The first study to investigate the relationship
between eating fruit and vegetables containing
pesticide residues and the quality of men’s semen
has shown a link with lower sperm counts and
percentages of normally-formed sperm.
The study, which is published online today (Tuesday)
in Human Reproduction, one of the world’s leading
reproductive medicine journals, shows that men who
ate the highest amount of fruit and vegetables with
high levels of pesticide residue had a 49% lower
sperm count and a 32% lower percentage of
normally-formed sperm than men who consumed the
least amount. An accompanying editorial says the
findings have important implications for human
health.
However, the study of 155 men showed that, overall,
the total amount of fruit and vegetables consumed
was unrelated to changes in any measurements of
semen quality in the group as a whole.
Assistant Professor of Nutrition and Epidemiology at
the Harvard T.H. Chan School of Public Health in
Boston (USA), Jorge Chavarro, said: “These findings
should not discourage the consumption of fruit and
vegetables in general. In fact, we found that total
intake of fruit and vegetables was completely
unrelated to semen quality. This suggests that
implementing strategies specifically targeted at
avoiding pesticide residues, such as consuming
organically-grown produce or avoiding produce known
to have large amounts of residues, may be the way to
go.”
Previous studies have shown that occupational
exposure to pesticides might have an effect on semen
quality, but so far there has been little
investigation of the effects of pesticides in diet.
Prof Chavarro, his student Dr Yu-Han Chiu and
colleagues analysed 338 semen samples from 155 men
attending a fertility centre between 2007-2012 as
part of the ongoing, prospective “Environment and
Reproductive Health” (EARTH) Study. The men were
eligible for the study if they were aged 18-55, had
not had a vasectomy, and were part of a couple
planning to use their own eggs and sperm for
fertility treatment.
The men’s diet was assessed by means of a food
frequency questionnaire, and they were asked how
often, on average, they had consumed how many
portions of fruit and vegetables, using standard
portion sizes such as one apple, or half an avocado.
The fruit and vegetables were categorised as being
high, moderate or low in pesticide residues based on
data from the annual United States Department of
Agriculture Pesticide Data Program.
Fruit or vegetables that were low in pesticide
residues included peas, beans, grapefruit and
onions. Those that had high residues included
peppers, spinach, strawberries, apples and pears.
These data took account of usual practice in food
preparation, such as whether the fruit and
vegetables had been peeled and washed.
The researchers divided the men into four groups,
ranging from those who ate the greatest amount of
fruit and vegetables high in pesticides residues
(1.5 servings or more a day) to those who ate the
least amount (less than half a serving a day). They
also looked at men who ate fruit and vegetables with
low-to-moderate pesticide residues.
The group of men with the highest intake of
pesticide-heavy fruit and vegetables had an average
total sperm count of 86 million sperm per ejaculate
compared to men eating the least who had an average
of 171 million sperm per ejaculate – a 49%
reduction. The percentage of normally formed sperm
was an average of 7.5% in men in the group with the
lowest intake and 5.1% in the men with the highest
intake – a relative decrease of 32%.
There were no differences seen between men in the
four groups who consumed fruit and vegetables with
low-to-moderate pesticide residues.
In fact, there was a significant trend towards
having a higher percentage of normally shaped sperm
among men who consumed the most fruit and vegetables
with low pesticide residues – a relative increase of
37% from 5.7% to 7.8%.
The authors write in their paper: “To our knowledge,
this is the first report on the consumption of
fruits and vegetables with high levels of pesticide
residue in relation to semen quality.” They
continue: “These findings suggest that exposure to
pesticides used in agricultural production through
diet may be sufficient to affect spermatogenesis in
humans.”
However, they point out that there are a number of
limitations to the study and further research is
needed. “Studies of men presenting to fertility
clinics like this one do over-represent men with
semen quality problems. In our study almost half of
the men had one or more semen parameters below the
World Health Organization reference limits. Because
of this, it is not possible to know whether our
findings can be generalised to men in the general
population. In particular, it is difficult to get an
accurate picture of how large the effect in the
general population might be,” said Prof Chavarro.
In addition, diet was only assessed once and could
have changed over time. The researchers did not have
information on whether or not the food was grown
conventionally or organically, and the exposure to
pesticides could have been misclassified as it was
not measured precisely for every individual man.
In an accompanying editorial, Dr Hagai Levine,
Visiting Scientist, from Hebrew University-Hadassah,
Israel, and Professor Shanna Swan, Professor of
Preventive Medicine, who are both at the Icahn
School of Medicine at Mount Sinai, New York (USA),
write: “Despite the relatively small sample size and
exposure assessment limitations, the paper makes a
convincing case that dietary exposure to pesticides
can adversely impact semen quality. While this
finding will need to be replicated in other settings
and populations, it carries important health
implications.”
They point out that poor semen quality “is the
leading cause of unsuccessful attempts to achieve
pregnancy and one of the most common medical
problems among young men…it has been suggested as an
important marker of male health, predicting both
morbidity and mortality… it is sensitive to
environmental exposures, including endocrine
disrupting chemicals, heat and life-style factors,
such as diet…Therefore, it can provide a sensitive
marker of the impacts of modern environment on human
health.”
See also
Exposure to organochloride pesticides affects semen
quality (23/03/2011)
For more information
Is dietary pesticide exposure related to semen
quality? Positive evidence from men attending a
fertility clinic
Fruit and vegetable intake and their pesticide
residues in relation to semen quality among men from
a fertility clinic
MDN |