Today’s Chemist at Work (ACS)

Journalist: Mary Ann Ryan

July, 1999

Chocolate lovers of the world, listen up: your day of vindication may be at hand. You have no doubt been indulging your cravings despite everything you know about the junk-food status of those candy bars, death-by-chocolate cakes, and hot fudge sundaes you eat. But now comes news from the ACS National Meeting in Anaheim, and other sources as well, holding out the hope that chocolate might not be all bad.

I am talking about papers presented at the Anaheim meeting entitled, "Chocolate: A Rich Source of Polyphenol Antioxidants in the American Diet," (1) "Capacity of Polyphenolic-Rich Beverages [including cocoa] to Inhibit LDL Oxidation," (2) and "Potential Cardiovascular Health Benefits of Oligomeric Procyanidins [a subclass of polyphenol antioxidants] Present in Chocolate and Cocoa." (3)

These findings intrigued me because a considerable body of published research on fruits and vegetables suggests that the antioxidant compounds found in these foods in abundance provide protection against cancer and cardiovascular disease. Teas and wine have also been identified as excellent sources of antioxidants. And now chocolate, considered sublime for its taste and texture but cursed (from a health standpoint) for the fat and sugar that invariably accompany them, is shown to be high in compounds with antioxidant activity. Could this boost chocolate up a few notches in the health column?

Following up on the Anaheim papers with a literature search on chocolate, I came across some additional information guaranteed to put a smile on the faces of chocoholics. How about "Chocolate Lovers May Live Longer," a December, 1998, Associated Press article reporting on a Harvard University School of Public Health study finding that people who consume candy live, on average, almost a year longer than those who don’t. (4) Or several publications based on research at Pennsylvania State University showing that stearic acid, the main saturated fatty acid in chocolate, does not raise blood cholesterol levels as other saturated fats do. (5) And finally a few reports that cast doubt on some firmly entrenched, negative beliefs about chocolate concerning caffeine content, migraine headaches, allergies, and addictive effects. (See the box, "Misconceptions About Chocolate.")

As I read these various reports, I felt as though I were being transported back in time to Woody Allen’s movie Sleeper from the 1970’s. The main character, Miles Monroe, is the owner of The Happy Carrot Health Food Store in Greenwich Village before he is frozen for 200 years. He wakes up after his long sleep to find that the new health foods are hot fudge, steak, and cream pies.

Although it is unlikely we will be elevating chocolate to health-food status anytime soon, the new findings about chocolate were interesting enough to prompt a further look into what is known about it and how consumption of it might affect health.

[SIDEBAR]:

Americans eat a lot of chocolate in the form of candy (about 4.6 kg/yr per person, or >10 lbs) but not as much as people in some of the northern European countries. Estimated chocolate intake in Switzerland, the country with the highest consumption, is 9.9 kg/yr (>20 lbs) for each person, double the U.S. amount. (ref.) A typical milk chocolate bar (1.4 oz) has a mass of 40 grams, so U.S. consumption would approximate 114 candy bars a year for every inhabitat, if we simplify things a bit by assuming that all chocolate candy intake is in the form of such bars. Each bar contains approximately 210 calories, 13 grams of fat (7 of which are saturated), 23 g of carbohydrate, and 3 g of protein. (ref)

Chocolate comes from beans harvested from the cocoa tree (Theobroma cacao), native to Central America. The beans are fermented, dried, roasted and pressed to give a chocolate liquor, which consists about a 50:50 mix of cocoa particles and cocoa butter.

If the chocolate liquor is further pressed to extract more of the cocoa butter (all but 10-25% of it), and the remaining paste cooled, ground, and sifted, cocoa powder results. The primary nutrients in cocoa besides the fats and fatty acids from the cocoa butter that remains in it, include various carbohydrates (a portion of which is the dietary fiber cellulose) and protein. Other contents present in smaller quantity are mineral salts (of Mg, P, Na, K, Ca, Fe, Zn, Cu, Mn), theobromine (the principal alkaloid of the cocoa bean), caffeine, polyphenols, and water.

· Unsweetened chocolate is a mixture of cocoa powder and refined cocoa butter.

It is too bitter to eat and is used mainly in baking.

· Dark chocolate (bittersweet and semisweet) contains cocoa, cocoa butter and

varying amounts of sugar.

· Milk chocolate has milk as well as cocoa, cocoa butter, and varying amounts of

sugar. Flavorings such as vanilla are sometimes added.

· White chocolate contains no chocolate liquor and no polyphenols, but only cocoa

butter, sugar, milk and flavorings.

Most of the ingredients of chocolate have been known for some time. Of greater interest are the new findings that chocolate contains substantial amounts of antioxidants in the form of complex mixtures of phenolic compounds, and that these may have beneficial effects on health. Some background on what is known about dietary antioxidants in general may be helpful before we look at those in chocolates.

