High Homocysteine Levels: a Possible Cause of Many Diseases
Currently being dubbed the new cholesterol, yet still known little about: the amino acid homocysteine is increasingly found at the forefront of medical attention, as it is linked to the pathogenesis of a number of diseases. Increased homocysteine levels are associated with blood vessel damage, which can lead to high blood pressure, heart attack and stroke.1,2 Aside from this too much homocysteine can deteriorate cell health, which is linked to dementia and Alzheimer’s.3 Correlation between homocysteine levels and depression, sight problems and osteoporosis are yet to be explored.
Today only around 50% of heart attacks and strokes can be medically explained, which is why there is intensive research taking place to try and identify other risk factors. Homocysteine is currently at the forefront of these studies and it is estimated that roughly 10% of heart attacks and strokes could be explained by high homocysteine levels.4,5
In high concentrations homocysteine causes damage directly to the cells and is sometimes referred to as a cell toxin. This can be misleading, however, because homocysteine is a necessary and natural metabolite (intermediate product of metabolism). Despite this it causes blood to thicken, so increases cardiovascular health risks on two counts.6
Homocysteine and Vitamin B12 Supplies
Homocysteine is usually found as a metabolite that accumulates in the cells and later processed into other substances, such as S-Adenosyl methionine (SAM). SAM plays a key role in the initial stages of synthesis for many health related substances, but folic acid and vitamin B12 are necessary for homocysteine conversion. If these vitamins are lacking the metabolic step cannot take place meaning that homocysteine remains and its levels accumulate further. The consequences of this often negatively impact health.
In another metabolic process taking place in the liver and kidneys homocysteine can be converted into methionine with the assistance of betaine, or it may also be broken down into cysteine with the help of vitamin B6. For this reason the presence of vitamin B12, folic acid, vitamin B6 and betaine are essential in ensuring homocysteine levels stay under control.
Homocysteinemia: an Indication of Vitamin B12 Deficiency?
Because of their close relationship homocysteine levels can be an indirect indication of a vitamin B12 deficiency. Elveated homocysteine levels, also known as homocysteinemia, is often an indication of a B12 deficiency, but a lack of folic acid may also be the cause of this. Since measuring vitamin B12 serum levels is somewhat unreliable, homocysteine levels are more commonly tested in order to achieve more accuracy.
To achieve a relevant diagnosis, homocysteine blood levels are measured. Below is a table detailing how current values are interpreted.
Homocysteine values µmol/L
critical level (urgent action should be taken)
Homocysteine Levels: Risky for Vegans and the Elderly
High homocysteine levels are most common amongst the elderly and vegans, the cause of which is usually vitamin B12 deficiency. The vegan diet is naturally low in B12, but elderly people often suffer from disorders that affect absorption. Around 40-60% of older people have elevated homocysteine levels.
Other factors that usually raise homocysteine levels include high consumption of alcohol and coffee, use of certain drugs, disorders affecting the stomach, intestine and liver. Further details can be found at our page on vitamin B12 deficiency.
Homocysteine – Just an Indicator?
Some have criticised the labelling of homocysteine as a risk factor. Norbert Fuchs argues that homocysteine is not so much a trigger of illness and disease but rather an indication of nutrient deficiency. It is this lack of nutrients that is the real issue, rather than the presence of homocysteine itself.7 Elevated homocysteine levels could merely signal a disturbance in transfers of methyl groups. These transfers are crucially important for the production and regeneration of new cells. In particular they are important for haematopoiesis (formation of blood cellular components), cardiovascular metabolism and the syntheses of neurotransmitters.
However a number of other substances are also necessary for the transfer of methyl groups. These include choline, betaine, vitamin B6, vitamin B12 (methylcobalamin), folate (methyl THF) and SAM. A deficiency in any of they may also result in symptoms classically associated with high homocysteine levels. With this in mind, it may not simply be a case of lowering homocysteine levels, but rather controlling and optimising nutrient intake and levels.
Lowering Homocysteine Levels Through Vitamin Intake
Whether homocysteine is a cause or simply an indication is just one side of the discussion. Placing this matter to one side, the best prevention against high homocysteine levels and nutrient deficiencies ultimately comes down to vitamin intake. In Germany, most commonly an increased amount of vitamin B12, folate or sometimes vitamin B6 or beatine is required.
Aside from the vitamin B12 supplements that are available, the are also products tailored to the reduction of homocysteine levels. These products contain a combination of the necessary nutrients required to do this. A blood test can identify whether a patient requires these types of supplement. In particular, vegans and elderly people should pay careful attention to their vitamin B12 intake, but usually a simple supplement should suffice.
1 Fanapour PC, Yug B, Kochar MS. Hyperhomocysteinemia: an additional cardiovascular risk factor. WMJ. 1999 Dec;98(8):51-4. Review. PubMed PMID: 10639897.
2 van Beynum IM, Smeitink JA, den Heijer M, te Poele Pothoff MT, Blom HJ. Hyperhomocysteinemia: a risk factor for ischemic stroke in children. Circulation. 1999 Apr 27;99(16):2070-2. PubMed PMID: 10217643.
3 SESHADRI, Sudha, et al. Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease. New England Journal of Medicine, 2002, 346. Jg., Nr. 7, S. 476-483.
4 Christine Vetter. Homocysteinämie – Risikofaktor für Herz und Gefäße. Zahnärztliche Mitteilungen 23/2003
5 Stanger O, Herrmann W, Pietrzik K, Fowler B, Geisel J, Dierkes J, Weger M; DACH-LIGA Homocystein e.V. DACH-LIGA homocystein (german, austrian and swiss homocysteine society): consensus paper on the rational clinical use of homocysteine, folic acid and B-vitamins in cardiovascular and thrombotic diseases: guidelines and recommendations. Clin Chem Lab Med. 2003 Nov;41(11):1392-403. Review. Erratum in: Clin Chem Lab Med. 2004 Jan;42(1):113-6. PubMed PMID: 14656016.
6 Guilland JC, Favier A, Potier de Courcy G, Galan P, Hercberg S. [Hyperhomocysteinemia: an independent risk factor or a simple marker of vascular disease?. 1. Basic data]. Pathol Biol (Paris). 2003 Mar;51(2):101-10. Review. French. PubMed PMID: 12801808.
7 Norbert Fuchs. Homocystein – Risikofaktor, der keiner ist. PharmaTimes, 04/2011