Studies
compare impacts of dietary red meat versus other protein sources.

Heart
disease is the leading cause of death for both men and women in the
United States and every year about 610,000 people die of heart
disease, for one in every four deaths. Statistics from the Cayman
Islands Economics & Statistics Office have revealed that diseases
of the circulatory system are the leading causes of death in Cayman
Islands.

In
concurrent studies, Cleveland Clinic researchers have uncovered new
mechanisms that demonstrate why and how regularly eating red meat can
increase the risk of heart disease, and the role gut bacteria play in
that process.

The
research, led by Stanley Hazen, M.D., Ph.D., builds upon previous
work showing TMAO (trimethylamine N-oxide) – a gut bacteria
byproduct formed during digestion – can lead to the development of
cardiovascular disease, including heart attacks and strokes. TMAO is
produced when gut bacteria digest choline, lecithin and carnitine,
nutrients that are abundant in animal products such as red meat and
liver and other animal products.

In
a new dietary intervention study published in the European Heart
Journal, the researchers found that a diet rich in red meat as the
primary protein source significantly increases circulating TMAO
levels, compared to diets with white meat or non-meat as protein
sources. The study showed chronic red meat consumption enhanced the
production of TMAO by gut microbes and reduced the kidneys’
efficiency of expelling it. Both enhanced production and reduced
elimination caused by a red meat diet contribute to elevation in TMAO
levels, which has been linked to the development of atherosclerosis
and heart disease complications.

High
levels of TMAO in the blood have been shown to be a powerful tool for
predicting future heart attack, stroke and death risks, according to
previous research initially spearheaded by Dr. Hazen and his team,
and subsequently replicated around the world. TMAO testing is now in
clinical use as a result. Dr. Hazen chairs the Department of Cellular
and Molecular Medicine in Cleveland Clinic’s Lerner Research
Institute and is co-section head of Preventive Cardiology &
Cardiac Rehabilitation in the Miller Heart &Vascular Institute.

The
study included 113 participants who sequentially (in random order)
were provided complete meal plans prepared using either red meat,
white meat or non-meat (mostly vegetarian) protein sources as 25
percent of their daily calories. All participants had a wash-out diet
in between meal plans.

After
one month of the red meat diet, the vast majority of study
participants experienced an elevation in TMAO levels in blood and
urine. On average, TMAO levels in the blood increased approximately
3-fold during the red meat diet, compared to the white meat or
non-meat diets, with some patients showing over a 10-fold rise.
Similar increases were observed in the urine. However, after patients
stopped the red meat diet, TMAO levels in the blood and urine
subsided over the following month.

The
study also revealed the unanticipated finding that a participant’s
chronic dietary choices impacted kidney function by changing the
effectiveness of the kidneys to expel compounds. For example, while a
red meat diet decreased TMAO excretion, the red meat diet increased
the excretion efficiency of carnitine and other carnitine-derived
metabolites.

“This
is the first study of our knowledge to show that the kidneys can
change how effectively they expel different compounds depending on
the diet that one eats – other than salts and water,” said Dr.
Hazen, who also directs Cleveland Clinic Center for Microbiome and
Human Health. “We know lifestyle factors are critical for
cardiovascular health, and these findings build upon our previous
research on TMAO’s link with heart disease. They provide further
evidence for how dietary interventions may be an effective treatment
strategy to reduce TMAO levels and lower subsequent risk of heart
disease.”

About
Cleveland Clinic

Cleveland
Clinic is a nonprofit multispecialty academic medical center that
integrates clinical and hospital care with research and education.
Located in Cleveland, Ohio, it was founded in 1921 by four renowned
physicians with a vision of providing outstanding patient care based
upon the principles of cooperation, compassion and innovation.
Cleveland Clinic has pioneered many medical breakthroughs, including
coronary artery bypass surgery and the first face transplant in the
United States. U.S. News & World Report consistently names
Cleveland Clinic as one of the nation’s best hospitals in its
annual “America’s Best Hospitals” survey.

Among
Cleveland Clinic’s 52,000 employees are more than 3,600 full-time
salaried physicians and researchers and 14,000 nurses, representing
140 medical specialties and subspecialties. Cleveland Clinic’s
health system includes a 165-acre main campus near downtown
Cleveland, 11 regional hospitals, more than 150 northern Ohio
outpatient locations – including 18 full-service family health
centers and three health and wellness centers – and locations in
Weston, Fla.; Las Vegas, Nev.; Toronto, Canada; Abu Dhabi, UAE; and
London, England. In 2017, there were 7.6 million outpatient visits,
229,000 hospital admissions and 207,000 surgical cases throughout
Cleveland Clinic’s health system. Patients came for treatment from
every state and 185 countries. Visit us at clevelandclinic.org.
Follow us at twitter.com/ClevelandClinic. News and resources
available at newsroom.clevelandclinic.org.