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Optimum Nutrition Serious Mass vs Supergut Prebiotic Bars

Short answer: Optimum Nutrition Serious Mass is the better pick on our scores (5.8 vs 4.6 out of 10).

The published reviews of Optimum Nutrition Serious Mass and Supergut Prebiotic Bars, lined up: the five scores, what one serving delivers against the studied dose, the real cost per serving and what each label leaves out. Figures as of 28 September 2026.

The short answer

Optimum Nutrition Serious Mass scores 5.8/10 against Supergut Prebiotic Bars's 4.6. The widest gap is evidence for the marketed claim: 7 for Optimum Nutrition Serious Mass, 3 for Supergut Prebiotic Bars.

Pick Optimum Nutrition Serious Mass if…

  • you want the stronger evidence behind what it is sold to do
  • you want a serving that matches the amount used in research
  • you want every amount on the label disclosed

Pick Supergut Prebiotic Bars if…

It does not lead on any criterion we score. Read its review for the case in its favour.

Criterion by criterion

The five criteria every review is scored on, published on the grading page. The overall score is their average.

Evidence for the marketed claim

How strong the research is for what the product is actually sold to do — not for the ingredient in general.

Optimum Nutrition Serious Mass7/10Leads
Supergut Prebiotic Bars3/10

Dose against the studied amount

Whether one serving delivers the amount used in the research behind the claim.

Optimum Nutrition Serious Mass6/10Leads
Supergut Prebiotic Bars5/10

Label transparency

Whether the Supplement Facts panel is published in readable text and every active amount is disclosed.

Optimum Nutrition Serious Mass5/10Leads
Supergut Prebiotic Bars4/10

Value against the generic equivalent

Cost per gram or per dose of the active ingredient, compared with the plainest version of the same thing.

Optimum Nutrition Serious Mass4/10
Supergut Prebiotic Bars4/10

Safety and tolerability

Known risks and interactions, how well characterised they are, and whether the label warns about them.

Optimum Nutrition Serious Mass7/10
Supergut Prebiotic Bars7/10

Dose against the studied amount

What one labelled serving delivers, placed against the range on each ingredient’s evidence page. Where a label gives no figure, there is nothing to place, and that is the finding.

Whey protein blendEvidence A

Where muscle protein synthesis maxes out: 20–25 g a dose

  • Optimum Nutrition Serious Mass50 g of protein per servingAbove range
  • Supergut Prebiotic BarsAbout 10 g of protein a bar

Rebaudioside A (stevia)Evidence D

No single studied range in label units, so amounts are shown but not placed.

  • Optimum Nutrition Serious MassNot in the formula
  • Supergut Prebiotic BarsNot stated

What it actually costs

Price divided by labelled servings, from a dated listing. A serving is whatever the label calls one, which is why the studied-dose row matters more than the headline figure.

  • Optimum Nutrition Serious MassAbout £32.95–£50.00 for the 2.73 kg tub at UK retailers in search listings on 28 September 2026 — roughly £4.12–£6.25 a serving. No per-serving figure: servings not recorded.
  • Supergut Prebiotic Bars$40.00 for 12 bars on Supergut’s store and $39.99 at GNC, with a first-order subscription price of $26.99 on Amazon.com, in listings read on 28 September 2026. No per-serving figure: servings not recorded.

Cost to reach a studied dose of Whey protein blend

  • Optimum Nutrition Serious MassCannot be worked out: amount or price missing
  • Supergut Prebiotic BarsCannot be worked out: amount or price missing

Label checks

What each label discloses, and what it leaves out. Read from the reviews, not from the marketing.

Optimum Nutrition Serious Mass

  • Every active ingredient has a stated amount
  • No third-party certification
  • Whey protein blend: a serving gives 50 g, above the 20–25 g a dose where muscle protein synthesis maxes out

Supergut Prebiotic Bars

  • 1 of 4 listed ingredients have no stated amount
  • No third-party certification

How this comparison is built

  • Scores are the ones already published in each review. Nothing is re-scored for the comparison, and a product leads a criterion only when it outscores the rest.
  • Doses are read from the label rows in each review and placed against the studied range on the matching ingredient page. A figure that is not printed is never estimated.
  • Costs use a dated retailer price divided by labelled servings. Prices in different currencies are never ranked against each other.
  • Only products in the same category, or ones a review names as an alternative, can be compared. Commission never changes what appears here.

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