نقص حمض الفوليك يزيد من فرص إنجاب طفل داون



كشفت دراسة، هي الاولى من نوعها في مصر، اجريت على أمهات الأطفال الداون باستخدام الهندسة الوراثية، ان نقص تناول الام الحامل للاغذية المحتوية على حمض الفوليك ـ متوافر في البقوليات ـ ادى الى زيادة نسبة الخلل في الانقسام الكرموزومي، الامر الذي ادى الى زيادة فرص انجاب طفل داون.

ويقول رئيس المركز القومي للبحوث الدكتور هاني الناظر لـ«الشرق الأوسط» ان طفل متلازمة «داون» يتميز بكبر حجم الرأس والتخلف العقلي، ويمثل مشكلة لدى العديد من الاسر، وانه امكن من خلال رسالة ماجستير بقسم بحوث الاطفال ذوي الاحتياجات الخاصة بالمركز، التوصل الى نتائج مهمة للغاية من خلال دراسة العوامل التي تؤدي الى زيادة نسبة انجاب طفل مصاب بمرض الداون من الامهات الصغيرات السن. واثبتت الدراسة عدم وجود طفرة في جين معين من الحمض النووي المستخرج من عينات الدم للامهات، وان هذه الطفرة لا تمثل عاملا مهما لزيادة نسبة انجاب طفل داون في الامهات المصريات، ولكن الشيء المهم الذي توصلت اليه الدراسة ان كمية حمض الفوليك الذي تناولته الامهات كان اقل من الكمية المطلوبة وذلك عند مقارنتها بالعينة الضابطة احصائيا، مؤكدا ان الدراسة اوصت بضرورة تغيير العادات الغذائية عند الامهات الحوامل والابتعاد عن تناول الوجبات السريعة والاهتمام بتناول الخضروات الورقية والبقوليات وفيتامين حمض الفوليك مع المتابعة الدقيقة لدى متخصص امراض نساء وولادة.
ويذكر الباحث المصري ان الدراسة حذرت من التعرض لدخان السجائر سواء بالتدخين المباشر او الجلوس مع مدخنين، وذلك للامهات الحوامل، حيث وجد ان هناك علاقة مباشرة بين التدخين وحدوث الخلل الكرموزومي، وقد اشرفت على هذه الدراسة الدكتورة نجوى عبد المجيد والدكتورة سعاد اسحق، وحصلت خلالها الطالبة علا حسني السيد على درجة الماجستير

الشرق الاوسط


التغذية السليمة للأم تمنع إصابة أطفالها بالإعاقة

واشنطن – العرب اونلاين – وكالات: فى دراسة جديدة نشرتها مجلة "التغذية" المتخصصة, كشف الباحثون عن أن استهلاك الأم للأطعمة الغنية بالعناصر الغذائية الضرورية كالحديد وحمض الفوليك خلال الشهر الأول من الحمل, قد يساعد فى حماية طفلها من الإصابة بمتلازم داون أو ما يعرف بالإعاقة المنغولية.
وأوضح الباحثون أن متلازم داون هو اضطراب تطورى ينتج عن خلل جينى فى الكروموسومات يؤدى إلى ظهور ثلاثة نسخ من كروموسوم 12 بدلا من وجود نسختين منه فقط, فيصاب الأطفال بملامح وجهية مميزة للمرض كالأنف الصغير المسطح وفم صغير وعيون جاحظة وآذان صغيرة, إضافة إلى التخلف العقلى والإعاقة الذهنية التى تتراوح فى شدتها من بسيطة إلى متوسطة, ويولد نصف الأطفال المصابين بهذا المتلازم مع مشكلات قلبية تتطلب تدخلا جراحيا, وقد يصاب الأشخاص أيضا بمشكلات فى السمع والبصر ونقص هرمونات الغدة الدرقية وإصابات انتانية متكررة, كما قد يواجهون خطرا أعلى للإصابة بسرطان الدم بحوالى 20 مرة من غيرهم.
وأشار الباحثون إلى أن خطر إنجاب طفل منغولى يزداد مع تقدم الأم فى السن, حيث تقل فرصة السيدة فى الخامسة والعشرين من عمرها, فى إنجاب طفل مصاب إلى حوالى واحد من كل ألف, بينما تزداد عند السيدة فى سن الخامسة والثلاثين لتبلغ واحدا من كل ,400 منبهين إلى أن الفحوصات التشخيصية والفحص الجنينى قد يساعد فى تحديد إصابة الطفل بالمرض قبل الولادة.
وبالرغم من أن الآلية الدقيقة التى تؤدى إلى حدوث خلل كروموسومى فى متلازم داون غير واضحة بعد, يعتقد الباحثون أن أخطاء معينة فى عمليات أيض حمض الفوليك قد تلعب دورا فى ذلك, لذا اعتمدت الدراسة الجديدة على تقييم تأثير استهلاك الأم لفيتامينات ومعادن معينة على نسبة الإصابة بمتلازم داون.
ووجد العلماء بعد مقارنة الاستهلاك الغذائى أثناء الحمل لعدد من أمهات أطفال مصابين بالمرض, وأمهات أطفال غير مصابين, أن فرصة إنجاب أطفال يعانون من الإعاقة المنغولية انخفضت بشكل كبير عند السيدات اللاتى تعاطين مكملات الحديد وحمض الفوليك فى الشهر الأول من الحمل, مقارنة باللاتى لم يتعاطين هذه العناصر, مشيرين إلى أن هذه المكملات لا تكون وقائية إذا تم تعاطيها بعد الشهر الأول, مما يدل على أن التغيرات الكروموسومية التى تؤدى إلى المرض تحدث بصورة مبكرة فى أول الحمل, لذا لابد من تعاطى العناصر الغذائية الوقائية فى ذلك الوقت فقط.
وتقترح النتائج أن استهلاك جرعات عالية من حمض الفوليك "6 - 10 ملليغرامات يوميا", يحمى أيضا من إصابة المواليد بالشفة المشقوقة وشقوق سقف الحلق, ولكن لابد من تعاطى مثل هذه الجرعات تحت إشراف الطبيب لأنها قد تؤدى إلى نقص الزنك.

