Increasingly, chocolate-makers turn to science | Science News for Students

Increasingly, chocolate-makers turn to science

Researchers are studying chocolate to boost its potential health benefits and produce more of this tasty treat
Feb 8, 2018 — 6:45 am EST
chocolate hearts
Chocolate is one of the most prized treats. But ensuring there will be enough of the raw ingredients to satisfy our hunger for it has candy-makers and farmers consulting scientists around the globe.


If you’re a fan of chocolate, every occasion is right for this treat. Feeling down? Eat some chocolate. Celebrating? Eat some more. Want to show your Valentine how special you think your sweetheart is? Offer up chocolate!

People have been enjoying chocolate as a food, drink and medicine for thousands of years. The ancient Maya and Aztecs called chocolate kakaw and used it as medicine.

They also made chocolate offerings to their gods. Chocolate comes from the cacao (Kuh-KOW) tree, and its scientific name reflects its history. Theobroma cacao translates to “cacao, food of the gods.” These days, chocolate is not just for deities. The treat has become popular around the world.

cacao pods
Different types of cacao pods on display.
Mark Guiltinan

It’s so popular, in fact, that people spend more than $90 billion on it each year. And that number just keeps growing.

People may eat chocolate because of its taste. And many adults justify that treat because they’ve heard it has health benefits. But chocolate’s popularity also has downsides. Scientists are scrambling to help farmers produce enough cacao to meet the growing demand for chocolate. One big challenge: Plant diseases threaten crop yields. So scientists are working hard to understand the cacao tree in hopes of protecting it. 

Ancient treat

Cacao is a tropical tree. And it's unusual: Its fruits, called pods, grow directly on the tree trunk. Inside the pod’s citrusy flesh are large, brown seeds. They are what hold the starting material for one of the world’s tastiest treats.

Those seeds, like the tree, are called cacao. After being harvested, they’re heaped in piles or poured into boxes to ferment. During this process, microbes break down the flesh. As they digest its sugars and other chemicals, they give off heat. That heat breaks down cells within the bean. This lets chemical reactions take place that produce the flavors we recognize in chocolate. After four to seven days, the seeds are laid in the sun to dry. Now they’re ready to be roasted and ground to make cocoa.

Cocoa is the basic ingredient in chocolate. When cocoa is mashed into a thick brown paste, it’s called chocolate liquor. Milk and dark chocolate both contain chocolate liquor. (Hardened cocoa liquor is also what chefs call unsweetened baking chocolate.) Cocoa butter is the fat in chocolate liquor. That fat can be separated out and used to make white chocolate. Chocolate candy also includes sugar, vanilla, lecithin and sometimes milk. (Lecithin is an emulsifier — a chemical that helps fatty and non-fatty ingredients stay smoothly mixed. That helps to stabilize the final product.)

The sweet confection we enjoy today is nothing like the original forms of cocoa. The Maya mixed cocoa, water and chili pepper to make a spicy, bitter drink. It wasn't until Spanish explorers sent cocoa back to Europe that candy makers came up with our modern, sweet version.

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chocolate consumption
People in the United States may consume a lot of chocolate, but they rank ninth in the world in the amount eaten per person each year.
Niall McCarthy/Statista

The ancient Maya and Aztec people also mixed cacao seeds with various herbs to make medicines. They used these to treat symptoms such as diarrhea, fever and cough. Cacao has a long history as a medicine — but scientists have only recently begun to investigate its benefits.

Cocoa for health

Cocoa contains antioxidants. These molecules stop chemical reactions that involve oxidation, which can damage the body’s cells. DNA — the molecule that gives instructions to each of our cells — is especially vulnerable. Damaged DNA can eventually lead to cancer. So antioxidants are an important part of our diet.

Many kinds of dark chocolate are high in antioxidants. Milk chocolate and white chocolate are not.

“Many research studies have shown that antioxidants protect DNA,” notes Astrid Nehlig. She is the director of research at the National Institute for Health and Medical Research in Strasbourg, France. Fruit, chocolate and coffee are all high in antioxidants. The DNA in people who consume a lot of these foods is less likely to break. And when it does, the body is more likely to repair it, Nehlig says.

sampling cacao
The author’s son tries the sweet flesh of a cacao pod harvested in the Amazon rainforest of Peru.
Jeff Stevens

Flavanols (FLAV-uh-nahls) are another important group of cocoa compounds. Arteries carry blood from the heart to organs and other tissues from head to foot. Flavanols can dilate — or widen — those arteries. That helps blood flow better, Nehlig explains. Many studies have shown that eating cocoa products can keep blood pressure low and help improve heart health, thanks in part to its flavanols.

