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Vlees en chemicaliŽn vervroegen puberteit bij meisjes
Uit twee studies blijkt dat zowel het eten van regelmatig vlees als ook de invloed van bepaalde chemicaliŽn kunnen leiden tot groeistoornissen en vervroegde puberteit bij meisjes. Uit een Engelse studie blijkt dat meisjes die veel vlees eten, gemiddeld genomen eerder in de puberteit komen. Meisjes die op jonge leeftijd veel vlees en eiwitten binnen krijgen, hebben een relatief grote kans om voor de eerste keer ongesteld te worden voordat ze de leeftijd van 12 jaar bereiken. Van de meisjes die op zevenjarige leeftijd gemiddeld meer dan 12 porties vlees per week eten hebben 75% meer kans dan zij die minder dan vier porties vlees per week eten. De onderzoekers kwamen tot hun bevindingen door de eetgewoontes van 3000 12-jarige meisjes te vergelijken. Uit eerdere studies blijkt dat ongesteldheid op jonge leeftijd gezondheidsrisico's met zich meebrengt. Zo zouden meisjes die vroeg ongesteld worden, later mogelijk een hogere kans hebben om borstkanker, diabetes en hartziektes te ontwikkelen. Uit een Amerikaanse studie blijkt dat blootstelling aan bepaalde chemicaliŽn zoals fenolen, ftalaten en Fyto-oestrogenen, die allen bekend staan als endocriene verstoorders die ingrijpen op het hormoonsysteem, ook tot groeistoornissen en vervroegde puberteit bij meisjes kan leiden. Deze chemicaliŽn worden in allerlei producten zoals nagellak, cosmetica, parfums, shampoo, zeep, als weekmaker in plastic en zelfs in medicijnen aangetroffen. In deze studie werden ruim 1.100 meisjes van 6-9 jaar onderzocht. Gekeken werd naar ruim 20 markers in de urine.
High meat diet 'linked to early periods'
Girls who eat a lot of meat during childhood tend to start their periods earlier than others, a study suggests.
UK researchers compared the diets of more than 3,000 12-year-old girls.
They found high meat consumption at age three (over eight portions a week) and age seven (12 portions) was strongly linked with early periods.
Writing in Public Health Nutrition, the researchers said a meat-rich diet might prepare the body for pregnancy, triggering an earlier puberty.
During the 20th Century, the average age at which girls started their periods fell fairly dramatically, although it now seems to be levelling off.
This is widely thought to be due to better nutrition and rising levels of obesity, which has an impact on hormones.
In the latest study, the team used data from a group of children followed from birth.
At the age of 12 years eight months, they split the girls into those who had already started their periods and those who had not.
Comparing their diets at the ages of three, seven and 10, they found that meat intake at a young age was strongly linked with earlier periods.
In fact, at age seven there was a 75% increased chance of having a period by age 12 in those eating the most meat compared with those who ate the least.
Although this finding was independent of body weight, the study repeated previous research showing that bigger girls tend to menstruate early.
Starting periods at an early age has been linked with an increased risk of breast cancer, possibly because women are exposed to higher levels of oestrogen over their lifetime.
But the researchers stressed there was no need for young girls to cut meat out of their diet as those with the highest meat consumption were eating a lot.
The seven-year-olds in the highest meat category were eating 12 or more portions a week, and the three-year-olds were having more than eight portions.
Girl eating hamburger Eating a lot of meat may promote good conditions for pregnancy
Study leader Dr Imogen Rogers, senior lecturer in human nutrition at the University of Brighton, said weight could not be the only factor in girls having periods earlier as the average age had not gone down further with increasing levels of obesity.
She added: "Meat is a good source of zinc and iron, requirements for which are high during pregnancy.
"A meat-rich diet could be seen as indicating suitable nutritional conditions for a successful pregnancy."
Dr Ken Ong, paediatric endocrinologist at the Medical Research Council, said there had been "vast shifts" in the timing of first periods over the past century.
He added that the link with meat consumption was a "plausible" one.
"This was not related to larger body size, but rather could be due to a more direct effect of dietary protein on the body's hormone levels."
