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Category: diabetes

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The study results of 218 overweight, postmenopausal women who had insufficient levels of vitamin D (like most people) at the beginning of the study found that weight loss (including exercise), in combination with vitamin D supplementation, had a greater effect on reducing chronic inflammation than weight loss alone.

Current thinking is that chronic inflammation is linked to various chronic diseases as well as cancers. So reducing chronic inflammation is good. From Medical Xpress:

Weight loss plus vitamin D reduces inflammation linked to cancer, chronic disease

For the first time, researchers at Fred Hutchinson Cancer Research Center have found that weight loss, in combination with vitamin D supplementation, has a greater effect on reducing chronic inflammation than weight loss alone. Chronic inflammation is known to contribute to the development and progression of several diseases, including some cancers.

"We know from our previous studies that by losing weight, people can reduce their overall levels of inflammation, and there is some evidence suggesting that taking vitamin D supplements can have a similar effect if one has insufficient levels of the nutrient," said lead and corresponding author Catherine Duggan, Ph.D., a principal staff scientist in the Public Health Sciences Division at Fred Hutch. 

To explore this question, Duggan and colleagues recruited 218 healthy, overweight older women who had lower-than-recommended levels of vitamin D (less than 32 ng/mL). The women then took part in a 12-month diet and exercise program (including 45 minutes of moderate-to-vigorous exercise five days a week). Half of the study participants were randomly selected to receive 2,000 IU of vitamin D daily for the duration of the year-long trial, and the other half received an identical-appearing placebo, or dummy vitamin. 

At the end of the study, all of the participants had reduced levels of inflammation, regardless of whether they took vitamin D, "which highlights the importance of weight loss in reducing inflammation," Duggan said. However, those who saw the most significant decline in markers of inflammation were those who took vitamin D and lost 5 to 10 percent of their baseline weight. These study participants had a 37 percent reduction in a pro-inflammatory cytokine called interleukin-6, or IL-6, as compared to those in the placebo group, who saw a 17.2 percent reduction in IL-6. The researchers found similar results among women in the vitamin D group who lost more than 10 percent of their starting weight. While IL-6 has normal functions in the body, elevated levels are associated with an increased risk of developing certain cancers and diabetes and may be implicated as a cause of depression, Duggan said.

Inflammation occurs when the body is exposed to pathogens, such as bacteria or viruses, which puts the immune system in overdrive until the "attack" ceases and the inflammatory response abates. Overweight or obese people, however, exist in a state of chronic inflammation. This sustained upregulation of the inflammatory response occurs because fat tissue continually produces cytokines, molecules that are usually only present for a short time, while the body is fighting infection, for example.

"It is thought that this state of chronic inflammation is pro-tumorigenic, that is, it encourages the growth of cancer cells," she said. There is also some evidence that increased body mass "dilutes" vitamin D, possibly by sequestering it in fat tissue."Weight loss reduces inflammation, and thus represents another mechanism for reducing cancer risk," Duggan said. "If ensuring that vitamin D levels are replete, or at an optimum level, can decrease inflammation over and above that of weight loss alone, that can be an important addition to the tools people can use to reduce their cancer risk."

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New research finding health benefits to humans from a four day low calorie diet - the Fasting Mimic Diet (FMD). Cutting calories to 34 to 54% of normal for a few days is obviously much easier to do than actual fastiing, so these results look very promising. In summary: the researchers found that in a small human trial, three cycles of this diet given to 19 subjects once a month for five days decreased risk factors and biomarkers for aging, diabetes, cardiovascular disease and cancer (and with no major adverse side effects). Three earlier posts on various types of minifasting health benefits: Minifasting May Benefit Health, Health Benefits of Feast and Famine Diet, Fasting and the Immune System. From Science Daily:

Diet that mimics fasting appears to slow aging

Want to lose abdominal fat, get smarter and live longer? New research led by USC's Valter Longo shows that periodically adopting a diet that mimics the effects of fasting may yield a wide range of health benefits. In a new study, Longo and his colleagues show that cycles of a four-day low-calorie diet that mimics fasting (FMD cut visceral belly fat and elevated the number of progenitor and stem cells in several organs of old mice -- including the brain, where it boosted neural regeneration and improved learning and memory.

