Protein is an important dietary compound that supplies the building blocks our body needs to build new tissues and maintain homeostasis. Many people have the mistaken notion that vegetarians don’t have a good source of protein because meats are so strongly associated with this macronutrient. However, there is an abundance of food sources that supply proteins and amino acids the body needs to far exceed the daily recommended intake of protein in the vegetarian diet.
But as much as we’d like to think that a protein is a protein is a protein, the body’s metabolism of proteins and amino acids differs depending on the source. It could be assumed that plant proteins are metabolized more quickly in the GI tract because the simple amino found in the plants do not have to be broken down by pepsin or protease in the stomach and small intestine. However, research shows that plant proteins are actually slightly less absorbable than animal meats, likely due to their enclosure in plant cellulose which is more difficult for the body to digest¹.
The good news is that plant proteins are between 78-85% digestible which is still a fairly high availability. Merely raising one’s intake of proteins by 10-20% can ensure that proper intake goals are met. Soy protein is by far the most digestible and high quality plant protein and is thus the most recommended vegan/vegetarian staple. Cooking also affects the digestibility of plant proteins, and it has been suggested that boiling improves protein quality whereas toasting or dry heating does the opposite.
Is there such thing as too much protein? Protein intake directly affects retention of calcium, so excessive protein intake may result in calcium depleting effects². For this reason it is extremely important that protein needs are not greatly exceeded. A good calculation for assessing your daily intake of protein is 0.8 grams of protein per kilogram of body weight. Protein needs are higher among children and teenagers, athletes, weight-trainers, and those experiencing muscle loss or physical trauma.
Returning to the issue of calcium retention, a study from pubmed.gov found that calcium depletion from protein intake is lowest among those who have a plant protein/animal protein intake ratio of 1:1.³ Therefore, for maximum benefits, it is suggested that non-vegan vegetarians get at least some of their daily protein from milk or eggs.
Finally, proteins from plant sources have been shown to lower total blood cholesterol, whereas proteins from animal sources contributes to blood cholesterol (4). Such an effect may decrease the risk of heart disease complications and contribute to cardiovascular health.
