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Standing by the counter at the pharmacist waiting to pick up my prescription, I couldn’t help noticing the prominent display of probiotics on the counter. It was two years ago, and I was reading everything I could find on microbiomes and probiotics – whether in books, journals or in shops – in preparation for writing my book The Microbiome: What Everyone Needs to Know…….Continue reading…
By: Berenice Langdon / The Conversation
Source: Popular Science
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Critics:
Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host interactions and unwanted side effects in rare cases. There is some evidence that probiotics are beneficial for some conditions, such as helping to ease some symptoms of irritable bowel syndrome (IBS).
However, many claimed health benefits, such as treating eczema, lack substantial scientific support. The first discovered probiotic was a certain strain of bacillus in Bulgarian yoghurt, called Lactobacillus bulgaricus. The discovery was made in 1905 by Bulgarian physician and microbiologist Stamen Grigorov.
The modern-day theory is generally attributed to Russian Nobel laureate Élie Metchnikoff, who postulated around 1907 that yoghurt-consuming Bulgarian peasants lived longer. A growing probiotics market has led to the need for stricter requirements for scientific substantiation of putative benefits conferred by microorganisms claimed to be probiotic.
Although some evidence claimed benefits are marketed towards using probiotic, such as reducing gastrointestinal discomfort, improving immune health, relieving constipation, or avoiding the common cold, such claims are strain-specific and cannot be extrapolated to other strains.
As of 2019, numerous applications for approval of health claims by European manufacturers of probiotic dietary supplements have been rejected by the European Food Safety Authority for insufficient evidence of beneficial mechanism or efficacy. Live probiotic cultures are part of fermented dairy products, other fermented foods, and probiotic-fortified foods.
Lactic acid bacteria (LABs), which are food fermenting bacteria, have the ability to prevent food spoilage and can improve the nutritive value of the foods they inhabit. Acid fermentation (as well as salting), remains one of the most practical methods of preservation of fresh vegetables, cereal gruels, and milk-cereal mixtures due to its low cost and energy requirements.
Fermented products that contain lactic acid bacteria include vegetables such as pickled vegetables, kimchi, pao cai, and sauerkraut; sourdough bread or bread-like products made without wheat or rye flour, amino acid/peptide meat-flavored sauces and pastes produced by fermentation of cereals and legumes; fermented cereal-fish-shrimp mixtures and fermented meats.
soy products such as tempeh, miso, and soy sauce; dairy products such as yogurt, kefir, buttermilk; and non-dairy products such as bee pollen. More precisely, sauerkraut contains the bacteria Leuconostoc mesenteroides, Lactobacillus plantarum, Pediococcus pentosaceus, Lactobacillus brevis, Leuconostoc citreum, Leuconostoc argentinum, Lactobacillus paraplantarum, Lactobacillus coryniformis, and Weissella spp. Kimchi contains the bacteria Leuconostoc spp.
bulgaricus, Lactobacillus helveticus, Lactobacillus kefiranofaciens, Lactococcus lactis, and Leuconostoc species. Buttermilk contains either Lactococcus lactis or L. bulgaricus. Other acidic bacteria, said to be probiotic,can be found in kombucha, including Gluconacetobacter xylinus, Zygosaccharomyces sp., Acetobacter pasteurianus, Acetobacter aceti, and Gluconobacter oxydans.
The manipulation of the gut microbiota is complex and may cause bacteria-host interactions. Though probiotics are considered safe, some have concerns about their safety in certain cases. Some people, such as those with immunodeficiency, short bowel syndrome, central venous catheters, and cardiac valve disease, and premature infants, may be at higher risk for adverse events.
In severely ill people with inflammatory bowel disease, a risk exists for the passage of viable bacteria from the gastrointestinal tract to the internal organs (bacterial translocation) as a consequence of bacteremia, which can cause adverse health consequences. Rarely, consumption of probiotics by children with lowered immune system function or who are already critically ill may result in bacteremia or fungemia (i.e., bacteria or fungi in the blood), which can lead to sepsis, a potentially fatal disease.
Probiotic supplements typically contain between one and ten billion colony-forming units (CFUs) per dose. A higher number of CFUs does not provide additional probiotic effects, but may have unintended consequences of causing digestive discomfort, such as bloating, gas, and diarrhea. Lactobacillus species have been suggested to contribute to obesity in humans, but no evidence of this relationship has been found.
As food products or dietary supplements, probiotics are under preliminary research to evaluate if they provide any effect on health. In all cases proposed as health claims to the European Food Safety Authority, the scientific evidence remains insufficient to prove a cause-and-effect relationship between consumption of probiotic products and any health benefit. There is no scientific basis for extrapolating an effect from a tested strain to an untested strain. Improved health through gut flora modulation appears to be directly related to long-term dietary changes.
Claims that some lactobacilli may contribute to weight gain in some humans remain controversial.Only limited, low-quality evidence exists to indicate that probiotics are helpful for treating people with milk allergy. A 2015 review showed low-quality evidence that probiotics given directly to infants with eczema, or in infants whose mothers used probiotics during the last trimester of pregnancy and breastfeeding, had lower risk of eczema.
Antibiotics are a common treatment for children, with 11% to 40% of antibiotic-treated children developing diarrhea. Antibiotic-associated diarrhea (AAD) results from an imbalance in the colonic microbiota caused by antibiotic therapy. These microbial community alterations result in changes in carbohydrate metabolism, with decreased short-chain fatty acid absorption and osmotic diarrhea as a result. A 2015 Cochrane review concluded that a protective effect of some probiotics existed for AAD in children.
The known risks of using probiotics for treating Clostridium difficile outweighs the uncertain benefits. Probiotic treatment might reduce the incidence and severity of AAD as indicated in several meta-analyses. For example, treatment with probiotic formulations including L. rhamnosus may reduce the risk of AAD, improve stool consistency during antibiotic therapy, and enhance the immune response after vaccination.
The potential efficacy of probiotics to treat AAD depends on the probiotic strains and dosage. One review recommended for children L. rhamnosus or Saccharomyces boulardii at 5 to 40 billion colony-forming units/day, given the modest number needed to treat and the likelihood that adverse events are very rare. The same review stated that probiotic use should be avoided in pediatric populations at risk for adverse events, such as severely debilitated or immune-compromised children.
Why prebiotics are as essential as probiotics for gut health
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