intended to be carnivorous - you knew that from examining his teeth, his stomach, and the account of him in the Bible. As mentioned, he would get scurvy if he had no vegetables in meat. The kidneys would be ruined by overwork. There would be protein poisoning and, in general hell to pay.”
By the time Dr. Stefansson was publishing his memoirs, however, he and another arctic explorer, named Andersen, agreed to eat an all-meat diet for an entire year under the supervision of doctors of New York City's Belleview Hospital (no, not in its famous psychiatric department, in the medical ward). The findings of the experiment published in the Journal of Biological Chemistry. It is only fair to note that the costs of the study were subsidized by a grant from the American meat packers association.
Stefansson insisted on being fed a diet of lean meat without fat to demonstrate the problems he encountered in the Arctic. While on this protein-only diet, he began to experience nausea and vomiting after just two days. When Stefansson and Andersen went back on a meat and fat diet, however, they experienced no particular problems. In fact, they appeared to be in “the best health of their lives.”
You and I, however, are not Arctic explorers. We may not be in the best health of our lives. For us, it might be a good idea to minimize our total meat consumption, and even to eat a little fat with the meat. But how much meat is too much? To get to the “danger zone” for human protein metabolism, 230 grams of protein per day, we would need to consume:
• 1100 grams (2-1/2 pounds) of lean ham.
• 1120 grams (2-1/2 pounds) boneless chicken.
• 1200 grams (2-3/4 pounds) of lean chuck roast.
• 8 kilos (18 pounds) of silken tofu (whether it's a good idea to eat tofu is another issue).
• 10-1/2 kilos (over 20 pounds, over 4 gallons) of chopped spinach.
Advocates of vegan diets insist that it is impossible to consume enough plant foods to build up toxic levels of protein. They are absolutely right. People who eat hunks of meat several times a day ignore the very real possibility of consuming too much protein, especially if the protein is consumed without fat (that is, the meat is strictly muscle meat, without any organ meats, marrow, or marbling). But most of us really are safe from either extreme as long as we avoid advice from diet purists.