Does Muscle Milk Have Microplastics? What Cytosport Won't Tell You

MicroPlastics Research DeskEditorial team

August 7, 2026

9 min read

Last reviewed: August 7, 2026 by the MicroPlastics Research Desk. Submit a correction or see our editorial standards.

Quick Answer

Muscle Milk has never been tested for microplastics or plasticizers, and Cytosport publishes neither its packaging material nor its ingredient list on its own product pages. We went looking for both in August 2026 and found neither. That makes this one of the least transparent products we have audited in any category — more opaque than a CeraVe moisturiser, which publishes every ingredient, and more opaque than an AeroPress, which names the polymer of every part. What we can say: the ready-to-drink shakes are sold in 11oz and 14oz plastic bottles, which is the same format as the one product in this category that was tested and flagged. That is a reason for caution, not a measurement.

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Dark plastic protein shake bottle, stainless shaker and dumbbell in a home workout space

Key Takeaways

Zero public test data. No phthalate study, no particle count, no third-party analysis.
Cytosport does not state the bottle material anywhere on musclemilk.com.
The product pages do not render a full ingredient list either — unusual even by this category's low standards.
The RTD range is small: two lines (Protein and Pro Protein), four flavours, two sizes.
Bottled format puts it in the same risk tier as Fairlife Core Power, the shake Consumer Reports wrote to a manufacturer about.
Muscle Milk is milk-protein based, so the ultrafiltration contact step applies here as well.
Powder is the same brand at lower exposure and lower cost per gram.

What Cytosport publishes about Muscle Milk

bottle material: Not statedbottle materialno resin code or polymer named anywhere on the brand site
musclemilk.com, checked Aug 2026
full ingredient list: Not renderedfull ingredient listproduct pages do not serve an ingredient panel in their page source
musclemilk.com product pages, Aug 2026
in any published study: Not testedin any published studyabsent from the Consumer Reports 85-food plasticizer survey
Consumer Reports, Jan 2024
RTD bottle sizes: 11oz / 14ozRTD bottle sizesacross Protein and Pro Protein lines in four flavours
musclemilk.com sitemap, Aug 2026

We tried to audit this properly and could not

Our method for brand questions is the same every time: go to the company's own website, read what it publishes, and report that. We do not use third-party ingredient databases, because they are user-uploaded and go stale. For CeraVe that method produced a full audit of 71 formulas. For AeroPress it produced a named polymer for every model.

For Muscle Milk it produced almost nothing. The product pages do not serve an ingredient list or a packaging statement. There is no materials page, no FAQ entry on packaging, no resin identification anywhere on the site.

We want to be careful about what that does and does not mean. It is not evidence that Muscle Milk is contaminated. Plenty of opaque products are perfectly fine. But it does mean that if you want to make an informed decision about this specific product, the manufacturer has not given you the means to.

What the format tells you

With no disclosure and no test data, the container format is the only signal left — and it is a real one. Muscle Milk's ready-to-drink shakes come in plastic bottles.

A bottled liquid is the highest-contact format in this category for three reasons that have nothing to do with the brand:

The polymer wall is the container. Not a thin liner film inside paperboard — the whole vessel.
Storage is measured in months. These sit filled from production to purchase to your fridge. Contact time is the dominant variable in every study of migration.
They get shaken, warmed and thrown in bags. Agitation and heat both accelerate release. This is a gym product; it lives in a gym bag.

None of that is a Muscle Milk problem specifically. It is a bottled-RTD problem, and it applies equally to every bottled shake on the shelf including the ones marketed as clean.

The range, and the better option inside it

Muscle Milk formats by plastic contact. Cytosport does not state packaging materials, so contact is described by format rather than by named polymer (checked August 2026).
Format	Plastic contact	Verdict
Muscle Milk protein powder	Dry powder in a tub	Clearly the lowest-exposure option in the brand. No liquid stored against polymer for months. Mix in stainless or glass.
Muscle Milk Protein Shake, 14oz	Full plastic bottle wall, months of storage	Higher-risk format. Material not disclosed.
Muscle Milk Protein Shake, 11oz	Same, higher surface-area-to-volume ratio	Marginally worse than the 14oz per unit of drink — smaller containers have proportionally more wall per millilitre.
Muscle Milk Pro Protein Shake	Same bottled format	Higher protein via more processing. Same container question, one extra step upstream.

The 11oz versus 14oz point is small but genuine and almost never mentioned: a smaller bottle has more container surface per millilitre of drink. If you are buying the same total volume, larger units mean less polymer contact per serving. That holds across the whole category, not just this brand.

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What to actually do

Move to the powder. Same brand, same protein, without months of liquid-against-plastic storage. It is also cheaper per gram.
If you buy ready-to-drink, prefer cartons or cans. Muscle Milk does not currently offer those, so this means changing brand — see the full ranking.
Buy the larger bottle. Less wall per millilitre.
Keep them cool. A gym bag in a hot car is the worst storage condition for any bottled drink.
Ask Cytosport what the bottle is made of. If enough people ask, it becomes a published answer. Right now it is not one.

Compare with Premier Protein, read the Fairlife audit that started this whole line of questioning, or see the full protein shake ranking. For powders specifically, microplastics in protein powder.

Frequently Asked Questions

Does Muscle Milk have microplastics?

No published study has measured microplastics or plasticizers in Muscle Milk, and Cytosport does not state what its bottles are made of on its own website, so there is no factual answer available. The ready-to-drink shakes use plastic bottles, which is the highest-contact format in this category and the same format as the shake Consumer Reports flagged at a competitor, but format is an inference rather than a measurement.

What is a Muscle Milk bottle made of?

Cytosport does not say. We checked musclemilk.com in August 2026 and found no resin identification code, no polymer name and no packaging materials statement anywhere on the site, including on individual product pages. Most opaque single-serve protein bottles of this type are HDPE or PET, but we are not going to state that as fact for this brand when the manufacturer has not.

Is Muscle Milk or Fairlife worse for microplastics?

Fairlife Core Power is the only one of the two with published data, and Consumer Reports measured one of the highest plasticizer levels in its 85-food survey in the chocolate shake. Muscle Milk has never been tested. Both use plastic bottles and both are ultrafiltered milk-protein products, so on format and process they sit in the same tier — the difference is that one has been measured and the other has not.

Is Muscle Milk powder better than the shakes?

On this specific question, yes. A powder is stored dry in a tub, so there is no liquid held against a polymer wall for months between filling and drinking, which is the exposure that drives migration. Mix it in a stainless steel or glass shaker and you have removed nearly all of the packaging question. It is also normally cheaper per gram of protein.

Why does the bottle size matter?

A smaller bottle has more container surface area per millilitre of drink than a larger one, so per serving there is proportionally more polymer in contact with the liquid. Buying the 14oz rather than two 11oz bottles slightly reduces contact for the same volume consumed. It is a marginal effect compared with switching format entirely, but it costs nothing.

Sources

Cytosport, Inc. (2026). Muscle Milk Protein and Pro Protein ready-to-drink range (no packaging material or ingredient panel published; checked August 2026). musclemilk.com.
Consumer Reports (2024). The Plastic Chemicals Hiding in Your Food (85 foods tested; Muscle Milk not among them). Consumer Reports.
European Food Safety Authority (2025). Microplastics and nanoplastics in food (contact time and temperature as dominant release variables). EFSA.

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