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Published on Leave a comment on Good Reason To Eat Vegetables Daily

New research further confirms a link between higher lutein levels (as measured in the blood) and the preservation of "crystallized intelligence" in older adults.  Crystallized intelligence is the ability to use the skills and knowledge one has acquired over a lifetime. Lutein is in foods such as leafy green vegetables, cruciferous vegetables (broccoli, brussels sprouts, cauliflower, and cabbage) and egg yolks. Lutein is also found in small amounts in other fruits and vegetables. Bottom line: eat a variety of fresh fruits and vegetables daily. [Original study.]Medical Xpress:

Study links nutrition to brain health and intelligence in older adults

A study of older adults links consumption of a pigment found in leafy greens to the preservation of "crystallized intelligence," the ability to use the skills and knowledge one has acquired over a lifetime.

Lutein (LOO-teen) is one of several plant pigments that humans acquire through the diet, primarily by eating leafy green vegetables, cruciferous vegetables such as broccoli, or egg yolks, said University of Illinois graduate student Marta Zamroziewicz, who led the study with Illinois psychology professor Aron Barbey. Lutein accumulates in the brain, embedding in cell membranes, where it likely plays "a neuroprotective role," she said. "Previous studies have found that a person's lutein status is linked to cognitive performance across the lifespan," Zamroziewicz said. 

The study enrolled 122 healthy participants aged 65 to 75 who solved problems and answered questions on a standard test of crystallized intelligence. Researchers also collected blood samples to determine blood serum levels of lutein and imaged participants' brains using MRI to measure the volume of different brain structures. The team focused on parts of the temporal cortex, a brain region that other studies suggest plays a role in the preservation of crystallized intelligence.

The researchers found that participants with higher blood serum levels of lutein tended to do better on tests of crystallized intelligence. Serum lutein levels reflect only recent dietary intakes, Zamroziewicz said, but are associated with brain concentrations of lutein in older adults, which reflect long-term dietary intake. Those with higher serum lutein levels also tended to have thicker gray matter in the parahippocampal cortex, a brain region that, like crystallized intelligence, is preserved in healthy aging, the researchers report..... "Our findings do not demonstrate causality," Zamroziewicz said. "We did find that lutein is linked to crystallized intelligence through the parahippocampal cortex."

Published on Leave a comment on Are You Getting Enough Magnesium?

Magnesium is a mineral found in the human body that is necessary for good health. New research analysed 40 studies and found that a diet rich in magnesium is associated with a reduced risk of stroke, heart failure, diabetes, and death ("all cause mortality").

Even though there are many magnesium rich foods, it is estimated that many people don't get enough magnesium in the diet, especially if they eat a lot of processed, low-fiber foods. Current Recommended Dietary Allowances (RDAs) are 320 mg daily for adult females and 420 mg daily for adult males (NIH magnesium fact-sheets - here and here). Especially good sources of magnesium are green leafy vegetables, legumes (beans), nuts, seeds, chocolate, and whole grains. In general, foods containing dietary fiber provide magnesium.From EurekAlert:

Dietary magnesium associated with reduced risk of heart disease, stroke and diabetes

A diet rich in magnesium may reduce the risk of diseases including coronary heart disease, stroke and type-2 diabetes according to a new meta-analysis published in the open access journal BMC Medicine. This analysis of the evidence on dietary magnesium and health outcomes is the largest to date, involving data from more than one million people across nine countries.

The researchers, from Zhejiang University and Zhengzhou University in China, found that people in the highest category of dietary magnesium consumption had a 10% lower risk of coronary heart disease, 12% lower risk of stroke and a 26% lower risk of type-2 diabetes compared to those in the lowest category. Their results also indicate that an extra 100 mg per day of dietary magnesium could also reduce risk of stroke by 7% and type-2 diabetes by 19%.

Magnesium is vital for human health and normal biological functions including glucose metabolism, protein production and synthesis of nucleic acids such as DNA. Diet is the main source of magnesium as the element can be found in foods such as spices, nuts, beans, cocoa, whole grains and green leafy vegetables.