The mouse tests were part of a three-tiered study on periodic fasting's effects -- testing yeast, mice and humans...Mice, which have relatively short life spans, provided details about fasting's lifelong effects. Yeast, which are simpler organisms, allowed Longo to uncover the biological mechanisms that fasting triggers at a cellular level. And a pilot study in humans found evidence that the mouse and yeast studies were applicable to humans.

In a pilot human trial, three cycles of a similar diet given to 19 subjects once a month for five days decreased risk factors and biomarkers for aging, diabetes, cardiovascular disease and cancer with no major adverse side effects, according to Longo.

The diet slashed the individual's caloric intake down to 34 to 54 percent of normal, with a specific composition of proteins, carbohydrates, fats and micronutrients. It decreased amounts of the hormone IGF-I, which is required during development to grow, but it is a promoter of aging and has been linked to cancer susceptibility. It also increased the amount of the hormone IGFBP-, and reduced biomarkers/risk factors linked to diabetes and cardiovascular disease, including glucose, trunk fat and C-reactive protein without negatively affecting muscle and bone mass.

Longo has previously shown how fasting can help starve out cancer cells while protecting immune and other cells from chemotherapy toxicity. 'It's about reprogramming the body so it enters a slower aging mode, but also rejuvenating it through stem cell-based regeneration,' Longo said. 'It's not a typical diet because it isn't something you need to stay on.'

For 25 days a month, study participants went back to their regular eating habits -- good or bad -- once they finished the treatment. They were not asked to change their diet and still saw positive changes. Longo believes that for most normal people, the FMD can be done every three to six months, depending on the abdominal circumference and health status. For obese subjects or those with elevated disease risk factors, the FMD could be recommended by the physician as often as once every two weeks. His group is testing its effect in a randomized clinical trial, which will be completed soon, with more than 70 subjects.

Despite its positive effects, Longo cautioned against water-only fasting and warned even about attempting the fasting mimicking diet without first consulting a doctor and seeking their supervision throughout the process....Longo also cautioned that diabetic subjects should not undergo either fasting or fasting mimicking diets while receiving insulin, metformin or similar drugs. He also said that subjects with body mass index less than 18 should not undergo the FMD diet.

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Stop drinking soda every day! Research finds that a daily sugar-sweetened beverage habit may increase the risk for non-alcoholic fatty liver disease (NAFLD). Earlier research has already linked daily sugar-sweetened beverages (typically soda) to type 2 diabetes and cardiovascular disease. And try to avoid high-fructose corn syrup in general (found in many highly processed foods) . From Medical Xpress:

Daily sugar-sweetened beverage habit linked to non-alcoholic fatty liver disease

A daily sugar-sweetened beverage habit may increase the risk for non-alcoholic fatty liver disease (NAFLD), researchers from the Jean Mayer USDA Human Nutrition Research Center on Aging (USDA HRNCA) at Tufts University report today in the Journal of Hepatology.

The researchers analyzed 2,634 self-reported dietary questionnaires from mostly Caucasian middle-aged men and women enrolled in the National Heart Lunch and Blood Institute (NHLBI) Framingham Heart Study's Offspring and Third Generation cohorts....The participants underwent a computed tomography (CT) scan to measure the amount of fat in the liver and the authors of the current study used a previously defined cut-point to identify NAFLD. They saw a higher prevalence of NAFLD among people who reported drinking more than one sugar-sweetened beverage per day compared to people who said they drank no sugar-sweetened beverages.

The relationships between sugar-sweetened beverages and NAFLD persisted after the authors accounted for age, sex, body mass index (BMI), and dietary and lifestyle factors such as calorie intake, alcohol, and smoking. In contrast, after accounting for these factors the authors found no association between diet cola and NAFLD.

