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This interesting study raises the possibility that eating certain foods or probiotics  (beneficial bacteria) may prevent diabetes. Note that Akkermansia is a bacteria with one species Akkermansia muciniphila . In Wikipedia:"Researchers have discovered that Akkermansia muciniphila may be able to be used to combat obesity and type 2 diabetes...The bacterium is naturally present in the human digestive tract at 3-5%, but has been seen to fall with obesity." Regarding Prevotella, in Wikipedia: "Studies also indicate that long-term diet is strongly associated with the gut microbiome composition—those who eat plenty of protein and animal fats typical of Western diet have predominantly Bacteroides bacteria, while for those who consume more carbohydrates, especially fiber, the Prevotella species dominate." From Science Daily:

Gut bacteria may contribute to diabetes in black males

African American men at elevated risk for developing type 2 diabetes may have fewer beneficial and more harmful intestinal bacteria, according to new research.

"The 'signature' of the gut microbiota -- the relative abundance of various bacteria and other microbes in the digestive system -- could be another useful tool in assessing a person's risk for developing diabetes," said Ciubotaru. Ciubotaru and her colleagues, including principal investigator Dr. Elena Barengolts,... found that a specific microbiota is associated with stable, normal blood glucose levels, while a different profile is associated with glucose levels that indicate pre-diabetes.

"The study provides additional reasons for physicians to recommend foods, such as prebiotics, which improve the growth and activity of helpful gut bacteria," said Barengolts. The gut microbiota helps digest food; fights infections; and plays an important role in keeping the immune system healthy. It is greatly influenced by genetics, diet and other environmental factors. Previous research has implicated an unhealthy or unbalanced microbiota as a contributing factor to metabolic disorders, including obesity and diabetes. The species that make up an individual's gut microbiota, as well as their abundance, can be identified by stool sample analysis.

The researchers determined the gut microbiotas of 116 African-American male veterans, age 45 to 75, participating in the D Vitamin Intervention in VA, or DIVA study. The aim of the DIVA study, which has 173 total participants and is funded by the Department of Veterans Affairs, is to determine if vitamin D supplementation can prevent diabetes in men with risk factors for developing the disease.

Participants were divided into four groups based on changes in their blood sugar levels as determined at the start and end of the one-year study. The groups included men whose glucose levels remained normal (non-pre-diabetic); those with stable levels indicative of pre-diabetes; those whose levels indicated a worsening of glucose control; and those whose levels improved. All the men provided stool samples for analysis of their gut microbiota.

Men whose blood sugar levels stayed normal over the year had more gut bacteria that are considered beneficial for metabolic health, whereas those who stayed pre-diabetic had fewer beneficial bacteria and more harmful bacteria. In addition, the group whose levels improved had more abundant Akkermansia--healthy bacteria--than the group that maintained normal blood sugar control throughout the year.

The study suggests that differences in the gut microbiota already exist in pre-diabetes, Barengolts said. Although the study found connections between composition of the gut microbiota and blood sugar control, Barengolts said further research is needed to confirm these findings and evaluate whether certain intestinal bacteria cause type 2 diabetes. However, based on other research her group has conducted and studies in animals, she speculated that the foods we eat affect our diabetes risk through our gut microbiota. If the mix of organisms in the intestinal tract is indeed responsible for the development of type 2 diabetes, she said, it may be possible to lower one's risk by changing the gut bacteria.

More details about that same study. From Medpage Today:

Prediabetes Patients Have Fewer Gut Bugs

They were put into one of four groups: those with a stable glucose tolerance, those with stable impaired fasting glucose or stable impaired glucose tolerance, those with worsened glucose tolerance, and those with improved glucose tolerance. There were significant differences in bacterial composition between the first and second groups (P=0.03) at the phylum level. Bacteroidetes was higher and Firmicutes was lower with worse glycemic control in the second group. 

Proteobacteria decreased over the period in groups 2 and 4 compared with group 1 (P=0.04 for both). At the family and genus levels, in group 2 versus group 1 there was less Prevotella, and a higher Bacteroides/Prevotella ratio in the second group at 5.6 to 2.7 (P=0.05). There was also less Enterobacteriaceae (P=0.03), and more Ruminococcae (P=0.01) and Veillonellaceae (P=0.02).

"We speculate that lower abundance of Prevotella may be associated with worsening glycemia, and, conversely, higher abundance of Akkermansia might be associated with improving glycemia, thus corroborating suggestions from previous studies," the researchers said.

Bottom line: try not to eat processed sweetened foods or drink sodas because high intake is linked to type 2 diabetes. Several studies point the finger in particular to high fructose corn syrup, which is the most frequently used sweetener in processed foods, particularly fruit-flavored drinks and soda. An earlier 2013 study from Europe found that drinking one 12-ounce sugar-sweetened soft drink a day can increase the risk of type 2 diabetes by 22%. Instead eat real whole foods like fruits and vegetables. From Medscape:

Added Sweeteners in Processed Foods Tied to Diabetes

A large body of evidence from animal studies and observational and clinical trials in humans suggests that eating processed foods with added sweeteners is contributing to the growing incidence of type 2 diabetes, a new review, published online January 29 in the Mayo Clinic Proceedings, concludes. Thus, "by limiting sugar to 5% to 10% of total caloric intake, the harmful effects of sugar, particularly fructose, on insulin resistance could be minimized," he and his colleagues conclude. This in turn "may protect against diabetes and its complications, including early mortality from cardiovascular causes."

About three-quarters of all packaged foods and beverages in the US contain added sugar, and it is estimated that Americans eat up to 22 to 47 teaspoons of sugar a day, including hidden sugar in processed foods, Dr DiNicolantonio said.

"High intakes of added sugars, especially in the form of sugar-sweetened beverages, are associated with an increased risk of type 2 diabetes." However, at the same time, "people should not be concerned about limiting fructose found in whole foods such as fruits and vegetables," she noted.

The AHA recommends limiting added sugars to no more than 6 tsp (24 g), or 100 calories, per day for women, and 9 tsp (36 g), or 150 calories, per day, for men and cutting sugar-sweetened beverage consumption to no more than 36 ounces, or 450 calories, per week.

From Science Daily:

Added fructose is a principal driver of type 2 diabetes, experts argue

Recent studies have shown that added sugars, particularly those containing fructose, are a principal driver of diabetes and pre-diabetes, even more so than other carbohydrates. Clinical experts challenge current dietary guidelines that allow up to 25 percent of total daily calories as added sugars, and propose drastic reductions in the amount of added sugar, and especially added fructose, people consume.

The totality of the evidence is compelling to suggest that added sugar, and especially added fructose (usually in the form of high-fructose corn syrup and table sugar), are a serious and growing public health problem, according to the authors.

While fructose is found naturally in some whole foods like fruits and vegetables, consuming these foods poses no problem for human health. Indeed, consuming fruits and vegetables is likely protective against diabetes and broader cardiometabolic dysfunction, explained DiNicolantonio and colleagues. The authors propose that dietary guidelines should be modified to encourage individuals to replace processed foods, laden with added sugars and fructose, with whole foods like fruits and vegetables