Keep Calm! Plants have protein!
“Keep Calm, Plants Have Protein!”. This phrase is printed on one of my favorite plant-promoting t-shirts. While I oftentimes cannot answer the question that most patients ask me, “How can I get more energy, doc?”, I can help them understand that a plant-based diet can provide them with all the protein they need!
How much protein do we need each day?
A common misconception is the amount of protein we need to consume daily. A popular formula endorsed by those in the fitness industry is to consume 1-1.5 grams of protein per pound of body weight (or 2.2-3.3g/kg) to optimize muscle growth or weight loss. Many patients assume this is the recommended goal for the general population. In fact, the recommended daily allowance (RDA) for protein is to consume only 0.8g/kg. Even this is felt to be nearly double the amount needed as part of a healthy diet! For a 180-pound man (82kg), the difference is 246g versus 66g of protein daily using the popular versus RDA formulas. It’s no wonder there’s so much confusion!(3)
Nutritional Density of Proteins
All foods are made up of the macronutrients carbohydrates, proteins, and fats, each of which have a caloric value. Protein and carbohydrates have 4 calories per gram compared with the 9 calories per gram found in fat.
Many foods also contain noncaloric micronutrients such as vitamins, minerals, and phytochemicals. Dr. Joel Fuhrman has created a formula called the nutrient density which is simply the ratio of micronutrients to macronutrients.(3) More nutritionally-dense foods, primarily from plants, have a higher percentage of noncaloric nutrients (micronutrients) per calorie (macronutrients). It’s important to keep this concept in mind when discussing high-quality sources of protein.
Animal versus Plant Proteins and Nutritional Value
All proteins are made up of a combination of 20 different amino acids, 9 of which are considered essential because our bodies cannot produce them.
Animal proteins are considered a complete protein as they contain all the essential amino acids in similar ratio to human muscle. Compared with plant-based protein, animal protein tends to be a better source of vitamin B12, the essential omega-3 fatty acid DHA, and a readily absorbed form of iron called heme-iron. As a result, many experts tout animal protein as being “high quality” when compared to plant-protein.(1)
Plant-based sources of protein are considered incomplete because they lack essential amino acids or contain amino acids in a ratio that is different than human muscle. As a result, they may be less efficiently utilized by the human body. Because only plant-based sources of protein contain fiber, in addition to phytonutrients, vitamins, and minerals not found in animal proteins, they are considered more nutrient dense than animal proteins according to Dr. Fuhrman’s formula. Contrary to the long-held belief that incomplete plant proteins need to be combined at each meal to make a complete protein, in reality our bodies can form complete proteins from the different amino acids ingested over a 24-hour period.
Animal versus Plant Proteins association with Heart Disease and Cancer
The landmark China Study demonstrated that ingestion of animal protein had a strong correlation with heart disease and cancer, whereas plant proteins were protective against these ailments.(2) The chart below, taken from the China Study book also shows a clear trend (moving left to right) of less heart disease and cancer in countries that consume greater amounts of unrefined plant food.
How is Animal Protein Harmful?
Consumption of all animal protein, including skinless white-meat chicken and low-fat dairy, raises cholesterol levels, while plant-based proteins lower cholesterol. In addition to lacking in the plant-based phytonutrients and antioxidants which protect us from heart disease and various forms of cancer, animal proteins contain saturated fats, the proinflammatory omega-6 fatty-acid arachidonic acid, and can promote high levels of the hormone IGF-I, all of which are disease promoting.