NAFLD is characterized by an accumulation of fat in the liver cells that is unrelated to alcohol consumption. NAFLD is diagnosed by ultrasounds, CT, MRI, or biopsy, and many of the approximately 25% of Americans with the disease don't experience any symptoms. Being obese or overweight increases the risk for NAFLD and people with NAFLD are at greater risk of developing cardiovascular disease and type 2 diabetes.Sugar-sweetened beverages are a major dietary source of fructose, the sugar that is suspected of increasing risk of NAFLD because of how our bodies process it.

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People are correctly raising the issue of whether the positive results (less diabetic nerve pain in type 2 diabetics) are due to the weight loss or to the vegan diet (which caused the quick weight loss)? I suspect it's the average 15 pound weight loss, which lowers inflammation and improves blood flow to the feet. And substituting whole plant-based foods (fruits, vegetables, whole grains, etc) for unhealthy highly processed foods has many health benefits, including controlling blood sugar. They all took B12 supplements because: B12 is found naturally only in animal products, so it's lacking in vegan diets; the diabetic medicine metformin lowers B12 levels; and a deficiency in vitamin B12 can actually cause nerve damage. Bottom line which applies to both diabetics and non-diabetics: some weight loss is good (if overweight), as is increasing beans, nuts, whole grains, vegetables, fruit and plant-based oils in the diet. From Medical Xpress:

Vegan diet might ease diabetic nerve pain

A vegan diet might help people with diabetes-related nerve damage shed weight and find some pain relief, a small pilot study suggests. Vegan diets are free of all animal products, including eggs and dairy. Instead, people get their protein, fat and all other nutrients from foods such as beans, nuts, whole grains, vegetables, fruit and plant-based oils.

In the new study, researchers tested whether a vegan diet could help people with type 2 diabetes and painful nerve damage in their feet or hands. The investigators found that over 20 weeks, the 17 people they assigned to the diet lost an average of 15 pounds. At the same time, blood flow to their feet improved and their pain eased up.

But it's not clear that you have to go vegan to do that. "It's hard to say that it's this particular diet, itself," said Dr. Maria Pena, an endocrinologist and weight-management specialist at Lenox Hill Hospital in New York City..... Losing extra fat can decrease inflammation in the body, and improve a person's mobility—both of which could help ease diabetic nerve pain, she explained. Plus, Pena said, better blood sugar control is key to reducing diabetic nerve pain—and the vegan dieters in this study did rein their sugar levels in. That shows the all-plant diet had benefits, according to Pena. But, she said, any diet that encourages weight loss and replaces processed foods with healthy "whole" foods might do the same.

About half of all people with diabetes eventually develop nerve damage because of chronically high blood sugar levels, according to the U.S. National Institutes of Health.The nerve damage—known as neuropathy—can occur anywhere, but most often affects the feet and legs. It can trigger sharp pain, burning sensations, tingling or sensitivity to even a light touch; it also makes people susceptible to serious foot problems, including ulcers and infections.

For the study, Wells and her colleagues recruited 34 adults with type 2 diabetes and painful neuropathy. They randomly assigned half to follow a vegan diet and take a vitamin B12 supplement; the rest took the supplement but stuck with their normal diets. The dieters were told to limit themselves to 20 to 30 grams of fat per day, and to load up on "low GI" foods, which are foods that do not cause a large surge in blood sugar.Breakfast might include oatmeal with raisins, Wells said, while dinner could be lentil stew, or a vegetable stir-fry with rice. After about five months, the vegan group had lost 15 pounds, on average, versus about 1 pound in the comparison group. They also reported bigger improvements on a standard pain-rating survey.

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This study, like previous research, found an association between increased dietary fiber intake (specifically from cereal and vegetable fiber) and a reduced risk of developing type 2 diabetes. However, they did not find this link with fruit fiber, and also if the person was obese. From Medical Xpress;

Study adds to evidence that increasing dietary fiber reduces the risk of developing diabetes

New research published today in Diabetologia (the journal of the European Association for the Study of Diabetes) indicates that consuming greater quantities of dietary fiber reduces the risk of developing type 2 diabetes. In this article the authors evaluated the associations between total fiber as well as fiber from cereal, fruit, and vegetable sources, and new-onset type 2 diabetes in a large European cohort across eight countries, in the EPIC-InterAct Study.

