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Cholesterol! The word
strikes fear into the hearts of many Americans. Popular press and
TV have dumbed down the basics of cholesterol:
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High total cholesterol is
associated with heart attack and stroke.
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LDL (low density
lipoprotein) Cholesterol is bad.
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HDL (high density
lipoprotein) Cholesterol is good.
Healthy Cholesterol Levles Aren't Quite That
Simple
There is in fact only one
kind of cholesterol. Whether obtained from the diet or synthesized
by the liver, it is immediately bound to specific carrier
substances, lipoproteins, and transported via the blood stream to
the 60 trillion cells of the body. LDL is the major lipoprotein
responsible for the transport of cholesterol TO the cells of the
body. HDL, in contrast, takes cholesterol FROM the cells of the
body and transports it back to the liver, where it is sequestered,
or metabolized and secreted in the intestine as bile.
Our bodies require a
certain amount of cholesterol for numerous cellular functions,
including cell membrane integrity, absorption of nutrients such as
fat-soluble vitamins, and synthesis of vitamin D and sex hormones.
Too much of it can hurt us, however. Research has demonstrated an
association between elevated LDL and atherosclerosis, a disease of
the arteries causing heart attack and stroke.
How does this work? When
the LDL-cholesterol combination (technically, LDLc) is present in
the blood at a high level, it diffuses across the endothelial cells
that line the interiors of blood vessels and is deposited just
underneath these cells. This leaves a pool of LDL within the wall
of the blood vessel. LDL is susceptible to attack by common
cellular oxidants, which in effect turn it rancid. When LDL is
present in the blood at normal healthy amounts, this does not
occur, as there are substances, such as HDL and cellular
antioxidants, to protect it from oxidation.
When the blood level of LDL
Cholesterol is too high, large amounts of LDL transfer across the
vessel wall, the antioxidant protection is overwhelmed, and LDL is
oxidized (turns rancid). Now it becomes toxic to the cell and
surrounding tissue. The process is aggravated by hypertension (high
blood pressure), a condition characterized by elevated vascular
pressure that can excessively stretch vessels and stimulate the
oxidation of LDL.
Once LDL is oxidized
(oxLDL), the immune system recognizes it as a substance that must
be removed. Unfortunately, this initiates a cascade of events,
causing the recruitment of disease-fighting cells of the immune
system and culminating in an inflamed condition (like a boil)
within the vessel wall. The final result is a vessel with a defect
that can initiate clot formation and heart attack or
stroke.
Since the liver has the
capacity to make cholesterol, we really don't need much of it from
the foods we eat. In general, western industrialized man has too
much LDL, largely as a result of sedentary lifestyles, and a diet
high in substances that promote cholesterol synthesis, such as
saturated fat, and trans fats. More than 90 million American adults
- about 50% - have unhealthy blood-cholesterol levels.
What can you do to avoid
being one of them? Recently, new standards have been suggested for
the desired level of HDL (>40mg/deciliter), LDL (<100mg/dl)
and total cholesterol (<200 mg/dl). As we age, these figures go
in the wrong direction. Total cholesterol and LDL go up; HDL goes
down. Most people can correct these markers of health to optimal or
near optimal levels with minimum effort and cost. This is one area
of healthcare that has real solutions. Various approaches are
available to either control these precursors of poor health or help
maintain levels that are already within the normal
range.
Diet and Lifestyle.
Diet does have an
effect, but the intensity of it varies with age, genetic
constitution and physical condition. The diet should include about
25-30% of total calories from fat. Less than 10% of these calories
should come from saturated fats (which raise LDL), and none from
trans fats (which raise LDL and lower HDL). A diet high in fruits
and vegetables (7 servings/day), nuts and fiber has been
demonstrated to promote a healthy lipid profile.
Lowering total cholesterol
by diet and keeping your total daily intake of cholesterol to less
than 300mg/day almost always improves the ratio of HDL/LDL. It
stimulates the synthesis of LDL receptors in liver cells, thus
decreasing the circulating level of the lousy cholesterol. Avoiding
a sedentary lifestyle and maintaining a regular exercise routine
can significantly improve the level of HDL.
Drugs.
OK, you did all that and your
cholesterol level, although improved, remains in the red zone, so
now what? Numerous ads on TV and elsewhere promote
cholesterol-lowering prescription drugs, but many of us are aware
of documented side effects from these drugs. On the other hand
these drugs, commonly referred to as statin drugs, do work. They
lower cholesterol by as much as 45-50% and raise HDL, while
lowering LDL and another circulating neutral fat, triglyceride. The
bottom line is they have been shown to work, and they decrease
mortality from atherosclerosis.
Supplements.
Dietary supplements can help improve and or maintain cholesterol
levels. One example is a plant-derived substance commonly known as
policosanol. Niacin (vitamin B3), in large doses (>1gm/day), has
a significant effect on lowering triglycerides, and raising HDL,
especially when used in combination with one of the statin drugs or
policosanol. Any decision to try these dietary supplements should
be taken under a health professional’s supervision, since these
products, like the statin drugs, may have side effects.
Another approach to help
maintain cholesterol levels that are already within the normal
range is to supplement with antioxidants, since the body's natural
inflammation response involves oxidants. The potent antioxidant
alpha lipoic acid may help by acting directly to neutralize
oxidants and indirectly by increasing levels of two key
antioxidants, vitamin C and glutathione, in the cells lining the
vessel walls. Lipoic acid also enhances synthesis of the chemical
messenger, nitric oxide, which in turn protects the function of
these cells and promotes vascular relaxation.
Whichever approach you
choose, the important thing for healthy aging is to get your
cholesterol under control and keep it there.
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This month we highlight
once again a study of the powerful antioxidant alpha lipoic acid.
Among the general population, double-blind, placebo-controlled
clinical trials, with human subjects, are perhaps the most widely
known form of healthcare testing. Studies in laboratory animals are
even more extensively used by pre-clinical scientists. To
understand fundamental biochemistry, however, scientists often use
cell cultures.
S
cientists at Vanderbilt
University School of Medicine examined the antioxidant effects of
alpha lipoic acid in cultured human endothelial cells (which line
our blood vessels). They found that alpha lipoic acid enhances both
the antioxidant defenses and the function of endothelial cells. For
details on how alpha lipoic acid protects the cells lining the
arteries to prevent inflammation, click here.
This Research Update
column highlights articles related to recent scientific inquiry
into the process of human aging. It is not intended to promote any
specific ingredient, regimen, or use and should not be construed as
evidence of the safety, effectiveness, or intended uses of the
Juvenon product. The Juvenon label should be consulted for intended
uses and appropriate directions for use of the
product.
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