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I Read the Labels on 4 Popular Protein Powders. Only One Has What the Other Three Leave Out
Optimum Nutrition, Transparent Labs, Promix and Aonic all sell themselves as serious protein. So I lined up their nutrition panels, ingredient lists and prices. I checked protein per scoop, what sweetens each one, whether it's labeled lactose-free, how much fiber you get, and what a tub or pouch costs.
By Erin Castellano
Last Updated November 12, 2026 | 5 min read
Why Protein
What to Look For
Top 4
Why So Many Protein Tubs End Up Half-Full in the Cupboard
Protein is the easy part. You need enough of it to recover from training, keep muscle as you get older, and stay satisfied between meals, and a shake is the simplest way to get there. The trouble usually starts with the powder.
Maybe you've been there. A big tub, a few weeks of shakes that taste like sweetened chalk, a stomach that grumbles after every one, and then the tub sits on a shelf until it expires.
What stood out reading them side by side: the protein number on the front is the easy part to compare. The back of the tub is where you find the artificial sweeteners, the lactose, the two-scoop servings and the missing fiber.
So before ranking anything, I settled on three things to check on every label.
3 Things to Check on the Back of Any Protein Tub
1.
How Much Protein One Scoop Gives You
Start with the serving size. Some brands reach their protein number with two scoops, others with one, and across the big names a serving lands anywhere from 24g to 32g. Check that it's a complete protein as well, meaning it carries all nine essential amino acids. Milk and whey proteins both do.
2.
What Sweetens It
Scan the ingredient list for sucralose and acesulfame potassium. Both are artificial sweeteners, and some of the best-known tubs still use them. Stevia, monk fruit and maple sugar are the usual alternatives. If you're cutting back on sugar, read the added sugar line on the panel too.
3.
Lactose and Fiber
Whey concentrate still carries lactose, and even a filtered isolate usually stops short of calling itself lactose-free. If dairy sits badly with you, look for those exact words on the bag. Then find the fiber line. Of the four here, only one lists more than a gram, and fiber is part of what makes a meal feel filling, so a few grams in the scoop is worth having.
Top 4 Protein Powders of 2026
Below are the four, compared on those three checks plus price, flavors and testing. Every number comes from each brand's own label, product page or policy page, checked in November 2026.
1. Aonic Fuel Protein Powder
by Aonic
32g
Protein per Serving
Pros
32g in one scoop: the most protein per serving of the four, at 180 calories, from milk protein with a complete amino acid profile
Labeled lactose-free: the only one of the four that claims it with no qualifier
5g of fiber: from soluble tapioca fiber, where the other three list less than a gram
No artificial sweeteners: stevia and monk fruit, with 0g added sugar
Plain ingredient list: milk protein isolate, skim milk powder, cocoa or vanilla extract, tapioca fiber, natural flavors, stevia, sea salt, monk fruit and a gum blend of cellulose gum, xanthan gum and carrageenan
Under $1 a scoop for members: $23.46 for a 24-scoop pouch, plus the yearly Aonic Club fee
Cost printed on the page: Aonic lists what each pouch costs to make, pack and ship, down to the cent
Buyers rate the taste: about half of its 155 reviews bring up the flavor, and most of those give five stars
HSA/FSA eligible: you can pay with pre-tax health account dollars
Cons
The under-$1 price needs Aonic Club: $49 for the first year, then $149 a year. Without it, a pouch is $63.99.
No returns or exchanges on any pouch, opened or sealed. It also mixes up thick, which splits reviewers, and comes in just two flavors.
The Verdict:
Aonic Fuel is the only powder here with 32g in one scoop, a lactose-free label and 5g of fiber. The other three each miss at least one of those.
Each scoop carries 32g of complete protein and 5g of fiber, while the other three top out at 28g with less than a gram of fiber.
The sweetener line is clean as well. It uses stevia and monk fruit with 0g added sugar, with cocoa in the chocolate and vanilla extract in the vanilla.
Two things to know before you buy. You get the low price only as an Aonic Club member, and Aonic doesn't advertise third-party testing the way the other three do.
The Bottom Line:
Each of the other three asks you to give something up: protein per scoop, a sweetener with nothing artificial in it, or a lactose-free label. Aonic Fuel is the one I'd pick for 32g in one scoop with none of those trade-offs, as long as the Club fee and the thick texture suit you.
Club members pay $23.46 for 24 scoops. The membership costs $49 for the first year and renews at $149, and orders under $50 add $7.49 shipping.
If you'll drink a shake most days, the $49 first-year fee beats the non-member price by your second pouch. After it renews at $149, it takes about five pouches a year to come out ahead. For an occasional pouch, the $63.99 non-member price is the one to compare.
Product details come from each brand's label and website as of November 2026. Individual results vary, so check the product page for current information.