The authors divided the study participants into four equally sized groups from lowest to highest fiber intake, and assessed their risk of developing type 2 diabetes over an average of 11 years' follow-up.They found that participants with the highest total fiber intake (more than 26 g/day) had an 18% lower risk of developing diabetes compared to those with the lowest total fiber intake (less than 19 g/day), after adjusting for the effect of other lifestyle and dietary factors. When the results were adjusted for body mass index (BMI) as a marker of obesity, higher total fiber intake was found to be no longer associated with a lower risk of developing diabetes, suggesting that the beneficial association with fiber intake may be mediated at least in part by BMI.

When the authors evaluated the different fiber sources, they found that cereal fiber had the strongest inverse association: those with the highest levels of cereal and vegetable fiber consumption had a 19% and 16% lower risk of developing diabetes respectively, compared with those with the lowest consumption of these types of fiber. Again, these associations disappeared when the results were adjusted for BMI. By contrast, fruit fiber was not associated with a reduction in diabetes risk. Cereals accounted for 38% of the total fiber intake, and were the main source of fiber in all the countries involved in the study (with the exception of France where vegetables were the main source).

The authors also undertook a meta-analysis, where they pooled the data from this EPIC-InterAct study with those from 18 other independent studies (eight in the United States, four in Europe, three in Australia, and three in Asia). The meta-analysis included over 41,000 new-onset cases of type 2 diabetes and found that the risk of diabetes fell by 9% for each 10 g/day increase in total fiber intake, and by 25% for each 10 g/day increase in cereal fiber intake. They did not find a statistically significant relationship between increasing either fruit or vegetable fiber and reducing diabetes risk.

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Controversy exists over whether healthy people should take statins because of possible side effects. This is another study finding a very elevated risk of new onset diabetes, high risk of diabetes complications, and obesity in statin users. This finding was also significant because the statins were given to healthy people (with no heart disease, diabetes, or severe chronic disease). Risks of diabetes, diabetes complications, and obesity were dose related. Statin users were also paired with similar non-statin users and then followed - thus the only differences between the 2 groups was whether they used statins. The researchers themselves write that when considering risks of statins, people should try for lifestyle changes (lose weight, eat healthy, exercise, stop smoking) rather than just rely on popping a pill. From Medical Xpress:

Strong statin-diabetes link seen in large study of Tricare patients

In a database study of nearly 26,000 beneficiaries of Tricare, the military health system, those taking statin drugs to control their cholesterol were 87 percent more likely to develop diabetes.

The study, reported online April 28, 2015, in the Journal of General Internal Medicine, confirms past findings on the link between the widely prescribed drugs and diabetes risk. But it is among the first to show the connection in a relatively healthy group of people. The study included only people who at baseline were free of heart disease, diabetes, and other severe chronic disease."In our study, statin use was associated with a significantly higher risk of new-onset diabetes, even in a very healthy population," says lead author Dr. Ishak Mansi. 

In the study, statin use was also associated with a "very high risk of diabetes complications," says Mansi. "This was never shown before." Among 3,351 pairs of similar patients—part of the overall study group—those patients on statins were 250 percent more likely than their non-statin-using counterparts to develop diabetes with complications. Statin users were also 14 percent more likely to become overweight or obese after being on the drugs....The study also found that the higher the dose of any of the statins, the greater the risk of diabetes, diabetes complications, and obesity.

A key strength of Mansi's study was the use of a research method known as propensity score matching. Out of the total study population, the researchers chose 3,351 statin users and paired them with non-users who were very similar, at baseline, based on array of 42 health and demographic factors. The only substantial difference, from a research standpoint, was the use of statins. This helped the researchers isolate the effects of the drugs.

On a wider scale, looking at the overall comparison between the study's roughly 22,000 nonusers and 4,000 users, and statistically adjusting for certain factors, the researchers found a similar outcome: Users of statins were more than twice as likely to develop diabetes.The researchers examined patient records for the period between October 2003 and March 2012. About three-quarters of the statin prescriptions in Mansi's data were for simvastatin, sold as Zocor.

