Which statement below is correct regarding protein quality in foods?[Fill in the blank]

Question

BlackTom AI · Accepted Answer

Let’s unpack each statement about protein quality in foods and see how they stack up.
Option a: 'Animal sources contain all the essential amino acids except lysine.' This claim is inaccurate because animal proteins are typically considered complete proteins, meaning they contain all the essential amino acids in adequate amounts, including lysine. The statement incorrectly singles out lysine as an exception and mischaracterizes animal proteins as lacking in some essential amino acids.
Option b: 'Soybeans contain all the essential amino acids for growth.' This aligns with the concept that certain plant proteins, notably soy, are considered complete because they provide all nine essential amino acids in sufficient amounts for growth. In many nutrition sources, soy is highlighted as one of the few plant-based proteins with a complete amino acid profile, making this statement correct.
Option c: 'Most nuts and legumes contain less lysine, therefore have reduced protein quality.' While lysine is a limiting amino acid in many cereals, legumes (including many nuts and legumes) generally have relatively higher lysine content compared to cereals. The blanket claim that most nuts and legumes have reduced protein quality due to low lysine oversimplifies and overgeneralizes their amino acid profiles; in many cases their protein quality is adequate or even high, depending on the comparison basis and the overall diet.
Option d: 'The protein quality of some grains is reduced due to less methionine.' It is true that methionine can be a limiting amino acid in some grains, but the classic and more dominant limiting amino acid for many common grains (like wheat, corn) is typically lysine or tryptophan, not methionine. Therefore, while methionine can be limiting in certain contexts, stating that the overall protein quality of some grains is reduced specifically due to less methionine is less accurate as a general rule compared to lysine being limiting in cereals. This makes the statement more questionable as a general rule about grain protein quality.
Overall, option b correctly states that soybeans contain all the essential amino acids for growth, while the other options contain factual inaccuracies or overgeneralizations about amino acid profiles in animal vs. plant proteins and which amino acids are typically limiting in grains or legumes.

Which statement below is correct regarding protein quality in foods?[Fill in the blank]

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