Know This Amino Acid- Homocysteine

July 22, 2020

Hcy, short for- Homocysteine (hoe-moe-sist-een) is an non-essential toxic amino acid derived as a by-product of protein metabolism in the process of conversion of Methionine to Cysteine. 

Methionine is an essential amino acid, meaning it cannot be produced by the body, hence should be provided through dietary sources. On the other hand, Cysteine is a non-essential amino acid which can be made in the body using Methionine

Methionine ————-> Homocysteine ————–> Cysteine

This is done by a process called Methylation and is highly dependent on vitamin derived cofactors, vitamin B12, Folic acid and vitamin B6. If this process is dysfunctional it causes a build-up of homocysteine in the bloodstream. 

The level of homocysteine in the plasma is increasingly being recognised as a risk factor for disease and seen as a predictor of potential health problems.

Your homocysteine levels (or H Score) are more important than cholesterol, your blood pressure and even your weight as a measure of your health. In recent years high homocysteine has proven to be a reliable indicator of risk for heart attacks, strokes, memory decline and Alzheimer’s.

Your homocysteine level or H score is well worth knowing – it’s more important than your cholesterol level.

For example, a massive US survey of 136,905 patients hospitalized for a heart attack found that 75 per cent had perfectly normal cholesterol levels and almost half had optimal cholesterol levels! Elevated homocysteine levels affect the interior lining of blood vessels in the body, increasing the risk of atherosclerosis or narrowing of blood vessels and can also increase formation of clots. This can result in early heart attack and stroke.

Why is Methylation Important?

The methylation cycle helps us to operate both physically and mentally, so it may not be surprising that many different functions in the body use this process. 

Some functions include nervous, cardiovascular and immune system activity, as well as energy production, heavy-metal detoxification and hormone balance. Another important bodily function that methylation is connected to is DNA (1).

Methylation is a process that is essential for our DNA to work properly, and it may be the link between our environment, nutrition and disease.

Methylation and homocysteine though get caught in a vicious cycle.

Excess homocysteine build-up will result in a dysfunctional methylation cycle and if your methylation process is dysfunctional due to deficiencies of B-12, B-6 and Folate it will result in a buildup of homocysteine leading to condition called hyperhomocysteinemia.

About Hyperhomocysteinemia 

Hyperhomocysteinemia is a state in which excess homocysteine is present in the body i.e above normal levels. As stated earlier, as per our optimal health guidelines, your H- Score should ideally be below 6.


The most common cause of hyperhomocysteinemia is an enzyme defect associated with homocysteine metabolism. Dysfunction of enzymes and cofactors associated with the process of Homocysteine conversion can possibly be causative factors.

Genetic errors in enzymes or absence of these enzymes are directly linked to the higher level of homocysteine. A deficiency in CBS i.e.,Cystathionine beta synthase is the most common reason for an increase in homocysteine because CBS converts homocysteine to cysteine (3).

Some other factors include:

-Diets deficient in nutrients which help in lowering homocysteine levels like- Folic acid, Vitamin B6 and B12, Zinc and TMG (trimethylglycine)

-Excessive Methionine (Protein) intake

-Certain diseases- Chronic renal failure as a result of which there is reduced elimination and Hypothyroidism in which antithyroid drugs can possibly cause the increased amounts. Also malignant tumors can cause Folate deficiency and altered Homocysteine conversion (3)

-Side effects of some drugs such as proton pump inhibitors, cholestyramine, metformin, methotrexate, nicotinic acid (niacin), fibric acid derivatives, and oral contraceptive pills (3)

 -Poor lifestyle – especially smoking and high coffee and alcohol intake

-In youth, elevated levels of homocysteine may arise due to sickle cell disease or nutritional factors. Studies have shown that consumption of meat and dairy based products can also bring about an increase in circulating levels of Homocysteine (4).

Such high levels of circulating Hcy pose a threat for underlying diseased conditions across different age groups, right from little children (high homocysteine levels have been associated with autism like symptoms) to the elderly. 

In pediatric populations, Hcy levels are important not only for cardiovascular disease, obesity, and renal disease, but the most interesting evidence concerns study of elevated levels of Hcy in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) (5).

 In another study, Homocystinuria was observed in newborns. Homocystinuria is a disorder of methionine metabolism, leading to an abnormal accumulation of homocysteine in blood and urine which is normally not detected in appreciable quantities in blood and urine (6). These high levels show probable vitamin b12 deficiency, MTHFR deficiency (6). The enzyme MTHFR is necessary for conversion of Homocysteine to Methionine and high circulating Homocysteine levels were observed because of apparent Folic Acid deficiency. Folic acid is needed for the functioning of MTHFR enzyme. The detection of these deficiencies early in life can help in timely course of action for treatment.

Studies of children and adolescents indicate elevated homocysteine levels are linked with elevated blood pressure levels and increased weight (7). 

Moreover, high levels of Homocysteine have the ability to damage blood vessels (3) and it is because of this reason that it is considered as a potent risk factor for the development of Cardiovascular diseases.

Some studies have found Hyperhomocysteinemia to be the underlying cause behind age related macular degeneration (AMD) as a result of increased inflammation. AMD causes loss in the centre of the field of vision, thus leading to blurred vision (3). Hearing loss is another disease provoked by high blood homocysteine level and is thought to be due to direct damage to neurons (3).

In pregnancy, Hcy levels were investigated in relation to the increased risk of adverse pregnancy outcomes such as baby born smaller in size than usual, high BP during pregnancy, recurrent abortions, low birth weight, or growth restriction within the uterus (5)

Further, research also revealed a relation between Ovarian cancer and high homocysteine levels due (8). Also, in a study conducted with postmenopausal women, hyperhomocysteinemia happened to cause colorectal cancer (3).

It is documented that Homocysteine affects bone mineral density.This could result in bones becoming less rigid, increasing the chances of fracture (9). High levels of Homocysteine are known to disrupt insulin signaling, thus, causing insulin resistance (4). Research has also shown hyperhomocysteinemia to cause Alzheimer’s disease due to its ability to worsen Beta-amyloid plaque formation, which are known to lead to the onset of the disease (10).

Finally, a focus on the principal pathologies of the elderly (cardiovascular and neurodegenerative disease, osteoporosis and physical function) are also presented due to high homocysteine levels. Elevations in blood homocysteine levels have shown to be associated with common problems seen with aging, such as cognitive impairment, dementia, depression, osteoporotic fractures, and functional decline (11).

It is said that Hcy is one of the best predictors of overall health and even the risk of death.

So you see, it’s important to keep your homocysteine levels below 6, tribe. It is an important marker of internal health and the earlier you identify the build-up, the better it is for you.

The good news is that homocysteine levels can be tested and high homocysteine levels can be normalised through iThrive’s approach (because we get to the root cause of your high levels). 

Get your homocysteine levels checked at the earliest and reach out to us at iThrive to learn how to bring them down to normal levels.


Ria Jain
Functional Nutritionist

Ria has a Master’s in Nutrition and Dietetics and is in a permanent research mode and keeps the rest of us at iThrive (Previously ThriveFNC) updated with her latest findings in the field of Nutrition. Her articles on iThrive's blog are an expression of her research findings. We really don’t know what we’d do without her support and her focus.

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