Did you know that without the special protein albumin, your body would swell up with water like a balloon? Without the protein rhodopsin our eyes wouldn’t be able to see light. Without hemoglobin in our red blood cells, oxygen couldn’t be transported throughout the body and carbon dioxide wouldn’t be excreted, resulting in self-poisoning. Did you know that a protein in semen promotes ovulation in a woman? Or that proteins make our blood clot? There are 100,000 different types of proteins in the body, all performing different functions. All of them are composed of a mere 20 building blocks that we call amino acids. These 20 amino acids create unbelievable diversity.
While all 20 amino acids are needed, 9 of them must be replaced from food we eat. These 9 are called essential amino acids because it’s essential that we consume them. Because animals are composed of protein, it makes sense that when people consume animals, they are getting all the amino acids. Plants as a whole also contain all 9 essential amino acids. Some plant foods, however, tend to have less of some amino acids that others are stronger in. When people eat a variety of plant foods, they are getting all 9 as well. While meat and dairy have been labeled as having higher quality protein that is highly absorbable, there are some behaviors of proteins that are typically not taken into consideration in our passion for protein.
The yesterday discussion that lives on in many minds revolves around ensuring getting enough protein and if that protein is complete or incomplete. Meanwhile we might be missing some other very significant protein facts that could impact our health more than we realize.
Apparently, there’s still a lot about protein that isn’t well known. For example, our present food culture bases a lot of its practices and recommendations on the concept that excess insulin in the blood is not good for us. Its role in promoting obesity and heightening the risk of certain diseases, such as cancer, is a primary focus. Since insulin naturally rises with carbohydrate intake, the carb is blamed for exaggerated insulin levels. But protein impacts insulin levels as well. Yes, amino acids have been found to modulate the secretion of insulin. Though in a different way than carbs, the kind of protein we eat influences insulin activity.1
Soy protein induced lower post-meal insulin to glucagon ratios while casein resulted in higher insulin to glucagon ratios.
Glucagon is another hormone that works in a somewhat antagonistic manner to insulin. It rises when blood sugar levels are low. Both are secreted in response to blood sugar but in opposite fashion. Glucagon prevents blood sugar levels from dropping too low while insulin prevents blood sugar from rising too high. Among its other actions, glucagon stimulates the breakdown of stored body fat, so it can be used as an energy source. In this way glucagon favors weight loss rather than weight gain.
In one study, volunteers ate identical meals except for the source of protein. Some ate soy protein while the others ate casein, a dairy milk protein. Soy protein induced lower post-meal insulin to glucagon ratios while casein resulted in higher insulin to glucagon ratios. This means that insulin levels were lower in comparison to glucagon when individuals ate plant protein, whereas when they ate animal protein the insulin levels were higher in relation to glucagon. This is thought to be the result of the difference in the proportion of amino acids in these foods.
Proportions of amino acids have also been observed to impact cholesterol levels and cardiovascular disease. Higher levels of specific amino acids, both lysine and branched chain amino acids, are associated with increased blood cholesterol levels. The researchers agree with the hypothesis that it is protein that is impacting insulin/glucagon ratios, which in turn has an effect on blood cholesterol levels.2 An experiment was conducted to assess the results from randomized, controlled trials, and it revealed that substituting 1-2 servings of plant protein for animal protein in the diet has a cholesterol-reducing effect.3
…substituting 1-2 servings of plant protein for animal protein in the diet has a cholesterol-reducing effect.3
A third unrecognized area that protein has been found to factor into disease progression is in non-alcoholic fatty liver disease (NAFLD). Dietary intake of 1,128 men and women, 20–70 years old, was assessed and compared with their fatty liver index (FLI). Protein popped up again as a factor. In fact, “Total protein intake and animal protein intake were positively associated with the highest FLI score versus the lowest. The opposite was seen for plant protein. Vegetable protein was associated with a lower FLI score.”4
A separate study involving 3,882 individuals completed a Food Frequency Questionnaire and underwent liver ultrasounds. The average age was 70 years old. “Our findings are in line with previous studies, which showed that patients with NAFLD consumed significantly more meat than controls even after adjustment for confounders and energy intake,” the researchers reported.5
“In contrast, the researchers found no correlation between vegetable protein, carbohydrates or dietary fiber with NAFLD.”6
The results of these studies aren’t being taken into consideration in our cultural belief that animal protein is superior to plant protein. They are not factored in when we discuss how nutrition impacts diabetes risk, elevated cholesterol levels, or fatty liver. Apparently, we need to get to know protein a little better.
Scripture asks its own “did you know?” questions. “Have you not known? Have you not heard? The everlasting God, the Lord, the Creator of the ends of the earth, neither faints nor is weary. His understanding is unsearchable. He gives power to the weak, and to those who have no might He increases strength. Even the youths shall faint and be weary, and the young men shall utterly fall, but those who wait on the Lord shall renew their strength; they shall mount up with wings like eagles, they shall run and not be weary, they shall walk and not faint” (Isaiah 40:28-31). There are facts that will change your life.
- M. McCarthy, “Vegan diets may reduce
of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity,” Med Hypothesis, 53(6):459-85. risk
- A. Sanchez & R. Hubbard, “Plasma amino acids and the insulin/glucagon ratio as an explanation for the dietary protein modulation of atherosclerosis,” Med Hypotheses, 1991 Aug;35(4):324-9, https://www.ncbi.nlm.nih.gov/pubmed/1943885.
- S. Li et al., “Effect of Plant Protein on Blood Lipids: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials,” J Am Heart Assoc, 12/20/17, 6(12), https://www.ncbi.nlm.nih.gov/pubmed/29263032.
- A. Rietman et al., “Associations between dietary factors and markers of NAFLD in a general Dutch adult population,” Euro J Clin Nutr, 9/13/17, 72;117-123, https://www.nature.com/articles/ejcn2017148.
- L. Alferink et al., “Animal protein linked to NAFLD in older, overweight patients,” Gut, 8/7/2018, https://www.healio.com/hepatology/steatohepatitis-metabolic-liver-disease/news/online/%7B724a82e1-a6b1-4a3b-819b-0b67767a0f21%7D/animal-protein-linked-to-nafld-risk-in-older-overweight-patients.
Risë Rafferty, RDN
Risë is a Registered Dietitian Nutritionist (RDN) and has been writing and teaching about health for many years. She loves the health message and takes great pleasure in seeing people thrive by the application of its principles. Her research and down-to-earth manner allow her to offer up the health message in both an intelligent and accessible manner. She and her husband, James Rafferty, have two children.