פורום השבוע אינדקס אופנה יוגה גברים וצירים היום שאחרי הצילו צירים תזונה מאמרים חדשות ראשי

3/9/2002 08:51 Adi מאת: מנצלת את הכותרת לשלוח משהו אוף טופיק ל EFRAT L (אסידופילוס כמובן -מצורף סיכום ארוך) כותרת: כמו שראית התעוררה סקרנותי בנוגע לאותו אסידופילוס, המאמרים שהחברות מפנות אליהן ישנים ולכן בטח לא נימצאים און ליין. אבל ניכנסתי ללנצט (מספיק מכובד) והדבר הכי חדש שמצאתי שם הוא סיכום של מה שיודעים, לא יודעת אם יש לך גישה ללנצט און ליין אז העתקתי הנה, בבקשה: The UK launch in September of a "probiotic version" of an established multivitamin product epitomises what is wrong with the commercialisation of probiotics, says Gregor Reid of the Lawson Research Institute (London, Ontario, Canada). "Apparently, it's being promoted for use in irritable bowel syndrome, gut disorders, and thrush--the latter being a clever way of implying it prevents or treats yeast infections. Where is the scientific evidence for these stated or implied claims?", says Reid, who is investigating the use of probiotics to prevent urogenital infections and who reported on the scientific basis of probiotics at the International Congress on Microbial Ecology and Disease (San Francisco, CA, USA; Sept 23-24). "Probiotics have been reduced to a very naïve and simplistic level in order to market products, but we will never have good explanations of their health-giving potential until we know more about the normal intestinal microflora", adds Gerald Tannock (University of Otago, Dunedin, New Zealand), editor of Probiotics: A Critical Review (1999, Horizon Scientific Press, Norfolk, UK). The concept of probiotics--live microbial food ingredients that have a beneficial effect on human health --was first proposed in the early 1900s by Russian Nobel Prize winner Elie Metchnikoff who suggested that Bulgarian peasants lived long healthy lives because they consumed fermented milk products. Lactobacillus, he proposed, had a positive effect on the microflora of the colon, decreasing toxic microbial activities. Today, bifidobacterium, Escherichia coli, Saccharomyces boulardii, and enterococci are also being investigated for their probiotic potential. But although probiotics have been available commercially for years, data on their benefits are inconclusive, says Mary Ellen Sanders (California Polytechnic State University, San Luis Obispo, CA, USA). "There are too few properly controlled human trials", she says. "We know from studies in germ-free animals that the endogenous flora influences health but we still must find out if feeding healthy people exogenous microbes will be of benefit." Nevertheless, there is evidence that probiotics may be useful in some disorders. For example, there are data that indicate that consumption of an inoculum of 109-1010 specific probiotic bacteria per day can ameliorate the symptoms of bacterial antibiotic-associated diarrhoea, notes Richard Hull (Baylor College of Medicine, Houston, TX, USA). When taking antibiotics, he explains, "you lose a lot of normal flora, and if they are replaced by harmful bugs, or if there's a harmful bug already there and it can now bloom, then you get diarrhoea. Replacement of the normal flora with a temporary coloniser such as lactobacillus can stop the bad guys getting in". The "other side of probiotics", continues Hull, involves colonising a body site which is normally sterile, but prone to infection, to keep out harmful bacteria. This is the basis of his work in catheterised hospital patients who get frequent urinary tract infections. Hull and co-workers in Sweden gave eight women with recurrent infections a strain of E coli known to colonise the bladder without causing symptoms; the women remained symptom-free. In another study, says Hull, men treated similarly remained symptom-free for up to 3 years. The strategy could help people with spinal-cord injury, or frail elderly patients, but is not for prevention of infection in healthy adults, he says. "You don't want to take somebody with a sterile bladder and intentionally contaminate it." The rationale behind Hull's experiments is well rooted in science, but probiotics are being touted for many conditions besides infections. Data on the use of probiotics in cancer, hypertension, allergies, and immune function are "intriguing, but they are not comprehensive", says Sanders. And "none of the studies says anything about the value of probiotics in healthy adults", which is the main market for these products. "How do studies in Peruvian children with diarrhoea translate to a healthy 45-year-old woman taking the product?", she asks. And though some studies show that probiotic intake can increase phagocytic activity and cytokine concentrations, "does that mean people will get fewer colds? Or have a decreased risk of cancer? We simply don't know". Another worry is that probiotic products--eg, freeze-dried supplements, "enhanced" yoghurt--are not subject to stringent quality control and labelling standards, so "it's hard to know what you're buying", says Sanders. Most labels do not adequately identify the microbes in the product. And they give the number of viable cells at the time of manufacture, rather than at the expiry date. Many factors affect probiotic survival, she warns, so until full information is provided routinely for each product, doctors who suggest probiotics to their patients should contact the manufacturer and ask what is known about the product. Proposed pathways of action include inhibition of pathogen growth or colonisation, and stimulation of host immune responses, but the mechanisms need to be clarified, says Sanders. And, adds Tannock, probiotic effects, if any, generally last only as long as someone takes the product. "The concept of permanently changing the intestinal microflora is one we can forget about", he says. "We all have our own strains of bacteria, and though we probably share a core of bacterial species, there is tremendous variability from person to person." Tannock and his colleagues have shown that about 40-50% of people have a stable lactobacillus population. For these people, he says, "an exogenous strain probably won't influence their microflora very much. But other people have an unstable population and for them, it might be easier to get the probiotic strain to predominate". These findings, warns Tannock, mean it will be important to know which strains are native to individuals before exogenous strains are added. And, he notes, although the pathogenicity of lactobacilli is generally low, one case has been reported in which a probiotic lactobacillus was found associated with a liver abscess. "I used to say nobody's ever been harmed by a probiotic, so if you think it may be helpful, why not try it? But now I'd be a bit nervous if they were used by somebody with a serious disease without medical supervision." Marilynn Larkin תוכן התגובה: תגובות נוספות 3/9/2002  08:14 זה מעוגן בחוק, באיגוד הגנים הפרטיים יוכלו לאמר לך בדיוק - Adi 3/9/2002  10:32 אז לגבי האצידופילוס לא החכמנו הרבה....ומשהו שאני קראתי - סאלוש 3/9/2002  10:39 סאלוש, אני מאד אהבתי את הסיכום - Adi 3/9/2002  11:18 כן, גם אני... - סאלוש 3/9/2002  23:47 הי עדי, תודה רבה לך - Efrat_L

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