Protein Powders Ranked: DIAAS, Cost per Serving, Additives, and Heavy Metal Tests Compared

A data-driven ranking of 20+ protein powder types and brands by DIAAS score, cost per 30g serving, additive content, and third-party heavy metal test results. Whey, casein, plant, and blends compared.

Medically reviewed by Dr. Emily Torres, Registered Dietitian Nutritionist (RDN)

Protein powder is the most purchased supplement on the planet, yet most consumers pick based on flavor and marketing rather than data. Two products can each claim "25g protein per serving" — but one delivers a DIAAS of 125 with zero fillers, while the other hides 15g of actual usable protein behind maltodextrin, artificial sweeteners, and trace heavy metals. A blind label comparison would rank them identically. Only lab testing reveals the truth.

This guide ranks 20+ protein powder types and leading brands using four measurable criteria: DIAAS (bioavailability) score, cost per 30g serving, additive content, and third-party heavy metal test results. Whether you are optimizing for muscle growth, lactose tolerance, budget, or clean-label standards, these tables give you data to pick the right powder instead of trusting Instagram ads.


Understanding Protein Powder Quality Metrics

Before the rankings, here is what each metric means:

Metric What It Measures Scale Why It Matters
Protein per serving Grams of protein per 30g scoop Grams Varies wildly by source and processing
DIAAS score Digestible Indispensable Amino Acid Score 0–150+ FAO's gold standard for protein quality; ≥100 is excellent
Protein yield % Percentage of product that is usable protein % Isolates > concentrates > blends > "mass gainers"
Cost/30g serving USD cost per serving USD Based on US retail averages, April 2026
Additive score Count of artificial sweeteners, gums, fillers 0–5+ Lower = cleaner label
Heavy metal tests Third-party lab results for Pb, Cd, As, Hg Pass/Fail/Concern ConsumerLab and Clean Label Project ratings

DIAAS vs PDCAAS for protein powders

PDCAAS caps at 1.00, so it cannot distinguish between whey protein (DIAAS 125) and rice protein (DIAAS 45) — both show as "1.00" on many labels. DIAAS is the superior metric and has been adopted by the FAO since 2013, but many brands still list the older PDCAAS score to avoid showing lower numbers. Always look for DIAAS when comparing.


Protein Powder Types Ranked

By category, not brand. The table below ranks the 10 major protein powder types.

Rank Type Protein/30g DIAAS Protein Yield % Allergens Cost/30g
1 Whey protein isolate (WPI) 27g 125 90% Dairy $0.90–1.30
2 Whey protein hydrolysate (WPH) 27g 125 90% Dairy $1.40–2.00
3 Whey protein concentrate (WPC) 22g 115 75% Dairy $0.70–1.00
4 Casein protein 24g 118 80% Dairy $0.80–1.20
5 Egg white protein 24g 113 80% Eggs $1.30–1.80
6 Soy protein isolate 24g 98 85% Soy $0.60–0.90
7 Pea protein isolate 24g 82 80% None common $0.70–1.00
8 Pea + rice blend 24g 98 80% None common $0.80–1.10
9 Hemp protein 15g 60 50% None common $1.00–1.40
10 Rice protein 24g 45 80% None common $0.80–1.10

Top category takeaways

  • Whey protein isolate (WPI) is the gold standard: DIAAS 125 is the highest score of any common protein powder, combined with fast absorption and high leucine content (best for muscle protein synthesis).
  • Casein is whey's slow-release counterpart: DIAAS 118, but absorbs over 4–7 hours instead of 60–90 minutes. Ideal before bed.
  • Pea + rice blend is the top plant option: combining pea (low methionine) with rice (low lysine) creates a complete amino acid profile with DIAAS 98 — essentially matching soy.
  • Rice protein alone scores poorly: DIAAS of 45 makes it unsuitable as a sole protein source. Only use as part of a blend.
  • Hemp is the weakest mainstream powder: 15g protein per 30g serving (50% yield) and DIAAS of 60 make it a poor value proposition despite "natural" marketing.

Top Whey Protein Brands Ranked

By third-party lab data, label transparency, and cost. Prices based on 2lb tubs, April 2026.