Original study. from BMC Medicine: Dietary magnesium intake and the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality: a dose–response meta-analysis of prospective cohort studies

Increasing dietary magnesium intake is associated with a reduced risk of stroke, heart failure, diabetes, and all-cause mortality, but not CHD [coronary heart disease] or total CVD [cardiovascular disease]. These findings support the notion that increasing dietary magnesium might provide health benefits....Magnesium is essential to all living organisms, as it controls the function of many crucial enzymes, including those that utilize or synthesize ATP ....

Published on Leave a comment on Baby Teethers Found To Contain BPA and Other Endocrine Disruptors

 Uh oh....A recent study found that every baby teether tested (and they tested 59 teethers), including all those labeled "BPA free", leached various parabens, bisphenols (including BPA or bisphenol A), and other endocrine disrupting chemicals. Infants chew and suck teethers to soothe the pain from their teeth emerging in the first year of life.

The researchers tested for 26 chemicals in three different types of teethers (solid plastic, gel-filled, and water-filled), and found parabens and bisphenols leaching from all of them. To see what leaches from the teethers, they placed the teethers into water - this is similar to what happens when babies mouth teethers and their saliva is exposed to chemicals in the teethers. The gel filled teethers leached the most chemicals overall. Even though 48 of the 59 teethers were labeled “BPA-free,” the results showed that the labels were misleading, because in this study BPA migrated (leached out) from all the teethers.

Endocrine disrupting chemicals can interfere with natural hormone function and are linked to a wide assortment of health problems (see posts on them). Even though the levels of the chemicals found were low, it is important to remember that effects from endocrine disrupting chemicals (hormone disruptors) are from very low levels. So exposing developing infants to these chemicals is of concern. What was disturbing is that these study results were far worse than a small study of teethers in Europe where the standards regarding endocrine disrupting chemicals are stricter than in the US. What should be done? Manufacturers should design products without using problem ingredients right from the start. Problem solved! From Science Daily:

Baby teethers soothe, but many contain low levels of BPA

Bisphenol-A (BPA), parabens and antimicrobials are widely used in personal care products and plastics. The U.S. and other governments have banned or restricted some of these compounds' use in certain products for babies and kids. But the compounds' presence in and leaching from teethers hasn't been thoroughly investigated. Now a study in the ACS journal Environmental Science & Technology reports that all tested plastic teethers contained BPA and other endocrine-disruptors that leached at low levels.

Studies have shown that in animals, endocrine-disrupting compounds (EDCs) -- which include BPA, parabens and antimicrobials -- can potentially interfere with hormones and have harmful developmental, reproductive and neurological effects. As a result, the European Commission in 2011 restricted the use of BPA in baby bottles. The U.S. followed suit a year later, banning it from baby bottles, and also from children's drinking cups....But very few if any studies have investigated whether the compounds are used to make teethers and if the compounds leach out of these products, which are designed to soothe babies' gums when their teeth come in. Kurunthachalam Kannan and colleagues wanted to see if the products contained EDCs and if the compounds could migrate out.

The researchers analyzed 59 solid, gel-filled or water-filled teethers purchased online in the U.S. for 26 potential endocrine-disrupting chemicals. Although most of the products were labeled BPA-free or non-toxic, all of them contained BPA. In addition, the researchers detected a range of different parabens and the antimicrobials triclosan and triclocarban in most of the teethers....Based on estimates of average use time and the body weight of a 12-month-old baby, calculations suggest that exposure to BPA and other regulated EDCs in teethers would be lower than the European standards for temporary tolerable daily intake levels. However, these thresholds are set for individual compounds. Current regulations do not account for the accumulation of multiple EDCs, note the researchers. Additionally, not all chemicals measured in the study are regulated.

Published on Leave a comment on A Daily Handful of Nuts Keeps the Doctor Away?

A large review of nut studies found that people eating a daily handful of nuts (about 20 g) have a lower risk of heart disease, cancer, stroke, premature death, and death from respiratory disease, type 2 diabetes, and infectious disease. Truly impressive. Benefits seem to be for all nuts, and also peanuts - which are called nuts, but are actually legumes (other posts about nut consumption benefits). An earlier post discussed how some of these effects could be to nuts lowering systemic inflammation throughout the body. Bottom line: try to eat a handful of nuts every day or most days a week for your health. And make it a variety of nuts - walnuts, almonds, hazelnuts, cashews, pistachios, pecans, Brazil nuts, and peanuts. From Science Daily:

A handful of nuts a day cuts the risk of a wide range of diseases

A large analysis of current research shows that people who eat at least 20g of nuts a day have a lower risk of heart disease, cancer and other diseases. The analysis of all current studies on nut consumption and disease risk has revealed that 20g a day -- equivalent to a handful -- can cut people's risk of coronary heart disease by nearly 30 percent, their risk of cancer by 15 percent, and their risk of premature death by 22 percent. An average of at least 20g of nut consumption was also associated with a reduced risk of dying from respiratory disease by about a half, and diabetes by nearly 40 percent, although the researchers note that there is less data about these diseases in relation to nut consumption.

