and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
Historical or traditional use (may
or may not be supported by scientific studies)
As recorded in ancient Sanskrit texts, coleus was used in Ayurvedic medicine1 to treat heart and lung
diseases, intestinal spasms, insomnia, and
Forskolin, a chemical found in coleus, activates the enzyme adenylate cyclase.2
This enzyme is a turnkey compound that initiates a cascade of critical events within every
cell of the body. Adenylate cyclase and the chemicals it activates comprise a “second
messenger” system that is responsible for carrying out the complex and powerful effects
of hormones in the body. Stimulation of the second messenger system by forskolin leads to
blood vessel dilation,3 inhibition of allergic reactions,4 and an
increase in thyroid hormone secretion.5 Forskolin has other properties as well,
including inhibition of the pro-inflammatory substance known as platelet-activating factor
(PAF)6 and inhibition of the spread of cancer cells.7
Studies in healthy humans, including at least one double-blind trial, have shown that
direct application of an ophthalmic preparation of forskolin to the eyes lowers eye
pressure,89 thus reducing the risk of glaucoma. Direct application of the whole herb to the
eyes has not been studied and is not recommended.
Forskolin may help dilate blood vessels and improve the forcefulness with which the heart
pumps blood. A preliminary trial found that forskolin reduced blood pressure and improved heart function in people
with cardiomyopathy.10 It is
unknown if oral coleus extracts would have the same effect. A small double-blind trial found
that inhaled forskolin could decrease lung spasms in asthmatics.11 It is unclear if oral
ingestion of coleus extracts will provide similar benefits.
How much is usually taken?
Coleus extracts standardized to 10 to 18% forskolin are available. While some doctors
expert in herbal medicine recommend 50–100 mg two to three times per day of standardized
coleus extract, these amounts are extrapolations and have yet to be confirmed by direct
clinical research.12 Most studies have used injected forskolin, so it is unclear if
oral ingestion of coleus extracts will provide similar benefits in the amounts recommended
above. Until ophthalmic preparations of coleus or forskolin are available, people with
glaucoma should consult with a skilled healthcare practitioner to obtain a sterile fluid
extract for use in the eyes.
Are there any side effects or interactions?
Few adverse effects of coleus have been reported. It should be avoided in people with ulcers, because it may increase stomach acid
levels. Direct application to the eyes may cause transitory tearing, burning, and itching. The
safety of coleus in pregnancy and
breast-feeding is unknown.
Are there any drug
Certain medicines may interact with coleus. Refer to drug interactions for a list of those medicines.
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. Dubey MP, Srimal RC, Nityanand S, Dhawan BN. Pharmacological studies
on coleonol, a hypotensive diterpene from Coleus forskohlii. J Ethnopharmacol
2. Seamon KB, Daly JW. Forskolin: A unique diterpene activator of
cAMP-generating systems. J Cyclic Nucleotide Res 1981;7:201–24 [review].
3. Wysham DG, Brotherton AF, Heistad DD. Effects of forskolin on cerebral
blood flow: Implications for the role of adenylate cyclase. Stroke
4. Marone G, Columbo M, Triggiani M, et al. Forskolin inhibits the
release of histamine from human basophils and mast cells. Agents Actions
5. Roger PP, Servais P, Dumont JE. Regulation of dog thyroid epithelial
cell cycle by forskolin, an adenylate cyclase activator. Exp Cell Res
6. Wong S, Mok W, Phaneuf S, et al. Forskolin inhibits
platelet-activating factor binding to platelet receptors independently of adenylyl cyclase
activation. Eur J Pharmacol 1993;245:55–61.
7. Agarwal KC, Parks RE. Forskolin: A potential antimetastatic agent.
Int J Cancer 1983;32:801–4.
8. Caprioli J, Sears M. Forskolin lowers intraocular pressure in rabbits,
monkeys and man. Lancet 1983;1:958–60.
9. Badian M, Dabrowski J, Grigoleit HG, et al. Effect of forskolin eye
drops on intraocular pressure in healthy males. Klin Monatsbl Augenheilkd
1984;185:522–6 [in German].
10. Kramer W, Thormann J, Kindler M, Schlepper M. Effects of forskolin on
left ventricular function in dilated cardiomyopathy. Arzneim Forsch
11. Bauer K, Dietersdorfer F, Sertl K, et al. Pharmacodynamic effects of
inhaled dry powder formulations of fenoterol and colforsin in asthma. Clin Pharmacol
12. Bone K, Morgan M. Clinical Applications of Ayurvedic and Chinese
Herbs: Monographs for the Western Herbal Practitioner. Queensland, Australia:
Phytotherapy Press, 1996.
The information presented in Aisle7 is for informational purposes only.
It is based on scientific studies (human, animal, or in vitro), clinical experience,
or traditional usage as cited in each article. The results reported may not necessarily occur
in all individuals. For many of the conditions discussed, treatment with prescription or over
the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist
for any health problem and before using any supplements or before making any changes in