The Evidence
It's a big claim, so here is a sample of the published data behind it. Below are 14 studies and regulatory labels covering ingredients brands use every day, taken by mouth or applied to skin and scalp. In every case, less than 7% of the amount in the product was absorbed or reached its target.
Each bar shows the reported figure against the 7% line.
Supplements, beverages, and oral wellness actives have to survive digestion, cross the gut wall, and get past the liver.
Absolute oral bioavailability under fasting conditions. Rises roughly fourfold with a high-fat meal.
Perucca E, Bialer M. Critical aspects affecting cannabidiol oral bioavailability and metabolic elimination, and related clinical implications. CNS Drugs. 2020;34(8):795-800. View source for Cannabidiol (CBD) →
After a 4 g oral dose, no quercetin was measurable in plasma or urine, ruling out absorption of more than 1% of the unchanged compound.
Gugler R, et al. Disposition of quercetin in man after single oral and intravenous doses. Eur J Clin Pharmacol. 1975;9(2-3):229-234. View source for Quercetin →
At least 70% of the dose was absorbed, but only trace amounts of unchanged resveratrol reached the blood. Most was converted by the gut and liver first.
Walle T, et al. High absorption but very low bioavailability of oral resveratrol in humans. Drug Metab Dispos. 2004;32(12):1377-1382. View source for Resveratrol →
Once the gut's active uptake system is saturated, only about 1% of a large oral dose is absorbed. Small dietary amounts are absorbed far more efficiently.
Institute of Medicine. Dietary Reference Intakes: Vitamin B12 (citing Berlin et al., 1968). National Academies Press, 1998. View source for Vitamin B12 (high-dose supplements) →
Oral bioavailability in rats, measured against intravenous dosing. Human bioavailability is described as similarly low due to poor absorption and first-pass metabolism.
Yang et al., 2007, as summarized in: UK Committee on Toxicity. Statement on the potential risk to human health of turmeric and curcumin supplements. 2024. View source for Curcumin (turmeric) →
Absolute oral bioavailability of silybin, the main active in silymarin, in rats.
Wu JW, et al. Analysis of silibinin in rat plasma and bile for hepatobiliary excretion and oral bioavailability application. J Pharm Biomed Anal. 2007;45(4):635-641. View source for Silybin (milk thistle) →
Absolute oral bioavailability in rats. The researchers point to intestinal efflux as a key reason.
Chen W, et al. Bioavailability study of berberine and the enhancing effects of TPGS on intestinal absorption in rats. AAPS PharmSciTech. 2011;12(2):705-711. View source for Berberine →
Topicals have to get past the stratum corneum, the skin's outer barrier, before they can reach the living layers where they work.
Only 0.01% of the applied peptide reached the living epidermis after 24 hours. None was found in the dermis; less than 1% entered the skin at all.
Kraeling MEK, et al. In vitro skin penetration of acetyl hexapeptide-8 from a cosmetic formulation. Cutan Ocul Toxicol. 2015. View source for Acetyl hexapeptide-8 (Argireline) →
Neither the collagen peptide KTTKS nor its palmitoylated form crossed human epidermis in detectable amounts.
Terpene conjugation study of KTTKS peptides. Journal of Cosmetic Science. Vol. 72, No. 5. View source for Palmitoyl pentapeptide (Pal-KTTKS) →
On human forearm skin, 0.056 of 13.33 µg/cm² applied crossed the skin.
Melendres JL, et al. In vivo percutaneous absorption of hydrocortisone: multiple-application dosing in man. Pharm Res. 1992;9:1164-1167. View source for Hydrocortisone →
Average absorption from normal, intact scalp (range 0.3% to 4.5%).
Minoxidil 2% topical solution prescribing information; see also Gupta AK, et al. Minoxidil: a comprehensive review. J Dermatolog Treat. 2022. View source for Minoxidil (scalp) →
Percutaneous absorption after single and 28-day use; 1.1% in long-term users.
Latriano L, et al. The percutaneous absorption of topically applied tretinoin and its effect on endogenous concentrations of tretinoin and its metabolites. J Am Acad Dermatol. 1997;36(3 Suppl):S37-S46. View source for Tretinoin (retinoic acid) →
Only 3 ± 2% of the applied dose is absorbed; at least 95% remains in the used patch.
LIDODERM (lidocaine patch 5%) prescribing information. View source for Lidocaine (patch) →
Approximately 6% of the applied dose is absorbed through the skin.
Voltaren Emulgel (diclofenac) Summary of Product Characteristics. View source for Diclofenac (gel) →
These are the ingredients studied, in the forms tested. Absorption depends on the molecule, the dose, and the formula around it, and some ingredients absorb well on their own. What this collection shows is a pattern: for many of the actives brands rely on most, the published numbers fall below 7%.
Study types are labeled on every card. “Human data” comes from clinical or volunteer studies. “Human skin (lab)” means human skin tested outside the body. “Animal study” results are from rats and are widely used to estimate oral bioavailability. “Regulatory label” figures come from approved drug labeling.
Why some entries are drugs. Regulators require absorption to be measured precisely for medicines, which makes drug labels some of the most reliable absorption data available. The skin and gut barriers work the same way on a cosmetic or supplement active as they do on a drug.
The ingredient is fixed. How it's delivered isn't. That's the problem SmartSorb™ was built to solve.
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