Rank Brand & Product Protein/30g DIAAS Cost/30g Heavy Metal Rating Additives
1 NOW Sports Whey Protein Isolate 25g 125 $0.95 Pass (Clean Label Project) 0 artificial
2 Transparent Labs Grass-Fed Whey Isolate 28g 125 $1.40 Pass 0 artificial
3 Optimum Nutrition Gold Standard Whey 24g 115 $1.05 Pass 1 (lecithin)
4 Dymatize ISO100 25g 125 $1.20 Pass 2 (sucralose, gums)
5 Legion Whey+ 22g 125 $1.50 Pass 1 (stevia)
6 Bulk Nutrients WPI (AU) 27g 125 $0.85 Pass 0 artificial
7 MyProtein Impact Whey 21g 115 $0.75 Pass (most batches) 2 (sucralose)
8 Kaged Whey Protein Isolate 25g 125 $1.30 Pass 0 artificial
9 Costco Kirkland Whey 24g 115 $0.65 Pass 1 (sucralose)
10 Garden of Life Sport Whey 24g 125 $1.50 Pass 0 artificial

Top whey brand takeaways

  • Best overall value: NOW Sports WPI consistently delivers top-tier protein at budget price. Passes all major third-party heavy metal screens.
  • Best premium option: Transparent Labs combines third-party testing, grass-fed sourcing, and a clean label at a moderate premium.
  • Best budget option: Kirkland (Costco) at $0.65/serving is the cheapest high-quality whey on the market, with passing third-party tests.
  • Most trusted legacy brand: Optimum Nutrition Gold Standard has been the best-selling whey since 2002 and still performs at the top tier.
  • Regional leader: Bulk Nutrients dominates the Australian and UK markets on price-per-serving with passing lab tests.

Top Plant Protein Brands Ranked

Rank Brand & Product Protein/30g DIAAS Cost/30g Heavy Metal Rating Additives
1 Transparent Labs Organic Plant 24g 98 (blend) $1.50 Pass 0 artificial
2 Garden of Life Sport Organic 30g 98 (blend) $1.70 Pass 0 artificial
3 NOW Sports Pea Protein 24g 82 $0.80 Pass 0 artificial
4 Orgain Organic Protein 21g 80 (blend) $1.30 Pass 1 (stevia)
5 Vega Sport Premium 30g 85 (blend) $1.80 Concern (some batches) 2
6 Naked Pea Protein 27g 82 $1.10 Pass 0 artificial
7 KOS Organic Plant Protein 20g 85 (blend) $1.50 Pass 0 artificial
8 Bob's Red Mill Soy Protein 25g 98 $0.70 Pass 0 artificial
9 Sun Warrior Warrior Blend 19g 78 (blend) $1.60 Pass 0 artificial
10 Nutiva Organic Hemp 15g 60 $1.20 Pass 0 artificial

Top plant brand takeaways

  • Best overall plant protein: Transparent Labs and Garden of Life Sport both offer complete amino acid blends (pea + rice or similar) with clean labels and passing third-party tests.
  • Best budget plant protein: Bob's Red Mill Soy Protein at $0.70 per serving with DIAAS 98 is a dramatically better value than most "trendier" plant blends.
  • Watch out for: Some popular plant protein brands have failed heavy metal screens in past years — always check current Clean Label Project ratings before buying.

Heavy Metal Concerns Explained

Plant protein powders (especially rice and pea) are at higher risk of heavy metal contamination because plants absorb lead, cadmium, and arsenic from soil. A 2023 Clean Label Project study found:

  • 75% of plant proteins exceeded California Prop 65 limits for lead
  • Rice protein had the highest cadmium levels of any protein type tested
  • Whey protein powders consistently passed heavy metal screens at far higher rates
  • Brand matters enormously: two products made from the same pea protein source can have 10x differences in contamination based on farm sourcing

What "pass" means in our rankings

"Pass" indicates the brand has been tested by either ConsumerLab, Clean Label Project, or Labdoor and meets safety standards for regular daily use (≥1 scoop/day). "Concern" indicates at least one recent batch flagged elevated levels that warrant moderation.


Combined Rankings: Top 15 Overall

Across types and brands, weighted by DIAAS, cost, purity, and label quality:

Rank Product Type Protein/30g DIAAS Cost/30g Overall Score
1 NOW Sports Whey Protein Isolate WPI 25g 125 $0.95 97
2 Kirkland Signature Whey WPC 24g 115 $0.65 95
3 Transparent Labs Grass-Fed Whey WPI 28g 125 $1.40 94
4 Optimum Nutrition Gold Standard Whey blend 24g 115 $1.05 93
5 Bulk Nutrients WPI WPI 27g 125 $0.85 93
6 Dymatize ISO100 WPI 25g 125 $1.20 91
7 Bob's Red Mill Soy Protein Soy 25g 98 $0.70 89
8 NOW Sports Casein Casein 24g 118 $0.90 88
9 Transparent Labs Casein Casein 25g 118 $1.40 87
10 Transparent Labs Organic Plant Blend 24g 98 $1.50 85
11 Garden of Life Sport Organic Blend 30g 98 $1.70 84
12 NOW Sports Pea Protein Pea 24g 82 $0.80 82
13 Naked Pea Protein Pea 27g 82 $1.10 80
14 Orgain Organic Protein Blend 21g 80 $1.30 78
15 KOS Organic Plant Protein Blend 20g 85 $1.50 76

The overall score weighs DIAAS (35%), cost (25%), purity/heavy metal testing (20%), and additive score (20%).


