Why is Homocysteine Harmful?
High levels of homocysteine have been linked to the
development of a number of common and potentially fatal conditions including
coronary heart disease and dementia.
Homocysteine has also been shown to play a crucial role as a key marker for
disease development determining longevity and health throughout a person’s life.
Pregnancy and
Newborns
Women with high homocysteine levels find it harder to
conceive, are at risk from repeated early miscarriages and are over twice as
likely to experience pregnancy complications.
5,883 women in Norway were followed through 14,492
pregnancies with their outcomes and complications recorded against their
homocysteine levels. When the upper quartile homocysteine level was compared
against the lower quartile, the higher homocysteine level led to a 32% increase
in risk of pre-eclampsia, 38% increase in premature birth and 101% increase in
very low birth weight.
Underachievement in
Adolescence
A recent unpublished study among Swedish school children
aged between 9 and 15 suggested that elevated levels of homocysteine could have
a direct impact on achievement at school and neuro-cognitive function. Both the
total sum of school grades and the grades achieved on 10 core subjects were
significantly and negatively associated with elevated levels of plasma
homocysteine.
Middle Years
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Coronary Heart Disease – Homocysteine
is believed to be a causal influence on the development of cardiovascular
disease and the subsequent likelihood of suffering heart attacks (myocardial
infarctions - MI’s). Homocysteine has the ability to change cholesterol into
a far more sinister version which attacks artery walls. As the arteries
become damaged other cells stick until they become clogged, thickened and
less flexible (atherosclerosis). Homocysteine also makes the blood clot more
easily so it is more likely to form a blockage and cause a heart attack.
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Analysis of 92 extensive studies have shown that a
homocysteine reduction of 3µmol/L through folic acid supplementation
reduces the risk of a heart attack by 16%.
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Stroke – Like heart attacks, strokes
are considered to be a type of cardiovascular disease and greatly influenced
by high homocysteine levels. Strokes affect the arteries leading to and from
the brain and can be caused by either a blood clot or a blood vessel
rupturing. These both in turn, block vital oxygen and nutrients reaching the
brain, starving cells and causing potentially irreparable damage.
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Results from the Framingham Study, which is following
three generations of the population of the US town of Framingham, have
confirmed the key role homocysteine plays as a predictor for stroke.
Individuals in the highest homocysteine level quartile have an 82% increased
chance of stroke, emphasising homocysteine as an independent causative agent
of stroke in elderly persons.
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In addition, homocysteine has been shown to have a far more powerful effect
on diabetics than non-diabetics. Elevated homocysteine combined with
diabetes results in a 90% increased risk of mortality within 5 years in
comparison to non-diabetics with high homocysteine levels.
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Osteoporosis - Osteoporosis, a
condition where the density of bone-mass decreases leading to fragile,
weakened bones, has been strongly linked to homocystinuria (elevated urinary
homocysteine) and associated with high homocysteine levels. Postmenopausal
women are particularly at risk from low estrogen levels. This in turn
appears to raise homocysteine and increase the chance of developing
osteoporosis later on in life.
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A Japanese study followed 628 patients aged 65 years or older for one year
after suffering a stroke. A dramatic increase in the number of subsequent
hip fractures was evident, twice to four times higher than that expected in
age-matched healthy control patients. Patients with homocystinuria also had
an increased prevalence of skeletal abnormalities, including osteoporosis,
which is a primary risk factor for hip fracture. Elevated homocysteine
concentrations appears to be independently associated with both osteoporosis
and the increased risk of hip fracture.
Later years
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Alzheimer’s and Dementia -
After 80 years of age, 20% of people develop dementia, the
most common form being Alzheimer’s disease. As homocysteine levels increase, DNA
within the brain is attacked by oxygen, damaged and eventually killed off, with
the body less able to repair damaged brain cells. Over time memory loss
increases as more and more cells die.
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At a recent conference on homocysteine, key findings
relating elevated homocysteine to dementia were presented. Data taken from the
Framingham Study found a homocysteine level of >10µmol/L increased the risk of
dementia in individuals over 60 years old by 75%. Furthermore, a homocysteine
level of over 14µmol/L amplified the risk of developing Alzheimer’s disease by
150%.
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