"I myself am a firm believer that these medications are very valuable for patients when there are clear and strict indications for them," he says. "But knowing the risks may motivate a patient to quit smoking, rather than swallow a tablet, or to lose weight and exercise. Ideally, it is better to make those lifestyle changes and avoid taking statins if possible."

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The statements in this editorial may be obvious to many, but it is nicely written and needs to be said. Basically it says that exercise will not help you overcome the ill effects of a poor diet. I agree with what was said, but felt that what was missing was mention that a poor diet also has negative effects on the microbiome (the community of microbes living within the person) - which we know is linked to health problems.

From Medscape: Workouts Do Not Work Off Ill Effects of Poor Die

Exercise enthusiasts cannot work off the ill effects of an unhealthy diet, say the authors of an editorial published online April 22 in the British Journal of Sports Medicine. "Let us bust the myth of physical inactivity and obesity," the authors write. "You cannot outrun a bad diet."

Physical activity levels in Western nations have remained flat during the past 3 decades, even as obesity rates have exploded. That observation is just one sign that calories, not lack of exercise, are driving the obesity crisis, argue Aseem Malhotra, MD, honorary consultant cardiologist at Frimley Park Hospital, United Kingdom, and science director for Action on Sugar, United Kingdom, and colleagues.

"However, the obesity epidemic represents only the tip of a much larger iceberg of the adverse health consequences of poor diet," the authors write. They say that the Lancet global burden of disease reports concluded that poor diet contributes to more disease than a combination of inadequate physical activity, alcohol, and smoking. As many as 40% of people with normal body weight will suffer from metabolic abnormalities typically associated with obesity, the authors write, including hypertension, dyslipidemia, nonalcoholic fatty liver disease, and cardiovascular disease.

Dr Malhotra and colleagues blame food industry marketing for promoting exercise over diet, comparing food industry public relations with discredited tactics used by the tobacco industry in the past. They say Coca Cola "pushes the message that 'all calories count'; they associate their products with sport, suggesting it is ok to consume their drinks as long as you exercise. However science tells us this is misleading and wrong."

The kind of calorie matters too, they emphasize. Calories from sugar promote fat storage and hunger; fat calories induce satiety. For every 150 calories consumed from sugar, there is an 11-fold increase in the prevalence of type 2 diabetes independent of weight or physical activity levels compared with consumption of 150 calories of fat or protein.

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Note that both eggs and high-fat dairy products were basically considered evil by the medical establishment for many years. Remember egg white omelettes?And now both are thought to have health benefits, especially reducing the risk of diabetes. From Science Daily:

Eating eggs reduces risk of type 2 diabetes, study indicates

Egg consumption may reduce the risk of type 2 diabetes, according to new research...Research has shown that lifestyle habits, such as exercise and nutrition, play a crucial role in the development of the disease. A new study has found that egg consumption was associated with a lower risk of type 2 diabetes as well as with lower blood glucose levels. Men who ate approximately four eggs per week had a 37 per cent lower risk of type 2 diabetes than men who only ate approximately one egg per week. This association persisted even after possible confounding factors such as physical activity, body mass index, smoking and consumption of fruits and vegetables were taken into consideration. The consumption of more than four eggs did not bring any significant additional benefits.

The dietary habits of 2,332 men aged between 42 and 60 years were assessed at the baseline of the Kuopio Ischaemic Heart Disease Risk Factor Study, KIHD, at the University of Eastern Finland in 1984-1989. During a follow-up of 19.3 years, 432 men were diagnosed with type 2 diabetes.

Also note that high meat consumption is linked to higher risk of diabetes. From Science Daily:

High-fat dairy products linked to reduced type 2 diabetes risk

Consumption of high-fat yoghurt and cheese are linked to a reduction in the risk of type 2 diabetes by as much as a fifth, according to new research. High meat consumption, on the other hand, is linked to a higher risk.

