Why is it 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A recent unpublished study among Swedish school children aged between 9 and 15 suggested that elevated levels of homocysteine could have a direct impact on achievement at school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.
Coronary Heart Disease
The Middle Years
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.
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%.
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.
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.
People with diabetes are at risk of having high homocysteine as abnormally raised body insulin levels (which control the sugar content of the blood) make it very difficult for the body to lower and maintain healthy levels of homocysteine.
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.
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 oestrogen levels. This in turn appears to raise homocysteine and increase the chance of developing osteoporosis later on in life.
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.
Alzheimer’s and Dementia
The later years
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.
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%.