In fact, improved blood flow seems to be the one benefit of cocoa products that holds up in study after study. Last year, medical researchers in Australia pored over 35 different studies. This type of investigation is called a meta-analysis. It looks at the big picture.

Eating cocoa compounds indeed appears to improve blood flow, these researchers reported. In April 2017, they shared their findings in the Cochrane Database of Systematic Reviews.

Improved blood flow helps the brain work better, notes Nehlig. So more blood reaching the brain means more energy for brain cells. Some research has found that learning and memory improve when people eat cocoa flavanols. But researchers do not yet know exactly how these compounds work, she adds.

It’s also unclear whether chocolate provided the flavanols in question. Researchers usually don’t give study participants chocolate. Instead, they give them cocoa flavanol supplements. So what? Certain candy-making processes may remove or alter the flavanols. That could erase their brain-sparing benefits. So it’s too soon to know whether cocoa flavanols might limit memory problems (including dementia) later in life.

Flavanols and other cocoa compounds may improve health in other ways, too. Studies suggest that molecules in cocoa can reduce symptoms ranging from anxiety to allergies. As encouraging as all such studies sound, it’s important to keep in mind that they often have come from labs funded by the chocolate industry.

Not all chocolate is a ‘health’ snack

cacao fermentation
A cacao grower in Columbia pours wet cacao seeds into a box. The seeds will ferment for up to seven days before being processed into cocoa.

Ready to rush out and buy chocolate for your health? First, consider this: Not all chocolate contains these potentially beneficial compounds.

Much of the chocolate sold today is low in cocoa flavanols, says Susan Miszewski. She works for Mars Symbioscience in Germantown, Md. “It is a common myth that chocolate with a high percent of cocoa solids (such as 70 percent dark chocolate) has higher levels of cocoa flavanols,” she says. Most chocolates do contain some of these flavanols. But that amount varies a lot, Mars scientists and their university colleagues have shown. So when it comes to these health boosters, she says, “chocolate is not a reliable source.”

The normal steps in harvesting a cocoa bean and processing it into a candy bar destroy flavanols along the way, she notes. Those processes include fermenting and roasting the seeds. Lowering the acidity of the cocoa also can break down flavanols. The acidity falls when chocolate makers add a base — or alkaline material — to cocoa. This alkalization makes chocolate less bitter, she says. But all of that processing means the final piece of chocolate has likely lost many of its initial health-boosting flavanols.

cacao harvest
These cacao seeds are clean and ready for processing.
Mark Guiltinan

And don’t forget: Even chocolate that still contains flavanols is chock full of calories, sugar and fat.

Scientists at Mars, the candy company that makes M&M’s, know the potential health benefits flavanols can offer. So they have developed a process to preserve them in cocoa, Miszewski says. Cocoa prepared in this new way isn't used in candy bars, though. So it won't make your sugary snack suddenly healthy. But Mars is using this material to develop potentially health-enhancing flavanol-rich products.

Long-lasting supply

Mars also has joined forces with other companies, universities and the U.S. Department of Agriculture to map the cacao genome. That’s the complete set of genes that make up the biological instruction manual in each of the plant’s cells. The resulting Cacao Genome Database is freely available for anyone to use.

Why build such a database? Between 40 million and 50 million people worldwide work in jobs related to cacao, cocoa and chocolate. So understanding and protecting the cacao tree is globally important.

cacao growing
Pods grow directly from the trunk of the cacao tree.
Mark Guiltinan

Long ago, Central and South American rainforests were the only source of cacao trees. As Spaniards and other Europeans colonized new parts of the world, they found the trees and eventually moved some of these trees with them. Now cacao grows across the world’s tropics. A whopping 70 percent of cacao today comes from Africa, where the climate is just right. Ghana and the Ivory Coast grow most of that — 60 percent of the world's total.

Growing cacao is a good way for farmers to earn money and support their families. But the demand for cacao keeps increasing. That makes it difficult for farmers to grow enough. Diseases also threaten their trees. Cacao-killing diseases would do more than take away a tasty treat — they also could plunge millions of people into poverty. Scientists are using the Cacao Genome Database in hopes of heading off both of these problems.

