Tilapia Not the Good Fish Seniors Assumed for
Fighting Heart Disease with Omega 3
Potentially dangerous for patients with heart
disease, arthritis, asthma and other allergic and auto-immune diseases
mostly senior citizens
July
8, 2008 When the healthcare community recommends something like
eating fish as a way to guard against heart disease, the most
endangered Americans that would be senior citizens rush to comply.
This time, however, things are being thrown into reverse by new research
finding that farm-raised tilapia, which became one of Americas
favorites in this rush to the fish shop, has very low levels of
beneficial omega-3 fatty acids and, perhaps worse, very high levels of
omega-6 fatty acids.
The researchers from Wake Forest University School
of Medicine say the combination could be a potentially dangerous food
source for some patients, mostly seniors, with heart disease, arthritis,
asthma and other allergic and auto-immune diseases that are particularly
vulnerable to an "exaggerated inflammatory response."
Inflammation is known to cause damage to blood
vessels, the heart, lung and joint tissues, skin, and the digestive
tract.
"In the United States, tilapia has shown the
biggest gains in popularity among seafood, and this trend is expected to
continue as consumption is projected to increase from 1.5 million tons
in 2003 to 2.5 million tons by 2010," write the Wake Forest researchers
in an article published this month in the Journal of the American
Dietetic Association.
They say their research revealed that farm-raised
tilapia, as well as farmed catfish, "have several fatty acid
characteristics that would generally be considered by the scientific
community as detrimental." Tilapia has higher levels of potentially
detrimental long-chain omega-6 fatty acids than 80-percent-lean
hamburger, doughnuts and even pork bacon, the article says.
"For individuals who are eating fish as a method to
control inflammatory diseases such as heart disease, it is clear from
these numbers that tilapia is not a good choice," the article says. "All
other nutritional content aside, the inflammatory potential of hamburger
and pork bacon is lower than the average serving of farmed tilapia."
The article notes that the health benefits of
omega-3 fatty acids, known scientifically as "long-chain n-3
polyunsaturated fatty acids" (PUFAs), have been well documented. The
American Heart Association now recommends that everyone eat at least two
servings of fish per week, and that heart patients consume at least 1
gram a day of the two most critical omega-3 fatty acids, known as EPA (eicosapentaenoic
acid) and DHA (docosahexaenoic acid).
But, the article says, the recommendation by the
medical community for people to eat more fish has resulted in
consumption of increasing quantities of fish such as tilapia that may do
more harm than good, because they contain high levels of omega-6 fatty
acids, also called n-6 PUFAs, such as arachidonic acid.
"The ratio of arachidonic acid (AA) to very
long-chain n-3 PUFAs (EPA and DHA) in diets of human beings appears to
be an important factor that dictates the anti-inflammatory effects of
fish oils," the researchers write. They cite numerous studies, including
a recent one that predicts "that changes in arachidonic acid to EPA or
DHA ratios shift the balance from pro-inflammatory [agents] to
protective chemical mediators which are proposed to play a pivotal
role in resolving inflammatory response" in the body.
For their study, the authors obtained a variety of
fish from several sources, including seafood distributors that supply
restaurants and supermarkets, two South American companies, fish farms
in several countries, and supermarkets in four states. All samples were
snap-frozen for preservation pending analysis, which was performed with
gas chromatography.
The researchers found that farmed tilapia contained
only modest amounts of omega-3 fatty acids less than half a gram per
100 grams of fish, similar to flounder and swordfish. Farmed salmon and
trout, by contrast, had nearly 3 and 4 grams, respectively.
At the same time, the tilapia had much higher
amounts of omega-6 acids generally and AA specifically than both salmon
and trout. Ratios of long-chain omega-6 to long-chain omega-3, AA to EPA
respectively, in tilapia averaged about 11:1, compared to much less than
1:1 (indicating more EPA than AA) in both salmon and trout.
The article notes that "there is a controversy
among scientists in this field as to the importance of arachidonic acid
or omega-6:omega-3 ratios vs. the concentration of long-chain omega-3
alone with regard to their effects in human biology." Those issues are
raised in an editorial in the same issue of the Journal.
The Wake Forest article anticipates that criticism
and notes that one human study involving AA showed a probable
gene-nutrient connection to coronary heart disease in a specific group
of heart disease patients. In another study, four subjects were removed
after consumption of high amounts of AA due to concerns about the effect
of the acid on their blood platelets.
Floyd H. "Ski" Chilton, Ph.D., professor of
physiology and pharmacology and director of the Wake Forest Center for
Botanical Lipids, is the senior author of the Journal article. He said
that in next month's Journal, he will publish a rebuttal to this month's
editorial.
"We have known for three decades that arachidonic
acid is the substrate for all pro-inflammatory lipid mediators," Chilton
said in an interview. "The animal studies say unequivocally that if you
feed arachidonic acid, the animals show signs of inflammation and get
sick.
"A New England Journal of Medicine article three
years ago said if you had heart disease and had a certain genetic
makeup, and you ate arachidonic acid, the diameter of your coronary
artery was smaller, a major risk factor for a heart attack," said
Chilton. "My point is that it's likely not worth the risk in this or
other vulnerable populations."
Chilton said tilapia is easily farmed using
inexpensive corn-based feeds, which contain short chain omega-6s that
the fish very efficiently convert to AA and place in their tissues. This
ability to feed the fish inexpensive foods, together with their capacity
to grow under almost any condition, keeps the market price for the fish
so low that it is rapidly becoming a staple in low-income diets.
"We are all familiar with the classical Hippocratic
admonition, Primum no nocere, 'First, do no harm.' I think it behooves
us to consider this critical directive when making dietary prescriptions
for the sake of health," Chilton said.
"Cardiologists are telling their patients to go
home and eat fish, and if the patients are poor, they're eating tilapia.
And that could translate into a dangerous situation."
Editor's Notes:
Co-authors of the study are Kelly L. Weaver,
Ph.D., Priscilla Ivester, Joshua A. Chilton, Martha D. Wilson, Ph.D.,
and Prativa Pandey, all with Wake Forest School of Medicine. The
research was funded by the National Center for Complementary and
Alternative Medicine and the Office of Dietary Supplements of the
National Institutes of Health (NIH), and by an NIH Molecular Medicine
training grant.
Wake Forest University Baptist Medical Center (www.wfubmc.edu)
is an academic health system comprised of North Carolina Baptist
Hospital, Brenner Children's Hospital, Wake Forest University
Physicians, and Wake Forest University Health Sciences, which operates
the university's School of Medicine and Piedmont Triad Research Park.
The system comprises 1,154 acute care, rehabilitation and long-term care
beds and has been ranked as one of "America's Best Hospitals" by U.S.
News & World Report since 1993. Wake Forest Baptist is ranked 32nd in
the nation by America's Top Doctors for the number of its doctors
considered best by their peers. The institution ranks in the top third
in funding by the National Institutes of Health and fourth in the
Southeast in revenues from its licensed intellectual property.
Keep up with the latest news for senior citizens, baby
boomers
July
8, 2008 When the healthcare community recommends something like
eating fish as a way to guard against heart disease, the most
endangered Americans that would be senior citizens rush to comply.
This time, however, things are being thrown into reverse by new research
finding that farm-raised tilapia, which became one of Americas
favorites in this rush to the fish shop, has very low levels of
beneficial omega-3 fatty acids and, perhaps worse, very high levels of
omega-6 fatty acids.