Other Adverse Effects of Animal Protein Consumption
The process of cooking meat at high temperatures, particularly grilling, can be dangerous. Heterocyclic amines (HCAs) are formed when substances in meat react at high temperatures such as during grilling and pan frying. Polycyclic aromatic hydrocarbons (PAHs) are created when fat and juices from grilled meats drip onto coals or fire. The resultant smoke that is formed contains PAHs which stick to the surface of the meat. Both HCAs and PAHs can affect our DNA in a way that can increase the risk of cancer. While the association of HCAs and PAHs with various forms of cancer has been more definitively demonstrated in animals, the relationship to cancer in humans is less well established, in part due variability in collecting accurate dietary histories and accounting for other contributing factors.(4)
L-arginine is an amino acid which is essential for production of nitric oxide (NO), a substance produced by the inner lining of our blood vessels (the endothelium) which dilates blood vessels, thins the blood, and acts as an anti-inflammatory, all mechanisms which counteract strokes and heart attacks. Certain plant foods such as beans, soy, and nuts, are high in L-arginine, and thus promote NO production. Conversely, animal protein not only lacks L-arginine, but can raise cholesterol levels which can contribute to high levels of a substance called ADMA. This leads to reduced levels of NO and its beneficial effects.(5)
Trimethylamine (TMA) is produced when bacteria in our gut metabolize certain compounds found only in animal protein such as choline in red meat, egg yolks, and dairy, and L-carnitine found in red meat. This is converted by the liver to a substance called TMAO which has been associated with accelerated plaque buildup in our blood vessels and a tendency to form blood clots, both of which can contribute to strokes and heart attacks. A recent study demonstrated a four-fold higher risk of death over a five year period in patients with coronary disease that had elevated TMAO levels. Interestingly, a substance called DMB which is found in plant foods including red wine and olives seems to counteract the negative effects of TMAO.(7,8,9)
What are some good sources of plant-based protein?
Now that we know plant protein is a superior alternative to animal protein to maintain health, what are some good sources? Keep in mind that all plant food has protein, including vegetable such as spinach and broccoli. The chart below gives some good examples of the amount of protein available in a typical serving size of a variety of plant foods. There are many great resources and similar charts available online.
Can athletes get enough protein to build muscle?
Many patients feel they just cannot get enough protein by consuming a plant-based diet. In patients that are more active, many are concerned that they will not be able to build muscle or maintain athletic performance. I like to point out that there are numerous elite professional athletes that excel because of, and not in spite of their vegan diets. Some of these include Venus Williams who has won multiple Women’s Grand Slam tennis titles, Kendrick Farris an Olympic weightlifter who competed in the 2016 games, MMA fighter Nate Diaz, NBA superstar Kyrie Irving, and super ironman athlete Rich Roll. Athletes typically consume more calories, and with more calories comes more protein, plenty to maintain muscle and strength. A great resource is the website nomeatathlete.com.
1. Brown, Mary Jane, PhD, RD. “Animal vs Plant Protein-What’s the Difference?”. Healthline.com. June 17, 2017. https://www.healthline.com/nutrition/animal-vs-plant-protein#section4
2. Campbell, T Colin, PhD. The China Study. Dallas. BenBella Books, 2005.
3. Fuhrman, Joel, M.D. Eat to Live. New York. Little, Brown, and Company, January, 2011.
4. “Chemicals in Meat Cooked at High Temperatures and Cancer Risk”. National Cancer Institute. https://www.cancer.gov/about-cancer/causes-prevention/risk/diet/cooked-meats-fact-sheet
5. Sibal, Latika, et. al. “The Role of Asymmetric Dimethylarginine (ADMA) in Endothelial Dysfunction and Cardiovascular Disease”. Curr Cardiol Rev. 2010 May; 6(2); 82-90.
6. Esselstyn, Caldwell, MD. Prevent and Reverse Heart Disease. New York. Penguin Group, 2008.
7. “The Gut, the Heart, and TMAO”. ClevelandHeartLab.com. August 1, 2016. http://www.clevelandheartlab.com/blog/the-gut-the-heart-and-tmao/
8. Zhu W, et. al. “Gut Microbial Metabolite TMAO Enhances Platelet Hyperreactivity and Thrombosis Risk”. Cell. 2016 Mar 24; 165(1):111-124.
9. Senthong, Vichai, MD. “Intestinal Microbiota-Generated Metabolite TMAO and 5-year Mortality Risk in Stable CAD: The Contributory Role of Intestinal Microbiota in a COURAGE-Like Patient Cohort”. J Am Heart Assoc. 2016 June; 5(6): e002816.