Peppermint and other herbs: how well minerals are released
What it found
In lab tests that mimic digestion, peppermint released some copper, manganese and zinc, but very little iron.
The amounts depended on the herb, its form and where it came from.
What they found
Animal and lab studies
Copper release
In lab tests, copper was released most from fresh rosemary (84%) and freeze-dried rosemary (79%). In other herbs it ranged from 24% to 45%, and was low in basil and peppermint capsules (4.9% and 5.3%).
Manganese release
In lab tests, manganese release was 37% to 52% in most plants. It was lower in all capsules (15% to 28%) and in dried peppermint (23%).
Zinc release
In lab tests, zinc release was above 38% in dried basil (53%), fresh peppermint (43%), freeze-dried peppermint (41%) and dried peppermint (38%). In all forms of rosemary it was 22% to 28%.
Iron release
In lab tests, iron had the lowest release of all the essential elements studied, at 0.04% to 1.8% in all forms of the herbs.
Toxic metals
In lab tests, nickel release was 27% to 39% in freeze-dried herbs and 10% to 28% in other forms. Lead release was low (6% to 16%) in almost all herbs, except dried basil (20%).
Freeze-drying
In lab tests, freeze-drying did not significantly change the release of manganese, copper and zinc compared with fresh herbs.
What the authors conclude
“The results obtained in our work may be a guide for consumers to use fresh or lyophilized herbs more often in their diet.”
Also in their conclusions
- They say the release of trace elements was highest in fresh and freeze-dried herbs and lowest in dietary supplements.
- They advise consumers to use fresh or freeze-dried herbs more often in their diet.
- They call for further research to understand the exact factors influencing the release of elements from plants.
How it was done
The authors wanted to know how much of the essential and toxic trace elements in herbs are actually released during digestion and made available for absorption, since the total amount in a plant does not always reflect what the body can use.
They used a lab digestion model with stomach and intestinal enzymes and an artificial dialysis membrane to study basil, peppermint and rosemary. They tested fresh, freeze-dried, dried and capsule forms, and measured the elements and total polyphenols.
What it can’t tell you
- This was a lab digestion model, not a study in people. It cannot show how much of these elements the human body actually absorbs or uses.
- The model does not include the full digestive tract or individual differences in digestion and absorption.
Who paid
- Conflicts
- The authors declare no competing financial interest.
- Authors work at
- Doctoral School of the University of Bialystok, Poland; University of Bialystok, Poland; Medical University of Bialystok, Poland
The paper
- Title
- Evaluation of the Bioaccessibility of Essential and Toxic Trace Elements in Basil, Peppermint, and Rosemary Using an In Vitro Gastrointestinal Digestion Model
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Sajkowska S, Moskwa J, Socha K, Leśniewska B (2025). Evaluation of the Bioaccessibility of Essential and Toxic Trace Elements in Basil, Peppermint, and Rosemary Using an In Vitro Gastrointestinal Digestion Model. Journal of agricultural and food chemistry. doi:10.1021/acs.jafc.4c10940Free full textPubMed 40020160DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error