A new review of studies looking at the
health effects of avocados finds that there is "satisfactory
clinical evidence" that the fruit can help to treat metabolic
syndrome.
Metabolic syndrome is defined as a
cluster of risk factors that can raise the risk of other health
conditions, such as type 2 diabetes, heart disease, and stroke.
Risk factors include abdominal obesity,
low levels of high-density lipoprotein (HDL) cholesterol - or "good"
cholesterol - high triglyceride levels, high blood pressure, and high
fasting blood sugar.
The presence of at least three of these
risk factors warrants a diagnosis of metabolic syndrome. According
to the American Heart Association, metabolic syndrome affects around
23 percent of adults in the United States.
Adopting a healthful diet is considered
one of the best ways to prevent or treat metabolic syndrome. The new
review - recently published in the journal Phytotherapy Research -
suggests that avocados should form a part of this diet.
Avocados are a fruit from the avocado
tree, or Persea americana, which is native to Mexico and Central and
South America.
A number of studies have documented the
possible health benefits of avocado. A study reported by Medical News
Today in 2014, for example, found that eating half an avocado with
lunch may aid weight loss, while more recent research linked the
fruit to reduced levels of low-density lipoprotein (LDL) cholesterol,
known as "bad" cholesterol.
These benefits have been attributed to
the bioactive components of avocados, which include carotenoids,
fatty acids, minerals such as calcium, iron, and zinc, and vitamins
A, B, C, and E.
For their review, co-author Hossein
Hosseinzadeh, of Mashhad University of Medical Sciences in Iran, and
colleagues set out to determine how these components might help to
combat the risk factors of metabolic syndrome.
Avocado has strongest effect on
cholesterol levels. To reach their findings, the researchers
analyzed the results of various in vivo, in vitro, and clinical
studies that investigated the effects of avocado on metabolic health.
Hosseinzadeh and colleagues found that
the fruit has the strongest impact on lipid levels - that is, levels
of HDL cholesterol, LDL cholesterol, total cholesterol, and
triglycerides.
As an example, the team points to one
study of 67 adults, of whom 30 had a healthy lipid profile and 37 had
mild hypercholesterolemia. After adhering to an avocado-enriched
diet for 1 week, both groups showed significant reductions in total
and LDL cholesterol and triglyceride levels.
"The reported mechanism of this
effect was regulating of the hydrolysis of certain lipoproteins and
their selective uptake and metabolism by different tissues such as
liver and pancreas," explain the authors.
"Another possible mechanism could
be related to the marked proliferation of the liver smooth
endoplasmic reticulum which is known to be associated with induction
of enzymes involved in lipid biosynthesis."
An 'herbal dietary supplement' can help
treat metabolic syndrome. The review also uncovered evidence that
avocado is beneficial for weight loss. The researchers cite one
study that found overweight or obese adults who ate one avocado every
day for 6 weeks experienced significant decreases in body weight,
body mass index (BMI), and the percentage of body fat.
Additionally, the team identified a
number of studies associating avocado intake with reductions in blood
pressure among patients with hypertension, and evidence suggests that
the fruit might also help to reduce atherosclerosis - the narrowing
or hardening of arteries caused by a buildup of plaque.
Notably, Hosseinzadeh and colleagues
found that it is not just the flesh of the avocado that can benefit
metabolic health - the peel, seed, and leaves of the fruit may also
help.
One study published in 2014, for
example, found that a daily dose of oil extracted from avocado leaves
led to reductions in total and LDL cholesterol and blood pressure.
Overall, the researchers conclude that
avocado may be effective for the treatment of risk factors associated
with metabolic syndrome, though further research is warranted. They
write: "In this review article, satisfactory clinical evidence
suggested that avocado can be used as herbal dietary supplements for
treatment of different components of [metabolic syndrome].
Although, avocado like other herbal
products is safe and generally better tolerated than synthetic
medications, there is limited scientific evidence to evaluate
different side effects because of contaminants, or interactions with
drugs. Besides, further studies need to be accomplished on the
metabolic effects of different parts of avocado for other possible
mechanisms."
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