The study, led by researchers from Imperial College London and the Norwegian University of Science and Technology, is published in the journal BMC Medicine. The research team analysed 29 published studies from around the world that involved up to 819,000 participants, including more than 12,000 cases of coronary heart disease, 9,000 cases of stroke, 18,000 cases of cardiovascular disease and cancer, and more than 85,000 deaths. While there was some variation between the populations that were studied....the researchers found that nut consumption was associated with a reduction in disease risk across most of them.

The study included all kinds of tree nuts, such as hazel nuts and walnuts, and also peanuts -- which are actually legumes. The results were in general similar whether total nut intake, tree nuts or peanuts were analysed. What makes nuts so potentially beneficial, said Aune, is their nutritional value: "Nuts and peanuts are high in fibre, magnesium, and polyunsaturated fats -- nutrients that are beneficial for cutting cardiovascular disease risk and which can reduce cholesterol levels. "Some nuts, particularly walnuts and pecan nuts are also high in antioxidants, which can fight oxidative stress and possibly reduce cancer risk. Even though nuts are quite high in fat, they are also high in fibre and protein, and there is some evidence that suggests nuts might actually reduce your risk of obesity over time."

The study also found that if people consumed on average more than 20g of nuts per day, there was little evidence of further improvement in health outcomes. [ORIGINAL STUDY]

Published on Leave a comment on Quitting Smoking Even Later In Life Reduces Risk of Death

Tobacco use is a leading cause of cancer and early death in the U.S. and throughout the world. According to a new study looking at people 70 years old and older, the good news is that quitting smoking at any time in life (even as late as the 60s) is better for immediate health and also reduces the risk of death.

The study compared people who had never smoked to people currently smoking - and found that in the 6 year follow up period current smokers were more than three times more likely to die than people who had never smoked. Furthermore, quitting smoking at any age was associated with a lower risk of death. Former smokers who quit smoking earlier in life received the largest benefit from quitting smoking. But even people who quit during their 60s were at substantially decreased risk of death (when compared to people who continued to smoke). Bottom line: It's never too late to quit smoking. But best is to never even start smoking. From MedicalXpress:

Quitting smoking at any age reduces the risk of death after 70

Tobacco use continues to be a major cause of cancer and premature death. Most studies of cigarette smoking and mortality have focused on middle-aged populations, with fewer studies examining the impact of tobacco cessation on disease and mortality risk among the elderly. A new study published in the American Journal of Preventive Medicine, found that people aged 70 or older currently smoking were more than three times more likely to die than never-smokers, while former smokers were less likely to die the sooner they quit.

Investigators reviewed data for more than 160,000 individuals aged 70 and over who participated in the NIH-AARP Diet and Health Study. They completed a questionnaire in 2004-2005 detailing their smoking use, and reported deaths were tracked until the end of 2011....For this study, participants still smoking in their 70s were identified as current smokers, and former smokers were classified by the decade of life when quitting. At the beginning of the study (2004-2005), the median age of participants was 75 years. Almost 56% were former smokers and 6% were current smokers. Males were less likely (31% vs 48% of females) to be never-smokers. 

During an average follow-up of 6.4 years, almost 16% of the participants died. While 12.1% of the never smokers died, 16.2%, 19.7%, 23.9%, and 27.9% of former smokers who quit between ages 30-39, 40-49, 50-59, and 60-69 years died, respectively. Current smokers fared the worst, with 33.1% dying. Mortality rates for women were lower than men at each level of smoking use.

