Effect of Lepidium meyenii (MACA) on sexual desireand its absent relationship with serum testosteronelevels in adult healthy men
G. F. Gonzales, A. Co´rdova, K. Vega, A. Chung, A. Villena, C. Go´n˜ez and S. Castillo
Instituto de Investigaciones de la Altura, and Department of Biological and Physiological Sciences (Faculty of Sciences andPhilosophy), Universidad Peruana Cayetano Heredia, Lima, Peru
Key words. Lepidium meyenii—men Maca—serum testosterone—sexual desire
ably the most commonly recognized and treated
blind placebo-controlled, randomized, parallel trial
sexual dysfunction. It affects more than 30% of men
in which active treatment with different doses of
aged 40–70 years (Feldman et al., 1994).
Maca Gelatinizada was compared with placebo.
Successful treatment of sexual dysfunction may
The study aimed to demonstrate if effect of Maca
not only improve sexual relationships, but also
on subjective report of sexual desire was because of
overall quality of life. Alternatives for treatment of
effect on mood or serum testosterone levels. Men
hypoactive sexual desire are scarcer. Testosterone is
aged 21–56 years received Maca in one of two
used because of its property to stimulate sexual
doses: 1500 mg or 3000 mg or placebo. Self-
desire in hypogonadal men (Matsumoto, 1994;
perception on sexual desire, score for Hamilton
Arver et al., 1996). Other compounds are potent
test for depression, and Hamilton test for anxiety
regulators of sexual behaviour in animals but not in
were measured at 4, 8 and 12 weeks of treatment.
An improvement in sexual desire was observed with
Despite the broad use of oral agents for erectile
Maca since 8 weeks of treatment. Serum testoster-
dysfunction (Boolell et al., 1996), and the use of
one and oestradiol levels were not different in men
testosterone for hypoactive sexual desire (Seidman,
treated with Maca and in those treated with
2000), many people in the world prefer the use of
placebo (P:NS). Logistic regression analysis showed
natural plants. Traditional herbs have been a
that Maca has an independent effect on sexual
revolutionary breakthrough in the management of
desire at 8 and 12 weeks of treatment, and this
erectile dysfunction and have become known world-
effect is not because of changes in either Hamilton
wide as treatment (Adimoelja, 2000). One example
scores for depression or anxiety or serum testoster-
is the broad use of ginseng because of its supposed
one and oestradiol levels. In conclusion, treatment
property to provoke sexuality (Kim et al., 1976).
More recently, aphrodisiac activity has been
described for the root of Lepidium meyenii (Maca), aPeruvian plant (Zheng et al., 2000; Cicero et al.,
2001). Additionally, a favorable effect on sperma-togenesis has been observed in adult male rats
Sexual function is an important component of
(Gonzales et al., 2001a) and in adult men (Gonzales
human quality of life and subjective well being.
et al., 2001b). Maca (L. meyenii) is a Peruvian
Sexual problems are widespread and adversely
hypocotyl which belongs to the Brassicaceae family
affect mood, well being, and interpersonal func-
and grows exclusively between 4000 and 4500-m
tioning (Laumann et al., 1999). Main sexual
altitude at the central Peruvian Andes. For centur-
problems are related to sexual desire and male
ies, it has been recognized traditionally for its
erectile dysfunction. Erectile dysfunction is prob-
properties to improve sexuality and fertility (seeObregon, 1998). Activity of the plant is located in
Correspondence: Gustavo F. Gonzales, Instituto de Investi-
the root. Actually, Maca is a commercially available
gaciones de la Altura, Universidad Peruana Cayetano Heredia,
product expended as a nutrient in different forms
Postal Office 1843, Lima, Peru. Fax 00 511 4821195; e-mail:[email protected]
including as tablets in the drugstore. Despite the
U.S. Copyright Clearance Center Code Statement: 0303-4569/2002/3406-0367 $ 15.00/0
spread use in Peru no scientific evidence exists that
(score ¼ 0), did not change (score ¼ 1), increased
mildly (score ¼ 3), or increased moderately to
The present study aimed to assess a role of Maca
for sexual desire and to determine if this effect isbecause of changes in mood or in serum testoster-
one and oestradiol levels in adult healthy men.
Mood was assessed using the Hamilton DepressionRating Scale (Mykletun et al., 2001), which has 17questions.
Anxiety was scored with the Hamilton Anxiety
Rating Scale (Lobo et al., 2002) which assesses
somatic and cognitive-affective aspects.
The study was a 12-week double-blind placebo-controlled, randomized, parallel trial in which two
doses of Maca Gelatinizada were orally adminis-tered and compared with the placebo.