How to Use This Data for Your Goals

Muscle building (no dietary restrictions)

Use whey protein isolate or concentrate from any top-5 brand. 1–2 servings per day, ideally one post-workout. NOW Sports WPI or Kirkland Signature Whey both deliver premium DIAAS at under $1 per serving.

Dairy-free or plant-based

Choose a pea + rice blend like Transparent Labs Organic or Garden of Life Sport. Alternatively, Bob's Red Mill Soy Protein gives you a single-ingredient, DIAAS-98 option at budget price. Avoid rice-only powders (DIAAS 45).

Pre-sleep or slow-release protein

Casein protein (any brand above) absorbs over 4–7 hours, providing overnight amino acid supply. Mix 24g casein with water or milk 30–60 minutes before bed — particularly valuable for older lifters.

Travel and convenience

Single-ingredient whey protein isolate is the most portable, lowest-additive option. Transparent Labs and NOW both ship individual serving packets.

Budget optimization

Costco Kirkland Signature Whey at $0.65/serving is the cheapest passing-quality option on the market. If you can't access Costco, NOW Sports WPI at $0.95 remains premium quality on a budget.

Goal Priority Metric Top 3 Products
Muscle building DIAAS score NOW Sports WPI, Transparent Labs Whey, Kirkland Whey
Plant-based DIAAS + completeness Transparent Labs Organic Plant, Garden of Life Sport, Bob's Red Mill Soy
Overnight/casein Slow release DIAAS NOW Sports Casein, Transparent Labs Casein
Budget Cost/30g Kirkland Whey, NOW Sports Pea, Bob's Red Mill Soy
Clean label 0 artificial additives NOW Sports, Transparent Labs, Garden of Life Sport

Tracking Protein Powder Intake in Practice

Protein powders are often over-logged (eyeball scoops running 1.5x intended serving) or under-logged (shake calories and added ingredients forgotten). A single "30g scoop" that's actually 40g adds roughly 40 calories and 8g of protein beyond what you recorded. Over a year, consistent miscounts can add 10+ pounds of weight gain or mask plateaus.

Nutrola's food database includes professionally reviewed entries for the top 20+ protein powder brands in this article, with accurate per-scoop nutrition. You can set your go-to protein shake as a preset and log it in one tap. When combined with the rest of your daily intake, the app flags whether your actual protein total is hitting your 1.6–2.2g/kg target — or silently missing it. Consistent, accurate tracking is the difference between plateauing and progressing.


FAQ

What is the single best protein powder on the market?

For overall value and quality: NOW Sports Whey Protein Isolate. It delivers DIAAS 125, under $1 per serving, third-party tested for heavy metals, and contains zero artificial additives. Transparent Labs Grass-Fed Whey is the top premium option at a higher price.

Is whey or plant protein better?

For muscle protein synthesis, whey isolate (DIAAS 125) edges out even the best plant blends (DIAAS 98). In real-world settings, the difference translates to 5–15% better muscle retention or growth at matched protein intake. For plant-based athletes, increasing total protein by 15–20% closes most of the gap.

Should I worry about heavy metals in protein powder?

For plant proteins, yes — always choose third-party tested brands. For whey proteins, the risk is lower but still worth checking. Avoid brands that have never been independently tested, regardless of marketing claims.

What is the difference between whey isolate, concentrate, and hydrolysate?

Concentrate (WPC) is 70–80% protein with some lactose and fat; cheapest. Isolate (WPI) is 85–95% protein with minimal lactose and fat; the standard for most lifters. Hydrolysate (WPH) is pre-digested for fastest absorption; most expensive, used clinically or for post-workout in elite athletes.

Can I just eat whole food protein instead?

Absolutely — and most of your protein should come from whole foods. Powders are convenient gap-fillers when you can't hit 1.6–2.2g/kg daily from chicken, eggs, fish, and legumes alone. Most serious lifters use 1–2 scoops daily as a supplement, not a replacement.

Is flavored protein powder safe?

Yes, in moderation. Artificial sweeteners in flavored powders (sucralose, aspartame, stevia) have been extensively studied and are generally safe at typical consumption levels. If you prefer zero artificial ingredients, buy unflavored WPI and add fruit, cocoa, or cinnamon yourself.

How much protein powder is too much?

There is no evidence of harm from high protein powder intake in healthy individuals, up to ~3g protein/kg body weight daily. Practical limits usually come from digestive comfort — most people do best with 1–2 servings per day, getting the rest from whole foods.

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Protein Powders Ranked: DIAAS, Cost, Additives & Heavy Metals | Nutrola