Methionine is part of essential amino acids, that is, those amino acids that are not synthesized in our body but must be assimilated with the diet. In its natural L-shaped form, it is a key component of the protein and its concentration should be optimal, otherwise protein synthesis becomes ineffective. Methionine is derived from cysteine, another sulfuric amino acid capable of creating protein bonds and releasing H + ions for oxidation. Methionine, therefore, has multiple functions:

  • participates in the synthesis of carnitine;

  • intervenes in the production of melatonin;

  • limits the accumulation of fat in the liver;

  • submits certain heavy metals to kelation;

  • together with cysteine, it is source of sulfur, necessary for the production of cartilage;

  • strengthens nails and hair and normalizes urinary pH;

  • prevents ammonium phosphate stones.


Urinary pH throughout the day undergoes continuous variations; it tends to be more alkaline in the day, especially after meals, and acid at night. These continuous variations towards acid have the purpose of defending the bladder and our body from the proliferation of bacteria and their ascension to the kidneys.

Bacteria responsible for urinary system have a growth optimum at pH values ​​between 7 and 8. As the urinary pH decreases, there is a slowdown in replication capacity (bacteriostatic effect) and then death of the pathogen due to cellular wall breakdown (bactericidal effect).

In addition, keeping the urinary pH at acid values ​​prevents over-saturation and precipitation of phosphates and consequent formation of stones that in the presence of bacteria can infect and produce struvite stones.

Why is it important for urinary pH to be acidic?

A large number of Gram-negative bacteria are able to alkaline urine by enzymatic degradation of the urea, creating favorable conditions for their growth.

Nitrate-reducing bacteria (Escherichia Coli, Aerobacter, Proteus, Klebsiella, Pseudomonas, Enterococcus, Staphylococci, etc.) convert food-based nitrates tino nitrites, often considered harbingers of infection along with leukocytes.

By restoring a slightly acid urinary pH, these nitrites are transformed into nitrogen oxide (nitric oxide), a particularly effective molecule in blocking bacterial replication.

Using antibiotics alone or supplements that do not restore urine pH to physiologically acidic values ​​may not be sufficient. If the pH is alkaline, ideal conditions for bacterial re-colonization remain and cystitis may relapse.

Taking L-Methionine and Vitamin C guarantees the production of H + ions, which lower urine pH in a dose-dependent manner, and make the urinary environment unfavorable to pathogens. Nitrites are rapidly transformed into nitric oxide which functions as a natural antibacterial and reduces bacterial charge without any side effects.

A urinary pH maintained at acidic levels prevents phosphate over-saturation and their precipitation, resulting in the formation of stones or incrustations on permanent catheters.

The national health system involves replacement of PVC catheters every 30 days and every 60 days of those in silicone. Incrustation of these glands requires early replacement with increased costs for Local Health Agencies and considerable discomfort for patients who can suffer mucous lesions while removing the catheter (scratch) and may need antibiotics.


Homocysteine ​​is an intermediate sulfuric amino acid produced during the conversion of methionine into cysteine. Normally, its plasma concentration is controlled by group B vitamins that convert it into cysteine ​​or re-convert it into methionine.

Homocysteine ​​tends to accumulate in the blood when sufficient amounts of folate and vitamin are not consumed. There are also genetic causes that lead to deficits in enzymes that transform homocysteine ​​and are:

  • cystationin-β-synthetase (CBS) mutation;

  • MTHFR mutation;

  • methionine synthase deficiency;

  • reduced cobalamin deficiency;

  • γ-cystationinase deficiency.

A homocysteine ​​buildup in the blood is termed hyperhomocysteinemia, a condition linked to the increased risk of some serious illness.

PESO mg Met + Cys/day

  • 50kg 950mg

  • 60kg 1140mg

  • 70kg 1330mg

  • 80kg 1520mg

A very common mistake suggests that to reduce the concentration of homocysteine ​​in the blood, it is necessary to reduce methionine intake. Such a choice can lead to the interruption of the synthesis process of new proteins and the degradation of existing muscle cells. In this regard, Dietary Reference Intakes establishes the quantity of sulfuric amine acids required; the recommended daily intake (RDA) for adults is 19mg/kg/day. In children, pregnant women and nursing women the daily RDA is even higher, because the need to synthesize proteins is greater.

In order to prevent accumulation of homocysteine, it is necessary first to keep healthy behavioral and dietary habits:

  • eliminate alcoholic beverages;

  • do not smoke;

  • limit the consumption of coffee that interferes with the absorption of vitamin B;

  • exercise;

  • take sufficient amounts of vitamins B6, B12 and folic acid.


The effect of methionine at the urinary level is dose-dependent, that is, the more one takes, the greater the effect on urinary pH. Each 100mg of Methionine is excreted in 0.6mmol of H + in urine. Two ACIDIF® tablets give 800mg of methionine inject and release in urine 4.8mmol of H +, used in the normalization of the urinary environment and in the transformation of bacterial nitrites into nitric oxide. The indicated dose is well below the daily RDA, so the acidifying effect obtained is completely physiological.

It is also possible to take methionine from animal proteins present in meat, eggs and dairy products. Cereals, legumes and seeds have significantly lower methionine concentrations (average 200mg per 100gr of product).   

In restricted dietary or vegetarian and vegan regimens, the amount of methionine taken daily may be lower. The potential for acidic kidney load of a food in a healthy organism is calculable and is defined as PRAL. Sulfur (S) and phosphorus (P) present in foods give an acidifying power; magnesium (Mg), potassium (K) and calcium (Ca) yield an alkalizing effect. A positive PRAL identifies an acidogenic food, a negative PRAL identifies an alkalizing food. The sum of the PRALs of all foods taken with the diet defines the body's acidic load.

The acid and alkaline amounts introduced with food are poured into the circulatory stream and trigger the buffer systems to maintain the blood pH between 7.35 and 7.45. Excess acid-alkaline amounts are eliminated in the urine. The alkaline load in the form of bicarbonate is recovered at the renal level, H+ acidic ions are excreted in the urine giving it an acid pH.

During 24 hours the urinary pH varies continuously; it tends be alkaline after meals, namely, when it receives an alkaline load, and acidic between meals and at night, when we do not ingest food. (see graph above).


The latest SIU guidelines for the treatment of urinary infections invite physicians to “use reasonably and appropriately antibiotic therapy to treat uncomplicated cystitis”, considering that the “moderate use of broad spectrum antibiotics such as fluorocinolones, cephalosporins and aminoglycoside has produced high resistance to antibiotics that is particularly concerning today”. The critical situation in terms of resistance to antibiotics has recently led many physicians to prescribe old-generation molecules for the management of urinary infections. Many of these antibiotics carry out optimal activity in the urinary acid environment (see table).