Short-Chain Fatty Acids (SCFA)

What are short-chain fatty acids?

Short-chain fatty acids (SCFA) contain 2-5 carbon (C) atoms. They are mainly produced during fermentation of the soluble dietary fiber by beneficial large intestinal bacteria. They include ^[2]:

• Acetic acid (2 C atoms)
• Propionic acid (3 C atoms)
• Butyric acid (4 C atoms)

SCFA Functions

SCFA are considered the main nutrients for the large intestinal lining cells; they also increase the blood flow, muscle activity and water absorption in the colon ^[1,2]. SCFA are partly used as food for beneficial bacteria and partly they are absorbed and metabolized – this is why soluble dietary fiber, from which colonic bacteria produce SCFA, has 1-3.8 Calories per gram ^[1].

SCFA Food Sources

The following soluble dietary fiber produces most SCFA in the large intestine ^[2,3]:

• Resistant starches from whole-grain cereals, barley, brown rice, beans, lentils, green bananas, cooked and cooled potatoes or pasta
• Pectin from apples, apricots, blackberries, carrots and oranges
• Fructooligosaccharides (FOS) and inulin from Jerusalem artichokes, onions, leeks, wheat, rye and asparagus
• Arabinoxylan
• Guar gum

Butyrate in Dairy

Butter, certain cheeses and cow’s milk contain considerable amounts of butyric acid in the form of butyrate (a compound of butyric acid and glycerol) ^[4]; note that these foods are also high in saturated fats.

In rancid butter, butyric acid appears in the free form–not bound to glycerol as in normal butter–and causes unpleasant odor.

SCFA (Butyrate) Supplements

Short-chain fatty acid supplements, mostly butyric acid salts, such as sodium, potassium, calcium and magnesium butyrate, are available without prescription (over-the-counter).

Butyrate supplements are–like other fatty acids–absorbed in the small intestine, so they cannot promote the growth of beneficial colonic bacteria or clean the large intestine (colon), as advertised. There is no scientific evidence about their effectiveness as liver or biliary tree cleansers, or ammonia or neurotoxin detoxifiers.

Possible Short-Chain Fatty Acids (SCFA) Benefits

• Adding resistant starches (which generate SCFA in the colon) to oral rehydration solution (ORS) may help to reduce acute diarrhea in small children ^[5], including diarrhea in cholera ^[1]. Cooked green bananas (high in resistant starches) or pectin (which is a soluble fiber), which both generate SCFA in the colon, may help to relieve chronic diarrhea in children ^[6].
• When feeding by mouth is not possible for certain periods of time, like after a gastrointestinal surgery, colonic lining may undergo a rapid degradation (atrophy). Short-chain fatty acids (SCFA) used in intravenous infusion help to nourish colonic lining and thus prevent its degradation ^[7].

There is INSUFFICIENT EVIDENCE about the effectiveness of short-chain fatty acids (SCFA) in the prevention or treatment of colorectal cancer ^[2,8,9], ischemic stroke, treating obesity, high blood cholesterol, diabetes type 2, sickle cell disease, Crohn’s disease and ulcerative colitis ^{[10,11,12,13]}, post-infectious irritable bowel syndrome (IBS) ^[7], increasing calorie delivery in cystic fibrosis ^[14], prevention ammonia or toxins absorption from the intestine, constipation, antibiotic-associated diarrhea.

The role of SCFA produced by the intestinal bacteria in immunity is not clear yet: they may either promote or inhibit inflammation in the body ^[17,18,19].

Ethyl Butyrate, Methyl Butyrate, Propionate

Ethyl butyrate and methyl butyrate are esters of butyric acid and ethanol or methanol. They have a fruity odor, so they can be used as food flavors added to orange juice, other fruit products or alcohol beverages, such as martini. Butyric acid is industrially produced by fermentation of starch by the bacterium Bacillus subtilis.

Propionic acid is also produced by bacteria from the genus Propionibacterium and is responsible for a specific flavor of Swiss cheese ^[15]. Propionic acid (E-number = E280) and its salts sodium propionate (E281), calcium propionate (E282) and potassium propionate (E283) can be used as food preservatives or flavorings; they are Generally Recognized As Safe (GRAS) by the U.S. Food and Drug Administration (FDA) ^[16].

Another short-chain fatty acid that is different than above ones is alpha-lipoic acid.