Proteinaholic: How much protein do we need, and what are the best sources?
At age 35, Dr. Garth Davis looked and felt like an old man. He had dark circles under his eyes, was overweight, had high cholesterol, and felt exhausted and run-down. He also had irritable bowel syndrome, which caused him severe abdominal cramps and the need to always be close to a bathroom.
Dr. Davis is a well-known bariatric surgeon and the former host of TLC’s “Big Medicine.” He routinely prescribed a high-protein, low-carb diet to his weight loss patients, only to see many of them back in his office months or years later having gained back all the weight they had lost. He himself was following a high-protein diet, and yet he was in very poor health. He knew that something didn’t make sense.
Dr. Davis set out on a quest to find out what humans really should be eating. He combed through research and examined the cultures around the world that live the longest lives and don’t suffer from Western diseases: obesity, diabetes, heart disease, and cancer.
In his book Proteinaholic, Dr. Davis shares what he learned, and it is one of the best sources of information on diet that I have found. There are two things in particular that set it apart. First, not only is the book impeccably researched and comprehensive, but Dr. Davis analyzes how each nutrition study is done so that we understand how the researchers got their results—and whether or not the results are reliable.
Second, when I picked up this book I thought it would take me a while to get through because it was so dense with research. But because Dr. Davis is such an excellent writer, it immediately turned into my fun reading book!
Why do we need protein?
Our bodies need to produce protein for many reasons—to metabolize food, grow and repair bodily tissues, replicate and repair DNA, provide structure to cells, transport molecules, and respond to stimuli.
In order to produce protein we need amino acids, which are the building blocks of protein. When we ingest protein in our food, our digestive system breaks it down into amino acids, and then we make every protein that our bodies need with these amino acids.
There are 20 amino acids that we need in order to live. Our bodies can produce 11 of them, referred to as the non-essential amino acids. The other 9 are called the essential amino acids, because we need to get them from our food—they are essential in our diet. We don’t need to get them all from a single food or a single meal; as long as we take in enough of the essential amino acids throughout the day, we’re fine. And it’s even been found that our gut microbiota can synthesize some of the essential amino acids from scratch, making them potentially non-essential.
Carbohydrate intake is critical in order for our bodies to utilize amino acids and produce protein. We need energy in the form of glucose (which we get from dietary carbohydrates) in order to repair and build the tissues of our body—like muscle. That’s why eating something that has a 3:1 or 4:1 ratio of carbs to protein (3 or 4 grams of carbohydrates to 1 gram of protein) is recommended in the post-workout recovery period when athletes need protein the most.
How much protein do humans actually need?
What everyone wants to know is: How much protein do humans actually need to consume? And, is there such a thing as too much protein? Dr. Davis delves deep into these topics in his book, and I’ll share a few of the most important points here.
The U.S. government recommended daily allowance (RDA) of protein is 46 grams for women and 56 grams for men. These numbers are based on estimates of how much protein we lose per day (through normal processes of cell breakdown and rebuilding) and how much protein we actually absorb and utilize from the food we eat (about 75%). These estimates are increased by 30% just to be safe—to allow for the fact that some people may have higher than average protein needs (like infants and people who are bedridden). So, the RDA of protein is likely more than many people actually need.
The problem is not with the RDA numbers, which equate to 0.8g/kg of lean body mass. (That means you should be eating 0.8 grams of protein per kilogram of lean body mass; if you want to find out your lean body mass, you can use a scale like this.) Various methods of research show that eating the RDA of protein is more than sufficient for people who lead an active lifestyle, but not high enough to cause health problems.
The problem is that we are eating far more than the RDA, and we’re getting our protein from unhealthy sources. The National Health and Nutrition Examination Survey (NHANES) found that men eat an average of 98 grams and women eat an average of 69 grams of protein per day. At a certain point, our bodies stop making use of protein. Researchers gave healthy test subjects steady infusions of pure amino acids for 8.5 hours and measured their muscle protein synthesis. They discovered what they call a “muscle full effect” after 90 minutes, meaning that muscle protein synthesis had reached a max level, after which muscle protein synthesis returned to baseline levels despite elevated levels of amino acids in the blood.
Another study found that muscle protein synthesis was maximally stimulated when healthy test subjects consumed 20 grams of protein after resistance exercise. The study also found that when protein is consumed in excess of the rate at which it can be utilized by the body, oxidation and ureagenesis (excess ammonia in the body) occur. These are signs that not only is the protein going to waste, but it could also be causing harm.
The worst sources of protein
Animal protein causes high levels of acid in the body
Animal products contain pathogens, hormones, pollutants, antibiotics, and fecal matter
A diet high in animal protein generates a large amount of acid in the body. Our bodies deal with this by resorbing calcium from our bones in order to buffer the acid. As a result, people on a high protein diet suffer more bone fractures. High levels of acid also cause or contribute to gout, kidney stones, poor pancreas and liver function, acid reflux, systemic inflammation, digestive issues, and skin issues.