"These data show that age at smoking initiation and cessation, both key components of smoking duration, are important predictors of mortality in U.S. adults aged 70 years and older," commented Dr. Nash. "In the NIH-AARP study population, younger age at initiation was associated with increased risk of mortality, highlighting the importance of youth and early-adult smoking on lifetime mortality risk, even among people who live to age 70 years. In addition, former smokers were at substantially reduced risk of mortality after age 70 years relative to current smokers, even those who quit in their 60s. These findings show that smoking cessation should be emphasized to all smokers, regardless of age."

Published on Leave a comment on Acetaminophen Is A Common Cause Of Liver Injury and Liver Failure

A recent article discussed the large assortment of medications (both prescription and non-prescription) that are linked to liver injury, commonly known as "Drug-induced liver injury" (DILI). While it occurs rarely (fewer than 10 in 10,000 persons who take the drug in question), many medications can result in liver injury - especially if taken in too large doses and for too long. The scary part is that 46% of people with acute liver failure in the U.S have the liver damage from acetaminophen. Acetaminophen is the main cause of drug induced liver injury and liver failure in the U.S. Acetaminophen is found not just in Tylenol, but in many non-prescription drugs - thus it is easy to take too large a dose. The liver helps remove toxins - thus we need to take good care of it. From Science Daily:

Acetaminophen, supplements and other medications may trigger drug-induced liver injury

More than 1,000 medications, with acetaminophen being the most common, have been associated with drug-induced liver injury (DILI). Diagnosis can be challenging due to the multitude of contributing factors, and timely recognition and clinical response may mean the difference between recovery and acute liver failure or even death. DILI affects an estimated fewer than 10 people in every 10,000 exposed persons. The condition is dose-dependent or an adverse reaction to a medication, dietary supplement or other substance. 

"The liver helps remove toxins, which makes it especially vulnerable to injury from either short-term intake above recommended levels or long-term usage that allows toxins to build up," Collins-Yoder said. "Recognizing the clinical signs and symptoms is crucial to prompt treatment and effective patient care." Depending on the contributing factors and the level of damage to the liver, patients with mild and moderate signs and symptoms may recover normal liver function after the triggering substance is identified and use is discontinued. Other patients may experience more severe damage, progressing to acute liver failure.

About 46 percent of persons with acute liver failure in the United States have liver damage associated with acetaminophen, making it the most common cause of DILI. Since acetaminophen is often an ingredient in over-the-counter and prescription pain medications, patients may take higher doses than needed. A more infrequent type of DILI is triggered by an adverse reaction to prescription medications, herbal dietary supplements or other substances, including: nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen, naproxen and others; antibiotics and antiviral agencies, such as amoxicillin-clavulanate, sulfamethoxazole-trimethoprim and nitrofurantoin; antileptic agents, such as volproic acid and carbamazepine; statins; novel anticoagulants; proton pump inhibitors; methotrexate; azathioprine; sulfasalazine; herbal and dietary supplements.

Published on Leave a comment on Is Autism Spectrum Disorder Linked To Pregnancy Flu Shots or The Flu?

A big concern nowadays is why some children develop autism, specifically autism spectrum disorder (ASD). Autism spectrum disorder is considered a life-long neurodevelopmental disorder that is thought to affect 1 out of 68 American children. While the causes of ASD are unknown in most cases, some studies report an association (higher risk) between a pregnant woman's infections and fever during pregnancy and risk of ASD in the baby, while other studies don't find such an association. Some studies also looked at the timing of infections during pregnancy, but again results have been mixed. A viral infection during the first trimester is associated with increased risk in some studies, while other studies report an increased risk with a second- or third-trimester bacterial infection.  So it has been unclear whether a flu (influenza) infection or flu vaccination during pregnancy is linked to autism spectrum disorder or not. Is there a link or not?

Why are pregnant women encouraged to get a flu shot (flu vaccine)? This is because pregnant women have an increased risk of complications from the flu infection. Studies also show that getting a flu vaccine during pregnancy reduces the risk of a preterm birth, a small-for gestational-age child, and a low-birth-weight child, and prevents influenza infection in newborns for up to 6 months.

