Flax has been part of human history for well over 30,000
years. Now, researchers from the Perelman School of Medicine at the University of Pennsylvania have discovered that it
might have a new use for the 21st century: protecting healthy tissues and
organs from the harmful effects of radiation. In a study published in BMC Cancer, researchers found that a
diet of flaxseed given to mice not only protects lung tissues before exposure
to radiation, but can also significantly reduce damage after exposure occurs.
“There are only a handful of potential mitigators of
radiation effect, and none of them is nearly ready for the clinic,” says
the principal investigator Melpo Christofidou-Solomidou, PhD, research
associate professor of Medicine, Pulmonary, Allergy, and Critical Care
Division. “Our current study demonstrates that dietary flaxseed, already
known for its strong antioxidant and anti-inflammatory properties, works as
both a mitigator and protector against radiation pneumonopathy.”
In several separate experiments, the researchers fed one
group of mice a diet supplemented with 10% flaxseed, either three weeks before
a dose of X-ray radiation to the thorax or two, four, or six weeks after
radiation exposure. A control group subjected to the same radiation dose was
given the same diet but receiving an isocaloric control diet without the
flaxseed supplement. After four months, only 40% of the irradiated control
group survived, compared to 70 to 88% of the irradiated flaxseed-fed animals.
Various studies of blood, fluids, and tissues were conducted.
Christofidou-Solomidou and her colleagues found that the
flaxseed diet conferred substantial benefits regardless of whether it was
initiated before or after irradiation. Mice on flaxseed displayed improved
survival rates and mitigation of radiation pneumonitis, with increased blood
oxygenation levels, higher body weight, lower pro-inflammatory cytokine levels,
and greatly reduced pulmonary inflammation and fibrosis.
The latter finding is especially exciting, because while
radiation-induced inflammatory damage can be potentially treated with steroidal
therapy (in radiotherapy patients for example), lung fibrosis is essentially
untreatable. “There’s nothing you can give to patients to prevent
fibrosis,” Christofidou-Solomidou points out. “Once a lung becomes ‘stiff’
from collagen deposition, it’s irreversible. We have discovered that flaxseed
not only prevents fibrosis, but it also protects after the onset of radiation
damage.”
Christofidou-Solomidou and her colleagues are focusing
further research on the bioactive lignan component of flaxseed, known as SDG
(secoisolariciresinol diglucoside), which is believed to confer its potent
antioxidant properties. The lignan component also “regulates the
transcription of antioxidant enzymes that protect and detoxify carcinogens,
free radicals and other damaging agents,” she says.
Flaxseed boasts many other qualities that make it
particularly attractive as a radioprotector and mitigator. “Flaxseed is
safe, it’s very cheap, it’s readily available, there’s nothing you have to
synthesize,” Christofidou-Solomidou notes. “It can be given orally so
it has a very convenient administration route. It can be packaged and
manufactured in large quantities. Best of all, you can store it for very long
periods of time.” That makes it especially interesting to government
officials looking to stockpile radioprotective substances in case of accidental
or terrorist-caused radiological disasters.
Coauthor Keith Cengel, MD, PhD, assistant professor of
Radiation Oncology at Penn, explains that in such cases, “a big issue is
the ‘worried well’—all the folks who probably weren’t exposed but are concerned
and want to do something.” Many potential radioprotectors, however, could
have risky side effects. Christofidou-Solomidou adds, “When you give
something to 4 or 5 million ‘worried well,’ you have people with preexisting
medical conditions. You can’t give just anything to people with heart disease,
for example. But this is absolutely safe. In fact, it is known to increase
cardiovascular health, a finding shown by another group of Penn investigators a
few years ago. It’s loaded with omega-3 fatty acids.”
Along with other researchers at the Perelman School of
Medicine, the authors are conducting further pilot studies on the potential of
flaxseed for mitigation of lung damage in patients awaiting lung transplants
and those undergoing radiation therapy for the treatment of intra-thoracic
malignancies. Christofidou-Solomidou is even conducting a pilot study for NASA
on the benefits of flaxseed for astronauts on extended deep space missions.
Lengthy space exploration missions require that the astronauts perform
extravehicular activities (EVAs) for repairs, during which they can face
exposure to high levels of solar and galactic radiation with the added risk
factor of breathing 100% oxygen. “Hyperoxia superimposed with radiation
could potentially cause some lung damage and some reason to worry for the
astronauts,” she says. “We are one of a handful of teams in the US that can
study radiation in addition to hyperoxia. So now we’re adding another level of
complexity to the one-hit, radiation damage studies; the double-hit model is
something novel, nobody has done it before.”