Too much meat, fish, nuts in pregnancy raises mental disorder risk in babies

Too much of a protein present in meat, cheese and beans in pregnancy may be linked to an increased risk of the baby developing schizophrenia later in life, new research suggests.

Scientists discovered that an ‘overload’ of a common amino acid – also found in fish and dairy products, as well as nuts and grains – caused symptoms of the mental health condition. In the first study of its kind, they discovered that when pregnant mice were given excess methionine, their offspring showed schizophrenia-like behaviour.

The researchers hope that their findings could lead to new anti-psychotic drugs. Study author Amal Alachkar from the University of California said: “Our study agrees with the saying, ‘we are what our mothers ate’.

“This is a very exciting area of research that we hope can be explored in greater depth.” High methionine foods include nuts, beef, lamb, cheese, turkey, pork, fish, shellfish, soy, eggs, dairy, and beans. The amino acid is greater in animal foods, particularly dairy. Chicken and fish have the highest levels, while milk, red meat, and eggs have less. Soy and beans, while a source of methionine, is thought to contain lower levels.

Schizophrenia is a severe long-term mental health condition where a person may not always be able to distinguish their own thoughts and ideas from reality. Symptoms can include hallucinations, delusions, muddled thoughts and changes in behaviour.

Methionine is an essential amino acid – one of the ‘building blocks’ of protein that help build and repair cells – that cannot be produced by the human body so must come from our food. It is required for growth and tissue repair and also helps break down fat in the liver and arteries. A deficiency in methionine can cause liver damage, muscle loss, fat loss, skin lesions, weakness, lethargy and slowed growth in children.

The researchers were keen to further explore findings from studies carried out in the 1960s and 1970s in which schizophrenic patients injected with methionine experienced worsened symptoms.

The exact cause of schizophrenia is unknown. However, most experts believe the condition is caused by a combination of genetic and environmental factors. Studies of people with the condition have shown there are subtle differences in the structure of their brains.

Knowing that the condition is a developmental disorder, the team hypothesised that administering three times the normal daily input of methionine to pregnant mice may produce pups that have also schizophrenia-like deficits, which is what occurred.

The team treated the mice – which are biologically similar to humans – with anti-schizophrenic drugs well used in therapy which had the same effects as in humans.

Alachkar added: “Our study points at the very important role of excess dietary methionine during pregnancy in fetal development, which might have a long-lasting influence on the offspring.”