Study shows how a ketogenic diet positively alters the gut microbiome

Study shows how a ketogenic diet positively alters the gut microbiome
Research has found microbiome alterations can be directly correlated with changes to ketone body levels
Research has found microbiome alterations can be directly correlated with changes to ketone body levels
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Research has found microbiome alterations can be directly correlated with changes to ketone body levels
Research has found microbiome alterations can be directly correlated with changes to ketone body levels

A comprehensive new study, led by scientists from UC San Francisco, is offering robust new insights into the way a ketogenic diet can influence the gut microbiome, and subsequently result in broader health benefits.

A ketogenic diet is based on the idea that limiting one’s intake of carbohydrates and sugars forces the body into a metabolic state known as ketosis. Instead of relying on carbohydrates for energy, ketosis involves the liver producing ketone bodies from stored fat.

The diet was originally developed a century ago as a treatment for pediatric epilepsy, but over recent decades it has become a popular weight-loss diet. And in tandem with a growing interest in the broad systemic influence of the gut microbiome on general health, studies have increasingly looked to how a ketogenic diet affects gut bacteria.

Peter Turnbaugh, an author on the new study, suggests it was a strange contradiction that inspired the research. We know high-fat diets lead to disease, and we know some of those negative health effects are modulated by changes in the gut microbiome. So how does a high-fat ketogenic diet result in such dramatically different effects from a general high-fat diet?

“I got interested in this question because our prior research showed that high-fat diets induce shifts in the gut microbiome that promote metabolic and other diseases in mice, yet ketogenic diets, which are even higher in fat content, have been proposed as a way to prevent or even treat disease,” says Turnbaugh. “We decided to explore that puzzling dichotomy."

To offer a rigorous insight into the effect of the ketogenic diet on a human gut microiobiome, the researchers recruited 17 non-diabetic overweight subjects for a two-month inpatient study. The subjects lived in a controlled hospital environment experiencing four weeks on a ketogenic diet (15 percent protein, 5 percent carbs, 80 percent fat) and four weeks on a standard diet (15 percent protein, 50 percent carbs, 35 percent fat).

Stool sampling revealed dramatic, and rapid, changes in microbial populations between the two diets. Significant changes were detected across 19 different bacterial genera. Of particular interest to the researchers was a major drop in Bifidobacteria levels when subjects shifted to a ketogenic diet.

Subsequent animal tests confirmed these microbiome differences between ketogenic and high-fat diets. More interesting, however, was the finding that the microbial shifts directly correlated with gradual changes in the levels of ketone bodies.

“This was a little surprising to me,” says Turnbaugh. “As someone who is new to the keto field, I had assumed that producing ketone bodies was an all-or-nothing effect once you got to a low enough level of carb intake. But this suggests that you may get some of the effects of ketosis quite quickly."

The study also found the microbial changes linked to a ketogenic diet could be generated by simply adding synthetic ketone bodies to a high-fat/high-carb diet. This suggests it is the particular metabolic shift to producing ketone bodies that is causing a downstream effect on the microbiome.

“This is a really fascinating finding because it suggests that the effects of ketogenic diets on the microbiome are not just about the diet itself, but how the diet alters the body’s metabolism, which then has downstream effects on the microbiome,” adds Turnbaugh. “For many people, maintaining a strict low-carbohydrate or ketogenic diet is extremely challenging, but if future studies find that there are health benefits from the microbial shifts caused by ketone bodies themselves, that could make for a much more palatable therapeutic approach.”

The new study was published in the journal Cell.

Source: UCSF

Starving our microbial self of prebiotics can have a whole array of negative consequences. Ketogenic diets have been shown to reduce the richness and diversity of our gut flora. Microbiome changes can be detected “within 24 hours” of switching to a high-fat, low-fiber diet. The lack of fiber starves our good gut bacteria, but we used to think dietary fat itself was nearly all absorbed in the small intestine. But based on studies using radioactive tracers, we now know that about 7 percent of the saturated fat in a fat-rich meal can make it down to the colon, which may result in detrimental changes in our gut microbiome, weight gain, increased leaky gut, and pro-inflammatory changes. For example, a drop in beneficial bifidobacteria and a decrease in overall short-chain fatty acid production—both of which would be expected to “increase the risk of…gastrointestinal disorders.” I feel to see how a reduction in drop in Bifidobacteria levels leads to the conclusion that there is beneficial health effects.
Ketogenic diets in a closed system - ie. in the world as we define it - may wreak havoc on our carefully constructed diets. But what has reduced the diversity and richness of our gut biome(s) is our dietary distance from the field as evidenced by the basic research on gut biome diversity. For over 30 years as we have researched gut flora, the question has been whether or not the higher incidence of 3rd world diseases that we consider auto-immune or genetic might have a dietary factor involved? We found the notion lacking in evidence even after the Biosphere project research by Roy Walford was published at the turn of the century (millennia) . There was evidence in the improvements across the board of the participants health while starved and forced to eat fresh produce. I'll provide a link. I know there are many who go on late night TV with the cures for all illnesses and have the recipe to fix leaky gut syndrome - while all of us providing care just watch our patients ignore proven mitigation therapies. Fortunately, I can see the benefit of a reduction in Bifidobacteria, something that is balanced at 5-10% of our gut biome, to a level of 2.5-5% as there are many bacilli found in other healthy cultures that we in the USA don't express. Just because the 'young & healthy' Americans have nearly 40-50% Bifidobacteria if they eat the recommended fiber with their western diet does not mean that the bacterial mix in the gut biome is healthy - it only means they have a robust immune and metabolic system that counters the unhealthy and sub-clinical state of their gut biome. There is so much that we don't really understand - which was why Dr. Walford's research has been left on the shelf - and this study elucidates a little, but leaves more questions to be answered. I hope they are answered in my lifetime and our food supply starts following the evidence instead of peoples limited understandings!
Aaaand cue the ketogenic diet skeptics in 3...2...1.... Apparently they are confused as to what a ketogenic diet is. It's a high-fat low CARBOHYDRATE diet, not a low fiber diet. It's pretty universally understood that fiber in your diet is essential for gut health, and it happens that a lot of vegetables are low in carbohydrates and make ideal foods for a ketogenic diet.
Edward Vix
Karmadjun, you must mean "first-world diseases", not "third-world", right?
T N Args
You need to overlay these findings with the general findings that keto diets aren't even safe, to the point of loss of life itself.

Also, eating the food in that photo will never induce ketosis -- not a chance.