Since our bodies store excess protein as fat, high protein diets are also related to obesity, as well as an increased risk of death by all causes. The diseases that Americans tend to suffer from the most are all strongly related to diets that are high in animal products, and therefore high in protein. This poses a challenge in research studies: How do you separate the protein from the saturated fat, cholesterol, heme iron, and other disease-causing elements found in animal products? Dr. Davis explores this topic in his book.
I’ll let you read Proteinaholic for all the details on how diets high in animal products lead to heart disease, hypertension, obesity, cancer, and diabetes (that’s right, too much sugar does not cause diabetes—dietary fat does). Let’s focus now on why we should be getting our protein from plant-based foods.
The best sources of protein
Behaviorally, most of us are omnivores, but biologically, humans are herbivores. (Interesting fact: Only herbivores can get atherosclerosis!) Our digestive system is optimally designed to metabolize plant foods, not animal foods. We can digest animal products, just like our carnivorous dogs and cats can digest the grains in the foods we give them, but doing so results in poor health and disease.
And if you want to get technical about it, we have the anatomical qualities of frugivores (plant-eaters that eat fruit, vegetables, and nuts): we can’t metabolize cellulose, our digestive system is about 9 times our body length (compared to 20 times body length in herbivores), and we have hands that can pick fruit and seeds and dig for roots. While fruit is low in protein, it contains plenty of free amino acids, which our bodies use to produce the proteins we need.
Would a plant-based diet that provides excess protein result in the same diseases as a diet with excess animal protein? Based on the research we have so far, the answer is no. The increased cancer risk and overall mortality resulting from high animal protein diets is not present in high plant protein diets. One reason that excessive plant protein is not harmful is that protein in plant foods is accompanied by base precursors (substances that are converted into bases in the body). Animal products contain acid precursors, which convert into acid in the body.
Animal protein comes along with lots of other bad stuff (listed in the previous section) that leads to disease and shortens our lives. Plant protein comes along with vitamins, enzymes, antioxidants, prebiotics, and fiber, all of which improve our health and lengthen our lives. Ninety-seven percent of Americans don’t get the RDA of fiber by a long shot—they get less than half of the RDA—and fiber protects us against diabetes, various cancers, metabolic syndrome, cardiovascular disease, obesity, high cholesterol, and high blood pressure. As Dr. Davis says, everyone asks vegans “Where do you get your protein?” but really, vegans should be asking everyone else “Where do you get your fiber?”
If you’re worried about getting enough protein on a plant-based diet, don’t. A study of over 71,000 people found that vegetarians and vegans get an average of 70% more protein than they need every day. As Dr. Davis assures us repeatedly throughout his book, if you’re eating enough calories of anything, even pizza and potato chips, you’re getting enough protein.
There are five places in the world where people live significantly longer, healthier lives than the rest of us: Okinawa, Japan; Sardinia, Italy; Nicoya, Costa Rica; Icaria, Greece; and the community of Seventh-day Adventists in Loma Linda, California. Dan Buettner describes these cultures in his book The Blue Zones, and Dr. Davis refers to them often. People living in Blue Zones cultures have remarkably low rates of obesity, heart disease, diabetes, and cancer, and they also eat diets low in animal protein and high in plant-based carbohydrates. Most of the calories in traditional Blue Zones diets come from grains, starchy tubers, legumes, vegetables, and fruit; animal products are eaten about once a week as a treat or garnish. For example, the diet of people living in Okinawa (where there are more centenarians per capita than anywhere else in the world) has about 7% protein (compared to the 15% that most Americans eat), and their diet is heavily based on a purple sweet potato they call “imo.”
Are you afraid of carbs? Don’t be.
Hopefully someone will write a book called Carbphobic for all the folks out there who aren’t so much addicted to protein as they are afraid of carbohydrates. One of my former ballet teachers literally said to my class, “Do you want to eat a bagel, or do you want to dance?” I later discovered that I have non-celiac gluten sensitivity, and was a big believer in the Paleo diet for 10 years, so it’s easy to see how I developed carbphobia. Luckily, as a result of all the nutrition research I’ve been reading over the past year, I’m now a recovered carbphobic.
Our body and brain run on glucose, which we derive from dietary carbohydrates. Our muscles need glucose for fuel. And while our muscles and liver can store excess glucose as glycogen for future needs, our brain cannot store fuel and requires a constant supply of glucose.
When we take in excess carbohydrates, our metabolism speeds up to use them. But without sufficient carbohydrates, the systems of our body can’t function efficiently; our bodies resort to breaking down fat (the state of ketosis) and protein to use as energy. These are not efficient sources of energy, nor is it healthy for us to be using fat and protein as our sole sources of energy for very long.
Want to learn more?
The information I’ve summarized in this post is only the tip of the protein iceberg, so if you’re interested in this topic I encourage you to read Dr. Davis’s outstanding book Proteinaholic!