Antibacterial Activity of Roasted Coffee Beans and Caffeine
A Potentially Healthy Beverage
Coffee is the beverage of choice for many people, who love its rich taste and aroma and its stimulating effect. The drink has been linked to a number of important health benefits. A new one may soon be added to the list. Researchers have found that under certain conditions roasted coffee beans and caffeine kill or hinder disease-causing bacteria.
Until quite recently, coffee wasn’t considered to be a health food. Coffee drinking was even considered to be a bad habit due to the drawbacks that some people experience. These include restlessness, irritability, inability to sleep, heartburn, stained teeth, and withdrawal symptoms when a person tries to stop drinking coffee. Now researchers are finding that coffee seems to have a variety of health benefits, including reducing the risk of type 2 diabetes, gallstones, liver cancer, Parkinson's disease, and Alzheimer's disease. Antibacterial action could be another great benefit of drinking coffee.
Most research into the antibacterial activities of roasted coffee beans has focused on effects in the mouth and the digestive tract.
Bacteria in the Mouth
Coffee may prevent the adhesion of Streptococcus mutans to teeth. This bacterium is the leading cause of tooth decay and forms a community called a biofilm on the surface of the teeth. The bacteria in a biofilm are surrounded by a protective coating of polysaccharides. Bacterial biofilms form in other places in the body, too. In the mouth, the film is also known as plaque.
The bacteria in the oral biofilm feed on fermentable carbohydrates that enter and remain in the mouth. As they break down the food they produce acid, which softens and destroys tooth enamel. Saliva has a limited ability to prevent the damage by washing the acid away, neutralizing it, and killing bacteria by enzyme action. Once plaque has formed it must be removed by tooth brushing and dental floss. Once it hardens into tartar (also called calculus), a dental hygienist or dentist has to remove it.
The seeds inside the red coffee berries, or coffee cherries as they are sometimes known, are pale green. They become yellow after being dried in the sun. When they're roasted they turn brown and become the familiar coffee "beans" that we buy in stores.
Coffee and Oral Health
One team of researchers tested different kinds of coffee to see if they could prevent Steptococcus mutans from adhering to simulated teeth. The researchers used hydroxyapatite beads that were coated with saliva in their experiment. Hydroxyapatite is the chief substance in tooth enamel.
The researchers found that both green and roasted coffee prevented the bacteria from sticking to the teeth. Some isolated coffee compounds had the same effect. The scientists think that certain chemicals in coffee bind to the tooth enamel, preventing the bacteria from attaching.
Another group of scientists tested green, roasted, caffeinated, and decaffeinated forms of Arabica coffee (Coffea arabica) and Robusta coffee (Coffea canephora), as well as isolated coffee compounds. They found that specific coffee compounds acting together were bacteriostatic. They didn't kill the bacteria but prevented them from growing and reproducing. The caffeinated coffees did a better job at hindering bacteria than the decaffeinated coffees and the lighter roasts of coffee did a better job than the darker ones. In addition, the researchers found that the caffeinated Robusta coffee prevented bacterial attachment and biofilm formation.
The discoveries described above are very interesting and could be very important as well. Results in a living body may not be the same as those obtained in lab equipment, however.
Black Coffee Without Milk, Cream, or Sugar
It's probably important that coffee is drunk black, without any additives, if a person hopes to experience oral health benefits. Milk and sugar can be harmful to teeth. Sweet or milky coffee drunk slowly is especially dangerous, since the saliva doesn't get a chance to repair any damage to the tooth enamel before it encounters another onslaught of harmful fluid.
One dentist has noticed an increase in tooth decay in people who spend hours in front of a computer screen, slowly sipping sweetened, milky coffee as they work. Even milky coffee without added table sugar (sucrose) can damage tooth enamel if it's drunk over a long period of time, since milk contains other types of sugars. This is the reason for baby bottle syndrome, also called baby bottle tooth decay, which can occur in babies who suck on a bottle of milk for a long time.
Research suggests that coffee may fight some of the harmful bacteria in our digestive tract without harming helpful ones.
Bacteria in the Digestive Tract
Strange as it may sound, the human body contains around ten times more bacteria than human cells. The bacterial population is often referred to as our microbiome. The bacteria in the microbiome live on our skin and inside internal passageways that connect to the outside world, including the respiratory tract and the digestive tract. The greatest number of bacteria reside in our large intestine.
Researchers are discovering that the bacteria in our large intestine have important effects on our lives, many of them beneficial. Depending on the species, they help to digest food, produce vitamins that we need, fight dangerous microbes, reduce inflammation, and boost immunity. They may also help to lower cholesterol and fight obesity. Some researchers say that since the intestinal microbiome is so important it should be thought of as an organ in our body.
The Large Intestine
Coffee and Intestinal Health
In the lab, coffee has been found to fight Salmonella enterica, a bacterium that causes serious gastrointestinal problems. It also fights other harmful bacteria sometimes found in our digestive tracts, including Serratia marcescens and harmful forms of Escherichia coli. Further research needs to be performed to determine whether these effects are the same inside our intestine.
A small study of sixteen people found that moderate coffee consumption (3 cups a day for 3 weeks) didn't kill the healthy bacteria in the subjects' large intestines and actually promoted the activity of Bifobacteria. Bifobacteria are believed to have beneficial effects on human health. Their role in the intestine isn't known for certain, but they may digest polysaccharides and reduce the numbers of unfriendly bacteria in the gut. Their metabolic activities produce a variety of chemicals, some of which may boost our immune system. Understanding the role of our resident Bifobacteria and their companions is a very important pursuit.
Coffee in Moderation Is Healthy
Researchers have shown that roasted coffee has many other benefits besides fighting bacteria. It's a very interesting beverage.
Moderate Coffee Consumption for Health
The antibacterial effect of roasted coffee on bacteria that infect humans has been confirmed by multiple researchers. The coffee has been tested on bacteria in lab equipment, however. It may have the same effect in our mouths and gastrointestinal tracts, but this isn't known for certain until human tests are performed.
The consensus of most researchers seems to be that moderate consumption of coffee is fine for someone who enjoys the drink and may provide important health benefits, but excess coffee intake should be avoided. The links between coffee and health are exciting, but some caution is needed when drinking coffee. As the video above shows, a survey of a large number of people showed that moderate coffee consumption (2 cups a day) reduced the risk of heart disease, whereas heavy consumption (6 or more cups a day) actually increased the risk of heart disease.
Coffee beans contain many different chemicals. There seem to be several compounds responsible for coffee's antibacterial effects. Their identities and mechanisms of action need to be clarified. Hopefully researchers will soon learn more about these compounds so that they can be extracted, enabling people who dislike coffee or who experience unpleasant results when drinking it to benefit from its protective effects.
- American Chemical Society. (2002, March 8). Coffee May Help Prevent Cavities. ScienceDaily. Retrieved July 30, 2017 from www.sciencedaily.com/releases/2002/03/020307074142.htm
- Coffee and Streptococcus Adhesion from the NIH (National Institutes of Health)
- Coffee Types and Antibacterial Effects from ScienceDirect
- A PDF Summary of Coffee's Effects on Oral Bacteria from Formatex Research Center (an organization that promotes scientific, technical, and industrial research)
- Hydrogen Peroxide From Coffee from the Royal Society of Chemistry
- Coffee and Healthy Gut Bacteria from the NIH
Questions & Answers
© 2012 Linda Crampton