Serum testosterone and oestradiol were determined
The Institutional Review Board of the Scientific
by radioimmunoassay (RIA) using an I125-testoster-
Research Office from the Universidad Peruana
one and I125-oestradiol, respectively, as radioactive
Cayetano Heredia approved the study.
marker. The assays have been performed usingcommercial kits (Diagnostic Products Co., LosAngeles, CA). All samples were run in a same
assay period. The within assay variation was 6.42%
Fifty-seven subjects (21–56 years) were included in
for oestradiol, and 5.5% for testosterone. Sensitivity
the study. All subjects were in apparently good
of testosterone assay was 4.0 pg ml)1 and that
health. Men were randomly placed in one of three
for oestradiol assay was 8.0 pg ml)1.
Two groups received active treatment whereas
the other group received placebo. For 12 weeks,one group (n ¼ 30) received three tablets of 500 mg
Data were analysed using the statistical package
each of gelatinized Maca (Maca Gelatinizada La
stata (version 7.0) for personal computer (Stata
Molina, Lima) per day (Maca 1.5 g). The second
Corporation, College Station, TX, USA).
group (n ¼ 15) received six daily tablets of gelatin-
Data are presented as frequencies. Data of serum
ized Maca (3000 mg) and it was defined as Maca
hormones were transformed to percentage. Data
3.0 g. The third group received tablets of placebo
were also analysed comparing Maca-treated groups
daily for the 12-week span in the same schedule as
with respect to placebo group. The differences
the Maca group. During the study, all men
between frequencies before and during treatment
maintained their usual eating regimen.
were assessed by the chi-squared test. Logistic
Most of the subjects did not smoke or use drugs
regression analysis was performed to assess the
for at least 3 months before study, nor did they use
independent effect of Maca on sexual desire after
controlling for scores of Hamilton Depression and
Laboratorios Hersil (Lima, Peru) provided the
Hamilton Anxiety test. For this analysis, sexual
tablets of gelatinized Maca (Maca Gelatinizada La
desire was the dependent variable, and it was
Molina). Each tablet contains 500 mg of dehydra-
dichotomized as follows: Values 0 and 1 were
recoded as 0 (no effect), and values 2 and 3 were
Venous blood samples were drawn after a 12-h
recoded as 1 (improvement in sexual desire). A
overnight fasting at 4, 8 and 12 weeks of treatment.
P < 0.05 was considered statistically significant.
Blood was centrifuged at 1000 g, and serum wascollected after centrifugation and kept frozen untilassayed for hormone measurements.
After 4 weeks of treatment, two men of the placebo
group reported that treatment increased sexual
Sexual desire was assessed using a subjective (self-
desire (16.6%), whereas at 8 and 12 weeks of
report) response about the effect of treatment on
treatment none of men from this group had
sexual desire at 4, 8 and 12 weeks of treatment. The
basal value (before treatment) was considered as 1.
In the Maca treated group, at 4 weeks, 24.4% of
Each subject was asked if treatment diminished
men manifested that treatment increased sexual
treated with Maca increased significantly the scorefor sexual desire at 4, 8 and 12 weeks of treatment(P < 0.01). However, when data in the Maca groupwere compared with placebo, the differences wereobserved at 8 and 12 weeks.
Multivariate analyses are shown in Tables 2–4.
Table 2 shows data observed at 4 weeks oftreatment. Treatment is assessed as dummy vari-able comparing the effect of Maca in relation toplacebo. Logistic regression analysis showed thatMaca had no effect on sexual desire. Scores ofdepression and anxiety tests and serum testosteroneand oestradiol levels were not related to sexualdesire in men. Tables 3 and 4 show data observedat 8 and 12 weeks of treatment with Maca (1.5 or3.0 g) or placebo. Treatment with Maca 1.5 g and
Prevalence of men whose treatment with placebo or
Maca 3.0 g are independent variables associated to
gelatinized Maca increased sexual desire. 4 weeks of treatment: P: NS
sexual desire at 8 and 12 weeks of treatment. No
(v2 ¼ 0.32); 8 weeks of treatment: P < 0.008 (v2 ¼ 7.01); 12 weeks oftreatment: P < 0.006 (v2
independent effect on sexual desire was observed
with score of neither depression and anxiety testsnor serum testosterone and oestradiol levels.
desire, whereas at 8 and 12 weeks of treatment, theprevalence of men manifesting increase of sexualdesire was 40.0 and 42.2%, respectively. Significant
differences between Maca-treated and placebo-treated
During the last decade an increase in the use of
(v2 ¼ 7.01; P < 0.008) and 12 weeks (v2 ¼ 7.6;
plants in metropolitan areas of developed countries
P < 0.006) of treatment (Fig. 1).
has been observed. A recent study in a metropolitan
Table 1 shows the scores for sexual desire
area of Minnesota demonstrates that herbs are used
measured as a subjective self report for the question
frequently to promote general health/well-being
if treatment had an effect on sexual desire. The
group treated with placebo did not change the score
Sexual difficulties are extremely prevalent among
for sexual desire (P:NS), whereas the overall group
both men and women (Leiblum, 1999). Plants are
Effect of different doses of Maca or placebo on self-report about effect of treatment on sexual desire in apparently healthy men
Data are mean ± standard error of mean (SEM).aP:NS; bP < 0.001 with respect to placebo. *P < 0.01 with respect to basal values (0 weeks).