FDA study finds possible link between Down syndrome
and lower maternal folic acid levels

A study funded by the Food and Drug Administration’s (FDA) Office of Women’s Health and conducted by FDA’s National Center for Toxicological Research (NCTR) has identified possible maternal risk factors for having a child with Down syndrome, a leading genetic cause of mental retardation that occurs in one out of every 700 live births. The preliminary study, published in the American Journal of Clinical Nutrition, found that mothers of children with Down syndrome show biochemical and genetic evidence of impaired folate metabolism.

"This study reflects the agency’s emphasis on state-of-the-art science as the basis for regulatory decisions," said Jane E. Henney, M.D., the Commissioner of Food and Drugs, "and lends additional support for the FDA’s March 1996 decision to require the fortification of certain grain products with folic acid."

Beginning in January 1998, FDA mandated the addition of 140 micrograms of folic acid, a B vitamin, to every 100 grams of certain grain products, such as flour, breakfast cereals, and pasta. This decision based on evidence that inadequate folate status in early pregnancy increases the risk of neural tube defects, was intended to reduce the incidence of birth defects in the brain and spinal cord in this country.

Down syndrome, or trisomy 21, is a complex genetic disease that is caused by an extra copy of chromosome 21. The origin of the extra chromosome is maternal in most cases and is due to an error in chromosome separation before conception. The results of the new study, led by S. Jill James, Ph.D., a biochemist at NCTR, indicated that mothers of children with Down syndrome have an imbalance in folate metabolism that may be explained, in part, by a common genetic variation in an enzyme involved in the folic acid pathway.

It is important to note that while this study may provide some new insights into possible causes of this disease, larger clinical studies will be necessary to confirm the NCTR findings and to definitively determine whether folic acid supplementation, at least 2 months before pregnancy, will reduce the incidence of Down Syndrome.

Source: U.S. Food and Drug Administration, September 28, 1999

http://www.fda.gov/bbs/topics/NEWS/NEW00690.html
http://medicalreporter.health.org/tm...nsyndrome.html



Folic acid may have no immediate impact on Down Syndrome

by Janet Wong

July 31, 2003 -- U of T researchers have found that fortifying foods with folic acid may not reduce the incidence of Down Syndrome. But they suggest we may to need to wait another 20 years or so for the next generation of women to give birth before the real answer is known.

Folic acid has been shown previously to dramatically decrease the incidence of neural tube defects (e.g. spina bifida) in newborns. Dr. Joel Ray, of the Departments of Medicine at U of T and St. Michael's Hospital, and co-researchers decided to examine the prevalence of Trisomy 21 (commonly known as Down Syndrome) following the introduction of folic acid fortification into most Canadian cereal grains by 1998. They examined prenatal and postnatal incidence rates of Trisomy 21 in Ontario, screening nearly 219,000 women prior to fortification and 118,000 women afterward. They found virtually no decline in the incidence of Trisomy 21 in relation to fortification.

However, Ray explains that folic acid and vitamin B12 are essential for the proper development of genes, which lie in chromosomes and are copied as cells divide. He says it's possible that part of the reason they saw no impact of folic acid fortification on Trisomy 21 rates is that the amount of folic acid intake was not high enough. But, he adds, another possibility may be that Trisomy 21 originates even before a woman is born.

