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The Paleo diet has been around for years and yet it continues to be controversial. The debate is whether following the Paleo diet long-term has health benefits or not? Supporters of the Paleo (Paleolothic) diet say it promotes gut health and is good for gut microbes, but recent research findings are a strike against this claim. The Paleo diet is based on the hypothesis that humans have not adapted to eating products of agricultural farming such as grains, dairy products, or legumes (beans), as well as all processed foods, so they should be avoided. Instead it stresses eating meat, fish, eggs, nuts, (some) fruits, and vegetables.

So what were the new research findings?  Australian researchers found that people who had been on a Paleo diet for more than a year ate lower amounts of resistant starch, and so had a different bacteria profile in the gut - with lower levels of some beneficial species. They also had high levels of a biomarker in the blood (trimethylamine-n-oxide or TMAO) that is linked to heart disease.

The problem seems to be the lower intake of resistant starch - which is a carbohydrate that resists digestion in the small intestine and ferments in the large intestine. As the fibers ferment they act as a prebiotic and feed the beneficial bacteria in the gut. More than one type of resistant starch can be present in a single food. And what foods contain resistant starches? Precisely some foods avoided in the Paleo diet: grains, rice, beans, peas, lentils, plantains, and green bananas. A number of studies find health benefits (e.g. gut health) from eating foods with resistant starches.

From Medical Xpress: Heart disease biomarker linked to paleo diet

People who follow the paleo diet have twice the amount of a key blood biomarker linked closely to heart disease, the world's first major study examining the impact of the diet on gut bacteria has found.  ...continue reading "Problems With Paleo Diet?"

Gut bacteria in children varies among different Asian countries. The microbiota profiled for the 303 subjects were classified into two main clusters: driven by Prevotella (P-type) or by Bifidobacterium/Bacteroides (BB-type) The majority of children in China, Japan and Taiwan harbored Bifidobacterium/Bacteroides (BB type),whereas those from Indonesia and Khon Kaen in Thailand mainly harbored Prevotella (P-type).Interesting in that even eating different types of rice result in different gut bacteria.From Asian Scientist:

Diet, Location And Your Kid’s Gut Bacteria

An Asia-wide study of the gut microbiota of primary school children has identified differences linked to diet and geographical location

The human intestinal tract hosts a large and diverse community of microorganisms—predominantly bacteria—which plays an important role in the host’s metabolism and ability to combat disease. In a study recently published in Scientific Reports, an international team of researchers led by Associate Professor Lee Yuan-Kun at the National University of Singapore examined fecal samples from 303 primary school children living in urban and rural cities of China, Japan, Taiwan, Thailand, and Indonesia. Unlike infants, children in the 7-11 age bracket have already developed a gut flora similar to that of adults but, unlike adults, they eat predominantly at home so their diets could be tracked more accurately.

The results show a strong correlation between the children’s gut microbiota and their place of residence and diet. The samples from China, Japan and Indonesia diverged the most, with Taiwan and Thailand filling the gaps in between, reflecting not only location but also patterns of human migration and agricultural exchanges. Bacterial communities in the gut vary widely between individuals, but they can be broadly classified into three types, according to the abundance of either Bacteroides, Prevotella, or Ruminococcus bacteria.The researchers found that Asian children display mainly the P-type (abundant in Prevotellaceae) and the BB-type (abundant in Bacteroidaceae and Bifidobacteriaceae), with the abundance of Bifidobacterium being a distinctive feature of the gut flora of Asian children.

P-type (Prevotella) gut communities are normally found in individuals with a high dietary intake of carbohydrates, while a diet rich in proteins and fats will favor a BB-type (Bifidobacterium/Bacteroides) community. Accordingly, the study revealed that Thai children living in Bangkok and eating a diet low in vegetables and fruit displayed a BB-type gut flora, while those living in Khon Kaen and eating a diet high in fruit and vegetables, displayed the P-type.

Not only was the P-type microbiota positively correlated with rice intake across the samples, but differences in contents of digestion-resistant starch across rice cultivars seemed to make a difference. P-type bacteria thrive in an environment rich in digestion-resistant starch, both because resistant starch is a substrate for bacterial fermentation and because it decreases the concentration of secondary bile acids—harmful to P-type bacteria—in the large intestine. After cooking, long grained Indica rice contains 6.6 percent digestion-resistant starch while short grained Japonica rice contains only 0.7 percent. The researchers suggest that the low content of resistant starch in Japonica rice might be the reason why 13 percent of Japanese children who ate a diet predominantly rice-based, still exhibited a BB-type microbiota. Other foodstuff were seen to be associated with P-type gut flora: soybeans (in the form of tempeh, not tofu) because of a high concentration of fiber; eggs, chicken and sweet potatoes because of their high content of vitamin A, which is thought to be beneficial to the growth of Prevotella bacteria.

The article can be found at: Nakayama et al. (2015) Diversity in Gut Bacterial Community of School-Age Children in Asia. 

Very interesting. Gives people a way to eat red meat, but not increase their colorectal cancer risk (by also eating resistant starch, e.g., potato salad or beans). From Science Daily:

Eating resistant starch may help reduce red meat-related colorectal cancer risk

Consumption of a type of starch that acts like fiber may help reduce colorectal cancer risk associated with a high red meat diet, according to a study. "Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster," said one researcher. "This finding supports consumption of resistant starch as a means of reducing the risk associated with a high red meat diet.

Unlike most starches, resistant starch escapes digestion in the stomach and small intestine, and passes through to the colon (large bowel) where it has similar properties to fiber, Humphreys explained. Resistant starch is readily fermented by gut microbes to produce beneficial molecules called short-chain fatty acids, such as butyrate, she added.

"Good examples of natural sources of resistant starch include bananas that are still slightly green, cooked and cooled potatoes [such as potato salad], whole grains, beans, chickpeas, and lentils. Scientists have also been working to modify grains such as maize so they contain higher levels of resistant starch," said Humphreys.

After eating 300 g of lean red meat per day for four weeks, study participants had a 30 percent increase in the levels of certain genetic molecules called miR-17-92 in their rectal tissue, and an associated increase in cell proliferation. Consuming 40 g of butyrated resistant starch per day along with red meat for four weeks brought miR-17-92 levels down to baseline levels.

The study involved 23 healthy volunteers, 17 male and six female, ages 50 to 75. Participants either ate the red meat diet or the red meat plus butyrated resistant starch diet for four weeks, and after a four-week washout period switched to the other diet for another four weeks.