Logistic regression analysis for the probablity that Maca, anxiety Hamilton score, depression Hamilton score, serum testosterone
and oestradiol levels affect self perception of improvement in sexual desire after 4 weeks of treatment
CI, confidence interval. Maca (1.5 or 3.0 g) were analysed as variable dummy with respect to placebo. Logistic Regression v2(6) ¼ 4.58; P > v2 ¼ 0.5984; Pseudo r2 ¼ 0.0755.
Logistic regression analysis for the probablity that Maca, anxiety Hamilton score, depression Hamilton score, serum testosterone
and oestradiol levels affect self perception of improvement in sexual desire after 8 weeks of treatment
Maca (1.5 or 3.0 g) were analysed as variable dummy with respect to placebo. Logistic Regression v2(6) ¼ 13.25; P > v2 ¼ 0.0393; Pseudo r2 ¼ 0.2382.
Logistic regression analysis for the probablity that Maca, anxiety Hamilton score, depression Hamilton score, serum testosterone
and oestradiol levels affect self perception of improvement in sexual desire after 12 weeks of treatment
Maca (1.5 or 3.0 g) were analysed as variable dummy with respect to placebo. Logistic Rregression v2(6) ¼ 16.12; P > v2 ¼ 0.0131; Pseudo r2 ¼ 0.2898.
extensively used to relieve sexual dysfunction, as it
Dharmasiri, 2000). Improvement of depression by
happens with ginseng, an essential constituent in
selective serotonin reuptake inhibitors in depressed
traditional Chinese medicine. At least six million
patients has been associated with improvement in
Americans use the root of this slow-growing
sexual functioning (Ekselitus & von Knorring, 2001;
Michelson et al., 2001). In this case, improvement in
The results of the present study demonstrate that
sexual desire was related to reversion of depression
another root, Maca (L. meyenii) which grows in the
rather than an effect of the increased serotonergic
central Andes of Peru in altitudes between 4000
activity, as serotonin stimulation inhibits sexual
and 4500 m may also improve sexual desire. In
fact, Maca (1.5 or 3.0 g day)1) administered orally
Maca is prescribed because of its supposed
in tablets during 12 weeks has a beneficial effect on
properties to decrease anxiety, depression, and
subjective sexual desire in adult healthy men. These
stress. However, the present study has demonstra-
data confirm results obtained in mice and rats
ted that the effect of Maca on sexual desire is
(Zheng et al., 2000; Cicero et al., 2001). Our results
independent of an effect on anxiety and/or depres-
demonstrate that effect of Maca in healthy men is
sion. Furthermore, improvement in sexual desire by
noticeable since 60 days of treatment. Certainly,
Maca was not related to any increase in serum
data at 30 days of treatment did not show differ-
testosterone or oestradiol levels. In fact, multivari-
ences between Maca treated men and placebo
ate analysis has demonstrated an effect of Maca on
sexual desire but this effect is independent of
We have not demonstrated a higher effect with
changes in scores for depression test, scores for
3.0 g compared to 1.5 g of Maca. We have not a
anxiety text, serum testosterone levels, and serum
clear explanation for this. Further studies will be
necessary to clarify a dose-response effect.
Effect of Maca on sexual desire could be because of
Sexual desire may be affected by behavioural
any unknown chemical signal, i.e., phyto-oestrogens.
depression, stress (Kumar et al., 2001), anxiety
Increase in serum testosterone levels in men with
(Rowland et al., 1987) and sedation (Ratnasooriya &
low desire by low serum testosterone levels resulted
in resumption of sexual activity (Jannini et al., 1999).
and the Universidad Peruana Cayetano Heredia
This is not the situation of our study as men were
apparently healthy. Brown et al., (1978) providedevidence that differences among men in circulatingtestosterone concentration within the normal range
do not account for differences in sexual activity andinterest. Ansong & Punwaney (1999) have studied
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BARRY H. SCHWAB, PH.D. EDUCATION Ph.D. Biostatistics, Medical College of Virginia, Richmond, Virginia, 1984 B.A. Statistics, State University of New York, College at Oneonta, 1980 Undergraduate Study Abroad, Tel Aviv University, Israel (1978 – 1979) EMPLOYMENT HISTORY 1984-present Janssen Research & Development, LLC (a J&J company) Vice President, Clinical
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