The researchers of a large study done in California found no association between autism spectrum disorder (ASD) risk and flu (influenza) infection during pregnancy or flu (influenza) vaccination during the second to third trimester of pregnancy. However, there was a suggestion of increased ASD risk among children whose mothers received flu vaccinations during the first trimester (though the researchers say the association was perhaps due to "chance". Bottom line: the study results were reassuring for pregnant women, but if one wanted to be ultra-cautious, then delay getting a flu shot until the second trimester of pregnancy. From Science Daily:

No association between mother's flu in pregnancy, increased child autism risk

A study of more than 196,000 children found no association between a mother having an influenza infection anytime during pregnancy and an increased risk of autism spectrum disorders (ASDs) in children, according to a new study published online by JAMA Pediatrics. The study by Ousseny Zerbo, Ph.D., of Kaiser Permanente Northern California, Oakland, and coauthors included 196,929 children born in the health system from 2000 through 2010 at a gestational age of at least 24 weeks.

Within the group, there were 1,400 mothers (0.7 percent) diagnosed with influenza and 45,231 mothers (23 percent) who received an influenza vaccination during pregnancy. There were 3,101 children (1.6 percent) diagnosed with ASD. The authors report no association between increased risk of ASD and influenza vaccination during the second and third trimesters of pregnancy. There was a suggestion of increased risk of ASD with maternal vaccination in the first trimester but the authors explain the finding was likely due to chance because it was not statistically significant after adjusting for multiple comparisons. The study cannot establish causality and has several limitations, including ASD status determined by diagnoses on medical records and not validated by standardized clinical assessment for all cases. [Original study.]

Published on Leave a comment on Poor Diets May Lead To Vitamin C Deficiency

  It turns out that scurvy and vitamin C deficiency is still around these days. Scurvy is a disease resulting from a lack of vitamin C. Most animals can synthesize vitamin C, but not humans. We must eat foods containing vitamin C to get the vitamin.

Vitamin C deficiency results in defective formation of collagen and connective tissues (in our bones, skin, tendons, muscles), and symptoms may include weakness, feeling tired, curly hair, sore arms and legs, bruising, bleeding gums, and impaired wound healing.

A recent small Australian study looked at diabetic persons with chronic foot wounds (foot ulcers that didn't heal after several months). Their vitamin C levels were tested and if found to be low, then they were given vitamin C supplements of 500 or 1000 mg daily, and the result was that within 2 to 3 weeks the wounds were healed. The one person with a zinc deficiency was given 50 mg daily of zinc supplement and that wound also promptly healed.

Treatment of scurvy is by taking vitamin C supplements (the Mayo Clinic recommends taking 400 to 1000 milligrams of vitamin C  daily for one week). Vitamin C deficiency can be easily prevented by a diet that includes fruits and vegetables. The recommended daily intake for adult women is 75 milligrams and for adult men it is 90 milligrams, which can be easily met by eating fruits and vegetables, especially if they are fresh (uncooked).

Good sources of vitamin C include: oranges, lemons, kiwi fruit, black currants, papaya, guava, pineapple, mango, strawberries, and vegetables such as bell peppers (red, yellow, green), tomatoes, potatoes, kale, brussels sprouts, and broccoli. It is possible to be vitamin C deficient even if the person is of normal weight or overweight - it all comes down to the diet and whether fruits and vegetables are eaten. Bottom line: Eat some daily!

From Medical Xpress: Poor diet sees scurvy reappear in Australia

Scurvy, a disease historically associated with old-world sailors on long voyages, is making a surprise comeback in Australia, with health officials Tuesday revealing a rare spate of cases. Caused by vitamin C deficiency, the condition used to be a common—and often fatal—curse among seafarers who went months without fresh fruit and vegetables.  ...continue reading "Poor Diets May Lead To Vitamin C Deficiency"

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Published on 12 Comments on Is Garlic The Source Of Beneficial Lactobacillus Sakei in Kimchi?

As you may have noticed, I write about the beneficial bacteria Lactobacillus sakei a lot. This is because it has turned out to be a great treatment for both chronic and acute sinusitis for my family and others (see post The One Probiotic That Treats Sinusitis). We originally found it in kimchi (it occurs in the kimchi during normal fermentation), but not all kimchi brands. Kimchi is a mix of vegetables (including typically cabbage) and seasonings, which is then fermented for days or weeks before it is eaten.

Why is L. sakei found in some kimchi, but not all? Which vegetable or spice is needed or important for encouraging L. sakei growth? It turns out it is not the cabbage - which is why L. sakei is not normally found in sauerkraut.

