This is the 5710th most frequent Japanese word.
たんぱく質
Protein.
Here, 'たんぱく質' refers generically to proteins as a concept in nutrition and health.
たんぱく質は健康にとって重要です。
Proteins are important for health.
In this example, 'たんぱく質' is used to specify the nutritional content of the food item in terms of protein.
この食品には豊富なたんぱく質が含まれています。
This food contains abundant proteins.
The sentence highlights the functional role of 'たんぱく質' in muscle development.