PROTEIN SECTION LECTURE #4

Question 1

What is protein quality?

Answer 1

Protein quality is a measure of how efficiently a protein can be used to make other body proteins.

Question 2

On what criteria does protein quality depend?

Answer 2

Protein quality depends on two criteria: amino acid (AA) digestibility and amino acid composition.

Question 3

How well are animal proteins absorbed compared to plant proteins?

Answer 3

Animal proteins are 90-99% absorbed, while plant proteins are 70-90% absorbed.

Question 4

What are antinutrients, and how do they affect protein absorption?

Answer 4

Antinutrients are compounds found in plant proteins that can inhibit the absorption of nutrients, affecting protein digestibility.

Question 5

Can the combination of foods affect protein digestibility?

Answer 5

Yes, other foods consumed together can change the digestibility of proteins.

Question 6

What role does the liver play in amino acid composition in the context of protein quality?

Answer 6

The liver produces nonessential amino acids which are a part of the amino acid composition criterion for protein quality.

Question 7

What are limiting amino acids?

Answer 7

Limiting amino acids are those amino acids that are supplied in less than the amount needed to support protein synthesis.

Question 8

Why are essential amino acids (EAAs) significant when considering protein quality?

Answer 8

Essential amino acids are significant because they tend to be the limiting amino acids, and an issue with ‘incomplete’ or ‘low quality’ protein foods is that they might not provide enough EAAs.

Question 9

What might the body do if essential amino acids are not provided by the diet?

Answer 9

If essential amino acids are not provided by the diet, the body can degrade its own proteins to get the essential amino acids needed.

Question 10

What is PDCAAS, and what does it measure?

Answer 10

PDCAAS stands for protein digestibility-corrected amino acid score.

It measures the quality of a protein based on both the amino acid requirements of humans and their ability to digest it. The highest score is 1, indicating the highest protein quality.

Question 11

What is DIAAS, and how is it different from PDCAAS?

Answer 11

DIAAS stands for digestible indispensable amino acid score, which is a newer method that provides a score based on the limiting amino acid in the food.

Unlike PDCAAS, DIAAS takes into account the individual digestibility of each essential amino acid.

Question 12

Why are methionine and lysine mentioned in the context of protein quality?

Answer 12

Both methionine and lysine are essential amino acids (EAAs), which means they cannot be synthesized by the body and must be obtained from the diet. They are often the limiting amino acids in dietary proteins that determine the overall protein quality.

Question 13

What does a DIAAS score of 1 mean?

Answer 13

A DIAAS score of 1 indicates that the protein source provides at least 100% of the indispensable amino acids required and that these are highly digestible.

Question 14

If a food has a PDCAAS score of 1, what does that tell you about its protein quality?

Answer 14

If a food has a PDCAAS score of 1, it means that after correcting for digestibility, it meets or exceeds the essential amino acid requirements of humans and is considered to be of the highest protein quality.

Question 15

What are complete proteins?

Answer 15

Complete proteins are those that contain all the essential amino acids (EAAs) that the body cannot produce on its own.

Question 16

What are incomplete proteins, and why are they considered harder to digest?

Answer 16

Incomplete proteins are those missing one or more essential amino acids. They are generally harder to digest, and most plant-based protein sources fall into this category.

Question 17

Why are plant proteins often considered to be of lower quality?

Answer 17

Plant proteins are considered to be of generally lower quality because they often contain less available amino acids, have a greater impact of limiting amino acids, and include the presence of antinutrients such as phytates, oxalates, and fiber, which can interfere with the absorption and use of amino acids.

Question 18

What effect do antinutrients have on protein quality?

Answer 18

Antinutrients can bind to essential nutrients and inhibit their absorption. In the context of protein quality, antinutrients like phytates, oxalates, and fiber can hinder the body’s ability to utilize amino acids, which can affect the overall quality and bioavailability of plant-based proteins.

Question 19

What are incomplete legumes, and why are they called incomplete?

Answer 19

Incomplete legumes are those that do not contain all the essential amino acids in sufficient quantities. They are considered incomplete because they are limited in tryptophan, cysteine, and methionine, which are essential amino acids.

Question 20

Why do soybeans have a lower PDCAAS score despite being a complete protein?

Answer 20

Soybeans have antinutrients which can decrease their digestibility, and even though they are considered to be a complete protein, these antinutrients can make it harder for the body to absorb all the amino acids, thus lowering their PDCAAS score.

Question 21

What is protein complementation, and why is it important for vegetarians and vegans?

Answer 21

Protein complementation is the practice of combining different plant foods to improve the overall protein quality of a diet. It is important for vegetarians and vegans because it ensures they receive all the essential amino acids needed for proper health, despite avoiding animal products.