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  • Methionine, longevity and schizophrenia: Can methionine induce madness?


    The Bottom Line

    • A low-methionine diet delays ageing in animals.
    • If delaying ageing is your aim, methionine-restriction might be an easier option than calorie-restriction.
    • High levels of dietary methionine can exacerbate psychopathological symptoms in schizophrenic people.


    • Severe methionine-restriction lowers fertility in animals.
    • Severe methionine-restriction stunts growth in young animals.
    • Cutting out methionine completely is incompatible with life.

    My advice

    • Eat more vegetables and fruit, which are low methionine foods.

    How bizarre that an amino acid, longevity and schizophrenia could all be related. It’s so easy to forget how profound an effect food can have on us.

    This post on methionine is a bit of a ramble to illustrate the curious connections between food and disease.

    Firstly, what exactly is methionine?

    • Methionine is an amino acid.
    • Amino acids are the building blocks of proteins.
    • High levels of methionine are found in certain protein containing foods such as meat, fish and eggs.
    • Fruit and vegetables are very low in methionine.

    I’m not proposing that you restrict or increase your intake of methionine containing foods – I’m just presenting the evidence that’s out there which overwhelmingly shows that restricting methionine intake in rats and flies increases their longevity.

    Methionine and madness
    Sometimes we do strange things to our bodies– for example some people (usually body builders and those on the Atkins diet) ingest exceedingly high amounts of proteins.
    Would they persist with their high-protein diets knowing that very high intakes of methionine have been found to exacerbate psychopathological symptoms in schizophrenic patients, and that restricting methionine in rats increases their longevity?

    Methionine and Paracetamol
    And did you know that methionine can reverse the toxic effects of Paracetamol if taken within the first few hours of an overdose?

    Dose clearly matters – 1g of Paracetamol gets rid of a headache and enables you to carry on with your life; but 10g of Paracetamol could extinguish your life.
    We need to remember that dosage is important not only with medication – how much you eat of a particular food matters too.

    A little bit of methionine is good for you; excluding it completely from your diet is incompatible with life; a one-off high dose can reverse the toxicity of a Paracetamol overdose; and lifelong over indulgence could possibly shorten your life.

    And so it is with most nutrients and toxins – quantity and timing matters.

    When it comes to taking medication, some of us think long and hard before taking anything; we wonder what the side effects might be and discuss the pros and cons with a doctor before taking anything.
    Yet when it comes to food, consuming a sugary doughnut fried in toxic omega-6 rich oil might not be given a second thought, (unless you are like me and totally obsessed with food, as a result of which I always feel a little bit guilty when eating anything unhealthy!).
    Ok, one doughnut isn’t going to kill anyone, but we can see with the worldwide escalation in obesity and diabetes that all the little doughnuts do add up – usually to lifelong chronic illnesses.

    So just as we stop and think before putting any medicine into our body, we should also think twice about what we are feeding our bodies on a daily basis.
    After all, food is not just a simple fuel for our bodies – food is also a type of environmental exposure.

    The saying goes that everyone on this planet is related by 7 degrees of separation. I would propose that it is probably only one or two degrees of separation between many diseases and food.

    Methionine Basics

    • Methionine is an essential nutrient.
    • Methionine is a sulphur containing amino acid (as is cysteine)
    • Essential nutrients are ones that our bodies cannot synthesise – we need to get them from our diet.
    • Besides building proteins, methionine is also essential for ‘DNA methylation’.
    • DNA is our genetic code.
    • DNA methylation is necessary for genetic stability, normal gene expression, and prevention of cells becoming cancerous.
    • Certain vitamins can moderate the effects of methionine – so as all our mothers probably told us, it is best to eat meat and veg together.

    Methionine, longevity and rodents

    • Methionine Restriction (MR) increases lifespan in rodents. (Surprising, but true).
    • This increase in lifespan occurs despite no restriction of total calories.
    • What we don’t know is whether this can be extrapolated to humans.

    The original experiments on MR in rats came about as a result of the the calorie restriction (CR) studies which showed that CR led to an increased lifespan in rodents and other species.

    It is probably only a question of time before someone somewhere forms a ‘Methionine Restriction Society’ , just as there are members of the ‘Caloric Restriction Society’, some of whom are being studied by scientists.

    How much methionine do we need?
    There is usually a narrow range of how much we need of a particular nutrient.
    Besides methionine, the other essential amino acids are – lysine, leucine, isoleucine, tryptophan, valine, threonine, phenylalanine, and histidine.
    10–20 mg/kg body weight is the amount of each essential amino acid needed from consumed protein every day.
    Too much of particular foods, as well as too little, can be detrimental.
    Usually we need only small amounts of ‘essential nutrients’, so don’t mistake ‘essential’ as a license to pig out on something – be it vitamin C or methionine.

    Why too much or too little methionine might be a bad thing

    Data from experiments on rats:

    • If you cut out methionine completely from rat diets, they become infertile, develop ‘fatty liver’ and die. (Not a good state of affairs!)
    • If their methionine intake is restricted by 80%, their lifespan increases by roughly 40%. (In these experiments the rats had free access to non-methionine containing foods, and so had unlimited total calories).
    • The increase in longevity did come at a cost if the methionine restriction was instituted in rat pups – they had stunted growth and were infertile. (Maybe methionine is one of the reasons why meat eating populations are usually taller than vegetarian ones?).
    • To date, no long-term methionine-restriction experiments have been done on humans.

    You might now be wondering whether carbohydrate or fat restriction have an effect on longevity – neither of them have been found to increase lifespan in animals.

    Methionine-restriction produces the following biological and biochemical effects in mice (who have unrestricted calories).

    • Lower levels of insulin, glucose and IGF-1
    • Enhances insulin sensitivity.
    • Reverses pre-existing insulin resistance.
    • Attenuates the age-associated increase in circulating triglycerides.
    • Reduces levels of mitochondrial oxidative damage
    • Limits fat deposition.
    • Restricts expansion of adipose tissue mass.
    • Uncouples peripheral fuel oxidation.
    • Increases the energy costs of maintenance and growth (possibly through increased energy expenditure).
    • Studies comparing MR with calorie restriction (CR) in rodents found that many of the beneficial physiological changes of CR were similar to MR.

    Let me know if you hear of any studies on methionine-supplemented-calorie-restricted animals – it would be interesting to see whether the methionine negates the calorie restriction benefits.


    • A low-methionine diet delays ageing in animals.
    • Meat, fish and eggs have high levels of methionine.
    • It is easier to restrict the intake of methionine containing foods than it is to restrict calories, so MR might be an easier alternative to CR.


    • Severe methionine-restriction lowers fertility in animals.
    • Methionine-restriction stunts growth in young animals.

    My advice, as always:
    Eat more vegetables and fruit.

    A little methionine-restriction might go a long way…

    And if you feel inclined to have a look at the references that I used to research this post:

    Posted in Latest evidence and tagged , .

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