Mark Guiltinan and Siela Maximova are plant biologists at Pennsylvania State University in University Park. They use the database all the time. “If there is a gene we are interested in, we can look it up in the database and use that information to design future experiments,” explains Guiltinan.

His group may look for a gene variant that may make these plants better at fighting off disease, for example. Or they may seek a gene to produce more flavorful fruit. They may even search for genes that allow the trees to grow more quickly.Such genes may already be known to exist in other, better-studied plants. Examples might include soybeans or corn. “We can find genes in cacao that are similar . . . to some of these,” Guiltinan says. And, he points out, “Often they share a similar function.”

He and Maximova can then test whether these genes actually work the same way in cacao trees as in other plants. The scientists don’t have time to wait for each seed to grow into a new tree. Instead, they have developed a way of cloning trees using the parts of one tree’s flowers (See "How to grow a cacao tree in a hurry".)

Then they check to see if the new trees make more pods, for example, or resist certain diseases. One such disease is called frosty pod. It makes cacao pods turn white and rot on the tree. Another is called witches’ broom. This infection spreads throughout the tree and can eventually kill it. Fungi cause both diseases.

Guiltinan and Maximova use their gene identification process to find trees that have several of the traits they want. The scientists then make many copies of those strong, healthy trees.

chocolate curls
Curls of finished chocolate, ready to be eaten.

So far, the researchers have helped to clone 100 varieties of cacao tree. The result? About 100 million cacao trees that come from these newfound varieties have been planted in fields across Indonesia. And, Guiltinan adds, those trees are living up to their potential. They are growing more pods and resisting disease.

“Cacao plants are great for the environment, protecting soil, water and habitat,” he notes. And the income from farming cacao can be a big help to people in developing countries, he adds.

The quest for strong and healthy cacao trees will be important for meeting the world’s growing demand for chocolate and cocoa. As more people learn about cocoa’s potential health benefits, that demand might grow even more. Scientists hope their work will ensure a long-lasting supply of cacao.

That should be good news for cacao growers — and chocolate lovers — everywhere.

Power Words

(more about Power Words)

agriculture     The growth of plants, animals or fungi for human needs, including food, fuel, chemicals and medicine.

allergy     The inappropriate reaction by the body’s immune system to a normally harmless substance. Untreated, a particularly severe reaction can lead to death.

antioxidant     Any of many chemicals that can shut down oxidation — a biologically damaging reaction. They do this by donating an electron to a free radical (a reactive molecular fragment) without becoming unstable. Many plant-based foods are good sources of natural antioxidants, including vitamins C and E.

anxiety     A nervous reaction to events causing excessive uneasiness and apprehension. People with anxiety may even develop panic attacks.

blood pressure     The force exerted against vessel walls by blood moving through the body. Usually this pressure refers to blood moving specifically through the body’s arteries. That pressure allows blood to circulate to our heads and keeps the fluid moving so that it can deliver oxygen to all tissues. Blood pressure can vary based on physical activity and the body’s position. High blood pressure can put someone at risk for heart attacks or stroke. Low blood pressure may leave people dizzy, or faint, as the pressure becomes too low to supply enough blood to the brain.

cacao    The name of a tropical tree and of the tree’s seeds (from which chocolate is made).

cancer     Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Some organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical can also be used as an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical reaction     A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).

climate     The weather conditions prevailing in one area, in general, or over a long period.

clone     An exact copy (or what seems to be an exact copy) of some physical object. (in biology) An organism that has exactly the same genes as another, like identical twins. Often a clone, particularly among plants, has been created using the cell of an existing organism. Clone also is the term for making offspring that are genetically identical to some “parent” organism.

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.

compound     (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.

database     An organized collection of information.

dementia     A type of mental disorder caused by disease or injury that causes people to gradually lose all or part of their memory. It may start out temporary and build to a permanent condition where the ability to reason also is impaired.

developing country     A relatively poor nation with little industry and a lower standard of living than industrial countries, such as the United States, Germany and Japan.

diet     The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health. (verb) To adopt a specific food-intake plan for the purpose of controlling body weight.

digest     (noun: digestion) To break down food into simple compounds that the body can absorb and use for growth. Some sewage-treatment plants harness microbes to digest — or degrade — wastes so that the breakdown products can be recycled for use elsewhere in the environment.

dilate    To temporarily swell or expand in size. 