Exposure To Three Classes Of Common Chemicals May Affect Female Development
Researchers at Mount Sinai School of Medicine have found that exposure to three common chemical classes phenols, phthalates and phytoestrogens in young girls may disrupt the timing of pubertal development, and put girls at risk for health complications later in life. The study, the first to examine the effects of these chemicals on pubertal development, is currently published online in the journal Environmental Health Perspectives.
"Research has shown that early pubertal development in girls can have adverse social and medical effects, including cancer and diabetes later in life," said Dr. Mary Wolff, Professor of Preventive Medicine and Oncological Sciences at Mount Sinai School of Medicine. "Our research shows a connection between chemicals that girls are exposed to on a daily basis and either delayed or early development. While more research is needed, these data are an important first step in continuing to evaluate the impact of these common environmental agents in putting girls at risk."
Phenols, phthalates and phytoestrogens are among chemicals known as endocrine disruptors, which interfere with the body's endocrine, or hormone, system. They are found in a wide range of consumer products, such as nail polishes, where they increase durability, and in cosmetics, perfumes, lotions, and shampoos, where they carry fragrance. Some are used to increase the flexibility and durability of plastics such as PVC, or are included as coatings on medications or nutritional supplements to make them timed-release.
Dr. Wolff, co-principal investigator Susan Teitelbaum, PhD, Associate Professor, Preventive Medicine, and their team from Mount Sinai's departments of Pediatrics and Microbiology recruited girls from the neighborhood of East Harlem, a unique minority population considered high risk. Working with Cincinnati Children's Hospital and Kaiser Permanente Northern California, they analyzed the impact of exposure to environmental agents in a study that included 1,151 girls from New York, greater Cincinnati and northern California.
The girls were between 6- and 8-years-old at enrollment and between 7 and 9 at analysis. Researchers collected urine samples from the study participants and analyzed them for phenols, phthalates, and phytoestrogens, including 19 separate urine biomarkers.
The data showed that the three classes of chemical compounds were widely detectable in the study population, and that high exposure to certain chemicals was associated with early breast development. The strongest links were seen with phthalates and phytoestrogens, which were also among the highest exposures. One phenol, two phytoestrogens, and a subset of phthalates (those found in building products and plastic tubing) were associated with later puberty. However, the phthalates found in personal products such as lotion and shampoo, especially those with fragrance, were related to earlier breast and pubic hair development.
"We believe that there are certain periods of vulnerability in the development of the mammary gland, and exposure to these chemicals may influence breast cancer risk in adulthood," Dr. Wolff continued. "Dietary habits may also have an impact. Further study is needed to determine how strong the link is."
Consistent with previous studies, researchers also found that body-mass index (BMI) played a role in the onset of puberty. About a third of the girls were considered overweight, which is also an indicator of early breast development. As a result, some of the chemical associations differed in more or less obese girls. Researchers continue to study the impact of diet on pubertal development and eventual breast cancer risk.
"Exposure to these chemicals is extremely common," Dr. Wolff continued. "As such, while the association between chemicals and pubertal development seems small, the impact on the overall population is significant."
Funding for the research was provided by a grant from the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH).
About The Mount Sinai Medical Center
The Mount Sinai Medical Center encompasses The Mount Sinai Hospital and Mount Sinai School of Medicine. The Mount Sinai Hospital is one of the nation's oldest, largest and most-respected voluntary hospitals. Founded in 1852, Mount Sinai today is a 1,171-bed tertiary-care teaching facility that is internationally acclaimed for excellence in clinical care. Last year, nearly 60,000 people were treated at Mount Sinai as inpatients, and there were nearly 450,000 outpatient visits to the Medical Center.
Mount Sinai School of Medicine is internationally recognized as a leader in groundbreaking clinical and basic science research, as well as having an innovative approach to medical education. With a faculty of more than 3,400 in 38 clinical and basic science departments and centers, Mount Sinai ranks among the top 20 medical schools in receipt of National Institute of Health (NIH) grants.
Source: The Mount Sinai Medical Center (Juni 2010)