A recent study looking at several kimchi samples found that garlic seems to be important for the development of various Lactobacillus bacteria, of which L. sakei is one. The results mean that raw garlic has very low levels of L. sakei, and it multiplies during kimchi fermentation. Note that as fermentation progresses, the bacterial species composition in the kimchi changes (this is called ecological succession).

Korean studies (here and here) have consistently found L. sakei in many brands of kimchi (especially from about day 14 to about 2 or 2 1/2 months of fermentation), but not all kimchi brands or recipes. L.sakei, of which there are many strains, is so beneficial because it "outcompetes other spoilage- or disease-causing microorganisms" and so prevents them from growing (see post).

Excerpts are from the blog site Microbial Menagerie: MICROBES AT WORK IN YOUR KIMCHI

Cabbage is chopped up into large pieces and soaked in salt water allowing the water to draw out from the cabbage. Other seasonings such as spices, herbs and aromatics are prepared. Ginger, onion, garlic, and chili pepper are commonly used. The seasonings and cabbage are mixed together. Now the kimchi is ready to ferment. The mixture is packed down in a glass container and covered with the brining liquid if needed. The kimchi sits at room temperature for 1-2 days for fermentation to take place....Kimchi does not use a starter culture, but is still able to ferment. Then where do the fermentation microbes come from?

Phylogenetic analysis based on 16S rRNA sequencing indicates that the kimchi microbiome is dominated by lactic acid bacteria (LAB) of the genus Leuconostoc, Lactobacillus, and Weissella. Kimchi relies on the native microbes of the ingredients. That is, the microbes naturally found on the ingredients. Because of this, there may be wide variations in the taste and texture of the final kimchi product depending on the source of the ingredients. In fact, a research group from Chung-Ang University acquired the same ingredients from different markets and sampled the bacterial communities within each of the ingredients. The group found a wide variability in the same ingredient when it was bought from different markets. Surprisingly, the cabbage was not the primary source of LAB. Instead, Lactic acid bacteria was found in high abundance in the garlic samples. 

Note that Lactobacillus sakei is an example of a lactic acid bacteria. More study details from  the Journal of Food Science: Source Tracking and Succession of Kimchi Lactic Acid Bacteria during Fermentation.

This study aimed at evaluating raw materials as potential lactic acid bacteria (LAB) sources for kimchi fermentation and investigating LAB successions during fermentation. The bacterial abundances and communities of five different sets of raw materials were investigated using plate-counting and pyrosequencing. LAB were found to be highly abundant in all garlic samples, suggesting that garlic may be a major LAB source for kimchi fermentation. LAB were observed in three and two out of five ginger and leek samples, respectively, indicating that they can also be potential important LAB sources. LAB were identified in only one cabbage sample with low abundance, suggesting that cabbage may not be an important LAB source.

Bacterial successions during fermentation in the five kimchi samples were investigated by community analysis using pyrosequencing. LAB communities in initial kimchi were similar to the combined LAB communities of individual raw materials, suggesting that kimchi LAB were derived from their raw materials. LAB community analyses showed that species in the genera Leuconostoc, Lactobacillus, and Weissella were key players in kimchi fermentation, but their successions during fermentation varied with the species, indicating that members of the key genera may have different acid tolerance or growth competitiveness depending on their respective species.

Although W. koreensis, Leu. mesenteroides, and Lb. sakei were not detected in the raw materials of kimchi samples D and E (indicating their very low abundances in raw materials), they were found to be predominant during the late fermentation period. Several previous studies have also reported that W. koreensis, Leu. mesenteroides, and L. sakei are the predominant kimchi LAB during fermentation (Jeong and others 2013a, 2013b; Jung and others 2011, 2012, 2013a, 2014). 

Published on Leave a comment on High Fiber Diet Protects The Colon’s Mucus Layer

An interesting study that showed that when gut microbes are deprived of dietary fiber (their food) they start to eat the natural layer of mucus that lines the colon. (The colon is part of the large intestine). This is important because the colon's mucus layer normally acts as a barrier to pathogenic microbes. Yes, it was done in mice, but the researchers feel that this study accurately models what also happens in humans. Their conclusion: when the microbes in the gut don't get enough dietary fiber from plants (such as whole grains, fruits, vegetables, seeds, nuts), then the microbes feed on the colon's mucus layer, which results in inflammation and makes the colon more vulnerable to pathogenic (disease causing) microbes. This is what some people refer to as "leaky gut".

