A healthy microbiome is a diverse microbiome. Short-chain fatty acids (SCFAs) are up-regulated in those with the healthiest microbiomes. SCFAs influence gastrointestinal health directly by acting as food for the cells lining the gut and by tightening the junctions between cells. SCFAs are also are increasingly associated with a wide range of systemic health benefits. These benefits include improved immunologic function, lower systemic inflammation, and anti-cancer effects. Individuals with the highest level of SCFAs tend to have the healthiest and most diverse gut flora.

Many SCFAs, including butyrate, propionate, and acetate, are produced through bacterial decomposition of fiber. SCFAs are formed by specific gut microbes, including Clostridiales, Lachnospira, Roseburia, and Faecalibacterium. Recently, another bacteria, Veillonella, appears to produce SCFA from lactic acid (a substance produced during exercise). In mice, Vellonella increases athletic performance.

Dysbiosis

Many diseases are associated with dysbiosis—a change in the healthy balance of normal gut flora. Dysbiosis is associated with a wide-range of factors, including dietary choices, infection, psychological stress, sedentary lifestyle, individual disease states, and medications (especially antibiotics).

How can I increase my SCFAs?

You can increase your body’s SCFAs by increasing the number of bacteria that produce these helpful substances. There are likely many factors we don’t yet understand about the manipulation of gut flora. However, there are at least three ways we know of to increase the production of SCFA: eating the right food, supplementation, and exercise.

Food

Increasing SCFA producing bacteria can be influenced by food choices. Whole plant-based foods contain fiber that acts as a food source for many SCFA producing beneficial bacteria. Processed foods lack substantial amounts of fiber, and so are detrimental to the growth of SCFA creating bacteria.

Supplements

Psyllium, found in supplements such as Metamucil, is a way of increasing your intake of fiber, although recent studies have shown fiber from whole plants is a better choice than supplementation.

Inulin, a fructooligosaccharide, is another supplement that stimulates the growth of SCFA producing bacteria. Inulin is in many foods, including Jerusalem artichoke, onions, and asparagus. In 2018 inulin was approved by the FDA for use by Big Food as an additive to processed foods.

A warning. In mice, inulin supplementation increased the incidence of hepatocellular carcinoma. The mechanism of the effect is unknown, and the finding has not been described in humans. Looking at the existing evidence, it seems safer to obtain dietary substances (such as inulin or probiotics) from whole food rather than from supplements.

Exercise

In mice, exercise increases microbial diversity, improves gut barrier function, and increases microbes that produce SCFA. SCFAs improved athletic performance, as mentioned in a previous blog entry.

In humans, a recent study demonstrated that aerobic training for 30-60 minutes 3 times a week showed benefits over six weeks including Increases in SCFA species and increased levels of SCFA in the stool.

SCFAs, produced by the human microbiome, play a significant role in human health. Understanding the impact of the microbiome and its by-products, such as SCFAs, is only in its infancy. I’m excited to watch the mysteries of the microbiota unfold.