Key takeaways
- A protein powder sold as a dietary supplement carries a 'Supplement Facts' panel; one sold as a food carries 'Nutrition Facts'.
- Compare powders by protein per gram of powder and cost per gram of protein, not by protein per scoop, because scoop sizes differ.
- The %DV for protein, when shown, must be based on protein corrected for quality (PDCAAS), against a Daily Value of 50 g.
- A proprietary blend lists its total weight, but not the amount of each ingredient inside it.
- Under DSHEA, FDA does not approve supplements before sale; manufacturers are responsible for safety and labelling, and FDA can act once products are on the market.
Protein powder tubs are covered in big numbers, but the useful ones are on the back. This guide walks through a US protein powder label panel by panel, using the FDA's labelling rules in the Code of Federal Regulations, so you can compare products on what they contain rather than what the front promises.
Supplement Facts or Nutrition Facts?
Start with the title of the panel. Protein powders are sold in the US either as dietary supplements or as conventional foods, and the label shows which:
| Panel title | What it means | Rules |
|---|---|---|
| Supplement Facts | Sold as a dietary supplement | 21 CFR 101.36 |
| Nutrition Facts | Sold as a conventional food | 21 CFR 101.9 |
Both must declare protein when it is present. The difference matters for oversight. FDA explains that under the Dietary Supplement Health and Education Act of 1994 (DSHEA), supplement makers are responsible for evaluating the safety and labelling of their products before marketing, and that FDA can take action against adulterated or misbranded supplements after they reach the market. In other words, the label is the manufacturer's statement, not an FDA approval.
The serving size is a scoop, not a standard
Every number on the panel is per serving, and powders define servings differently: one scoop, two scoops, or a weight in grams. That makes per-scoop comparisons misleading. Convert to protein per gram of powder instead.
A worked example. Powder A has 24 g of protein in a 30 g serving: 24 ÷ 30 = 80% protein. Powder B has 25 g in a 40 g serving: 25 ÷ 40 = 62.5% protein. B has more protein per scoop, but A is the more concentrated powder; the rest of B's serving is something else, such as carbohydrate, fat or flavouring.
Price works the same way. If A costs $40 for 30 servings, it holds 30 × 24 = 720 g of protein, about 5.6 cents per gram. If B costs $35 for 25 servings, it holds 25 × 25 = 625 g, also about 5.6 cents per gram: the cheaper tub is not cheaper protein.
Grams of protein, and the %DV
The panel gives protein in grams per serving, rounded to the nearest gram. The %DV for protein is different. Under 21 CFR 101.9, it is optional on most foods but required when a protein claim is made, and whenever it appears it must be calculated from the corrected amount of protein: grams multiplied by the protein digestibility-corrected amino acid score (PDCAAS), capped at 1.00. The FDA's Daily Value for protein is 50 g for adults and children 4 or more years of age; it is a labelling reference, not a personal target. Under 21 CFR 101.36, a Supplement Facts panel that declares protein lists its %DV using the same corrected method. So a powder with a lower-quality protein can show a lower %DV than its grams would suggest. Complete versus incomplete proteins explains protein quality.
Proprietary blends
Some labels group ingredients under a heading such as "Proprietary Blend" or a branded name. Under 21 CFR 101.36, the label must give the total weight of the blend and list the other dietary ingredients inside it in descending order of predominance by weight, but it does not have to state the amount of each. A blend of several proteins and added ingredients therefore tells you what is in it, and in what order, but not how much of each.
Added ingredients and allergens
Below the protein line, read the rest of the panel and the ingredient list:
- Sugars: the panel lists total and added sugars when present, which separates sweetened powders from unsweetened ones; added sugars versus total sugars explains the two lines.
- Fibre, fats and calories: these show what the non-protein part of the serving is made of.
- Allergens: FDA notes that federal law names nine major food allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and, since 1 January 2023, sesame. FDA explains that the food source of a major allergen must be named at least once, either in parentheses after the ingredient, such as "whey (milk)", or in a "Contains" statement next to the ingredient list, so check both places.
Putting it together
A quick routine for any tub: check the panel title, convert protein to grams per gram of powder, work out the cost per gram of protein, look for proprietary blends and added sugars, and read the allergen statement. Reading nutrition labels covers the standard food panel in more depth.
When you log a shake, use the label's grams per serving for the amount you actually used. Protein Diet Tracker, one of our health and nutrition apps, rolls entries into daily totals for protein, calories, carbohydrates and fat against goals you set yourself.
Good to know
Frequently asked questions
Why does my protein powder say Supplement Facts?
What does proprietary blend mean on a label?
How do you compare protein powders fairly?
Why is the %DV for protein lower than I expected?
Sources
- 21 CFR 101.36: Nutrition labeling of dietary supplements (opens in a new tab)eCFR, US Government Publishing Office — accessed
- 21 CFR 101.9: Nutrition labeling of food (opens in a new tab)eCFR, US Government Publishing Office — accessed
- Daily Value on the Nutrition and Supplement Facts Labels (opens in a new tab)US Food and Drug Administration — accessed
- Dietary Supplements (opens in a new tab)US Food and Drug Administration — accessed
- Food Allergies (opens in a new tab)US Food and Drug Administration — accessed
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