A review published August 4, 2026 in Substance Abuse and Rehabilitation traces how kratom products have moved from traditional leaf preparations to a broad commercial range, and it offers a useful framework for understanding what different formats actually are. The paper, by Shereen Aly and Oliver Grundmann of the University of Florida College of Pharmacy, is a literature review. It summarizes earlier studies and surveys rather than reporting a new trial, so its statements about formats are best read as a map of existing evidence, including the gaps.
The review begins with tradition. In Southeast Asia, it says, kratom is mainly consumed by chewing fresh leaves or brewing them into a tea decoction. Dried leaf travels more easily and can be used over a longer period, which the authors cite as a reason dried products are more popular in other countries. The dried, powdered leaf remains the primary product in the United States, the review reports, and extracts derived from it are also in use. Powder is therefore the baseline against which most other formats can be understood.
What is in that baseline matters for everything that follows. The authors put total alkaloid content in native kratom leaf products at roughly 2 to 5 percent by weight. More than 40 alkaloids have been identified, and mitragynine is the most abundant and best studied. The alkaloid 7-hydroxymitragynine, usually shortened to 7-OH, is described as absent from fresh native leaf. The review says it is likely formed through oxidation while leaf is processed into dried products, and that it appears only in minor amounts in some U.S. products. The authors say the naturally occurring amounts are likely insufficient to produce a substantial pharmacological effect, though they stress that more research is needed. That is the review’s interpretation of the evidence rather than a settled finding, but it explains why the paper treats ordinary leaf and concentrated or chemically altered products as different categories.
Capsules and tea bags can stay close to leaf. A capsule packages a measured quantity of powder, although the review notes capsules can hold extract powders as well, and a tea bag preparation is a way of brewing leaf. The review cites research indicating that the onset of effects is faster with capsules and extract powders than with tea bag preparations and loose powder. It also notes that capsules and extract powders allow people to take larger quantities while avoiding the leaf’s bitter taste. A study the review cites, which tracked self-reported effects by product type, found faster onset and stronger reported effects with extract powders and capsules than with leaf powder, along with greater variability in dosing among individual users. Self-reported data of that kind show patterns rather than precise measurements, and the review does not present them as definitive.
Extracts are a different category. The review describes extracts as containing five to 50 times the alkaloid content of native leaf, and it groups enriched extracts, resins and isolates among what it calls chemically altered or concentrated products. Purified compounds, including mitragynine and semi-synthetic 7-OH, sit furthest from leaf. The authors caution that concentrated products and purified compounds are likely to carry a higher risk of dependence than native leaf, while acknowledging that controlled clinical evidence on this point is lacking and that studies of the differing abuse potential of kratom preparations are still needed. For readers, the literacy point is that the word kratom on a product can describe very different material depending on whether it is ground leaf or a concentrate.
Beyond capsules, tea and extracts, the review lists edibles, tablets, gummies, liquid shots and vaping products among the newer forms, and it compares the trend to the diversification of the commercial cannabis market. Because liquid shots and edibles deliver alkaloids in dissolved form, the authors say they may be absorbed faster, but they present this as a possibility rather than a measured result. They also note that many of these dosage forms are further removed from traditional use and that the pharmacokinetic and pharmacodynamic differences between them still need study. In other words, the evidence base for gummies, shots and tablets is thinner than for leaf powder and tea, and claims about how formats compare should be read with that in mind.
The review attributes the growth in formats to several drivers: perceived potency and consistency, versatility, convenience and consumer demand. It says concentrated alkaloids in consumer-friendly formulations can offer more predictable effects than leaf, whose composition varies, and that diversification lets researchers focus on specific alkaloids. It reports that diversification has increased since 2021. Those are the authors’ descriptions of market motives, and the paper sets them beside the caution about concentrates described above, so both sides of the trade-off appear in the same text.
On regulation, the review says kratom is not recognized by the FDA as a dietary supplement, that several applications to treat it as a new dietary ingredient have been submitted without approval, and that U.S. states have taken different routes. Some ban kratom products outright, while others regulate them through measures such as age restrictions, laboratory testing, labeling requirements and limits on 7-OH. The authors’ recommendations lean toward oversight of the products themselves. They call for state and federal monitoring to ensure good manufacturing practices and quality control, for clear serving and composition information, and for education of health care providers about product differences and potential drug interactions. Such measures are format-neutral: testing, standards and clear information can apply whether a product is leaf powder, a capsule or a concentrate.
The review has limits worth stating. It is a literature review rather than a new study, much of its format-specific evidence comes from surveys and self-reported data, and the authors repeatedly say research on newer dosage forms is incomplete. It also centres on health outcomes and reaches more cautious conclusions about concentrates than about leaf, so readers who want the full pharmacology, dependence and safety discussion should consult the original paper. For format literacy, the main takeaway is straightforward: powder, tea bags and capsules are ways of preparing or packaging ground leaf, although capsules can also hold extracts, while extracts, isolates and many newer forms can contain far more concentrated or chemically altered material, and the research comparing them is still developing.