Category: Natural chemicals
Introduction and description
Methionine is an essential amino acid and together with cysteine, is one of only two sulphur-containing amino acids.
An essential amino acid cannot be synthesised in the body, as such it has to be ingested and is thus the starting point for many subsequent transformations. The following paragraphs describe some of the functions, although the interactions and function dependencies are such that it is impossible to list them all.
Methionine levels affect the amount of sulphur-containing compounds, such as glutathione, in the liver. Glutathione and other sulphur-containing peptides (small proteins) play a critical role in defending against toxic compounds.
When higher levels of toxic compounds are present, more methionine is needed. This is why you see expressions such as Methionine is “Glutathionigenic” [Martindale’s 29th], or an “Antidote (Acetaminophen) - Dosage: 10 g/16hr/man/orl “[also Martindale’s 29th], or an “Antidote (Paracetamol) - Dosage: 10 g/16hr/man/orl “ [again Martindale’s 29th] or is an “Antioxidant” [Dr J Duke].
Choline assists detoxification reactions in the liver. But if inadequate supplies of choline are being obtained from the nutrients in food, choline can be synthesized from methionine or serine.
Sulphur is, in its own right, an exceptionally important mineral and has a part to play in healing problems like acne; dandruff; in seborrheic dermatitis, the skin problems caused by cosmetics, and in problems related to keratin, a major component of the skin, thus functionally we would expect that Methionine via its sulphur has similar activity – and it does. Simply put it is one key to skin health. But methionine appears to play a part in the formation of certain types of components used to form healthy skin. In the following experiment the researchers overdosed the rats used to see what would happen:
Although excess methionine intake …. did not alter the collagen content of their skin, it caused an increase in the content of type III collagen and a decrease in crosslinked collagen. In addition, newly synthesized collagen in the neutral salt extract increased in the excess methionine group, indicating that crosslinked collagen decreases as excess methionine was intubated. PMID: 3566975
What the research highlights is the link between methionine and cross linked and type III collagen. From other research there appear to be indications that the production of keratin is dependent on Methionine.
It also appears to be key to the health of the hair. “Loss of methionine has been linked to senile greying of hair. Its lack leads to a buildup of hydrogen peroxide in hair follicles, a reduction in tyrosinase effectiveness, and a gradual loss of hair color”.
There are activities that show that eye health is also dependent on Methionine. The eye is made up of similar connective tissue to the skin and the cornea in particular has abundant tissue dependent on Methionine. Without adequate Methionine in the diet we can get cataracts.[source Pizzorno, J.E. and Murray, M.T. 1985. A Textbook of Natural Medicine.]
Methionine is Lipotropic. Lipotropic compounds are those that help catalyse the breakdown of fat during metabolism in the body. This is why you sometimes see sentences like “Methionine is hepatoprotective” – protective of the liver, or that Methionine has “a fat-dissolving effect and reduces the depositing of fat in the liver”.
A lipotropic nutrient promotes or encourages the export of fat from the liver. Lipotropics are necessary for maintenance of a healthy liver, and for burning the exported fat for additional energy.
Methionine is not the only lipotropic.
Without lipotropics, such as choline and inositol, fats and bile can become trapped in the liver, causing severe problems such as cirrhosis and blocking fat metabolism. Choline is essential for fat metabolism. Choline functions as a methyl donor and it is required for proper liver function. Like inositol, choline is a lipotropic. Inositol exerts lipotropic effects as well.
But Methionine is a major lipotropic compound in humans too. Again we also see sentences that say Methionine is ‘antihepatotic’ meaning protective against Hepatitis, a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells.
Sex hormone balance
One fascinating aspect about how much Methionine we need is that it is connected to the reproductive system!
Progesterone is made from cholesterol. The progestogens are then the precursors of all other endogenous steroids, - the androgens, estrogens, and other steroids such as the glucocorticoids, mineralocorticoids, and neurosteroids.
When progesterone/estrogen levels are high, the body requires more methionine. It essentially restores balance. As the production of progesterone/estrogens needs cholesterol, the process has the effect of reducing bile flow through the liver and increasing bile cholesterol levels. Methionine acts in opposition to this process restoring balance and ensuring progesterone and estrogen levels do not become too high – deficiency and overdose both being undesirable.
The lipotropics flush away the excess cholesterol and fats and thus since the raw material from which all the sex hormones is made has been reduced, the levels of sex hormones go down too.
Overdosing on methionine has a very serious effect on folate levels, meaning that methionine is key to keeping the balance of folate correct, folate is key to the reproductive cycle of women
Oral methionine supplements (8.0 g daily for 4 days) were given to five normal volunteers who continued to eat their usual diet. This treatment resulted in a significant fall in serum folate concentration. Three days after the end of treatment concentrations had not completely returned to control values. PMID: 97644
Parasympathetic nervous system
Acetylcholine is the endogenous ligand that controls the parasympathetic nervous system – the system for relaxation. Acetylcholine is made from Choline and acetyl coenzyme A, thus in general Methionine has no effect on this system. But, if inadequate supplies of choline are being obtained from the nutrients in food, choline can be synthesized from methionine in the body.
When we stand back and look at these functions, there does appear to be yet again a link to the reproductive cycle as a whole. Methionine through the effects it has on the sex hormones regulates ageing. But it is via the hormones, as ageing is reproductive system dependent.
In effect, the primary mechanism involved in ageing are progesterone, estrogen and the androgens which are themselves dependent on cholesterol. But cholesterol levels are also regulated by the lipotropics, one of which is Methionine – a key one. Thus if Methionine gets out of balance, then so will the cholesterol levels and the hormone levels.
This is why hair goes grey if methionine levels fall. It is not a direct association but an indirect one: – low methionine – low cholesterol – low hormones – grey hair
And why skin ages:
Low methionine – low cholesterol – low hormones – ageing skin
And why eyes deteriorate:
Low methionine – low cholesterol – low hormones – failing eyesight
An observation from Dr Duke's database provides the plant sources for Methionine, the following provides some example other food sources.
Food sources of Methionine USDA Nutrients database
Chicken, broilers or fryers
Fish, tuna, light, canned
Beef, cured, dried eg Bresaola
- Dr Duke's list of chemicals and activity for the Shallot 017969
- Dr Duke’s list of Chemicals and their Biological Activities in: Cucurbita pepo L. (Cucurbitaceae) -- Zucchini 027494
- REVERSIBLE MYELONEUROPATHY IN A YOUNG WOMAN 027601