See Aonic Fuel →
2. Transparent Labs Grass-Fed Whey Protein Isolate
by Transparent Labs
28g
Protein per Serving
Pros
28g of protein: from grass-fed whey isolate, at 130 calories a scoop
Third-party certified: the tub carries the Informed Choice and Informed Protein marks
Nothing artificial: sweetened with stevia, with no artificial colors or preservatives
Lean macros: 1g of carbs and 1g of sugar a scoop
23 flavors: about as many as Optimum Nutrition, and far more than Promix or Aonic
Cons
Virtually lactose-free: that's the brand's own wording, and it still tells people with severe lactose intolerance not to use whey powders
No fiber: the panel lists 0g
$64.99 a 2 lb tub: for 30 scoops, or $58.49 on subscription. The 4 lb tub is $98.99 on subscription for 55 scoops
Less protein per scoop: 28g, four grams short of Aonic
The Verdict:
Transparent Labs is the pick for anyone who wants testing they can verify. The Informed Choice and Informed Protein marks sit right on the tub, the isolate keeps carbs and sugar to a gram each, and you can choose from 23 flavors.
It falls short on the third check. The panel lists 0g of fiber, and the lactose claim stops at virtually lactose-free, which matters if dairy gives you trouble.
The Bottom Line:
If lactose doesn't bother you and a testing seal matters most, this is a strong tub. It costs $64.99 for 30 scoops ($58.49 on subscription) and comes with a 45-day refund or store credit window.
Rankings reflect our comparison of each brand's published label, prices and policies. Individual results vary.
3. Promix Vanilla Whey Protein Powder
by Promix
25g
Protein per Serving
Pros
Four Ingredients: Grass-fed whey concentrate, maple sugar, vanilla extract and sunflower lecithin
No Gums: Nothing added to thicken it
Lab Limits Published: Its testing page lists third-party limits for heavy metals and glyphosate
90-Day Refunds: On one-time orders, even once the bag is opened
Cons
Two Scoops a Serving: It takes two scoops to reach 25g of protein
4g of Added Sugar: The maple sugar adds it to every serving
Not Labeled Lactose-Free: It's a whey concentrate, which Promix calls minimally filtered
No Fiber: The panel shows 0g
$64 a Bag: For 31 servings, $57.60 on subscription, or $44.80 a bag in a monthly 5-bag bundle
The Verdict:
Promix keeps its vanilla whey about as simple as protein powder gets. There are four ingredients, no gums, and a testing page that spells out its lab limits for heavy metals and other contaminants.
What you trade for that simplicity shows up on the panel. A serving is two scoops for 25g of protein, the maple sugar brings 4g of added sugar, and it's a concentrate with no lactose-free claim. There's no fiber in it either.
The Bottom Line:
For a short ingredient list and a 90-day refund window on one-time orders, Promix is a good bag. If you're watching added sugar or lactose, it's a harder sell.
Rankings reflect our comparison of each brand's published label, prices and policies. Individual results vary.
4. Optimum Nutrition Gold Standard 100% Whey
by Optimum Nutrition
24g
Protein per Serving
Pros
Banned Substance Tested · stated on the product page, with the Informed Choice mark on the tub
24 Flavors · in sizes from a 0.68 lb tub up to a 10 lb bag
5.5g of BCAAs · naturally occurring, per 31g scoop
Cons
Double Rich Chocolate is sweetened with acesulfame potassium, an artificial sweetener
The label lists natural and artificial flavor
ON says its whey is low in lactose but not lactose-free
Less than 1g of fiber per scoop
24g a Serving · the lowest of the four
The Verdict:
Gold Standard is the name most people already know, and it backs that up with banned-substance testing and 24 flavors. Buy the 10 lb bag on subscription and it's also one of the lower prices per gram here, at $184.00 for 149 scoops.
The Bottom Line:
Where it loses ground is the ingredient list. Acesulfame potassium sweetens the Double Rich Chocolate, the flavor is partly artificial, it isn't lactose-free, and the fiber line reads under a gram. In its favor, ON offers a 60-day satisfaction guarantee (refund or replacement), and subscriptions save 20% with free shipping.
Rankings reflect our comparison of each brand's published label, prices and policies. Individual results vary.
Our Top Pick: Aonic Fuel Protein Powder
Put all four labels side by side and only Aonic Fuel offers all of this:
32g of protein in a single scoop (the most of the four)
Labeled lactose-free with no qualifier (the only one here)
5g of fiber per scoop (the others have less than 1g)
Stevia and monk fruit for sweetness, with 0g added sugar
HSA/FSA eligible, so you can pay with pre-tax health account dollars
$23.46 a pouch for Aonic Club members (under $1 a scoop)
A free Aonic Hydration 30-pack for Club members
Members pay $23.46 a pouch plus the Club fee: $49 the first year, then $149 a year.
What Makes Aonic Different
I haven't seen another protein brand print what a tub costs to make.
Aonic prints the full cost of a pouch on its product page: $14.88 in ingredients, $2.00 for manufacturing, $1.00 for packaging, and the rest for freight, packing and a 10% handling fee.
Club members pay that $23.46 a pouch, which Aonic calls at-cost pricing. The yearly Club fee is charged on top.
See Aonic Club Pricing →
My Final Take
A protein shake only helps if you keep drinking it, so the label matters as much as the grams.
32g in one scoop. Lactose-free on the label. 5g of fiber. Sweetened with stevia and monk fruit.
No other powder on this list puts all four on the same bag.
Get Aonic Fuel at Member Price →
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#1 AONIC Fuel Protein Powder