Research has shown that dark chocolate can be good for the heart and more. Now scientists report evidence that chocolate might not be acting alone. In some cases, it may get help from bacteria hanging out in your gut. Those bacteria can break down certain compounds in the chocolate. And it’s those smaller molecules that can relax blood vessels to help the heart, a Louisiana team reported March 19 at the American Chemical Society meeting in Dallas, Texas.
Chocolate’s health claims are not new. Back in the 1500s, explorers venturing to the New World saw natives downing unsweetened dark-cocoa drinks to relieve everything from fevers to kidney problems. If that sounds crazy, consider this: Fairly recently scientists have discovered that some chemicals in chocolate can fight skin cancer. Others protect our teeth. And a host of studies have proposed that chocolate can benefit the heart.
In those heart studies, a group of specific compounds called flavanols appeared responsible. Not surprisingly, some dark chocolates contain these compounds. (To be clear, the good stuff comes from the cocoa beans — chocolate’s key ingredient — not the butter or sugar in chocolate candy. Those ingredients can clog arteries or feed bacteria that rot your teeth.)
The flavanol findings really puzzled chemists. Some noted that cocoa doesn’t appear to have enough of the beneficial compounds to help the heart. Many cocoa chemicals glom together. This creates super-structures, known as polymers. And polymers make up about 90 percent of the chemicals in cocoa powder. These biggies can’t help if they don’t get into the blood. But they are too large to pass out of the gut’s wall and into the bloodstream. Many scientists therefore suspected that cocoa chemicals must just stay in the digestive tract until they got excreted as waste.
But such scientists had failed to account for the activity of bacteria in our gut. Some of these bacteria may come from mom, at birth. Others hitchhike into the gut along with foods and beverages. Indeed, yogurt can deliver some especially beneficial ones.
Studying good ‘bugs’
People tend to think of germs — bacteria and other microbes — as bad. But many of the bacteria that move into the human gut actually offer a host of benefits. There are some that help break down foods, releasing nutrients. Others fight disease-causing germs that might taint foods. Still more manufacture vitamins from the foods we eat, keep the immune system healthy or neutralize poisons produced by disease-causing germs. By adulthood, the body hosts 10 times as many bacterial hitchhikers (many of them health-promoting) as they do actual human cells.
Could these beneficial gut bugs chew up the non-digestible cocoa polymers into smaller, healthy bits? A research team led by John Finley and Maria Moore set out to explore that possibility. Finley is a food scientist at Louisiana State University in Baton Rouge. Moore is a college student who works in his lab.
They developed an artificial digestive tract — a series of test tubes in which reactions can take place. These mimic what happens as the gut breaks down food. The researchers added the cocoa powder used to make dark chocolate along with stomach and pancreatic enzymes — chemicals that speed up chemical reactions during digestion. (They didn’t use dark-chocolate candy because its fat and sugar could have interfered with the reactions and altered the results.)
After letting these materials interact, the scientists washed the sample. That left behind a lot of undigested material. That’s what the scientists would work with. And this is where their experiment turned a bit, well, nasty.
After food passes through the stomach and small intestine, it enters the large intestine. This organ is loaded with bacteria. They convert any of food’s sugars or starches into acids, gases and alcohol. They do it through a process called fermentation. (Fermentation also gives rise to wine, beer and yogurt.)
But to trigger that fermentation, the researchers needed samples of the bacteria present in the human gut. Since they couldn’t reach in and scoop some out, they did the next best thing: They scavenged some that had been excreted in the researchers’ own stool (in other words, they pooped into a pot and saved it). Pee-ew!
“It was stinky,” Moore told Science News for Students. “But that’s why we keep air freshener in the lab.”
The team fermented the undigested cocoa material by mixing it with these stool bacteria. And those microbes released a host of compounds. Among them were some of the same ones that blocked the inflammation of cardiovascular cells (those from the heart or blood vessels) in experiments that Finley’s lab had done earlier. Finley reported his team’s findings earlier this week.
