Relation Between Homocysteine, Folic Acid, Vitamin B6 And Vitamin B12

A homocysteine It is an amino acid produced by the body, where it acts directly in the metabolism of methionine.

Therefore, methionine is converted to S-adenosylmethionine, to then form homocysteine.

Once formed, homocysteine ​​can make its way to remethylationwhich consists of a new reconversion of homocysteine ​​to methionine.

When this happens, the new transformation of homocysteine ​​into methionine depends on the presence of folic acid, vitamin B6 and vitamin B12.

better understand the relationship between homocysteine, folic acid, vitamin B6 and vitamin B12 in the course of this article.

Increased homocysteine ​​levels impact cardiovascular health

High levels of homocysteine ​​in the bloodstream, known as hyperhomocysteinemia, have the ability to change the structure of arteries and veins.

Thus, the increased production of homocysteine ​​may favor the appearance of some heart diseases such as heart attack, coronary heart disease and stroke.

However, the relationship between the occurrence of hyperhomocysteinemia and the increased chances of developing coronariopatias graves still not fully clarified by science.

According to some authors, the chances of this happening are greater in these situations:

  • In the presence of oxidative damage to the endothelium
  • Through proliferation (enlargement) of endothelial smooth muscle
  • Through oxidation of low-density lipoproteins (bad cholesterol)

Folic acid, vitamin B6 and vitamin B12 are essential to prevent hyperhomocysteinemia

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As previously stated, homocysteine ​​remethylation or new conversion to methionine requires the help of the folic acid and vitamin B12.

In other words, folic acid needs to be present in the remethylation step, while vitamin B12 and vitamin B6 act as an essential cofactor.

For this reason, it is important to maintain a diet rich in foods that are sources of folic acid, vitamin B6 and vitamin B12.

Supplementation is interesting when homocysteine ​​levels are already highhowever, it has not yet been proven that it is 100% effective in combating hyperhomocysteinemia.

How does the body eliminate excess homocysteine?

When faced with an excess of homocysteine, the saturation happens, forcing the organism to transform the amino acid into cysteine ​​again.

This reaction is called transfuration. After transsulfuration, cysteine ​​is transformed into sulfate, so that it can then be excreted in the urine. In this step, the help of vitamin B6 is extremely necessary.

Causes of hyperhomocysteinemia

The increase in the concentration of homocysteine ​​in the blood can happen for different reasons. Nonetheless, the main causes are:

  1. Methionine deficiency, due to low intake of methylcobalamin (B12)
  2. Deficiency of folate, the active form of folic acid
  3. Decreased activity of cystathionine B synthetase (CBS)
  4. Alcoholism
  5. smoking
  6. Methionine deficiency, due to depletion of vitamin B12 in the blood
  7. Advanced age
  8. severe kidney failure
  9. hypothyroidism
  10. Use of drugs that alter folate, vitamin B6, or vitamin B12 metabolism

homocysteine ​​transfuration

As previously mentioned, in addition to remethylation, homocysteine ​​can follow another path, the transfuration.

In this case the amino acid is catalyzed by an enzyme, cystathionine B synthetase (CBS). Then, with the help of vitamin B6, CBS can act, transforming homocysteine ​​into cysteine ​​and alpha-ketobutyrate.

Therefore, the decrease in CBS activity can also generate hyperhomocysteinemia.

Role of cysteine ​​in the body’s health

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The cysteine ​​formed from the transforation of homocysteine ​​plays an important role in maintaining health.

Among its functions is the promotion of enzyme and protein health, where it promotes their stability and maturity.

Furthermore, cysteine prevents changes in the structure of proteins, reduces inflammation and the generation of DNA damage.

In addition, some studies indicate that lipid peroxidation is greater when cysteine ​​levels are lower.

The same can be said of the reduction in bone mass observed in women in the menopausal period, where the low cysteine ​​concentration increases the chances of fracture.


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So that homocysteine ​​levels are not elevated, the metabolism of the substance depends on the participation of folic acid, vitamin B12 and vitamin B6.

While the conversion of homocysteine ​​to methionine is controlled by folic acid and vitamin B12, excretion needs the help of vitamin B6.

The literature points out that increased levels of homocysteine ​​predispose to the onset of heart disease

However, the transformation of homocysteine ​​to cysteine ​​via transfuration should not be ignored.

Low cysteine ​​production is linked to cellular oxidation, increased inflammation, weakened bones, and damage to enzymes and proteins in the body.

To prevent the unregulated increase in homocysteine ​​and the low production of cysteine, a healthy diet is essential. For this, foods rich in folic acid, vitamin B6 and vitamin B12 are essential.

What to do to avoid hyperhomocysteinemia and low cysteine ​​production

Food sources of folic acid

As you saw, folic acid participates in the transformation of homocysteine ​​into methionine through remethylation.

One of the ways to improve the performance of this vitamin is to increase the intake of folate-rich foods:

  • Brewer’s yeast
  • cooked black beans
  • Okra
  • Spinach
  • green soybean
  • Peanut
  • Beet
  • Nuts
  • Hazelnut
  • Brussels sprouts
  • Sunflower seed
  • Bull’s liver
  • chicken liver
  • Arugula
  • Corn
  • french bread

Food sources of B6 (Pyridoxine)

Vitamin B6 is essential in the excretion stage of excess homocysteine, through the transformation of cysteine ​​into sulfate.

So, the food sources of pyridoxine prevent the low production of cysteine ​​and help to eliminate the excess in the urine:

  • Cooked chicken
  • Sunflower seeds
  • baked potato
  • Roasted peanuts
  • Cassava flour
  • Nut
  • fresh plum
  • Avocado
  • Wheat germ
  • Banana
  • Bull’s liver
  • chicken liver
  • Salmon
  • Hazelnut

Food Sources of Vitamin B12 (Cobalamin)

Adequate intake of food sources of cobalamin allows the correct transformation of homocysteine ​​into methionine.

In addition to preventing hyperhomocysteinemia, food sources of vitamin B12 prevent the accumulation of fat, through the mobilization and removal of excess lipids and toxic agents from the liver:

  • beef liver
  • chicken liver
  • grilled beef steak
  • grilled sardines
  • Crab
  • grilled tuna
  • mozzarella cheese
  • ox heart
  • raw oysters
  • whole cow’s milk

When is supplementation necessary?

A folic acid, B6 and B12 supplementation should be done in cases of deficiency verified in exams.

Overall, a healthy and diverse diet already ensures the recommended daily intake of these nutrients.

Therefore, avoid taking folic acid, vitamin B6 and vitamin B12 supplements without direct supervision by a doctor or nutritionist.


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