From horny goat weed to ginseng and
maca, over-the-counter dietary supplements sold to improve male sexual health
contain a wide variety of “natural” ingredients. Researchers from Wake Forest
Baptist Medical Center reviewed the scientific evidence for the most common
ingredients to determine if they are effective – and most importantly – safe.
The results are published online ahead of print in the Journal of Sexual
“While certain natural supplements we reviewed show promise for improving
mild sexual dysfunction, they lack robust human evidence,” said Ryan Terlecki,
M.D., associate professor of urology and senior author. “In addition, because
of concerns that some products are impure or weak, we do not routinely
recommend these products to our patients.”
For some products, there is no scientific evidence to support
claims that can positively impact erectile function, libido and sexual
performance. And perhaps most troubling, some products that are advertised as
being “natural,” contain traces of phosphodiesterase-5-inhibitors (PDE5Is), the
same class of medication that includes prescription drugs such as Viagra®,
used to treat erectile dysfunction. One study revealed that 81 percent of
tested samples of over-the-counter products purchased in the U.S. and Asia contained
“PDE5Is cannot yet be legally sold over the counter in this
country,” said Terlecki. “Men who use these medications without a physician’s supervision
run the risk of taking them inappropriately. Patients with advanced heart
disease, for example, or who take nitrates, such as nitroglycerin, should not
use PDE5Is as it may cause an unsafe drop in blood pressure. Likewise, men with
severe liver impairment or end-stage kidney
disease requiring dialysis should avoid these products.”
addition, Terlecki said, men with
enlarged prostates who take medications such as Flomax® (tamsulosin),
terazosin or doxazosin need to know how to time the dosing of the two
medications to avoid causing dizziness and potential falls, which may result in
An estimated 40 to 70 percent of men experience some form of
sexual dysfunction during their lives. Due to concern regarding costs of
prescription drugs, or embarrassment over discussing sexual concerns with their
physicians, some men turn to over-the-counter products. According to a recent
nationwide survey, 50 percent of respondents reported using dietary supplements
for a variety of conditions.
“There is a dizzying array of formulations available and the
health effects of nutraceuticals are often confusing to patients and medical
practitioners alike,” Terlecki said. “We reviewed the current evidence
available for each of the ingredients in top-selling men’s health products to
provide urologists with a guide they could use to counsel their patients.
“Patients are paying more than $5 per day to take products with no
proven effectiveness,” he said. Products included in the survey ranged in cost
from 83 cents to $5.77 per day.
In addition to the lack of scientific evidence for some products, Terlecki
noted that purity is also a concern. Because dietary supplements are currently
classified as foods, rather than drugs, it is the manufacturers themselves who
are largely responsible for ensuring the safety, purity and efficacy of the products.
Four major retailers have been targeted by the New York attorney general for
selling misleading supplements.
Below, the authors summarize some of the results of an extensive
literature search for ingredients in top-selling products:
DHEA seems relatively safe as the data
does not show a significant impact on hormone levels. The data is weak to
suggest a benefit.
Fenugreek is seen in about a third of the
top-selling men’s health supplements. One study noted a benefit in terms of
improving sexual arousal and orgasm, as well as muscle strength, energy and
well-being. There were no adverse events reported in that study and other
studies also show this to be a safe supplement.
Ginkgo Biloba has been marketed to treat
numerous conditions. There is no convincing data to support its use in men with
erectile dysfunction. It can cause headaches, seizures and significant
bleeding, especially if patients are taking Coumadin.
Ginseng is the most common ingredient in
top selling men’s health supplements. It can cause headache, upset stomach,
constipation, rash, insomnia and can lower blood sugar (caution in diabetics).
Horny Goat Weed is generally safe with rare
reports of toxicity (fast heart rate and hypomania). There is no evidence in
humans of benefit for sexual function.
L-arginine is the most common amino acid
seen in men’s health supplements, also in about a third of top sellers. It has
the theoretical potential to improve erectile function in some patients and
seems relatively safe. It has been associated, however with a drop in blood
pressure, but without a significant change in heart rate.
Maca is the most common vegetable
among top selling men’s health supplements. In animal research, use of maca was
associated with increased sexual behavior. There have been rare reports of toxicity,
such as mild increase in liver enzymes and blood pressure.
Tribulus: No evidence of benefit in
humans. Two reports of liver and kidney toxicity in young men taking high
Yohimbine has shown promise for improving
male sexual function in some studies. This drug has been used for a long time. It can cause
hypertension, headache, agitation, insomnia and sweating.
Zinc appears to be safe, but there is
no evidence of benefit in normal individuals. Zinc deficiency is very rare in
of the study were: Tao Cui, M.D., Robert C. Kovell, M.D., and David C. Brooks,
M.D, Ph.D,, Wake Forest Baptist.