DNA     (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.

emulsify    To blend two materials together that do not ordinarily want to mix and stay blended. An additive that helps keep such blended materials from separating again is known as an emulsifier.

environment     The sum of all of the things that exist around some organism or the process and the conditions that those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

fat     A natural oily or greasy substance occurring in plants and in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat is also a vital nutrient, though it can be harmful to one’s health if consumed in excessive amounts.

fermentation    (v. ferment) The metabolic process of converting carbohydrates (sugars and starches) into short-chain fatty acids, gases or alcohol. Yeast and bacteria are central to the process of fermentation. 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.

fruit     A seed-containing reproductive organ in a plant.

gene     (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

genome     The complete set of genes or genetic material in a cell or an organism. The study of this genetic inheritance housed within cells is known as genomics.

habitat     The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

infection     A disease that can spread from one organism to another. It’s usually caused by some sort of germ.

Maya     A native American culture developed by people who lived between 2500 B.C. and 1500 A.D. in what is now parts of southern Mexico (its Yucatan Peninsula) and Central America. At its height (between about 250 and 900 A.D.), the density of people in some Mayan cities was equal to that in Medieval Europe.

meta-analysis     An investigation of data from a broad range of studies in a given area of research. It often comes from essentially pooling together data from a series of small studies, none of which on their own might have had the statistical power to make broad generalizations from their findings. Such studies also suffer from a weakness: The studies they draw upon may not be similar enough to safely mash-up. It might be like looking for the effects of apples by combining studies on apples and oranges. Or anticipating effects in children from studies that had focused almost entirely on the elderly. Strong meta-analyses are those which comb through data from very similar types of studies.

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).

organ     (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.

oxidation     A process that involves one molecule’s theft of an electron from another. The victim of that reaction is said to have been “oxidized,” and the oxidizing agent (the thief) is “reduced.” The oxidized molecule makes itself whole again by robbing an electron from another molecule. Oxidation reactions with molecules in living cells are so violent that they can cause cell death. Oxidation often involves oxygen atoms — but not always.

pH     A measure of a solution’s acidity. A pH of 7 is perfectly neutral. Acids have a pH lower than 7; the farther from 7, the stronger the acid. Alkaline solutions, called bases, have a pH higher than 7; again, the farther above 7, the stronger the base.

rainforest     Dense forest rich in biodiversity found in tropical areas with consistent heavy rainfall.

resistance     (as in disease resistance) The ability of an organism to fight off disease. 

tissue     Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

trait     A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.

variant     A version of something that may come in different forms. (in biology) Members of a species that possess some feature (size, coloration or lifespan, for example) that make them distinct. (in genetics) A gene having a slight mutation that may have left its host species somewhat better adapted for its environment.


Journal: K. Ried, P. Fakler and N.P. Stocks. Effect of cocoa on blood pressure. Cochrane Database of Systematic Reviews 2017. Issue 4. Article No. CD008893. Published online April 25, 2017. doi: 10.1002/14651858.CD008893.pub3.

Journal: H Schmitz & H.-Y. Shapiro. The future of chocolate. Scientific American. Vol. 24, published online May 28, 2015. doi: 10.1038/scientificamericanfood0615-28.

Journal: R. Latif. Health benefits of cocoa. Current Opinion in Clinical Nutrition & Metabolic Care. Vol. 16, published online October 2013. doi: 10.1097/MCO.0b013e328365a235.

Journal: A. Nehlig. The neuroprotective effects of cocoa flavanol and its influence on cognitive performance. British Journal of Clinical Pharmacology. Vol. 75, published online July 10, 2012. doi: 10.1111/j.1365-2125.2012.04378.x.

Journal: S.R. Bauer et al. Cocoa consumption, cocoa flavanols, and effects on cardiovascular risk factors: An evidence-based review. Current Cardiovascular Risk Reports. Vol. 5, published online February 2, 2011. doi: 10.1007/s12170-011-0157-5.

Journal: S.N. Maximova et al. Field performance of Theobroma cacao L. plants propagated via somatic embryogenesis. In Vitro Cellular & Developmental Biology — Plant. Vol. 44, published online October 23, 2008. doi: 10.1007/s11627-008-9130-5.