Is it safe to buy peanut butter in plastic jars?
Use caution. Peanut butter is oily and stored for a long time, so glass is the better jar when you can choose it.
What's actually in it
Peanut butter is mostly peanuts and oil. It can sit in the same jar in a warehouse, store, pantry, and fridge for months.
The study data does not say every plastic peanut butter jar is unsafe. It does support a practical rule: oily foods stored for a long time are good candidates for glass.
What the research says
A 2025 study in J Hazard Mater tested 109 food samples and found plasticizers in 85% of analyzed samples. The researchers also found packaging-related differences for plastic additives such as ATBC and DEHA.
A 2015 study in Food Addit Contam Part B measured phthalates in edible oils and found the highest phthalate levels in oil samples held in polyethylene terephthalate, or PET, containers.
Neither study tests peanut butter jars directly. The honest takeaway is still useful: choose peanut butter in glass when the price makes sense. If your favorite brand comes in plastic, keep it cool and transfer it to glass after opening.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Plastic additives in the diet: Occurrence and dietary exposure in different population groups. | J Hazard Mater | 2025 |
| Migrated phthalate levels into edible oils. | Food Addit Contam Part B Surveill | 2015 |