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Proteins are large molecules made up of amino acids and are present in and vital to every living cell. They help make up hair, skin, nails, tendons, ligaments, and muscles; as they hold together, protect, and provide structure to the body. As enzymes, proteins function in metabolism. As antibodies, proteins are integral to a healthy immune system. Although our bodies prefer to use fats and carbohydrates for energy, proteins do provide energy in certain circumstances.

Amino acids are the building blocks of protein molecules and there are 20 different types. These can be categorized into two groups – essential and non-essential. Essential amino acids must be consumed through food as our bodies cannot create them through our own metabolism. Non-essential amino acids are those can be produced through other amino acids and substances in the diet and metabolism. These amino acids can be arranged in millions of different ways to create different proteins, each with their own specific function.

Proteins along with carbohydrates and fats are considered macronutrients. Protein and carbs have 4 calories/gram, while fat has 9 calories/gram.

How much protein one needs is dependent on several factors: age, sex, weight, muscle mass, activity level, and health should all be taken into consideration when determining protein requirements. The Acceptable Macronutrient Distribution Range (AMDR) for each macronutrient is:

Protein: 10-35%

Carbohydrate: 45-65%

Fat: 20-35%

For example, someone who consumes 2000 cals/day should aim to get 10-35% (200-700cals) of those calories from protein sources.

More specifically, the Recommended Daily Allowance (RDA) for sedentary people is 0.8 grams of protein per kilogram of body weight per day. Children, adolescents, and pregnant or lactating women require more protein because it is especially needed during times of growth and development.

Strength and endurance athletes also require more protein. Regular exercise increases the transport of oxygen to body tissues. To carry more oxygen, we need to produce more hemoglobin – the protein that carries oxygen in the blood. A range of 1.2g – 1.7g per kg of body weight is advised for athletes.

https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/SR25/nutrlist/sr25a203.pdf

Check out that link for an alphabetical list of foods and their protein content.

As I mentioned in a previous post, the combination of grains and legumes, or lugumes paired with nuts and seeds will create complete proteins. So yes, vegetarians get their fill.