Inflammation normally helps the body fight infections. But sometimes it goes into overdrive, quite inappropriately. This can happen, for instance, when people develop heart disease, diabetes or Alzheimer’s. All are disorders that commonly afflict older people. Small cocoa-based chemicals that relieve or delay inflammation might help people manage the ravages of these diseases.
“The results are exciting,” says Luke Howard. A food scientist at the University of Arkansas in Fayetteville, he did not work on the new cocoa study. However, he adds, “there are limitations when you use a model system,” as the researchers did here. Health-promoting chemicals formed during fermentation would go through the gut wall, then into the blood. During that process, the chemicals can change somewhat. The model digestive tract that Finley’s team used lacked that last moving-through-the-gut-wall step.
Finley’s team hopes to get around this problem. It’s already planning to do a small trial in people. Each day, participants would consume about 50 grams of cocoa powder. It’s an amount comparable to what would go into three or four cups of dark hot chocolate. Researchers would later collect blood and stool samples to check for proteins that might signal a drop in inflammation.
Earlier this week, scientists in Boston announced plans for a similar study. Theirs won’t be such a sweet deal for participants, however. Rather than sipping cocoa or nibbling bonbons, they’ll get cocoa’s key nutrients in the form of a pill.
Finley thinks foods are better than pills. He mixes a heaping tablespoon of cocoa powder into his oatmeal each morning. “I wouldn’t do it if I didn’t think it was good for me,” he told Science News for Students.
Alzheimer’s disease An incurable brain disease that can cause confusion, mood changes and problems with memory, language, behavior and problem solving. No cause or cure is known.
cardiovascular An adjective that refers to things that affect or are part of the heart and the system of vessels and arteries that move blood through the heart and tissues of the body.
circulation (in biology) A term that refers to the pumping of blood through the arteries, and smaller types of vessels (and from there into other organs and tissues).
cocoa A powder derived from the solids (not the fats) in beans that grow on the Theobroma cacao plant, also known as the cocoa tree. Cocoa is also the name of a hot beverage made from cocoa powder (and sometimes other materials) mixed with water or milk.
diabetes A disease where the body either makes too little of the hormone insulin (known as type 1 disease) or ignores the presence of too much insulin when it is present (known as type 2 diabetes).
enzymes Molecules made by living things to speed up chemical reactions.
fermentation A process that releases energy as microbes feast on materials, breaking them down. One common byproduct: alcohol and short-chain fatty acids. Fermentation is a process used to liberate nutrients from food in the human gut. It also is an underlying process used to make alcoholic beverages, from wine and beer to stronger spirits.
flavanol A group of plant-derived compounds. Some of these are antioxidants, meaning they can fight cellular damage from oxidation — often resulting in heart-healthy benefits. Among the best known of these antioxidant flavanols is epicatechin, found in some teas and cocoa-based products.
germ Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
inflammation The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It is also an underlying feature responsible for the development and aggravation of many diseases, especially heart disease and diabetes.
microbe (short for microorganism) A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
nutrients Vitamins, minerals, fats, carbohydrates and proteins needed by organisms to live, and which are extracted through the diet.
polymer Substances whose molecules are made of long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).
vitamin Any of a group of chemicals that are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be made by the body.
J. Cutraro. “Gut microbes and weight.” Science News for Students. April 11, 2008.
S. Ornes. “Slimming germs.” Science News for Students. Oct. 4, 2013.
S. Ornes. “Gut instinct.” Science News for Students. June 22, 2011.
J. Raloff. “Medicinal chocolate…Part 2.” Science News. Feb. 28, 2008.
J. Raloff. “Chocolate constituent bests fluoride.” Science News. May 22, 2007.
J. Raloff. “Chocolate as sunscreen.” Science News. June 7, 2006.
J. Raloff. “Prescription strength chocolate, revisited.” Science News. Feb. 22, 2006.
J. Raloff. “Chocolate therapies.” Science News. Sept. 16, 2002.
E. Sohn. “Gut germs to the rescue.” Science News for Students. June 26, 2003.