For several years, this substance has been mentioned in the media from time to time in connection with vascular calcification, heart attacks and strokes. However, very few people know exactly what it is all about. Homocysteine is an intermediate product in human protein metabolism, more precisely in the breakdown of methionine. This amino acid must be supplied daily in the diet and serves the body as an important source of sulfur, among other things. Homocysteine, on the other hand, is a toxic waste product and is therefore quickly bound, converted back into methionine with the help of vitamin B12 and folic acid, or further broken down with the help of vitamin B6 and excreted for the most part through the kidneys.
Causes of elevated homocysteine levels
The metabolic pathways described are important in understanding the pathway by which potentially dangerous excess homocysteine can occur in the blood. Here are some of the causes:
- As we age, kidney function declines and homocysteine levels naturally increase (by about 10% every 10 years).
- If not enough folic acid and vitamins of the B group are supplied through the diet, homocysteine can not be converted and thus eliminated. Excessive coffee consumption hinders the absorption of folic acid and B vitamins in the gastrointestinal tract.
- With methionine-rich food (eg eggs, fish, offal, Brazil nuts, corn) is increased homocysteine.
- Numerous drugs affect methionine metabolism and “consume” the B vitamins or folic acid, so that they can no longer adequately perform their tasks. These include antibiotics, tuberculosis drugs, antiepileptic drugs, the pill, rheumatism drugs and expectorants.
- Certain diseases also increase the total need for vitamin B and folic acid, such as diabetes, cancer, liver disease or nerve diseases (neuropathies).
- In renal impairment, the homocysteine is no longer sufficiently degraded and excreted.
- Rarely, there is an underlying congenital disease of amino acid metabolism, where the metabolic pathway itself is disturbed (homocysteinuria).
Incidentally, lack of exercise also seems to drive up the amount of homocysteine.
Too much homocysteine is dangerous
Homocysteine damages the body in several ways. For example, it activates blood platelets – promoting blood clot formation. It damages cells, for example, on the inner walls of blood vessels directly and – via the activation of various mechanisms – also indirectly. It encourages scavenger cells to migrate into the vessel walls and muscle cells to change. The consequences? Permanently elevated homocysteine levels in the blood (hyperhomocysteinemia) presumably promote vascular calcification and thus the development of corresponding diseases: Heart attack, stroke, arterial occlusive disease – diseases from which, after all, almost every 2nd German citizen dies. It also seems to increase the risk of venous thrombosis. In addition, it is discussed that homocysteine is also a risk factor for Alzheimer’s disease and dementia caused by vascular changes, as well as for age-related macular degeneration (AMD), a common visual disorder that increases with age.
Determine homocysteine
Determination of homocysteine concentration in the blood is done to determine the individual risk for atherosclerosis and corresponding secondary diseases, especially in patients who also have other risk factors such as elevated blood lipid levels; also if homocysteinuria is suspected. The blood sample is taken in the morning on an empty stomach, 2-3 days beforehand no food rich in methionine should be consumed and as little coffee as possible should be drunk.
The normal value is below 10 μmol/L (micromol per liter). If homocysteine levels are elevated, therapy with folic acid, vitamin B6, and vitamin B12 supplements is recommended – depending on the extent and other risk factors – and on a long-term basis.
