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Myprotein Slow-Release Casein vs Optimum Nutrition Opti-Men

The published reviews of Myprotein Slow-Release Casein and Optimum Nutrition Opti-Men, 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

Myprotein Slow-Release Casein scores 7.6/10 against Optimum Nutrition Opti-Men's 5.0. The widest gap is value against the generic equivalent: 8 for Myprotein Slow-Release Casein, 3 for Optimum Nutrition Opti-Men.

Pick Myprotein Slow-Release Casein if…

  • you want better value against the plain generic version
  • you want the stronger evidence behind what it is sold to do
  • you want every amount on the label disclosed

Pick Optimum Nutrition Opti-Men 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.

Myprotein Slow-Release Casein7/10Leads
Optimum Nutrition Opti-Men4/10

Dose against the studied amount

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

Myprotein Slow-Release Casein7/10Leads
Optimum Nutrition Opti-Men5/10

Label transparency

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

Myprotein Slow-Release Casein8/10Leads
Optimum Nutrition Opti-Men5/10

Value against the generic equivalent

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

Myprotein Slow-Release Casein8/10Leads
Optimum Nutrition Opti-Men3/10

Safety and tolerability

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

Myprotein Slow-Release Casein8/10
Optimum Nutrition Opti-Men8/10

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.

Vitamin DEvidence A

NHS daily amount to adult upper limit: 10–100 mcg a day

  • Myprotein Slow-Release CaseinNot in the formula
  • Optimum Nutrition Opti-Men10 µg (200% NRV)In range

Folic acidEvidence A

USPSTF recommended range: 400–800 mcg a day

  • Myprotein Slow-Release CaseinNot in the formula
  • Optimum Nutrition Opti-MenB6 5.4 mg, B12 9.0 µg, niacin 54 mg, folic acid 90 µg and others at 45–386% NRV

Green tea extractEvidence C

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

  • Myprotein Slow-Release CaseinNot in the formula
  • Optimum Nutrition Opti-MenNot disclosed on the listings we could readUndisclosed

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.

  • Myprotein Slow-Release CaseinAbout £23.95–£41.99 for 1 kg and £48.99 for 2.5 kg at UK retailers in listings read on 28 September 2026. No per-serving figure: servings not recorded.
  • Optimum Nutrition Opti-MenAbout £14.95–£19.99 for 90 tablets at UK retailers in search listings on 28 September 2026 — roughly 50p–67p a day. No per-serving figure: servings not recorded.

Label checks

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

Myprotein Slow-Release Casein

  • Every active ingredient has a stated amount
  • No third-party certification

Optimum Nutrition Opti-Men

  • 1 of 6 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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