For years, dark chocolate lovers have rejoiced as study after study has reported that the sweet treat has impressive cardiovascular benefits. Based on this peer-reviewed science, the BaleDoneen Method has long “prescribed” a daily dose of dark chocolate (in small amounts) as part of our evidence-based approach to the prevention of heart attacks, strokes, diabetes, dementia, and other chronic illnesses. 

Recently, a Consumer Reports investigation found that some popular brands of dark chocolate contain potentially harmful levels of two heavy metals: lead and cadmium. Does that mean you stop eating dark chocolate for heart health? For expert answers, we talked to Dr. Brea Seaburg, DNP, ARNP, a Certified Culinary Medicine Specialist and cardiovascular disease prevention specialist at The Prevention Center for Heart & Brain Health in Spokane, Wash.

What did the Consumer Reports investigation reveal?

Using a mix of brands, scientists at Consumer Reports (CR) tested 28 dark chocolate bars for lead and cadmium. To evaluate the potential health risks, the team used California’s maximum allowable dose level (MADL) for lead (0.5 micrograms) and cadmium (4.1 micrograms). These levels were selected because there are no federal limits for these metals in most foods and the scientists believe that the California standard is the most protective of consumer health.

The team found that 23 of the brands contained amounts of lead or cadmium, or both, that exceeded the California standard. The five brands that CR rated as “safer choices because they were below the MADL for both types of heavy metal were:

  • Mast Organic Dark Chocolate 80% Cocoa
  • Taza Chocolate Organic Deliciously Dark Chocolate 70% Cacao
  • Ghirardelli Intense Dark Chocolate 86% Cacao
  • Ghirardelli Intense Dark Chocolate Twilight Delight
  • Valrhona Abinao Dark Chocolate 85% Cacao

Brands that were high in lead included Godiva, Lindt, Hershey’s and Trader Joe’s; and those high in cadmium included Lindt, Dove, and Beyond Good. Trader Joe’s, Theo, and Lily’s were among those that tested high in both metals. CR scientists report that eating as little as one ounce (28.24 grams) per day of the 23 brands that tested high in one or both metals would put an adult over the California MADL.

What are the risks of eating food that contains heavy metals?

If consumed regularly, heavy metals pose the greatest threat to children and pregnant women. In children, particularly those under age 5, lead exposure can cause developmental delays, impair brain and nervous system development, lower IQ, and boost risk for attention deficit hyperactivity disorder (ADHD) and other behavioral problems, according to the World Health Organization. No amount of lead is considered safe for children.

In adults, frequent exposure to lead raises risk for nervous system issues, high blood pressure, reproductive issues, and memory problems. Information on the health effects of cadmium is limited, with a recent study reporting that this metal is found in many common foods in trace amounts that are unlikely to be harmful. People with long-term occupational exposure to cadmium may develop stomach problems, kidney damage, and fragile bones, reports the CDC.

What are the cardiovascular benefits of dark chocolate?

Derived from the pods of the cacao tree, whose botanical name, Theobroma, means “food of the gods,” dark chocolate is rich in flavanols and polyphenols, antioxidant compounds also found in tea, wine, fruits and vegetables. Recent research suggests that dark chocolate has the following benefits for heart health:

  • Lower risk for coronary artery disease (CAD). In the latest study of chocolate’s effects on heart health, researchers from the Cleveland Clinic and other centers analyzed findings from six studies that included 336,289 people. Published in European Journal of Preventive Cardiology, the analysis linked eating chocolate more than once a week to an 8 percent reduction in risk for developing CAD (plaque in the arteries that can lead to a heart attack).
  • Chocolate may help prevent irregular heartbeats. In a recent Harvard study of more than 55,000 people, eating moderate amounts of chocolate lowered risk for atrial fibrillation (AF), a common and dangerous type of heart arrhythmia that elevates risk for stroke, heart failure, cognitive decline, dementia and early death.
  • Reduced risk for heart attacks and strokes. In a study of nearly 20,000 people ages 35 to 65, those who ate the most chocolate had a 39 percent lower risk for heart attack and stroke. The researchers also linked chocolate consumption to lower blood pressure, a factor that may explain its protective properties, since high blood pressure is the leading risk for stroke and a major contributor to heart attacks.
  • Protection against high blood pressure during pregnancy. A Yale study of 2,291 pregnant women found that those who ate more than five servings of chocolate a week reduced their risk of developing pre-eclampsia, pregnancy-induced high blood pressure, by up to 40 percent, compared to women who ate less than one serving a week. Pre-eclampsia is a potentially life-threatening condition that affects about 5% of American moms-to-be and raises their risk for heart disease later in life.
  • Healthier levels of cholesterol and other markers of heart health. Products rich in cacao flavanols (such as dark chocolate or cocoa) may reduce inflammation, triglycerides and insulin resistance (the root cause of almost all cases of type 2 diabetes, as well as 70 percent of heart attacks), according to an analysis of clinical trials that included more than 1,100 people. The researchers also linked these foods to healthier levels of HDL (good) and LDL (bad) cholesterol.

Should I swear off dark chocolate — or not?

At the BaleDoneen Method, we continually update our approach to cardiovascular disease (CVD) prevention, treatment and reversal based on the latest science. Drawing on current evidence, we continue to recommend a daily “dose” of 7 grams of dark chocolate (about ¼ ounce) to support heart and brain health in adults, based on large studies showing that people who consume this amount have significantly lower risk for heart attack, stroke and other CV events than those who eat lower amounts or none.

We also recommend selecting dark chocolate from the brands that Consumer Reports found to be “safer choices,” and following a heart-healthy diet that is high in fruits and vegetables. For optimal CV protection, we advised that our patients follow a diet based on their DNA and the comprehensive arterial wellness program presented in our new book, Healthy Heart, Healthy Brain: The Proven Personalized Path to Protect Your Memory, Prevent Heart Attacks and Strokes, and Avoid Chronic Illness.

For more information on healthy eating, check out our blog posts “For Vibrant Heart Health, Eat the Rainbow,” “The Ten Best and Worst Foods for Your Heart and Brain Health,” “Ten Things to Know About the American Heart Association’s New Dietary Guidelines, and “The Sweet Truth About Fresh Fruit, Fructose and Heart Health.” Also visit our blog for a wide selection of delicious, heart-healthy recipes.