Research shows that changes in the diet (high fiber vs low fiber) quickly results in changes in the gut microbes in humans and rodents - so it's important to consistently eat a lot of a variety of plant fiber. Currently the recommended daily fiber intake for adults is for 28 to 35 grams (chart of some high fiber foods). They found that some bacteria strains flourished the best in low or no fiber conditions and it was these bacteria that were involved in breaking down the mucus layer. The research also showed that what are called "prebiotics" (purified forms of soluble fiber similar to what some processed foods and supplements contain) also resulted in thinning of the colon's mucus layer - they did not properly feed the gut microbes. From Medical Xpress:

High-fiber diet keeps gut microbes from eating colon's lining, protects against infection

It sounds like the plot of a 1950s science fiction movie: normal, helpful bacteria that begin to eat their host from within, because they don't get what they want. But new research shows that's exactly what happens when microbes inside the digestive system don't get the natural fiber that they rely on for food. Starved, they begin to munch on the natural layer of mucus that lines the gut, eroding it to the point where dangerous invading bacteria can infect the colon wall. In a new paper in Cell, an international team of researchers show the impact of fiber deprivation on the guts of specially raised mice. The mice were born and raised with no gut microbes of their own, then received a transplant of 14 bacteria that normally grow in the human gut. 

The findings have implications for understanding not only the role of fiber in a normal diet, but also the potential of using fiber to counter the effects of digestive tract disorders. "The lesson we're learning from studying the interaction of fiber, gut microbes and the intestinal barrier system is that if you don't feed them, they can eat you," says Eric Martens, Ph.D., an associate professor of microbiology at the University of Michigan Medical School....Using U-M's special gnotobiotic, or germ-free, mouse facility, and advanced genetic techniques that allowed them to determine which bacteria were present and active under different conditions, they studied the impact of diets with different fiber content - and those with no fiber. They also infected some of the mice with a bacterial strain that does to mice what certain strains of Escherichia coli can do to humans - cause gut infections that lead to irritation, inflammation, diarrhea and more.

The result: the mucus layer stayed thick, and the infection didn't take full hold, in mice that received a diet that was about 15 percent fiber from minimally processed grains and plants. But when the researchers substituted a diet with no fiber in it, even for a few days, some of the microbes in their guts began to munch on the mucus.They also tried a diet that was rich in prebiotic fiber - purified forms of soluble fiber similar to what some processed foods and supplements currently contain. This diet resulted in the same erosion of the mucus layer as observed in the lack of fiber.

The researchers also saw that the mix of bacteria changed depending on what the mice were being fed, even day by day. Some species of bacteria in the transplanted microbiome were more common - meaning they had reproduced more - in low-fiber conditions, others in high-fiber conditions. And the four bacteria strains that flourished most in low-fiber and no-fiber conditions were the only ones that make enzymes that are capable of breaking down the long molecules called glycoproteins that make up the mucus layer....  Just like the mix of bacteria, the mix of enzymes changed depending on what the mice were being fed, with even occasional fiber deprivation leading to more production of mucus-degrading enzymes.

Images of the mucus layer, and the "goblet" cells of the colon wall that produce the mucus constantly, showed the layer was thinner the less fiber the mice received. While mucus is constantly being produced and degraded in a normal gut, the change in bacteria activity under the lowest-fiber conditions meant that the pace of eating was faster than the pace of production - almost like an overzealous harvesting of trees outpacing the planting of new ones. 

When the researchers infected the mice with Citrobacter rodentium - the E. coli-like bacteria - they observed that these dangerous bacteria flourished more in the guts of mice fed a fiber-free diet. Many of those mice began to show signs of illness and lost weight. When the scientists looked at samples of their gut tissue, they saw not only a much thinner or even patchy mucus later - they also saw inflammation across a wide area. Mice that had received a fiber-rich diet before being infected also had some inflammation but across a much smaller area. [Original study]

A thick mucus layer (green), generated by the cells of the colon's wall, provides protection against invading bacteria and other pathogens. This image of a mouse's colon shows the mucus (green) acting as a barrier for the "goblet" cells (blue) that produce it. Credit: University of Michigan