Why should antioxidants be important to health? Cells in the body are constantly exposed to reactive oxygen species (ROS) such as hydrogen peroxide (H202), superoxide anion(O2-), hydroxyl radical (OH-), and hypochlorous acid (HOCl) which are capable of causing cellular damage. Most of the ROS are produced in the course of ordinary biological processes and are prevented from doing harm by the body’s internal antioxidant defense systems; i.e., antioxidant enzymes within the cells. However, the defense system is not perfect, and some ROS escape it. Furthermore, illnesses, aging, or external factors such as air pollution, smoking, or the effects of UV radiation can lead to additional ROS and overwhelm the internal defenses. This is where food sources of antioxidants become important, forming a second line of defense to scavenge free radicals and prevent damage.

Consumption of fruits and vegetables – good sources of antioxidants – have been found to correlate positively with protection against cardiovascular disease, cancer, and cataracts, as well as slowing the effects of aging. In addition to fruits and vegetables, tea and wine are also high in antioxidant compounds. Some researchers believe that it is the antioxidants in wine that are responsible for the "French paradox," the finding that moderate wine consumption correlated with the lower mortality rate from heart disease in certain people in France despite their intake of foods high in saturated fat. Phenolic antioxidants have been shown to inhibit the oxidation of LDL cholesterol, and mounting evidence suggests that it is the oxidized form of LDL that leads to the buildup of fatty plaques in arteries.

Vitamin C, E, and beta-carotene are antioxidants. However, these substances are only part of a much larger mix of antioxidant compounds found in fruits and vegetables. Therefore, much of the recent research has reported "total antioxidant activity" or "total antioxidant capacity" of specific foods or beverages. (See the box on "Foods and Beverages High in Antioxidants" for more information.)

More recent research by Joe Vinson at The University of Scranton, who has been studying total polyphenols in foods and beverages in the American diet, turned his attention to chocolate. His studies have shown that on a weight basis, " … the concentration of polyphenols in milk chocolate is higher than in red wines, black or green teas. It is 20 times higher than in tomatoes, 2 times higher than in garlic and over 3 times higher than in grapes." He also notes that dark chocolate provides over twice the level of polyphenols as milk chocolate per serving. However, white chocolate contains no polyphenol antioxidants.

Harold Schmitz, Group Manager for the Analytical and Applied Sciences Group at M&M/MARS, says that an important next step in studying antioxidants in chocolate and other foods will be to gain an understanding of the biological effects of different fractions of the polyphenolic compounds, rather than just looking at total polyphenols. His group, working in collaboration with researchers at UC Davis, has developed an analytical method based on HPLC/MS for separating and identifying procyanidins, a diverse subgroup of polyphenols. (7) They are finding that not only do procyanidins collectively have antioxidant activity and possible cardiovascular benefits, but that different fractions of procyanidin oligomers (e.g., dimers, trimers, tetramers, etc.) have different antioxidant potentials and, therefore, probably different biological potentials.

This last point raises an important issue. Because little is known about the physiological effects of specific antioxidants in the complex mixtures found in chocolate, fruits, vegetables and other sources, and because these mixtures do not contain exactly the same compounds (there is some overlap, but there are many differences), it is wise to follow the standard advice of dieticians: health is best served by eating a wide variety of foods and a balanced diet. In other words, don’t start substituting chocolate for broccoli thinking you will get the identical antioxidant benefit.

So, how much chocolate can I eat?

Taking into consideration all that has been said above about chocolate, we are still left with the question as to whether it is generally a good food for health. As with many questions in life, this one does not have a simple answer. Chocolate is usually consumed in forms that have a high sugar and fat content, and for this reason ought to be limited in the diet. Yet the antioxidants it contains are likely to be positive for health, although more in vivo research needs to be done to confirm this. I asked Julie Seed, a dietician at the Francis Stern Nutrition Center of Tufts University, how she might assess chocolate’ s place in the diet in light of its high antioxidant content. She said, "We would still need to consider whether it is the preferred source of these compounds, which are also abundant in fruits and vegetables." There is no definitive answer. But at least we have more evidence than we did a few years ago that chocolate is a more complex and interesting food than we may have thought, and that it may have some health benefits.

[SIDEBAR]:

Chocolate causes migraine headaches. A double-blind, placebo-controlled study of chocolate’s ability to induce headaches in 63 women with chronic headache was conducted at the University of Pittsburgh Pain Evaluation and Treatment Institute in 1997. Conclusion: Contrary to the commonly held belief of patients and physicians, chocolate does not appear to play a significant role in triggering headaches in typical migraine, tension-type, or combined headache sufferers." (Source: Cephalalgia 1997 Dec. 17(8):855-62)

Chocolate is a common cause of allergies: A recent study showed that only one out of 500 people who thought they were allergic to chocolate actually tested positive. (ref. needed)

Chocolate is Addictive: Although many people experience cravings for chocolate, there is little evidence from existing studies that these are due to addiction. The Mayo Clinic Health Letter (February, 1995) says, "It’s more likely chocolate cravings occur simply because chocolate tastes so good."

[SIDEBAR]

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REFERENCES [to be added]