The basic definition of short chain fatty acids (SCFAs) is that they are a form of fatty acid that is around six carbon atoms long.
They are produced by bacteria in your large intestine as a side effect of breaking down carbohydrates, but they can also be synthesized from other fats in the body.
Although SCFAs are produced during digestion, it’s also possible to get short chain fatty acids from food sources directly. Short chain fatty acid foods are actually quite important for your health and being deficient in SCFAs can interfere with your colon.
It’s also possible that there are broader health effects to be gained from SCFAs, but the evidence is not as clear-cut as would be preferred.
Why Short Chain Fatty Acids Are Important for Health
So, what do short chain fatty acids do? When examining this, the focus tends to be placed on one acid in particular: butyrate. Butyrate is the main source of energy for the cells in your colon, and your colon is something you want to stay on friendly terms with.
Feed your colon and you will help it stay happy, healthy, and motile. Due to the way that short chain fatty acids interact with the mucous lining of the colon (it helps regulate the lining’s acidity), it’s theorized butyrate acid is capable of promoting mineral absorption as well as protecting against the formation of polyps.
Lastly, butyrate has been suggested to have a role in the prevention or treatment of various diseases that can affect the colon’s mucous layer, such as ulcerative colitis or even cancer. It’s important to keep in mind, however, that while butyrate has shown the ability to inhibit the growth of tumor cells in a petri dish, this is a far cry from proving it can do the same thing in an actual person.
Regardless of whether it can stop tumors or colon disease, the main health benefits of short chain fatty acids—and butyrate acid in particular—is that they are used as food by your colon cells and are therefore essential for the various colonic functions you enjoy in your daily life.
Effects of Dietary Fibers on Short Chain Fatty Acids
It’s possible to obtain SCFAs directly from food sources such as milk or butter. This poses a problem for anyone trying to minimize dietary fats and is especially a problem for vegans.
However, SCFAs can be produced by your body during the breakdown of other nutrients, one of them being dietary fiber. This is due to a similar mechanism to how SCFAs are produced from carbohydrates. The bacteria in your gut consume some of the fiber as it ferments and they release SCFAs as a byproduct—in other words, your colon gets some of its power from bacteria poo.
This is actually important since butyrate gets absorbed very quickly by the body in its normal form. Without fermenting fiber to produce SCFAs, butyrate might never reach your colon and your colon cells would be without food. As mentioned earlier, a happy colon is important.
The main dietary fibers associated with SCFA production are pectin, resistant starch, fructooligosaccharides, and cellulose. Thanks to this, eating foods such as jam, fruits, or cereals can help keep your SCFAs at an adequate level.
Health Benefits of Short Chain Fatty Acids
Besides their use as a colonic foodstuff, short chain fatty acids have various effects throughout your body that are important for maintaining proper health.
1. Inflammatory Bowel Disease
As mentioned, butyrate is suspected to be protective against ulcerative colitis, but there is another SCFA, acetate, that has been found to offer similar effects. Specifically, animal studies have shown that both acetate and butyrate supplements can reduce levels of bowel inflammation in mice. In humans, the effect of supplementation has not been as fully observed.
What has been noticed, though, is that deficiencies of SCFAs are linked to worsening inflammatory bowel disease. There has also been a small study suggesting that butyrate supplements could improve Crohn’s disease or even send it into remission. That said, smaller studies tend to show exaggerated effects due to the small sample size, so it’s unclear how significant this effect might be on the population at large.
Short chain fatty acids have been shown to have mixed results in both humans and animals when it comes to managing insulin sensitivity or blood sugar levels. SCFAs are definitely shown to improve enzyme activity in the liver and muscles and this in turn helps steady blood sugar. When animal studies are examined, the blood sugar effect is seen in both diabetic and non-diabetic mice. However, when humans alone are looked at, the results become much more muddled.
There is some evidence that SCFAs can still offer improved blood sugar control and insulin sensitivity, but the effect seems to predominantly apply to those who are already overweight or insulin-resistant. In other words, SCFAs may potentially help diabetics manage their blood sugar and respond to insulin but non-diabetics of normal weight may not see an improvement.
