Butyric Acid, Bacteria and Colon Health

The large intestine of humans hosts a huge population of bacteria. Researchers have discovered that some of these bacteria convert the soluble fiber and resistant starch that are present in undigested food into short-chain fatty acids. One of these fatty acids, called butyric acid, has important health benefits in the colon. The colon is the longest section of the large intestine. Butyric acid helps maintain a healthy intestinal lining and has also relieved symptoms in people with inflammatory bowel disease. In addition, butyric acid may lower the risk of colon cancer.

The amount of butyric acid formed in the colon depends on which bacteria live there. It’s also determined by the size of the bacterial population that is able to produce the butyric acid and by how long the soluble fiber or resistant starch stays in the colon. If undigested food moves rapidly through the colon the bacteria won’t have time to produce much butyric acid.

The human body can’t digest soluble fiber. Good sources of soluble fiber include barley, oatmeal, beans, peas, and many types of vegetables and fruits. Soluble fiber dissolves in the water present in the digestive tract, forming a gel, and is known to lower the level of LDL cholesterol (the so-called “bad” cholesterol) in the blood.

Resistant starch is starch that we are unable to digest, or that we digest very slowly. The amount of resistant starch in a food depends not only on the identity of the food but on factors such as whether the food is cooked or raw, whether it is cooked and then cooled (which changes the nature of the starch) or on how ripe a fruit it is. Some good sources of resistant starch are cooked and then chilled potatoes, rice and pasta, unripe bananas, legumes such as navy beans and lentils, and high-amylose corn. Resistant starch has little effect on blood sugar level and is therefore classified as non glycemic or low glycemic.

The glycemic index of a food that contains resistant starch depends on the proportion of resistant starch to other, higher glycemic carbohydrates in the food. The glycemic index is a number that represents the ability of a food to raise the level of glucose in the blood. Generally, a higher glycemic index food and a higher blood sugar are considered to be bad, since they may lead to an increase in body fat and a higher risk of diabetes and heart attacks.

Another health benefit of both soluble fiber and resistant starch is that they can be fermented by certain colon bacteria to produce butyric acid.

A fat molecule is composed of a glycerol molecule joined to three fatty acid molecules. The whole structure is sometimes known as a triglyceride. Butyric acid, also called butanoic acid, is a fatty acid present in some triglycerides. Butyric acid is sometimes referred to as butyrate. Butyric acid and butyrate actually have slightly different structures, although they are very similar.

Butyric acid is a short-chain fatty acid (SCFA), as opposed to a medium-chain or long-chain fatty acid. SCFAs have an acid group at one end of their molecule and a “tail” or chain containing fewer than six carbon atoms attached to the acid group.

Some foods contain relatively high concentrations of butyric acid, including butter and parmesan cheese. Butter contains 3% to 4% butyric acid. Kombucha tea also contains butyric acid. The kombucha culture is a mixture of bacteria and yeasts. If the culture is placed in tea that has been sweetened with sugar and the microbes are allowed to ferment the sugar, a variety of chemicals are produced, including butyric acid.

Butyric acid has a very unpleasant odor and smells like vomit. In fact, butyric acid is present in vomit. When butter becomes rancid, enzymes produced by bacteria release the butyric acid from the fat molecules, producing the typical rancid smell. Butyric acid got its name from “butyrum”, the Latin word for butter, which in turn was based on a similar Greek word.

Concentrated butyric acid must be handled very carefully, not only because of its nauseating smell, but also because it’s corrosive. At low concentrations, however, butyric acid is safe, and in very low concentrations it’s used as a flavoring agent in food.

Butyric acid is a saturated fatty acid. Saturated fats, which contain saturated fatty acids, have a reputation for creating health problems if eaten in excess. These problems include raising the amount of cholesterol in the blood, causing fatty plaque deposits in arteries, which may lead to a heart attack or a stroke, and increasing the risk of some types of cancer. However, researchers are discovering that not all saturated fats produce these effects. Butyric acid and other short-chain fatty acids actually have health benefits.

Butyric acid is the main food source of the colonocytes, cells in the lining of the colon. Butyric acid therefore supports the colonocytes, helping them to function properly and maintaining the integrity of the intestinal lining.

Butyric acid may also prevent and reverse the colon inflammation experienced by people suffering from Crohn’s disease and ulcerative colitis, the two types of inflammatory bowel disease. Butyric acid enemas have reduced colon inflammation symptoms in patients. Unfortunately, butyric acid enemas smell bad and patients are not always willing to undergo the treatment. Another problem with an enema is that the butyric acid doesn’t stay in the colon for very long. Researchers are therefore investigating the use of probiotic supplements which contain bacteria that can make butyric acid. If the probiotic bacteria multiply in the colon and become permanent inhabitants, the patient will have a continuous supply of butyric acid.

Apoptosis – programmed cell death - is a normal process in cells. For example, cells may be stimulated to undergo self-destruction if their DNA is damaged so severely that it can’t be repaired, or if there are too many cells in an area. Cancer cells, however, do not undergo apoptosis, and continue to multiply. In experiments with lab animals butyric acid has been found to inhibit multiplication of cancerous colonocytes and stimulate apoptosis in the cells. More research is needed, however, before scientists agree that butyric acid can prevent or cure colon cancer in humans.

Since butter contains butyric acid it could be used to support gut health. However, butter also contains longer chained, less healthy fatty acids, and should be eaten in moderation.

Maintaining a helpful population of colon bacteria is very important. As scientists learn more about what different bacteria do in the colon, and also learn how to effectively add new bacteria to the colon population, it may be possible for us to eat probiotic supplements that supply us with new bacteria - such as those that produce butyric acid - that will prevent or treat specific health problems. The researchers will need to ensure that the bacteria survive their journey through the digestive tract to the large intestine and that sufficient numbers of the bacteria are delivered to the colon.