"A woman's eggs are formed when she herself is a fetus in her mother's womb," says Ray. "So while taking folic acid may have no impact on the eggs of a woman now to prevent Trisomy 21, it may modify the eggs of her daughter to reduce the risk when she has her own child."

This research, published in the July 30 issue of the American Journal of Medical Genetics Part A, was supported by the Ontario Ministry of Health and Long-Term Care.

http://www.news.utoronto.ca/bin5/030731b.asp

Folic acid may help prevent Down Syndrome


A new study suggests women who don't metabolize folic acid
properly have a greater risk of having a Down syndrome child

September 29, 1999
Web posted at: 5:31 p.m. EDT (2131 GMT)

(CNN) -- Women with a genetic mutation which interferes with the body's ability to absorb folic acid are at higher risk for having children with Down syndrome, according to a study sponsored by the Food and Drug Administration (FDA). The results have researchers wondering if folic acid supplements can help reduce the risk of Down syndrome, as they reduce the risk of spina bifida.

The government study, published in the American Journal of Clinical Nutrition, found mothers who had trouble metabolizing folic acid were 2.6 times more likely to have a child with Down syndrome.

But FDA Commissioner Dr. Jane Henney said this research has provided only one clue to solving the mystery of Down syndrome. She pointed out that millions of women appear to have this genetic abnormality, but only a very small percentage have a child with Down syndrome. So it is not the genetic mutation alone which triggers the condition.

"There seems to be both a genetic issue here and nutritional issue here. And if the diet is high in folic acid then the opportunity for Down syndrome or the risk of Down syndrome appears to be less," Henney said.

Researchers studied 107 women whose average age was 30. Of those, 57 had given birth to a child with Down syndrome.

The FDA researchers did not give women any folic acid supplements, so they cannot predict if supplements would help reduce risk or in what doses they might help. They say treatment studies are needed to make these determinations.

If folic acid does prove helpful, women would need to take it well before they conceive.

"Folic acid is very important co-factor in how DNA works, how cells function. So there are many potential mechanisms for folate to work," said Dr. Kenneth Rosenbaum of Children's Hospital.

Folic acid, which is a B vitamin found in leafy green vegetables, beans, tuna, eggs and other foods, is already proven to help prevent neural tube defects such as spina bifida.

In 1996, the FDA recommended certain grain products including some cereals be fortified with folic acid. This latest study is b**** touted as further evidence its recommendations were well founded.

"This finding just adds support not only to the fortification plan , but that it might be helpful in other ways. And we will have to keep monitoring to see if that was the right amount of fortification," Henney said.

Down syndrome is a genetic disorder that combines metal retardation with physical abnormalities such as a broad, flat face and slanting eyes. Those with Down syndrome are at high risk of heart defects, visual or hearing problems and other health-related difficulties.

There are 250,000 Americans with the condition, according to March of Dimes estimates.

http://www.cnn.com/HEALTH/women/9909/29/folic.acid/



Folic Acid Also Helpful for Down's Syndrome Prevention



Women who are pregnant may be able to reduce their newborn’s risk of Down’s syndrome by taking folic acid before pregnancy, according to researchers.

Folic acid, found in supplements and foods such as broccoli, protects against neural-tube defects, and researchers have found that families with a high-risk of such defects may also be at an increased risk of Down’s syndrome, or vice versa.

There may be a link between the two conditions, so researchers suggest a dose of five mg of folic acid could reduce the risk of Down's syndrome as well the risk of neural-tube defects (NTD) in newborns.

NTDs, which are the abnormal development of the neural tube, which becomes the brain or spinal cord, in early pregnancy, can cause serious mental and physical impairment. Spina bifida and anencephaly, the partial or complete absence of the brain, are the most severe NTDs.

Mothers of babies with NTDs have been found to have problems metabolizing folic acid, which may also be a risk factor for trisomy 21, the chromosomal abnormality that causes Down’s syndrome.

In a study of 493 families who had had a previous pregnancy which was affected by NTD and 516 families who had had a pregnancy affected by Down's syndrome, there were five times the number of Down’s syndrome affected pregnancies among the NTD group as expected from women of the same age.

Further, there was an increase in NTD cases in the families at a higher risk of Down's syndrome.

Researchers recommend that women take extra folic acid before conception and in the first two months of pregnancy, saying that folate supplementation during this time has the potential to reduce the risk of Down's syndrome.

Lancet April 19, 2003;361:1331-35

http://www.mercola.com/2003/may/3/folic_acid.htm

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