3. Weight Loss
The effects of SCFAs on weight loss are both promising and highly limited. Mostly animal studies are available and they suggest that butyrate can reduce fat storage and improve fat burning. However, the effect once again seems to be observed primarily in obese mice and not in normal or overweight ones. More research, particularly human research, is needed in this area to draw further conclusions.
4. Heart Health
Fiber intake is known to result in a lowered risk of heart disease, and one of the possible explanations for this is the production of short chain fatty acids. SCFAs have been shown in both animals and people to reduce cholesterol levels, and fiber has been tied to lowered inflammation to a certain degree. However, these effects are not consistent and observed effects seem to depend on both the type of fiber involved and the specific source. The evidence right now says that SCFAs don’t increase your risk of heart disease, at least.
5. Colon Cancer
The exact effects that short chain fatty acids may have on colon cancer range from “unclear” to “none.” Although SCFAs have been known to either inhibit or kill cancer cells in a petri dish, this is not always reliable evidence as to how it will work in the human body. It’s worth keeping in mind that even vodka (or a handgun) will kill cancer cells in a petri dish.
Animal studies that look at high-fiber diets do show some links between high fiber intake and reduced rates of colon cancer. Whether this is due to SCFAs (butyrate gets to the colon through fiber) or some other component of fiber is unclear. Human studies have also been done, but these results have been mixed at best and seem to either show some connection or no link at all, depending on the study consulted.
Digestion of Short Chain Fatty Acids
SCFAs are somewhat different among fats in the way they are digested by the body. Normally, fats are broken up by enzymes in the mouth and stomach and then they travel to the small intestine where the liver gets busy. The liver produces bile which emulsifies the fats and then they are broken down even further by the pancreas so that they end up in a form your body can actually use. Short chain fatty acids, possibly because of their short chains, are able to be digested and absorbed directly from the stomach without needing to go through this process.
Food Sources for Short Chain Fatty Acids
There are a few different foods that contain either the fiber needed by your gut bacteria to produce SCFAs or foods that actually have short chain fatty acids of their own. Here are some short chain fatty acids food examples:
- Whole grain cereals, brown rice, beans, lentils, green bananas, and pasta are forms of resistant starches and can be used to fuel the production of SCFAs.
- Apples, apricots, oranges, and carrots are possible sources of pectin. Pectin is also used in the creation of jams and marmalades so those products could be consumed as well.
- Fructooligosaccharides come from Jerusalem artichokes, onions, leeks, wheat, rye, and asparagus.
- Butyrate can be obtained directly by eating butter, cheese made with cow’s milk, and cow’s milk itself (especially whole milk), however these foods are also known for being high in saturated fats. While a glass of milk each day isn’t going to unduly impair your health, trying to get your butyrate from cheese or butter may.
Incidentally, butyric acid is one of the culprits behind the smell of rancid butter. The more you know!
A Word about Supplements
Short chain fatty acids are available as over-the-counter supplements, but their use should be discouraged under most circumstances. Getting a nutrient from a supplement is not the same as getting it from a food source or your own body’s production. This is especially true since butyrate gets absorbed too quickly to reach the colon unless it’s from a fermenting fiber.
Furthermore, while SCFA deficiencies can cause some health problems, too much can also interfere with your body’s ability to handle fats, blood sugar, and other things that SCFAs normally help with. There is insufficient evidence at this time to suggest that having short chain fatty acids in above-normal levels, whether from diet or supplement, produces any health improvements or protective effects.
Sources for Today’s Article
Dave, A., “Digestion of Short-Chain Fatty Acids,” Livestrong web site, last updated August 19, 2015; http://www.livestrong.com/article/439570-digestion-of-short-chain-fats/, last accessed April 6, 2016.
Brown, M., “How Short-Chain Fatty Acids Affect Health and Weight,” Authority Nutrition web site, April 2016; https://authoritynutrition.com/short-chain-fatty-acids-101/, last accessed April 6, 2016.
“Short-Chain Fatty Acids (SCFA),” Nutrient Reviews web site; http://www.nutrientsreview.com/lipids/short-chain-fatty-acids-scfa.html, last accessed April 6, 2016.