Research that compares historical dietary protein levels with typical levels today, commonly finds that early hunter gatherer humans ate a lot more protein. Analysis of the ratios of nitrogen and carbon in ancient bones can reveal details of protein sources in their diet. Early explorers and people studying native diets have documented these higher levels. For example, the Inuit in Northern Canada, lived primarily on seal, caribou and fish accompanied by lots of fat and very little carbohydrate and their protein level was medium to high. The Red Indians on the American plains ate a high protein meat and organ diet from herbivores such as deer and bison, with very little of the animal not used in some way. Early explorers commented on how very fit and healthy these people were. They had none of the metabolic diseases that are common now and apart from a higher infant mortality, their life expectancy was very similar to humans today.
Hunter gatherers typically ate about 30% protein and body builders can sometimes get up to 40% protein but to do this they consume special pea or whey protein powder supplements for muscle building. It takes a strong focus on building up the protein in the diet to do this. Even a steak only contains 16-21% protein, you would need to eat a lot of steak and you would struggle to eat that much. Even a whole egg only contains 6 grams of protein.
There is a known condition that afflicted some early Arctic explorers called “rabbit starvation”, which could occur during periods of poor hunting, when some explorers ate mostly rabbits because they were available. Rabbits have very very little fat, and this lack of fat caused sickness due to excess production of ammonia. The same issue plagued Vilhjalmur Stefansson during the first few weeks of his year-long 1928 demonstration of survival on an all-meat diet, because the initial diet provided by the hospital, failed to include sufficient fat. It seems that there is an upper limit to protein for humans which is around 40% of your calories. Levels above this can overwhelm the liver’s ability to convert nitrogen from protein into urea, causing ammonia levels to increase leading to stress in the body. Vilhjalmur Stefansson is quoted as saying that rabbit starvation in the arctic could kill a person more quickly than eating nothing.
This suggests that about 40% of calories as protein, is a hard upper limit for humans. However, 40% is very difficult to get to because the protein is buried in food with fats, carbohydrates and vitamins, so you get the other stuff as well. Not only that, but your protein thermostat turns off your appetite as your protein consumption rises, making it harder and harder to continue eating.
What about the bottom end of the protein scale? The official recommended daily allowance (RDA) is about 0.8 grams of protein per kilogram of body weight, however, I understand this is an absolute minimum. Going below this could mean that many of your body maintenance functions are not happening as they should. Things like cell replacement, muscle repair, bone growth, hair growth, joint repair, etc. If you experience brittle hair and nails or wounds take a long time to repair, then maybe your protein level is too low. Your body has no way to store protein so you need to get it every day, maybe every meal and eating more on one day will not carry forward.
I have seen it suggested that the majority of older people in USA are only getting about 12% of their calories as protein. One of the biggest issues with this is that their body will try to get the protein it needs for maintenance by taking it from other parts of their body such as from their muscles, bones and connecting tissue. The result, a loss of muscle mass and a reduction in strength. Many older people die after struggling to recover after a fall, and falls are much more common when strength declines. Keeping strength and muscle mass up should be a key objective for ageing people.
A very poor diet with consistent low protein can lead to a result where only about 5% protein becomes the normal dietary level. To deal with this the body will reduce critical maintenance and the person becomes a “lightweight” version of what they could be. Small muscles, thin bones, lightweight organs, lower level of immunity etc. Valter Longo, a gerontology researcher experimented on mice and discovered that a reduced calorie diet increased their lifespan. Some people are betting, with their lives on this, seeking a longer lifespan by reducing calories, however, this has never been proven in people and we are much more likely to have serious falls than laboratory mice are. If you chose to reduce calories, make sure that it is not the protein that you reduce.
Without sufficient protein, a person gets weaker and weaker, gradually losing the ability to live fully. They struggle to get into and out of a car. Struggle to climb stairs. If they are driving, they may not be able to brake hard enough in an emergency. They may not be able to get out of a lounge chair without help. They cannot shower themselves without support. They tire quickly doing simple tasks. Eventually their heart loses the ability to keep them alive.
I hear that some women choose to avoid protein in order to ensure that they don’t develop “ugly” muscles. Be reassured that this is impossible from just eating a medium protein level diet as recommended here.
Personally, even at 70, I like to be strong enough to be able to do what is wanted without a struggle. Lifting heavy groceries, hitching the trailer onto the car, climbing stairs, digging the garden, carrying loads when required. A regular resistance exercise regime will help and it can be very satisfying.
Older people also don’t absorb protein efficiently, so if you are a bit older, I suggest you try to keep your protein intake to a minimum of about 1.5 grams per kilogram of body weight. For a 70 kg man this means 105 grams of protein each day. To do this make sure you are eating plenty of meat, eggs and fish. Beans contain protein, but soy beans, grains including wheat and legumes can contain protease inhibitors and these can prevent the breakdown of dietary proteins into their amino acids, thus preventing you getting access to some of the protein you eat. This means that reducing the level of these in your diet may also help, particularly avoiding refined wheat flour. Are you in danger of overloading your kidneys? Apparently not unless you already have kidney disease, because it is almost impossible to drive protein levels to the very high levels required.
It is interesting to note that one way a farmer can fatten animals is to reduce the protein level in their feed. This causes the animals to eat more in order to satisfy their protein thermostat. Perhaps a higher level in a human diet will make you feel full sooner, reducing the calories you eat regularly.
During pregnancy a woman needs protein with the Mayo Clinic recommending 71 grams per day, although surely this will vary due to different activity levels and different size women. UCSF Health suggests a minimum level of 60 grams per day or 20-25% of your calories from protein. With a baby growing and most of their growth requiring protein, best not to skimp on this.
For a very readable guide to losing weight, diet and maintaining your health, take a look at my book linked to the blog at www.takebackyrhealth.com.
Regards George Elder