However, the new study indicates that it is high-fat dairy products specifically that are associated with reduced risk."Those who ate the most high-fat dairy products had a 23 per cent lower risk of developing type 2 diabetes than those who ate the least. High meat consumption was linked to an increased risk of type 2 diabetes regardless of the fat content of the meat," said Ulrika Ericson, who conducted the study.

The researchers studied the eating habits of 27,000 individuals aged 45 to 74. The participants took part in the Malmö Diet and Cancer study in the early 1990s, in which they provided details of their eating habits. Twenty years on, over ten per cent -- 2 860 people -- had developed type 2 diabetes.

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The researchers think that repeated courses of antibiotics destroy the gut bacteria resulting in gut bacteria imbalance. From Red Orbit:

Antibiotic overuse could up diabetes risk, study says

Repeated use of some antibiotics could increase a person’s risk of developing type 2 diabetes, according to research published online Tuesday in the European Journal of Endocrinology. In the study, scientists from the University of Pennsylvania found that men and women who had ever been prescribed with at least two courses of specific types of antibiotics were more likely to eventually be diagnosed with type 2 diabetes than those who had taken no more than one.

The antibiotics used in the research came from one of four categories, according to LiveScience: penicillins, cephalosporins, quinolones and macrolides. The authors reviewed a database of UK patients, looking at the number of antibiotic prescriptions given to over 200,000 diabetic patients at least one year before those individuals were diagnosed with the condition...They found that the more courses of antibiotics that were prescribed to a person, the greater the risk that he or she would go on to develop the disease.

Patients who had been prescribed between two and five courses of penicillin increased their risk of diabetes by 8 percent, according to the Daily Mail, and the risk increased by 23 percent for those receiving more than five courses of the frequently used antibiotic versus the one- or no-course group.

Those who were given between two and five courses of quinolones, which are used to treat respiratory and urinary tract infections, had an increased diabetes risk of 15 percent, and those receiving more than five courses saw that risk shoot up by 37 percent. 

Those who were given just one course of antibiotics showed no such increase in diabetes risk, the researchers reported. Nor was there any link found between exposure to anti-virals and anti-fungals and diabetes risk. The reason for the association between frequent antibiotic use and the risk of diabetes is not clear, but may be related to a gut bacteria imbalance, they wrote.“Gut bacteria have been suggested to influence the mechanisms behind obesity, insulin resistance and diabetes in both animal and human models. Previous studies have shown that antibiotics can alter the digestive ecosystem,” added lead author Dr. Ben Boursi.

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Discussions of the benefits of dietary fiber seem to be everywhere this week.

From Forbes: Eat Whole Grains For A Long Life, New Study Says

Eating lots of whole grains – especially those high in cereal fiber – may help people live longer, according to new research. The study out in BMC Medicine this week suggests that eating hefty amounts of cereal fibers can help reduce the risk of death from a number of causes, including cancer and diabetes, by almost 20%. Previous research has certainly linked whole grains to the reduction of certain chronic diseases and to reduced mortality, but this one is the largest of its kind to show a reduction in death from a number of different causes. So if you want to live longer, grab a bowl of cereal. The less refined, the better.

Whole grains are grains in their most unadulterated form, still containing the endosperm, bran, and germ – most of the plant’s nutritional value lies in the bran and germ. When grains go through milling to become processed or refined, they’re typically stripped of the bran and germ parts, along with a number of B vitamins, fiber, and iron.

In the new study, the Harvard Medical School team tracked over 367,000 healthy people who were taking part in the NIH-AARP Diet and Health Study, for an average of 14 years. ..It turned out that people who ate more whole grains – 1.2 ounces of per day, on average – had a 17% reduced risk of death, compared to those who ate much less, around 0.13 ounces per day. And when it came to the cereal fiber itself, people who ate the most had a 19% reduced risk of death from any cause, compared to those who ate the least.

The researchers even broke it down by disease: People who ate the highest amounts of whole grains had a 48% reduced risk of death from diabetes, and an 11% reduced risk of dying from respiratory diseases. And people who ate the most cereal fiber had 15% and 34% reduced risk of death from cancer and diabetes, respectively. 

