Combining
Lab Tests Helps Identify Heart Risks
Measuring total and high-density lipoprotein (HDL) cholesterol
along with a third blood marker, C-reactive protein (CRP), appears to be the
best strategy for assessing women's cardiovascular risk, according to a study
in the Journal of the American Medical Association (JAMA).
Experts say the new findings will likely play an important
role in any new screening guidelines.
"At the end of the day, you can pretty much get where you
need to be with total [cholesterol], HDL, and CRP," says study author Dr. Paul
Ridker, director of the Center for Cardiovascular Disease Prevention at Brigham
and Women's Hospital in Boston.
"It's a win-win situation, in that some individuals who
are currently estimated to be at moderate risk will be at quite high risk when
we measure CRP, so we can do a better job of targeting therapies," Dr. Ridker
adds.
On the other hand, he notes, "there are probably other patients
whose risk isn't as high as we thought, so we can save them the toxicity of
the drugs."
Cholesterol is a waxy substance that can be found in all
parts of your body. It aids in the production of cell membranes, some hormones,
and vitamin D.
The cholesterol in your blood comes from two sources: the
foods you eat and your liver. However, your liver makes all of the cholesterol
your body needs.
Cholesterol and other fats are transported in your blood
stream in the form of spherical particles called lipoproteins. The two most
commonly known lipoproteins are low-density lipoproteins (LDL) and high-density
lipoproteins (HDL).
CRP is a special type of protein produced by the liver that
is only present during episodes of acute inflammation.
The most important role of CRP is its interaction with the
complement system, which is one of the body's immunologic defense mechanisms.
While cholesterol levels have long been key in predicting
cardiovascular risk, the search for new, reliable measurements has continued
because experts say half of all heart attacks and strokes occur in individuals
with normal cholesterol levels.
Dr. Ridker first discovered CRP, a marker of inflammation,
about a decade ago.
While CRP is not currently part of the regular panel of
tests, 25 major studies now suggest that CRP levels predict future cardiovascular
events in both men and women.
"This high-sensitivity CRP has been getting a lot of positive
feedback, showing that it actually can add some information, especially in
intermediate risk, and may be important to follow," says Dr. Mary Ann McLaughlin,
an assistant professor of medicine at Mount Sinai School of Medicine in New
York City.
At the same time, Dr. Ridker points out, physicians are
under increasing pressure to use more expensive tests, focused on blood compounds
such as apolipoprotein A-I and B100.
There has been little data to support using these tests,
however, he says.
For this study, Dr. Ridker and his colleagues followed 15,632
initially healthy women, ages 45 and older, for a decade. All of the women
were enrolled in the ongoing Women's Health Study.
Dr. Ridker's team measured blood levels of total cholesterol,
LDL (“bad”) cholesterol, HDL (“good”) cholesterol,
non-HDL cholesterol, the apolipoproteins A-I and B100, high-sensitivity CRP,
and several ratios of these measurements.
Women with the highest levels of total cholesterol faced
twice the risk of future heart disease, the researchers report, while those
with the highest levels of non-HDL cholesterol were at a risk that was 2.5
times greater.
Even more impressive was the finding that women with the
highest blood levels of CRP faced triple the risk of cardiovascular events
such as heart attack or stroke.
"Perhaps of equal importance, these all measure different
facets of risk and thus are 'additive' to each other," Dr. Ridker explains.
"Also important is that these risks are adjusted for age,
smoking, blood pressure, diabetes, and obesity, and thus are fully independent
of 'traditional' risk factors for heart disease," he says.
All of this means that standard lipid measures - namely,
the ratio of total cholesterol to HDL cholesterol - rather than more complex
measures such as apolipoproteins A-I and B100, should be the physician's primary
method of evaluating cardiovascular risk, the researchers conclude.
"They're saying that adding these extra tests did not give
them any more information," Dr. McLaughlin remarks. "The bottom line is that
we can still use the good old ratio of total to HDL, or the non-HDL cholesterol,
as predictors of cardiovascular risk and that should be good enough."
And CRP was icing on the cake. "CRP adds a lot of information
on risk," Dr. Ridker says.
"There's a great debate going on right now whether to add
CRP to the guidelines, whether the [previous] decision to go with non-HDL cholesterol
was a good one and whether or not expensive lipid measures are required," Dr.
Ridker adds. "This paper will be very influential for thinking about these
issues."
Always consult your physician for more information.
