Mehr Fernsehen macht weniger Spermien

Um 44 Prozent reduziert - Es kommt auf die körperliche Bewegung an

Mehr als 20 Stunden vor dem Fernseher pro Woche lässt bei 18- bis 22-jährigen Männern die Zahl der Spermien im Vergleich zu Altersgenossen mit geringer Zeit vor dem Bildschirm um 44 Prozent sinken. Umgekehrt treiben mehr als 15 Stunden moderaten bis intensiven Ausgleichssport bei Männern die Spermienanzahl um 73 Prozent in die Höhe - im Vergleich zu solchen, die sehr wenig Sport betreiben. Diese Ergebnisse haben US-Forscher im "British Medical Journal" veröffentlicht.

Untersucht wurden in der Studie 189 Männer aus Rochester im US-Staat New York. Es ging in der Studie von Audrey Jane Gaskins und Jorge Chavarro von der Harvard School of Public Health (Boston) um die Bestimmung des Einflusses eines sitzenden Lebensstils bei gesunden jungen Männern auf die Spermienqualität.

Je nach TV-, DVD- oder Videokonsum bzw. je nach dem zeitlichen Engagement beim Sport zeigten sich die Veränderungen bei der Zahl der Spermien, nicht aber bei ihrer Beweglichkeit und bei anderen Kriterien. Eine geringere Spermienzahl muss nicht unbedingt eine Einschränkung der Fertilität bedeuten. Mehr als die Hälfte der Probanden hatte Normalgewicht, drei Viertel waren Nichtraucher. (tha)

Quelle: British Medical Journal

LAS GRASAS SATURADAS DISMINUYE EN UN 41% EL NÚMERO DE ESPERMATOZOIDES

 25 Enero, 2013
Las grasas perjudican la calidad del esperma

El consumo de grasas saturadas disminuye en un 41 por ciento el número de espermatozoides y en un 38 por ciento el esperma, según ha mostrado un equipo de investigadores daneses de Rigshospitalet, en Copenhague (Dinamarca), liderados por Tina Jensen.

Para realizar este estudio, que ha sido publicado en The American Journal of Clinical Nutrition, los investigadores encuestaron y examinaron a 701 hombres jóvenes daneses de unos 20 años de edad y realizaron chequeos entre los años 2008 y 2010. A todos ellos, se les preguntó también sobre los alimentos que comían en los últimos tres meses, y se les pidió una muestra de semen. Posteriormente, dividieron los resultados en cuatro grupos, dependiendo de si la cantidad de la ingesta de energía consumida provenía de las grasas saturadas, y compararon la cantidad de esperma de los hombres de cada grupo.

De esta forma, los expertos comprobaron que aquellos que consumían menos de 11,2 por ciento de grasas saturadas tenían una concentración media de espermatozoides de 50 millones por mililitro de semen. «No podemos decir que tiene un efecto causal, pero creo que otros estudios han demostrado que la ingesta de grasa saturada ha demostrado una conexión a otros problemas y ahora también para el recuento de esperma», ha señalado Jensen.

Por debajo de lo normal

De hecho, la Organización Mundial de la Salud define como normal que los hombres tengan más de 15 millones de espermatozoides por mililitro de semen y, en este estudio, tanto el 13 por ciento de los hombres que pertenecían al grupo de menor contenido de grasa, como el 18 por ciento de los hombres del grupo de mayor contenido graso, se situaron por debajo de ese nivel.

No obstante, esta investigación no es la primera en la que se relaciona la dieta con la producción y calidad de espermatozoides, ya que en el año 2011 investigadores brasileños descubrieron que comer más granos -trigo, avena o cebada- está asociado a una mejor concentración y movilidad de espermatozoides, y que ingerir fruta aumenta la velocidad y la agilidad del esperma.

Otro trabajo, publicado en 2012 en Human Reproduction, mostró que los hombres con dietas más ricas en grasas tienen menos esperma y de peor calidad, mientras que aquellos que ingieren más alimentos con grasas polinsaturadas omega-3 -presentes en el pescado y el aceite- tienen un esperma de mejor calidad.

