Chocolate: The New
Chester J. Zelasko, Ph.D. |
December 1, 2006
In the spirit of the
holiday season, and in light of some interesting research, I thought it
appropriate to talk about one of our favorite foods--chocolate. For years,
chocoholics have claimed that chocolate must be a health food because they
feel better when they eat it. It turns out they may be right!
Here’s a brief review of the latest research--but before you reach for that
chocolate candy, be sure to read the entire Newsletter.
In the first study of the possible benefits of chocolate that caught my
attention, researchers examined the effects of dark chocolate and white
chocolate on patients recently diagnosed with hypertension who had not
started a treatment plan (1). In a cross-over study, subjects either
received 100 grams of dark chocolate or 90 grams of white chocolate for 15
days. Those who ate dark chocolate had an average decrease in systolic blood
pressure of 12 mm Hg and a decrease in diastolic blood pressure of 8 mm Hg.
In addition, LDL-cholesterol decreased 3.4 mg/dl. One of the key factors in
the study is that the subjects remained isocaloric. The calories in the
amounts of chocolate used in the study equals about 500 calories. The
subjects had to remove 500 calories from fat and sugar in their diets to be
replaced by the white or dark chocolate.
In another study, subjects were given dark-chocolate food bars containing
plant sterols (2). Sterols are sort of the plant equivalent of cholesterol
in animals and have been shown to lower serum cholesterol when used in
margarines. In a double-blind, placebo-controlled study, subjects with
elevated cholesterol levels who received the dark chocolate food bars with
sterols for six weeks lowered their total cholesterol almost 5% and the
LDL-cholesterol (the lethal cholesterol) 6%. That’s very significant because
for every 1% you lower your cholesterol, you lower your risk of heart
disease 2%. While this study included a factor other than dark chocolate,
researchers demonstrated that a good-tasting, snack-food bar can have a
positive effect on cardiovascular risk factors.
Researchers studied the effects of a single dose of dark chocolate on young
volunteers (3). They found that dark chocolate caused a vasodilation of the
brachial artery, with the peak dilation occurring about an hour after eating
the chocolate. The dilation of blood vessels could explain the decrease in
blood pressure found in other studies.
What’s Special About Dark Chocolate?
In a word, phytonutrients. Specifically, this class of phytonutrients is
called polyphenols. While the exact mechanism of action is not known, it
seems that polyphenols have a beneficial effect on the cells that line
arteries known as endothelial cells. In addition, this class of polyphenols
also acts as antioxidants and has been shown to prevent oxidation of
LDL-cholesterol in test-tube studies (4). That’s important because while
LDL-cholesterol is bad, oxidized LDL-cholesterol is very, very bad.
Certainly more research is warranted but this is important, because of all
the money spent on foods that contain antioxidants, chocolate ranks third
behind fruits and vegetables (4). The key is that most money is spent on
milk chocolate, which does not contain as many polyphenols but has more
sugar and saturated fat. Education will be a key component of getting people
to switch to the right type of chocolate.
Which types of chocolate are those? In a recently published paper,
researchers examined the antioxidant, polyphenol, and procyanidin content of
various forms of chocolate (5). Natural cocoa powder, baking chocolate, and
dark chocolate ranked best in terms of highest levels of antioxidant
activity, total polyphenols, and procyanidins, another type of
Since the holiday season is fast approaching, and the cold weather to go
with it, looks like it’s time for home-made hot chocolate made with cocoa
What This Means for You
With each media announcement of studies on the potential benefits of dark
chocolate, health experts express their concern because even dark chocolate
contains fat and sugar. As mentioned earlier, education must be part of the
process so we make the right choices. And there’s still much more research
to go. For example, most studies use 100 grams (3.3 ounces) of dark
chocolate. We don’t know if 50 or even 25 grams would get the same positive
effect, a smaller effect, or no effect at all. We also don’t know how often
you should eat chocolate to get the positive effects: every day, three times
a week--who knows?
What should you do? Other than making hot chocolate with cocoa powder, it
seems reasonable to eat one ounce of dark chocolate per day. There are two
qualifications. First, you must cut out about 150 calories from
carbohydrates and fat elsewhere in your diet. The other is that you have to
like chocolate. I know chocoholics are saying, “Duh!” but I know that some
people will try anything they think will help their health, whether they
enjoy it or not. There are many other foods that can lower the risk of heart
disease, so try one of those if you don’t like chocolate. But if you love
chocolate, an ounce a day together with that apple might just keep the
- Grassi, D. et al. Cocoa reduces blood pressure and insulin
resistance and improves endothelium-dependent vasodilation in
hypertensives. Hypertension. 2005;46(2):398-405.
- Polagruto, JA et al. Cocoa flavanol-enriched snack bars containing
phytosterols effectively lower total and low-density lipoprotein
cholesterol levels. J Am Diet Assoc. 2006;106(11):1804-1813.
- Vlachopoulos C, et al. Effect of dark chocolate on arterial function
in healthy individuals. Am J Hypertens. 2005;18(6):785-91.
- Vinson, JA et al. Chocolate is a powerful ex vivo and in vivo
antioxidant, an antiatherosclerotic agent in an animal model, and a
significant contributor to antioxidants in the European and American
diets. J Agric Food Chem. 2006; 54(21):8071-6.
- Miller, KB et al. Antioxidant activity and polyphenol and
procyanidin contents of selected commercially available cocoa-containing
and chocolate products in the United States. J Agric Food Chem.