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If it tastes good it must be bad, so the saying goes,
but delicious dark chocolate may be the exception to the rule, say researchers
in the journal Hypertension.
In addition to all the pleasurable sensations associated
with the sweet, it may also help lower blood pressure by an average of 10
percent while improving the body's sensitivity to insulin, researchers report.
However, this benefit applies only to dark chocolate,
which is rich in flavonoids - the same antioxidant compounds found in fruits,
vegetables, and whole grains that are known to help lower blood pressure,
the researchers say.
"It turns out that chocolate is not only a pleasurable
food, but it fits in quite nicely with the other healthy recommendations," says
coauthor Jeffrey B. Blumberg, a professor of nutrition and a senior scientist
at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts
University.
"We found that three ounces of dark chocolate per day
over several weeks reduced blood pressure in patients with essential hypertension
and also seemed to provide a benefit on their insulin sensitivity," he adds.
In the study, Dr. Blumberg's team had 10 men and 10 women
eat 3.5 ounces of dark chocolate every day for 15 days. All of these people
had high blood pressure and none were taking blood pressure medications.
First, the researchers asked five of the men and five
of the women to eat dark chocolate while the others ate white chocolate,
which contains no flavonoids. Then after another week of no chocolate, the
groups "crossed over" and ate the other chocolate.
In the 15 days they were eating dark chocolate, individuals
displayed an average 11.9 mm Hg (millimeters of mercury) drop in their systolic
blood pressure (the top number in a blood pressure reading) and a 8.5 mm
Hg drop in diastolic blood pressure (the lower number).
However, there was no drop in blood pressure when they
ate flavonoid-free white chocolate, the researchers found.
Given these results, Dr. Blumberg believes that dark chocolate
can be good for you.
"Dark chocolate can be included as part of a healthful
diet in patients who have hypertension," he says.
However, he cautions that you cannot just add it on top
of your diet.
"It's still a high-calorie food,” he says. “You
don't want to have excess calories or put on weight if you have hypertension.
But as part of a healthful diet, it is something that you can enjoy and not
feel you are violating the principles of a healthful diet."
Dr. Blumberg thinks that being able to enjoy some chocolate
can also make it easier to stay on a healthy diet that is rich in fruits,
vegetables, and whole grains.
One expert sees this study as part of a body of evidence
that shows that chocolate is good for us.
"Dark chocolate may be health-promoting," says Dr. David
L. Katz, an associate clinical professor of public health and director of
the Prevention Research Center at Yale University School of Medicine.
Dr. Katz, who is doing his own research into the benefits
of chocolate, notes that chocolate is rich in not only antioxidants, but
also magnesium and fiber.
"The predominant saturated fat in dark chocolate, stearic
acid, does not raise cholesterol or harm blood vessels," he adds.
"Milk chocolate and white chocolate do not offer any known
health benefits, and provide more calories, sugar, and potentially harmful
oils than dark chocolate," Dr. Katz says, but "dark chocolate may well prove
to be health food."
According to Dr. Katz, there are many unanswered questions
about chocolate: What is the optimal dose of dark chocolate? How high does
the cocoa content need to be to offer health benefits? Who in the population
stands to benefit from eating dark chocolate? Are the benefits of liquid
cocoa and solid chocolate the same? Can people eat chocolate without gaining
weight?
"These answers, and others, will come in time," Dr. Katz
says. "For now, it's clear that not all chocolate is created equal. But it's
delicious to think that indulgence and health may both reside beneath the
same wrapper."
Another expert is more cautious. Without more definitive
data on whether chocolate promotes weight gain that might outweigh its benefits,
Dr. Jeffrey Mechanick, the director of the Metabolic Support Service at Mount
Sinai School of Medicine, is hesitant to recommend it as a health food. "I
would never tell a heart patient or a diabetic to eat more dark chocolate," he
says.
For patients who do not have these health problems, Dr.
Mechanick is more lenient.
"Having a treat every once in a while is fine," he says. "My
preference is that you have dark chocolate, because it's looking like maybe
dark chocolate may have some benefit. But there are no data to support that
it's truly beneficial. It's still unproven that it's beneficial and there
could be risks involved."
Dr. Mechanick also warns that the data about the benefits
of dark chocolate should not mean replacing other high blood pressure therapy
with chocolate.
"Chocolate is not an alternative to traditional lifestyle
changes or to taking medications to reduce risk of heart disease or to treat
diabetes," he says.
Always consult your physician for more information.
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