Sin embargo, ese estudio y la mayoría de los otros analizaron estas asociaciones en base a hombres que buscan tratamientos de fertilidad y que, por tanto, pueden no ser representativos de todos los hombres.

Identical twins start to differ in the womb, study shows

Dr Rebecca Hill Progress Educational Trust BioNews, London Despite sharing the same womb, identical twins are born with different alterations to their DNA that can affect the activity of individual genes. These modifications, known as epigenetic markers, are thought to be caused by environmental factors. The process adds chemical tags to the DNA, which alters a gene's activity, but not its sequence. Although previous studies have shown that identical twins do have different sets of epigenetic markers, it was thought that the changes occurred after birth, when the twins experience different environments. However, in this, the first analysis of the epigenetic profiles of newborn human babies, the team from Murdoch Children's Research Institute, Australia show that differences are already apparent straight after birth. 'Twins, like the rest of us, sit in their own amniotic sac and have their own individual experiences', lead researcher Dr Jeffrey Craig told International Business Times. The study, published in Genome Research, suggests that even small differences in womb environment, such as availability of nutrients or the influence of the placenta and umbilical cord, could be responsible. Dr Craig added: 'Sometimes one placenta could be in the best place in the womb, while the other twin might be shunted off to the side somewhere'. The results also showed that twins who shared a placenta were even more likely to be epigenetically different, potentially because the twins would have had to share the same source of nutrition, and so one would potentially get more than the other. The study, which analysed the umbilical cords, cord blood and placentas from 22 identical and 12 non-identical pairs of twins, showed that the epigenetic profiles of identical twins were more similar than those of non-identical twins. Additionally, differences in birth weight between the twins corresponded to differences in epigenetic markers on genes known to be associated with metabolism, growth and heart disease. Dr Karen Lillycrop, an epigeneticist at the University of Southampton, told Science News that current evidence suggests that 'in terms of metabolism these epigenetic changes can have very long-term effects'. Co-author Dr Richard Saffery hopes the work will add to our understanding of how epigenetic changes influence future health: 'This has potential to identify and track disease risk early in life, or even to modify risk through specific environmental or dietary interventions'.

Every sperm is special

Every sperm is special, genome sequencing shows

Antony Blackburn-Starza Progress Educational Trust 2 August 2012 Results of the first study to sequence the genomes of individual sperm cells obtained from one person have revealed significant genetic differences between them, confirming the belief that each sperm is unique. It is hoped the technique could be applied in fertility treatments to identify genetic mutations that may occur in the recombination process. 'For the first time we were able to generate an individual recombination map and mutation rate for each of several sperm from one person', said Professor Barry Behr from Stanford University in California, USA, who was involved in the study. 'Now we can look at a particular individual, make some calls about what they would likely contribute genetically to an embryo, and perhaps even diagnose or detect potential problems'. The team overcame significant technical obstacles to sequence each individual sperm cell, and by using a novel technique the researchers managed to separate 91 sperm cells and amplify their DNA for sequencing. The results showed that recombination - a naturally occurring process whereby chromosomes in the sperm are shuffled around during meiosis - was observed in unexpected places, suggesting this shuffling process is unique in each cell. The findings could explain why siblings have significant genetic differences between them, confirming the recombination process as being partly responsible for genetic diversity. Whereas previous studies have only looked at recombination across populations, this was the first study to observe the process in individuals. The team now hopes its findings can be applied to fertility treatments, with some commentators saying the technique could also be used to study cancer. Study leader Stephen Quake, professor of bioengineering at Stanford University, said: 'People have difficulty conceiving children due to reproductive disorders, and this will provide a very effective way to analyse when there are problems with their sperm'. Jianbin Wang, a member of Professor Quake's team, explained the technique could also be used to select eggs for IVF. 'We can use those cells to analyse an egg's genome, and screen for genetic diseases', he said. This would be an improvement on existing, more difficult techniques, explained the New Scientist. 'Our technique may make the process easier', said Wang. The research was published in the journal Cell.