What Is Homocysteine?
Homocysteine is a non-protein alpha-amino acid that is intimately linked to vitamin B12. Blood levels of B12 and homocysteine are inversely proportional – so the more B12 you have, the less homocysteine you have.
Why Is Homocysteine Important?
High levels of homocysteine (a condition known as ‘hyperhomocysteinemia’) are associated with a variety of physical and mental health problems, including coronary artery disease, early pregnancy loss, strokes, Alzheimer’s disease and neural tube defects.
Ultimately, people with elevated homocysteine have a singificantly increased risk of mortality.
What Causes These Problems?
When it comes to homocysteine and its associated health problems, it can be difficult to separate correlation from causation. The reason for this is its close connection to vitamin B12 (and also to folate aka vitamin B9).
Some of the symptoms of high homocysteine may actually be symptoms of B12 deficiency and vice versa, as the two conditions tend to go hand in hand.
However, it’s known that a patient with elevated homocysteine levels will be more prone to endothelial cell injury, which generally leads to inflamed blood vessels. This can then result in atherosclerosis (basically a thickening of the artery walls) and consequently ischemia, where the blood supply to various tissues is restricted.
This chain of consequences is one of the possible mechanisms by which homocysteine could cause an increased risk of coronary artery disease. But as mentioned above, it’s difficult to completely rule out independent factors.
Why Is There A Connection Between B12 And Homocysteine?
These two chemicals are closely related because of a reaction that occurs between them inside your body.
Methionine is another amino acid, one that you get from the protein in your diet. This can be internally converted into homocysteine, but the reaction is reversible. Converting homocysteine back into methionine requires the use of vitamin B12 – which is why high B12 levels will reduce the amount of homocysteine in your body.
In fact, this reaction is so consistent that measuring homocysteine levels can sometimes provide a better picture of a patient’s B12 status than you would get from measuring the amount of B12 directly. This is because different people at different life stages may store more or less B12 in tissues rather than in the blood, which could potentially lead to a misdiagnosis of vitamin B12 deficiency.
Folate deficiency may also cause increased levels of homocysteine.
What Can You Do About It?
Unfortunately, it seems that lowering your homocysteine levels may not actually reduce the risks. Several scientific studies have found this to be the case, although there’s a chance that it may help some patients to reduce their risk of suffering a stroke. It could be the case that prevention is better than cure.
For non-meat eaters, elevated homocysteine is normally caused by a lack of vitamin B12 rather than insufficient folate. This is particularly true for vegans, but the conclusion holds for vegetarians and even lacto-ovo vegetarians to a slightly lesser degree.
If you don’t eat meat (or if you’re over the age of 50 and thus likely suffer from impaired B12 absorption), then taking regular vitamin B12 supplements should ensure that your homocysteine levels always stay within healthy limits.
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