Butyrate (from the Ancient Greek word for "butter") is a short-chain fatty acid (SCFA) that occurs naturally in butter and other foods and is also produced by microbes in the gut. Microbial production of short-chain fatty acids, including acetate and propionate, occurs in the colon during the fermentation of indigestible fibers found in plant foods such as legumes, fruits, nuts, cereals, and whole grains. In the gut, butyrate is the preferred fuel source for colonocytes, the skin-like cells that line the colon.
Butyrate participates in a wide array of metabolic pathways in the body. Accordingly, low concentrations of butyrate in the blood, colon, liver, and brain have been identified in various diseases. Generally, increasing butyrate levels benefits health. More specifically, research supports the role of butyrate in the following:
Beta-hydroxybutyrate (BHB) is a ketone body that can be synthesized from butyrate, dietary fats, body fat, or ketogenic amino acids. Endogenous (i.e., produced by the body) ketones, including acetone and acetoacetate and beta-hydroxybutyrate, are a primary source of cellular energy when glucose availability is low. Ketones increase in concentration in the brain, liver, heart, muscle, and other tissues during exercise, fasting, and carbohydrate restriction on a ketogenic diet.
Research demonstrating strategies to increase butyrate and BHB includes:
Below is a selection of summaries from current research investigating the role of butyrate in health and disease.
A healthy gut microbiota contains a diverse population of bacterial species, each with unique metabolic requirements. Butyrate is an important fuel source for human cells and microbes in the gut; however, not all bacteria can produce butyrate. Bacterial genera that carry butyrate-producing genes, such as Faecalibacterium and Lachnospira are vital to a healthy gut ecosystem. The findings of one report demonstrate the ability of exercise training to increase butyrate-producing microbes in the gut.
The researchers recruited 18 adults with an overweight BMI and 14 with a lean BMI. Participants completed six weeks of supervised endurance exercise training (30-60 minutes, three times per week) and then six weeks of sedentary activity. The researchers collected a stool sample before the exercise training period, after the exercise training period, and after the sedentary activity period.
Overall, exercise increased the concentration of butyrate-producing microbes in the gut microbiota and the expression of butyrate-producing genes by those microbes. Exercise increased the concentration of SCFAs in stool from participants with a lean BMI but not participants with obesity. Exercise-induced changes to the gut microbiota mostly reversed over the six-week sedentary period.
These results demonstrate the responsiveness of the gut microbiota to beneficial changes in behavior. Specifically, exercise increases butyrate production in the gut, which may reduce chronic disease risk.
The gut microbiota is a complex and dynamic population of microorganisms subject to change throughout an individual's lifespan in response to aging. Findings from a new study demonstrate that altering the gut microbial population may change the trajectory of brain aging.
The authors transplanted gut microbiota samples from healthy young or old mice into young germ-free mice. Eight weeks after the transplant, the mice that received microbial samples from the old mice demonstrated increased neurogenesis – the process of forming new neurons – in the hippocampus region of their brains.
Further analysis revealed that these mice also had larger numbers of butyrate-producing microbes in their colons. Butyrate was associated with an increase in growth factors and subsequent activation of key longevity signaling pathways in the livers of the recipient mice. When butyrate alone was given to the recipient mice, it promoted neurogenesis, too.
The findings from this study may have relevance for dietary interventions to maintain or improve brain health.
What dietary and lifestyle factors can improve symptoms of leaky gut (i.e., increased intestinal permeability)?
Early evidence supports the consumption of dietary fiber and some probiotic-containing foods and supplements for improving symptoms of leaky gut. Some of the mechanisms involved in this improvement may involve increased butyrate production in the gut. Specific information regarding nutrients and doses can be found in this review.
How can I increase butyrate/BHB while fasting or eating a ketogenic diet?
Consuming an exogenous ketone supplement increases serum concentrations of BHB; however, these supplements can have a very unpleasant smell/taste. Some evidence suggests that medium chain triglycerides (MCTs) may increase serum BHB levels in a dose-dependent manner, meaning the more MCTs consumed, the greater the BHB levels. However, there is a lot of variation from person to person.
Beta-hydroxybutyrate is an endogenous ketone compound derived from butyrate and lipids. Beta-hydroxybutyrate is a source of cellular energy and can be converted to other cellular energy carriers, such as nicotinamide adenine dinucleotide (NAD+).
Intestinal permeability is modulated by butyrate produced via fermentation of dietary fiber by gut microbes, strengthening barrier integrity and reducing the risk of disease.