The study cannot of course determine causation, since it’s just observational...Still, a number of studies have pointed to a strong connection between whole grains and improved health and longevity in recent years. It may be the anti-inflammatory properties of fiber per se – and its effect of reducing c-reactive protein (CRP) and tumor necrosis factor – that are responsible for their health benefits. If you’re going to up your grain intake, make sure to choose whole ones, like steel cut oats, quinoa, or even whole grain bread, over refined ones like cereal flakes or white bread. 

From Scientific American: Fiber-Famished Gut Microbes Linked to Poor Health

Your gut is the site of constant turf wars. Hundreds of bacterial species—along with fungi, archaea and viruses—do battle daily, competing for resources. Some companies advocate for consuming more probiotics, live beneficial bacteria, to improve microbial communities in our gut, but more and more research supports the idea that the most powerful approach might be to better feed the good bacteria we already harbor. Their meal of choice? Fiber.  

Fiber has long been linked to better health, but new research shows how the gut microbiota might play a role in this pattern. One investigation discovered that adding more fiber to the diet can trigger a shift from a microbial profile linked to obesity to one correlated with a leaner physique. Another recent study shows that when microbes are starved of fiber, they can start to feed on the protective mucus lining of the gut, possibly triggering inflammation and disease.

"Diet is one of the most powerful tools we have for changing the microbiota," Justin Sonnenburg, a biologist at Stanford University, said earlier this month at a Keystone Symposia conference on the gut microbiome. "Dietary fiber and diversity of the microbiota complement each other for better health outcomes." In particular, beneficial microbes feast on fermentable fibers—which can come from various vegetables, whole grains and other foods—that resist digestion by human-made enzymes as they travel down the digestive tract. These fibers arrive in the large intestine relatively intact, ready to be devoured by our microbial multitudes. Microbes can extract the fiber's extra energy, nutrients, vitamins and other compounds for us. Short-chain fatty acids obtained from fiber are of particular interest, as they have been linked to improved immune function, decreased inflammation and protection against obesity.

Today's Western diet, however, is exceedingly fiber-poor by historical standards. It contains roughly 15 grams of fiber daily, Sonnenburg noted. For most of our early history as hunter-gatherers, we were likely eating close to 10 times that amount of fiber each day. "Imagine the effect that has on our microbiota over the course of our evolution," he said.

Not all helpful fiber, however, needs to come from the roots and roughage for which our ancestors foraged, new research suggests. Kelly Swanson, a professor of comparative nutrition at the University of Illinois at Urbana-Champaign, and his team found that simply adding a fiber-enriched snack bar to subjects' daily diets could swing microbial profiles in a matter of weeks... The findings were published in the January issue of the American Journal of Clinical Nutrition.

As gut microbes are starved of fermentable fiber, some do die off. Others, however, are able to switch to another food source in the gut: the mucus lining that helps keep the gut wall intact and free from infection. In a recent study presented at the Keystone meeting, Eric Martens of the University of Michigan Medical School, postdoctoral researcher Mahesh Desai and their colleagues found that this fuel switch had striking consequences in rodents. A group of mice fed a high-fiber diet had healthy gut lining, but for mice on a fiber-free diet, "the mucus layer becomes dramatically diminished," he explained at the meeting. This shift might sometimes have severe health consequences. Research by a Swedish team, published last year in the journal Gut, showed a link between bacteria penetrating the mucus layer and ulcerative colitis, a painful chronic bowel disease.

A third group of mice received high-fiber chow and fiber-free chow on alternating days—"like what we would do if we were being bad and eating McDonald's one day and eating our whole grains the next," Martens joked. Even the part-time high-fiber diet was not enough to keep guts healthy: these mice had a mucus layer about half the thickness of mice on the consistently high-fiber diet. If we can extend these results to humans, he said, it "tells us that even eating your whole fiber foods every other day is still not enough to protect you. You need to eat a high-fiber diet every day to keep a healthy gut." Along the same lines, Swanson's group found that the gut microbiomes of his adult subjects reverted back to initial profiles as soon as the high-fiber bars were discontinued.