Translation guide
The English word 'protein' refers to a macronutrient essential for building muscle and repairing tissue. In Japanese, it is commonly expressed with the loanword プロテイン in fitness and supplement contexts, while タンパク質 is the scientific/biological term. The choice depends on context: food labeling, casual conversation, or sports nutrition.
protein (nutrient)
protein (supplement)
Referring to protein in food, diet, or biological contexts.
The standard scientific and everyday term for protein as a nutrient. Used on food labels, in biology, and in general conversation about diet.
This food is rich in protein.
Protein is necessary for building muscle.
Loanword from English, strongly associated with protein supplements, powders, and fitness culture. Not typically used for protein in natural foods.
I drink a protein shake after working out.
Specifically referring to protein powder, shakes, or supplements.
The default term for protein supplements. Can be used alone or in compounds like プロテインパウダー.
Which protein powder do you recommend?
A more formal or descriptive term for protein supplements, sometimes seen on product labels.
Use タンパク質 when talking about protein in food, biology, or nutrition science. Use プロテイン for protein supplements, powders, and shakes. Using プロテイン for natural food protein sounds unnatural.
Eggs are rich in protein.
I mix protein powder with water and drink it.
I ate a protein bar.
Please be careful with your intake of protein supplements.